Roald Bahr

• Serner, Andreas; Chamari, Karim; Hassanmirzaei, Bahar; Moreira, Francisco; Bahr, Roald & Massey, Andrew [Show all 9 contributors for this article] (2024). Time-loss injuries and illnesses at the FIFA world cup Qatar 2022. Science and medicine in football. ISSN 2473-3938. doi: 10.1080/24733938.2024.2357568.
• Steffen, Kathrin; Bahr, Roald; Clarsen, Benjamin Matthew; Fossan, Bjorn; Fredriksen, Hilde & Gjelsvik, Hilde [Show all 15 contributors for this article] (2024). Comprehensive periodic health evaluations of 454 Norwegian Paralympic and Olympic athletes over 8 years: What did we learn? British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2023-107942.
• Bache-Mathiesen, Lena Kristin; Bahr, Roald; Sattler, Tine; Fagerland, Morten Wang; Whiteley, Rod & Skazalski, Christopher M. (2024). Causal inference did not detect any effect of jump load on knee complaints in elite men's volleyball. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 34(5). doi: 10.1111/sms.14635.
• Thorarinsdottir, Solveig; Amundsen, Roar; Larmo, Arne Feilberg; Pedersen, Roar; Andersen, Thor Einar & Bahr, Roald [Show all 7 contributors for this article] (2024). Groin injuries in women's premier league football in Norway: A two-season prospective cohort study describing clinical and imaging characteristics. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 34(4). doi: 10.1111/sms.14611.
• Sandmo, Stian Bahr; Dietrichs, Espen & Bahr, Roald (2024). When You Hear Hoofbeats, Don't Forget the ZEBRA: Paroxysmal DYSKINESIAS as A Cause of Atypical Movements in Athletes. Current sports medicine reports. ISSN 1537-890X. 23(2), p. 38–40. doi: 10.1249/JSR.0000000000001137.
• Amundsen, Roar; Thorarinsdottir, Solveig; Larmo, A.; Pedersen, R.; Andersen, Thor Einar & Møller, Merete [Show all 7 contributors for this article] (2024). #ReadyToplay: hamstring injuries in women’s football–a two-season prospective cohort study in the Norwegian women’s premier league. Science and medicine in football. ISSN 2473-3938. doi: 10.1080/24733938.2024.2305389.
• Wik, Eirik Halvorsen; Chamari, Karim; Tabben, Montassar; Di Salvo, Valter; Gregson, Warren & Bahr, Roald (2024). Exploring growth, maturity and age as injury risk factors in high-level youth football. Sports Medicine International Open. ISSN 2367-1890. 8. doi: 10.1055/a-2180-4594. Show summary

  Rapid somatic growth and biological maturity status may affect injury patterns in youth football, yet firm conclusions cannot be drawn from the existing research. We aimed to explore growth velocity, maturity and age as injury risk factors in 95 academy players (11.9-15.0 years), using anthropometric (height and body mass), maturity (skeletal age), injury and football exposure data collected prospectively over three seasons (2016/17-2018/19). We compared the relative quality of mixed-effects logistic regression models with growth velocity for 223 growth intervals (average 113 days) included as fixed effects, and adjusted for age (chronological or skeletal) plus load (hours/week). Associations were considered practically relevant based on the confidence interval for odds ratios, using thresholds of 0.90 and 1.11 to define small beneficial and harmful effects, respectively. We observed harmful effects of older age on overall (OR: 2.61, 95%CI: 1.15-5.91) and sudden onset (1.98, 1.17-3.37) injury risk. Significant associations (p<0.05) were observed for higher body mass change and greater maturity on sudden onset injuries, and for higher hours/week on gradual onset, bone tissue and physis injuries. Future studies should include larger samples, monitoring athletes from pre-adolescence through maturation, to enable within-subject analyses and better understand the relationship between growth, maturation and injuries.

• Clarsen, Benjamin Matthew; Berge, Hilde Moseby; Bendiksen, Fredrik; Fossan, Bjørn; Fredriksen, Hilde & Haugvad, Lars [Show all 11 contributors for this article] (2023). Injury and illness among Norwegian Olympic athletes during preparation for five consecutive Summer and Winter Games. British Journal of Sports Medicine. ISSN 0306-3674. 58(1), p. 18–24. doi: 10.1136/bjsports-2023-107128. Show summary

  Objective: To describe the patterns of health problems among Norwegian Olympic candidates during their preparations for five consecutive Olympic Games (London 2012, Sochi 2014, Rio de Janeiro 2016, PyeongChang 2018 and Tokyo 2020). Methods: This was a descriptive epidemiological study using the Oslo Sports Trauma Research Center Questionnaire on Health Problems to collect data on all self-reported health problems from Norwegian Olympic candidate athletes for 12–18 months prior to each Olympic Games. Team physicians and physiotherapists followed up the athlete reports, providing clinical care and classifying reported problems according to the International Olympic Committee 2020 consensus statement on methods for recording and reporting of epidemiological data on injury and illness in sport. Results: Between 2011 and 2020, 533 athletes were included in the Norwegian Olympic team monitoring programme, with a 78% response to the weekly questionnaire. During this time, athletes reported 2922 health problems, including 1409 illnesses (48%), 886 overuse injuries (repetitive mechanism, 30%) and 627 acute injuries (traumatic mechanism, 21%). Diagnostic codes were recorded for 2829 (97%) of health problems. Athletes reported, on average, 5.9 new health problems per year (95% CI: 5.6 to 6.1), including 1.3 acute injuries (CI: 1.2 to 1.4), 1.7 overuse injuries (CI: 1.6 to 1.9) and 2.9 illnesses (CI: 2.7 to 3.0). Each year, female and male athletes lost an average of 40 and 26 days of training and competition due to health problems, respectively. The diagnoses with the highest health burden were anterior cruciate ligament rupture, respiratory infection, lumbar pain and patellar tendinopathy. Conclusion: The injury burden was particularly high among female athletes and in team sports, whereas endurance sports had the greatest burden of illness. Our data provide a compelling argument for prioritising medical care and investing in prevention programmes not just during the Olympic Games, but also the preparation period.

• Amundsen, Roar; Thorarinsdottir, Solveig; Clarsen, Benjamin Matthew; Andersen, Thor Einar; Møller, Merete & Bahr, Roald (2023). #ReadyToPlay: health problems in women's football-a two-season prospective cohort study in the Norwegian premier league. British Journal of Sports Medicine. ISSN 0306-3674. 58(1), p. 4–11. doi: 10.1136/bjsports-2023-107141. Show summary

  Objectives: To describe the prevalence, incidence and burden of all health problems in the Norwegian women’s premier league. Methods: During the 2020 and 2021 seasons, players in the Norwegian women’s premier league reported all health problems (sudden-onset injuries, gradual-onset injuries and illnesses) weekly, using the Oslo Sports Trauma Research Centre Questionnaire on Health Problems. Team medical staff diagnosed reported problems using the Sport Medicine Diagnostic Coding System. We calculated average weekly prevalence, incidence and burden of all health problems reported. Results: We included 294 players (age: 22±4 years) from 11 teams. Response rate to the weekly questionnaire was 79%. On average, 32% (95% CI: 31% to 33%) of the players reported at least one health problem at any time and 22% (95% CI: 21% to 23%) reported a substantial health problem negatively affecting their training volume or performance. The overall incidence was 10.7 health problems per 1000 hours of football exposure. Sudden-onset injuries were most severe (68% of the total time loss), followed by gradual-onset injuries (25%) and illnesses (8%). Thigh was the most common injury location (26%), while knee injuries were most severe, causing 42% of the total injury time loss. Anterior cruciate ligament (ACL) injuries alone caused 30% of the total injury time loss. Conclusion: One in five players had a health problem negatively affecting their training volume or performance at any time. Sudden-onset injuries represented the most burdensome health problem. Thigh injuries were most frequent, while knee injuries, ACL injuries especially, were most severe.

• Amundsen, Roar; Møller, Merete & Bahr, Roald (2023). Performing Nordic hamstring strength testing with additional weight affects the maximal eccentric force measured: do not compare apples to oranges. BMJ Open sport & exercise medicine. ISSN 2055-7647. 9(4). doi: 10.1136/bmjsem-2023-001699. Full text in Research Archive Show summary

  Background: Nordic hamstring test devices are commonly used to measure maximal eccentric hamstring force. The ability to control the final phase of the exercise has been adopted as a criterion to add weight when testing, without substantial evidence. We investigated if adding weight affected the maximal force measured, and if there were differences between players who could and could not control the final phase. Methods: Female (n=84) and male (n=56) football players performed a Nordic hamstring strength test with 0, 5 and 10 kg. We used visual inspection to assess the ability to control the final phase (approximately last 20°), as per previously published studies. Results: Maximal force was higher when tested with 5 kg (females: +8 N (2%), p<0.001; males: +18 N (4%), p<0.001) and 10 kg (females: +17 N (5%), p<0.001; males: +27 N (6%), p<0.001) compared with 0 kg. This was the case for both groups, those who could control the final phase (5 kg: +16 N (4%), p<0.001; 10 kg: +28 N (7%), p<0.001) and those who could not (5 kg: +9 N (3%), p<0.001; 10 kg: +15 N (4%), p<0.001). Conclusion: Both players who could and could not control the final phase of the Nordic hamstring test demonstrated higher maximal force when adding weight to testing. Therefore, this should not be used to decide if players should perform testing with or without weight. Either all participants or none should be tested with weight, and the same approach should be used both for pre-testing and post-testing.

• Skazalski, Christopher M.; Whiteley, Rod; Sattler, Tine; Kozamernik, Tilen & Bahr, Roald (2023). Knee, Low Back, and Shoulder Problems Among University and Professional Volleyball Players: Playing With Pain. Journal of athletic training. ISSN 1062-6050. 59(1), p. 81–89. doi: 10.4085/1062-6050-0476.22. Full text in Research Archive Show summary

  Context: The knee, low back, and shoulder account for the majority of overuse injuries in volleyball; unfortunately, previous studies utilized methodology that failed to examine the extent of their injury burden and impact on performance. Objective: To develop a more accurate and complete understanding regarding the weekly prevalence and burden of knee, low back, and shoulder problems within the highest levels of men's volleyball – including the role that preseason complaints, match participation, player position, team, and age have on complaints. Design: Descriptive epidemiology study. Setting: Professional volleyball clubs and NCAA Division I program Patients or Other Participants: Seventy-five male volleyball players, representing four teams playing in their country's respective premier league (Japan, Qatar, Turkey, United States) participated over a 3-season period. Main Outcome Measure(s): Players completed a weekly questionnaire (Oslo Sports Trauma Research Center Overuse Injury Questionnaire; OSTRC-O) reporting pain related to their sport and the extent to which knee, low back, and shoulder problems affected participation, training volume, and performance. Problems leading to moderate or severe reductions in training volume or performance, or the inability to participate were defined as substantial problems. Results: The average weekly prevalence of knee, low back, and shoulder problems, based on 102 player-seasons, was: knee – 31% (95% CI, 28–34%), low back – 21% (18–23%), and shoulder – 19% (18–21%). Most players (93%) reported some level of knee, low back, and/or shoulder complaints during the season (knee: 79%; low back: 71%; shoulder: 67%) and 58% experienced at least one episode of substantial problems (knee: 33%; low back: 27%; shoulder: 27%). Players with preseason complaints continued to have more in-season complaints than teammates without preseason problems (average weekly prevalence – knee: 42% vs. 8%, P <.001; low back: 34% vs. 6%, P <.001; shoulder: 38% vs. 8%, P <.001). Conclusion: Nearly all included elite male volleyball players experienced knee, low back, or shoulder problems – and the majority had at least one bout that substantially reduced training participation or sports performance. These findings suggest that knee, low back, and shoulder problems result in greater injury burden than previously reported.

• Waldén, Markus; Mountjoy, Margo; McCall, Alan; Serner, Andreas; Massey, Andrew & Tol, Johannes L. [Show all 16 contributors for this article] (2023). Football-specific extension of the IOC consensus statement: methods for recording and reporting of epidemiological data on injury and illness in sport 2020. British Journal of Sports Medicine. ISSN 0306-3674. 57(21), p. 1341–1350. doi: 10.1136/bjsports-2022-106405. Show summary

  Several sports have published consensus statements on methods and reporting of epidemiological studies concerning injuries and illnesses with football (soccer) producing one of the first guidelines. This football-specific consensus statement was published in 2006 and required an update to align with scientific developments in the field. The International Olympic Committee (IOC) recently released a sports-generic consensus statement outlining methods for recording and reporting epidemiological data on injury and illness in sport and encouraged the development of sport-specific extensions. The Fédération Internationale de Football Association Medical Scientific Advisory Board established a panel of 16 football medicine and/or science experts, two players and one coach. With a foundation in the IOC consensus statement, the panel performed literature reviews on each included subtopic and performed two rounds of voting prior to and during a 2-day consensus meeting. The panel agreed on 40 of 75 pre-meeting and 21 of 44 meeting voting statements, respectively. The methodology and definitions presented in this comprehensive football-specific extension should ensure more consistent study designs, data collection procedures and use of nomenclature in future epidemiological studies of football injuries and illnesses regardless of setting. It should facilitate comparisons across studies and pooling of data.

• Ngai, Aston Seng Huey; Beasley, Ian; Materne, Olivier; Farooq, Abdulaziz; Tabben, Montassar & Chebbi, Souhail [Show all 11 contributors for this article] (2023). Fractures in professional footballers: 7-years data from 106 team seasons in the Middle East. Biology of Sport. ISSN 0860-021X. 40(4), p. 1117–1124. doi: 10.5114/BIOLSPORT.2023.125588. Full text in Research Archive
• Chamari, Karim; Schumacher, Yorck Olaf; Chaabane, Mokhtar; Rekik, Raouf Nader; Chebbi, Souhail & Daoud, Ramadan [Show all 10 contributors for this article] (2023). Impact of COVID-19 lockdown on injury risk in Qatar's professional football. Journal of Science and Medicine in Sport. ISSN 1440-2440. doi: 10.1016/j.jsams.2023.09.008. Show summary

  Objectives: To compare injury incidence, burden and characteristics between the pre- and post-COVID-19 lockdown periods in Qatari professional football. Design: Prospective cohort study. Methods: Injury and exposure data for two post-COVID-19 lockdown periods [early post-lockdown period: short-term ~ 2 months (54 matches) and late post-lockdown period: long-term 8-months (183 matches)] were compared to the benchmark of the same periods from the three previous seasons (2017/18–2019/20). Results: We observed no difference in overall, training or match incidence between early post-lockdown period and the benchmark reference. However, this short-term period resulted in lower burden for overall- (RR 0.80, P < 0.0001), training- (RR 0.73, P < 0.0001) and match-injuries (RR 0.40, P < 0.0001) compared to the benchmark. During late post-lockdown period match injury incidence (RR 0.72, P = 0.0010) and match injury burden (RR 0.69, P < 0.001) were lower than the benchmark. In contrast, both overall- (RR 1.30, P < 0.001) and training-injury burden (RR 1.65, P < 0.001) were higher. A significant increase in adductor strains in both post-lockdown periods was observed. Conclusions: Immediately after the COVID-19 lockdown (short-term effect), there was no difference in injury incidence but a lower injury burden compared to benchmark. Moreover, the rapid return to competition for the successive season (long-term effect) was associated with a higher overall- and training-injury burden, but a lower match-injury burden compared to the benchmark.

• Tabben, Montassar; Nader Rekik, R; Chebbi, S; Chaabane, M; Daoud, Rula Ghandour & Schumacher, Yorch Olaf [Show all 8 contributors for this article] (2023). Effect of Covid-19 lockdown on football injuries in the Qatar stars league. In Della Villa, F & Susta, D (Ed.), Football Medicine - The Pursuit of Excellence - Abstract book. Calzetti Maricci editori. ISSN 9788860286871. p. 625–626.
• Kotsifaki, Roula; Sideris, Vasileios; King, E.; Bahr, Roald & Whiteley, Rodney (2023). Preventing or performance - can we have both? Vertical jump testing after ACLr. In Della Villa, F & Susta, D (Ed.), Football Medicine - The Pursuit of Excellence - Abstract book. Calzetti Maricci editori. ISSN 9788860286871. p. 274–275.
• Amundsen, Roar; Thorarinsdottir, Solveig; Larmo, Arne; Pedersen, R.; Andersen, Thor Einar & Møller, Merete [Show all 7 contributors for this article] (2023). Hamstring injuries in the Norwegian women's Premier League. In Della Villa, F & Susta, D (Ed.), Football Medicine - The Pursuit of Excellence - Abstract book. Calzetti Maricci editori. ISSN 9788860286871. p. 210–211.
• Reier-Nilsen, Tonje; Stang, Julie; Flatsetøy, Hanne; Isachsen, Martine; Ljungberg, Henrik & Bahr, Roald [Show all 7 contributors for this article] (2023). Unsupervised field-based exercise challenge tests to support the detection of exercise-induced lower airway dysfunction in athletes. BMJ Open sport & exercise medicine. ISSN 2055-7647. 9(3). doi: 10.1136/bmjsem-2023-001680.
• Kotsifaki, Roula; Sideris, Vasileios; King, Enda; Bahr, Roald & Whiteley, Rod (2023). Performance and symmetry measures during vertical jump testing at return to sport after ACL reconstruction. British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2022-106588. Full text in Research Archive Show summary

  Objective: Vertical jump tests are more sensitive in revealing asymmetries in performance metrics at the time of return to sport after anterior cruciate ligament (ACL) reconstruction (ACLR) than horizontal hop tests. However, it remains unclear which vertical tests (bilateral or unilateral) and which metrics (kinetics or performance) are most effective in informing the rehabilitation status and readiness for return to sport. We aimed to investigate the status of athletes during vertical jump testing at return to sport after ACLR. Methods: A dual force platform system was used to evaluate jumping performance of 126 recreational and professional athletes at the time of return to sport after ACLR, as well as 532 healthy control participants. Performance and kinetic metrics were collected during four jump tests: double-leg countermovement jump, single-leg countermovement jump, double-leg 30 cm drop jump and single-leg 15 cm drop jump. Between-limb and between-group differences were explored using mixed models analyses. Results: At the time of return to sport after ACLR, athletes still presented significant differences favouring the uninvolved side, particularly in the symmetry of the concentric impulse (p<0.001) in all jumps compared with the control group. Peak landing force asymmetry was greater in the ACLR group than the controls during the countermovement (p<0.001, MD=−11.6; 95% CI –15.4 to –7.9) and the double-leg drop jump (p=0.023, MD=−8.9; 95% CI –14.9 to –2.8). The eccentric impulse asymmetry was significantly greater (p=0.018, MD=−3.8; 95% CI −5.8 to –1.7) in the ACLR group during the single-leg drop jump only. Jump height was significantly lower (p<0001) in the ACLR group compared with controls in all tests except the double-leg drop jump. Conclusion: At the time of return to sport after ACLR, despite passing the traditional discharge criteria, athletes remained asymmetrical during all vertical jump tests, in the concentric (push-off) phase, during landing from bilateral jumps and for most performance metrics. Clinicians should aim to restore not only symmetry in ground reaction forces but also absolute performance metrics such as jump height, reactive strength index and contact times, to potentially reduce injury risk and improve overall athletic performance.

• Isern, Cecilie Benedicte; Kramer-Johansen, Jo; Tjelmeland, Ingvild Beathe Myrhaugen; Bahr, Roald & Berge, Hilde Moseby (2023). A 3-year population-based study of exercise-related sudden cardiac arrest among 12- to 50-year-old Norwegians. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. doi: 10.1111/sms.14400. Full text in Research Archive Show summary

  Introduction: Regular exercise is associated with reduced risk of cardiovascular disease. Paradoxically, an increased risk of sudden cardiac arrest (SCA) is documented during or immediately after exercise and in athletes compared to the nonathletic population. Our objective was to identify, through multiple sources, the total number of exercise-related versus non-exercise-related SCA in the young population in Norway. Methods: We collected primary data from the prospective Norwegian Cardiac Arrest Registry (NorCAR) for all patients aged 12–50 suffering SCA of presumed cardiac cause from 2015 to 2017. We collected secondary data about prior physical activity and the SCA, through questionnaires. We searched media reports for SCA incidents in sports. Exercise-related SCA is defined as SCA during or <1 h after exercise. Results: Overall, 624 patients, median age 43 years, were included from NorCAR. Two thirds (393) replied to the study invitation, of whom 236 answered the questionnaires: 95 survivors and 141 next of kin. The media search resulted in 18 relevant hits. With a multiple source approach, we identified 63 cases of exercise-related SCA, equivalent to an incidence of 0.8/100 000 person-years, versus 7.8/100 000 person-years of non-exercise-related SCA. Among those who answered (n = 236), almost two thirds (59%) exercised regularly, most commonly (45%) 1–4 h/week. Endurance exercise (38%) was the most prevalent type of regular exercise and the most common activity during exercise-related SCA (53%). Conclusion: The burden of exercise-related SCA was low (0.8 per 100 000 person-years) and ten times lower than non-exercise-related SCA in the young population in Norway.

• Rekik, Raouf Nader; Bahr, Roald; Cruz, Flavio; Read, Paul; Whiteley, Rod & D'hooghe, Pieter [Show all 8 contributors for this article] (2023). Mechanisms of ACL injuries in men's football: A systematic video analysis over six seasons in the Qatari professional league. Biology of Sport. ISSN 0860-021X. 40(2), p. 575–586. doi: 10.5114/BIOLSPORT.2023.118024. Full text in Research Archive Show summary

  To assess the mechanisms of ACL injury in male professional football players in Qatar across multiple seasons using systematic video analysis. 15 ACL injuries occurred in competition among the professional football teams that participated in an injury Surveillance Programme during 6 seasons (2013/2014 to 2018/2019). High-definition broadcast videos of these injuries were analyzed (49 views; 34 slow motion) by five analysts who independently described the injury mechanisms (situation, behavior, biomechanical characteristics) using validated observational tools. A knee valgus mechanism was observed in two-thirds of the cases (1 with direct contact to the knee, 3 with indirect contact (other body parts) and 6 with no contact). No visible valgus was reported in 2 of the direct knee contact injuries, while 3 cases of non-contact and indirect contact injuries were unclear. We observed 4 main categories of injury situation among those (n = 12) classified as non-contact/indirect contact (multiple combinations were possible): pressing (n = 6), tackling or being tackled (n = 4), blocking (n = 3) and screening (n = 2). Direct contact injuries (n = 3) were suffered by 2 players during tackling and 1 whilst being tackled. Contact injuries represented only 20% of ACL injuries occurring during competition in Qatari professional soccer players. Independent of the playing situation, knee valgus was frequently observed (10/15 cases). Pressing was the most common situation (6/15 cases) leading to injury. Landing after heading was not reported in any of these ACL injuries.

• Moseid, Nils Fredrik Holm; Lemyre, Nicolas; Roberts, Glyn; Fagerland, Morten; Moseid, Christine Holm & Bahr, Roald (2023). Associations between health problems and athlete burnout: a cohort study in 210 adolescent elite athletes. BMJ Open sport & exercise medicine. ISSN 2055-7647. 9(1), p. 1–11. doi: 10.1136/bmjsem-2022-001514. Full text in Research Archive Show summary

  Objectives: We studied associations between the burden of health problems and athlete burnout in a population of athletes from Norwegian Sport Academy High Schools. Methods: This is a mixed prospective/retrospective cohort study. We included 210 athletes, 135 boys and 75 girls, from endurance, technical and team sports. We used the Oslo Sports Trauma Centres Questionnaire for Health Problems to collect 124 weeks of health data. During the first 26 weeks, athletes reported the health data prospectively using a smartphone app. For the following 98 weeks, we collected health data by interviewing athletes at the end of their third year in Sport Academy High School. At the time of the interview, the athletes also completed a web-based questionnaire, including the Athlete Burnout Questionnaire and covering social relations in sports and school, coach relations and living conditions. Results: A greater burden of health problems was associated with a higher score for athlete burnout (B: 0.16, 95% CI 0.09 to 0.22, p<0.001). In a multivariable model, this was true for both illnesses (B: 0.21, 95% CI 0.10 to 0.32, p<0.001), acute injuries (B: 0.16, 95% CI 0.04 to 0.27, p=0.007) and overuse injuries (B: 0.10, 95% CI 0.002 to 0.18, p=0.011). This was also true in gender and sports category subgroups. The coach having a high influence on training week was associated with a lower score for athlete burnout. Conclusion: A greater burden of health problems was associated with greater symptoms of athlete burnout in athletes attending Sport Academy High Schools.

• Nilsen, Daniel Hoseth; Furnes, Ove Nord; Kroken, Gard; Robsahm, Trude Eid; Johnsen, Marianne Bakke & Engebretsen, Lars [Show all 9 contributors for this article] (2022). Risk of total hip arthroplasty after elite sport: Linking 3304 former world-class athletes with the Norwegian Arthroplasty Register. British Journal of Sports Medicine. ISSN 0306-3674. 57(1), p. 33–39. doi: 10.1136/bjsports-2022-105575. Full text in Research Archive Show summary

  Objectives: At present, there is no cure for osteoarthritis (OA), but severe hip joint degeneration can require total hip arthroplasty (THA). The literature on OA after elite sport is limited. We hypothesise that elite athletic activity increases the risk of receiving a THA later in life. Methods: We linked a cohort of former Norwegian world-class athletes (1402 females and 1902 males, active 1936–2006) to the Norwegian Arthroplasty Register (THA performed 1987–2020). We used standardised incidence ratio (SIR), one-minus Kaplan-Meier and relative Cox regression (relative HR, RHR), with 95% CIs, and funnel plots at age 75, to assess THA risk for different sport disciplines, joint impact categories of sport disciplines and sex. The risk of THA for the corresponding general Norwegian population was used as reference. Results: We found an overall increased risk for THA for the former elite athletes (SIR 2.11, 95% CI 1.82 to 2.40) at age 75 years, compared with the general population. THA risk at age 75 years was 11.6% for female athletes and 8.3% for male athletes. SIR was 1.90 (95% CI 1.49 to 2.31) for female and 2.28 (95% CI 1.87 to 2.70) for male athletes. Among males, high joint impact sport disciplines were associated with increased risk compared with low-impact sport disciplines (RHR 1.81, 95% CI 1.06 to 3.08, p=0.029). Conclusion: Having been an elite athlete was associated with a doubling of THA risk compared with the general population for both sexes. High joint impact sport disciplines were associated with subsequent THA for male athletes.

• Bonke, Elena M.; Clauwaert, Amanda; Hillmann, Stefan M.; Tacke, Uta; Seer, Caroline & Yhang, Eukyung [Show all 22 contributors for this article] (2022). Neurological soft signs are associated with reduced medial-lateral postural control in adolescent athletes. Journal of the Neurological Sciences. ISSN 0022-510X. 445:120516, p. 1–40. doi: 10.1016/j.jns.2022.120516. Show summary

  Introduction: Neurological soft signs (NSS) are minor deviations from the norm in motor performance that are commonly assessed using neurological examinations. NSS may be of clinical relevance for evaluating the developmental status of adolescents. Here we investigate whether quantitative force plate measures may add relevant information to observer-based neurological examinations. Methods: Male adolescent athletes (n = 141) aged 13–16 years from three European sites underwent a neurological examination including 28 tests grouped into six functional clusters. The performance of tests and functional clusters was rated as optimal/non-optimal resulting in NSS+/NSS- groups and a continuous total NSS score. Participants performed a postural control task on a Balance Tracking System measured as path length, root mean square and sway area. ANCOVAs were applied to test for group differences in postural control between the NSS+ and NSS- group, and between optimal/non-optimal performance on a cluster- and test-level. Moreover, we tested for correlations between the total NSS score and postural control variables. Results: There was no significant overall difference between the NSS+ and NSS- group in postural control. However, non-optimal performing participants in the diadochokinesis test swayed significantly more in the medial-lateral direction than optimal performing participants. Moreover, a lower total NSS score was associated with reduced postural control in the medial-lateral direction. Conclusion: Our findings demonstrate that NSS are related to postural control in adolescent athletes. Thus, force plate measures may add a quantitative, objective measurement of postural control to observer-based qualitative assessments, and thus, may complement clinical testing.

• Bonke, Elena M.; Bonfert, Michaela V.; Hillmann, Stefan M.; Seitz-Holland, Johanna; Gaubert, Malo & Wiegand, Tim L.T. [Show all 25 contributors for this article] (2022). Neurological soft signs in adolescents are associated with brain structure. Cerebral Cortex. ISSN 1047-3211. 33(9), p. 5547–5556. doi: 10.1093/cercor/bhac441. Full text in Research Archive Show summary

  Neurological soft signs (NSS) are minor deviations in motor performance. During childhood and adolescence, NSS are examined for functional motor phenotyping to describe development, to screen for comorbidities, and to identify developmental vulnerabilities. Here, we investigate underlying brain structure alterations in association with NSS in physically trained adolescents. Male adolescent athletes (n = 136, 13–16 years) underwent a standardized neurological examination including 28 tests grouped into 6 functional clusters. Non-optimal performance in at least 1 cluster was rated as NSS (NSS+ group). Participants underwent T1- and diffusion-weighted magnetic resonance imaging. Cortical volume, thickness, and local gyrification were calculated using Freesurfer. Measures of white matter microstructure (Free-water (FW), FW-corrected fractional anisotropy (FAt), axial and radial diffusivity (ADt, RDt)) were calculated using tract-based spatial statistics. General linear models with age and handedness as covariates were applied to assess differences between NSS+ and NSS− group. We found higher gyrification in a large cluster spanning the left superior frontal and parietal areas, and widespread lower FAt and higher RDt compared with the NSS− group. This study shows that NSS in adolescents are associated with brain structure alterations. Underlying mechanisms may include alterations in synaptic pruning and axon myelination, which are hallmark processes of brain maturation.

• Nordstrøm, Anine; Bahr, Roald; Bache-Mathiesen, Lena Kristin; Clarsen, Benjamin Matthew & Talsnes, Ove (2022). Association of Training and Game Loads to Injury Risk in Junior Male Elite Ice Hockey Players: A Prospective Cohort Study. Orthopaedic Journal of Sports Medicine (OJSM). ISSN 2325-9671. 10(10). doi: 10.1177/23259671221129646. Full text in Research Archive Show summary

  Background: Training and game loads are potential risk factors of injury in junior elite ice hockey, but the association of training and game loads to injuries is unknown. Purpose: To investigate the association of chronic training and game loads to injury risk in junior male elite ice hockey players. Study Design: Cohort study; Level of evidence, 2. Methods: In this prospective cohort study, we monitored all health problems among 159 male junior ice hockey players (mean age, 16 years; range, 15-19 years) at sports-specific high schools during the 2018-2019 school year. Players reported their health problems every week using the Oslo Sports Trauma Research Center Overuse Questionnaire on Health Problems (OSTRC-H2). The number of training sessions and games was reported for 33 weeks. We calculated the previous 2-week difference in training/game loads as well as the cumulative training/game loads of the previous 2, 3, 4, and 6 weeks and explored potential associations between training/game loads and injury risk using mixed-effects logistic regression. Results: The players reported 133 acute injuries, 75 overuse injuries, and 162 illnesses in total, and an average of 8.8 (SD ±3.9) training sessions and 0.9 (SD ± 1.1) games per week. We found no association between the difference of the two previous weeks or the previous 2- 3- and 4-week cumulative, training or game load and acute injuries, nor the difference of the two previous weeks, or the previous 4- and 6-week cumulative, training or game load and overuse injuries (OR, ∼1.0; P > .05 in all models). Conclusion: In the current study of junior elite ice hockey players, there was no evidence of an association between cumulative exposure to training/game loads and injury risk. This open-access article is published and distributed under the Creative Commons Attribution - NonCommercial - No Derivatives License (https://creativecommons.org/ licenses/by-nc-nd/4.0/), which permits the noncommercial use, distribution, and reproduction of the article in any medium, provided the original author and source are credited. You may not alter, transform, or build upon this article without the permission of the Author(s). For article reuse guidelines, please visit SAGE’s website at http://www.sagepub.com/journals-permissions

• Whiteley, Rodney; Gregson, Warren; Bahr, Roald; Tabben, Montassar; Chamari, Karim & Lolli, Lorenzo [Show all 7 contributors for this article] (2022). High-speed running during match-play before and after return from hamstring injury in professional footballers. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 32(10), p. 1502–1509. doi: 10.1111/sms.14219. Full text in Research Archive Show summary

  Hamstring injuries constitute the single largest cause of lost playing time in professional football. While restoring high-speed running ability is paramount for rehabilitation from these injuries, little evidence exists regarding the extent of return to sport running performance after hamstring injury in football. We examined medical and match performance data available from a sample of 38 professional soccer players competing in the Qatar Stars League (N = 1426 observations) to describe high-speed running performance during match-play prior and subsequent to a hamstring strain injury. Multivariable-adjusted random-effects generalized additive models estimated post- versus pre-hamstring injury differences in maximal speed (km/h), high-speed running (>20 km/h), and sprinting (>25 km/h) distance. Mean effects and uncertainty (95% confidence interval, CI) were interpreted against the estimated random match-to-match variability in maximal sprinting speed, high-speed running distance, and sprinting running distance of ±1.67 km/h (95% CI, 1.62–1.72 km/h), ±102 m (95% CI, 99–105 m), and ±60 m (95% CI, 58–61 m), respectively. The estimated post- versus pre-hamstring injury mean differences in maximal sprinting speed, high-speed running distance, and sprinting running distance primary outcomes were −0.25 km/h (95% CI, −0.38 to −0.12 km/h), −43 m (95% CI, −56 to −30 m), and −22 m (95% CI, −29 to −16 m). Players returning to football match-play after hamstring strain injury experienced reductions in high-speed match physical performance that were well within normal match-to-match variation in performance.

• Amundsen, Roar; Sæther Heimland, Janita; Thorarinsdottir, Solveig; Møller, Merete & Bahr, Roald (2022). Effects of High and Low Training Volume with the Nordic Hamstring Exercise on Hamstring Strength, Jump Height, and Sprint Performance in Female Football Players: A Randomised Trial. Translational Sports Medicine (TSM). ISSN 2573-8488. 2022. doi: 10.1155/2022/7133928. Full text in Research Archive Show summary

  The evidence-based hamstring strengthening programme for prevention of hamstring injuries is not adopted by football teams because of its high training volume. This study on female football players investigated if high-volume training with the Nordic hamstring exercise is more effective on hamstring strength, jump height, and sprint performance than low-volume training. We also examined the time course of changes in muscle strength during the intervention period. Forty-five female football players were randomised to a high- (21 sessions, 538 total reps) or low-volume group (10 sessions, 144 total reps) and performed an 8-week training intervention with the Nordic hamstring exercise during the preseason. We tested hamstring strength (maximal eccentric force with NordBord and maximal eccentric torque with isokinetic dynamometer), jump height, and 40 m sprint before and after the intervention. The NordBord test was also performed during training weeks 4 and 6. Both groups increased maximal eccentric force (high-volume: 29 N (10%), 95% CI: 19–38 N, , low-volume: 37 N (13%), 95% CI: 18–55 N, ), but there were no between-group differences (). Maximal eccentric torque, jump height, and sprint performance did not change. Maximal eccentric force increased from the pretest to week 6 (20 N (7%), 95% CI: 8 to 31 N, ), but not week 4 (8 N (3%), 95% CI: −2 to 18 N, ). High training volume with the Nordic hamstrings exercise did not lead to greater adaptations in strength, jump height, or speed than a low-volume programme. Players in both groups had to train for at least 6 weeks to improve maximal eccentric force significantly.

• De Luca, Alberto; Karayumak, Suheyla Cetin; Leemans, Alexander; Rathi, Yogesh; Swinnen, Stephan & Gooijers, Jolien [Show all 15 contributors for this article] (2022). Cross-site harmonization of multi-shell diffusion MRI measures based on rotational invariant spherical harmonics (RISH). NeuroImage. ISSN 1053-8119. 259. doi: 10.1016/j.neuroimage.2022.119439. Full text in Research Archive
• Jauhiainen, Susanne; Kauppi, Jukka-Pekka; Krosshaug, Tron; Bahr, Roald; Bartsch, Julia & Äyrämö, Sami (2022). Predicting ACL Injury Using Machine Learning on Data From an Extensive Screening Test Battery of 880 Female Elite Athletes. American Journal of Sports Medicine. ISSN 0363-5465. p. 2917–2924. doi: 10.1177/03635465221112095. Full text in Research Archive Show summary

  Background: Injury risk prediction is an emerging field in which more research is needed to recognize the best practices for accurate injury risk assessment. Important issues related to predictive machine learning need to be considered, for example, to avoid overinterpreting the observed prediction performance. Purpose: To carefully investigate the predictive potential of multiple predictive machine learning methods on a large set of risk factor data for anterior cruciate ligament (ACL) injury; the proposed approach takes into account the effect of chance and random variations in prediction performance. Study Design: Case-control study; Level of evidence, 3. Methods: The authors used 3-dimensional motion analysis and physical data collected from 791 female elite handball and soccer players. Four common classifiers were used to predict ACL injuries (n = 60). Area under the receiver operating characteristic curve (AUC-ROC) averaged across 100 cross-validation runs (mean AUC-ROC) was used as a performance metric. Results were confirmed with repeated permutation tests (paired Wilcoxon signed-rank-test; P < .05). Additionally, the effect of the most common class imbalance handling techniques was evaluated. Results: For the best classifier (linear support vector machine), the mean AUC-ROC was 0.63. Regardless of the classifier, the results were significantly better than chance, confirming the predictive ability of the data and methods used. AUC-ROC values varied substantially across repetitions and methods (0.51-0.69). Class imbalance handling did not improve the results. Conclusion: The authors’ approach and data showed statistically significant predictive ability, indicating that there exists information in this prospective data set that may be valuable for understanding injury causation. However, the predictive ability remained low from the perspective of clinical assessment, suggesting that included variables cannot be used for ACL prediction in practice.

• Bjørneboe, John Andreas; Heen, Anders; Borud, Einar Kristian; Bahr, Roald; Clarsen, Benjamin Matthew & Norheim, Arne Johan (2022). Introducing a new method to record injuries during military training: a prospective study among 296 young Norwegian conscripts . BMJ Military Health. ISSN 2633-3767. doi: 10.1136/bmjmilitary-2022-002088. Show summary

  Introduction: Most epidemiological studies in the field of military medicine have been based on data from medical records and registries. The aims of this study were to test a self-reporting injury surveillance system commonly used in sports medicine in a military setting, and to describe the injury pattern among Norwegian army conscripts during a period of military training. Method: A total of 296 conscripts in His Majesty the King’s Guard were asked to report all injuries each week for 12 weeks, using a modification of the Oslo Sports Trauma Research Center Questionnaire on Health Problems (OSTRC-H2). We recorded all injuries irrespective of their need for medical attention or consequences for military participation. In addition, we retrieved data on injuries recorded by military physicians in the medical record from the Norwegian Armed Forces Health Register. Results: The mean weekly response rate was 74%. A total of 357 injuries were recorded, of which 82% were only captured through the OSTRC-H2 and 3% only in the medical records. The average weekly prevalence of injury was 28% (95% CI: 25% to 31%), and 10% (95% CI: 8% to 12%) experienced injuries with a substantial negative impact on training and performance. The greatest injury burden was caused by lower limb injuries, with knee and foot injuries as the predominant injury locations. Conclusion: The OSTRC-H2 is suitable for use in a military setting and records substantially more injuries than the standard medical record. The prevalence of injuries among conscripts is high and comparable with many elite sports.

• Kotsifaki, Argyro; Van Rossom, Sam; Whiteley, Rod; Korakakis, Vasileios; Bahr, Roald & Sideris, Vasileios [Show all 7 contributors for this article] (2022). Single leg vertical jump performance identifies knee function deficits at return to sport after ACL reconstruction in male athletes. British Journal of Sports Medicine. ISSN 0306-3674. 56(9), p. 490–498. doi: 10.1136/bjsports-2021-104692. Full text in Research Archive Show summary

  Objectives: Vertical jump performance (height) is a more representative metric for knee function than horizontal hop performance (distance) in healthy individuals. It is not known what the biomechanical status of athletes after anterior cruciate ligament (ACL) reconstruction (ACLR) is at the time they are cleared to return to sport (RTS) or whether vertical performance metrics better evaluate knee function. Methods: Standard marker-based motion capture and electromyography (EMG) were collected from 26 male athletes cleared to RTS after ACLR and 22 control healthy subjects during single leg vertical jumps (SLJ) and single leg drop jumps (SLDJ). Performance outcomes, jump height and the Reactive Strength Index, were calculated. Sagittal plane kinematics, joint moments and joint work were obtained using inverse dynamics and lower limb muscle forces were computed using an EMG-constrained musculoskeletal model. Muscle contribution was calculated as a percentage of the impulse of all muscle forces in the model. Between-limb and between-group differences were explored using mixed models analyses. Results: Jump performance, assessed by jump height and Reactive Strength Index, was significantly lower in the involved than the uninvolved limb and controls, with large effect sizes. For the ACLR group, jump height limb symmetry index was 83% and 77% during the SLJ and SLDJ, respectively. Work generation was significantly less in the involved knee compared to uninvolved limb and controls during the SLJ (p<0.001; d=1.19; p=0.003, d=0.91, respectively) and during the SLDJ (p<0.001; d=1.54; p=0.002, d=1.05, respectively). Hamstrings muscle contribution was greater in the involved compared to the uninvolved limb and controls, whereas soleus contribution was lower in the involved limb compared to controls. Conclusions: During vertical jumps, male athletes after ACLR at RTS still exhibit knee biomechanical deficits, despite symmetry in horizontal functional performance and strength tests. Vertical performance metrics like jump height and RSI can better identify interlimb asymmetries than the more commonly used hop distance and should be included in the testing battery for the RTS.

• Kotsifaki, Argyro; Van Rossom, Sam; Whiteley, Rod; Korakakis, Vasileios; Bahr, Roald & D’Hooghe, Pieter [Show all 10 contributors for this article] (2022). Between-Limb Symmetry in ACL and Tibiofemoral Contact Forces in Athletes After ACL Reconstruction and Clearance for Return to Sport. Orthopaedic Journal of Sports Medicine (OJSM). ISSN 2325-9671. 10(4). doi: 10.1177/23259671221084742. Full text in Research Archive Show summary

  Background: Current return-to-sport (RTS) criteria after anterior cruciate ligament (ACL) reconstruction (ACLR) include demonstrating symmetry in functional and strength tests. It remains unknown if at the time that athletes are cleared to RTS, they exhibit between-limb symmetry in ACL and tibiofemoral contact forces or if these forces are comparable with those in uninjured athletes. Purposes: To (1) examine ACL and tibiofemoral contact forces in athletes who underwent ACLR and were cleared to RTS and (2) compare the involved leg to the healthy contralateral leg and healthy controls during functional tasks. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 26 male athletes who underwent ACLR were tested at the time of RTS during tasks that included single-leg vertical, horizontal, and side jumps; cutting maneuvers; and high-intensity running. We used an electromyography-constrained musculoskeletal modeling workflow to estimate ACL and tibiofemoral contact forces and compared the results with those of 23 healthy male participants. Results: The ACLR group presented no differences in peak tibiofemoral contact forces in the involved limb compared with the control group. However, there were significant between-limb differences mainly due to higher contact forces in the uninvolved (healthy) limb of the ACLR group compared with the control group. In the ACLR group, ACL forces were significantly higher in the uninvolved limb compared with the involved limb during cutting and running. Lateral contact forces were lower in the involved compared with the uninvolved limb, with large effect sizes during cutting (d = 1.14; P < .001) and running (d = 1.10; P < .001). Conclusion: Current discharge criteria for clearance to RTS after ACLR did not ensure the restoration of symmetric loading in our cohort of male athletes. ACL force asymmetry was observed during cutting and running, in addition to knee loading asymmetries on several tasks tested.

• Vermeulen, Robin; Whiteley, Rod; van der Made, Anne D.; van Dyk, Nicol; Almusa, Emad & Geertsema, Celeste [Show all 11 contributors for this article] (2022). Early versus delayed lengthening exercises for acute hamstring injury in male athletes: a randomised controlled clinical trial. British Journal of Sports Medicine. ISSN 0306-3674. 56(14), p. 792–800. doi: 10.1136/bjsports-2020-103405. Full text in Research Archive Show summary

  Background: To evaluate the efficacy of early versus delayed introduction of lengthening (ie, eccentric strengthening) exercises in addition to an established rehabilitation programme on return to sport duration for acute hamstring injuries in a randomised controlled superiority trial. Methods: 90 male participants (age: 18–36 years, median 26 years) with an MRI-confirmed acute hamstring injury were randomised into an early lengthening (at day 1 of rehabilitation) group or a delayed lengthening (after being able to run at 70% of maximal speed) group. Both groups received an established rehabilitation programme. The primary outcome was time to return to sport (ie, time from injury to full unrestricted training and/or match play). The secondary outcome was reinjury rate within 12 months after return to sport. Other outcomes at return to sport included the Askling H-test, hamstring strength, clinical examination and readiness questions. Results: The return to sport in the early lengthening group was 23 (IQR 16–35) days and 33 (IQR 23–40) days in the delayed lengthening group. For return to sport (in days), the adjusted HR for the early lengthening group compared with the delayed lengthening group was 0.95 (95% CI 0.56 to 1.60, p=0.84). There was no significant difference between groups for reinjury rates within 2 months (OR=0.94, 95% CI 0.18 to 5.0, p=0.94), from 2 to 6 months (OR=2.00, 95% CI 0.17 to 23.3, p=0.58), and 6 to 12 months (OR=0.57, 95% CI 0.05 to 6.6, p=0.66). Conclusion: Accelerating the introduction of lengthening exercises in the rehabilitation of hamstring injury in male athletes did not improve the time to return to sport nor the risk of reinjury.

• Sandmo, Stian Bahr; Matyasova, Katarina; Filipcik, Peter; Cente, Martin; Koerte, Inga Katharina & Pasternak, Ofer [Show all 10 contributors for this article] (2022). Changes in circulating microRNAs following head impacts in soccer. Brain Injury. ISSN 0269-9052. 36(4), p. 560–571. doi: 10.1080/02699052.2022.2034042. Full text in Research Archive Show summary

  Aim: To explore the short-term effects of accidental head impacts and repetitive headers on circulating microRNAs, accounting for the effects of high-intensity exercise alone. Methods: Blood samples were collected from professional soccer players at rest. Repeat samples were drawn 1 h and 12 h after three conditions: (1) accidental head impacts in a match, (2) repetitive headers during training, and (3) high-intensity exercise. 89 samples were screened to detect microRNAs expressed after each exposure. Identified microRNAs were then validated in 98 samples to determine consistently deregulated microRNAs. Deregulated microRNAs were further explored using bioinformatics to identify target genes and characterize their involvement in biological pathways. Results: Accidental head impacts led to deregulation of eight microRNAs that were unaffected by high-intensity exercise; target genes were linked to 12 specific signaling pathways, primarily regulating chromatin organization, Hedgehog and Wnt signaling. Repetitive headers led to deregulation of six microRNAs that were unaffected by high-intensity exercise; target genes were linked to one specific signaling pathway (TGF-β). High-intensity exercise led to deregulation of seven microRNAs; target genes were linked to 31 specific signaling pathways. Conclusion: We identified microRNAs specific to accidental head impacts and repetitive headers in soccer, potentially being useful as brain injury biomarkers.

• Nordstrøm, Anine; Bahr, Roald; Clarsen, Benjamin Matthew & Talsnes, Ove (2022). Association Between Preseason Fitness Level and Risk of Injury or Illness in Male Elite Ice Hockey Players: A Prospective Cohort Study. Orthopaedic Journal of Sports Medicine (OJSM). ISSN 2325-9671. 10(2). doi: 10.1177/23259671221076849. Full text in Research Archive Show summary

  Background: Little is known about the association between physical fitness and the risk of injury or illness in ice hockey. The least-fit players may be more prone to injury and illness. Purpose: To examine the association between preseason fitness level and injury or illness risk among elite ice hockey players during the regular season. Study Design: Cohort study; Level of evidence, 2. Methods: A total of 133 male ice hockey players in the GET League (the premier professional league in Norway) completed 8 different exercises (40-m sprint, countermovement jump, 3000-m run, squat, bench press, chin-ups, brutal bench, and box jump) at the annual 1-day preseason testing combine. During the 2017-2018 competitive season, the players reported all health problems (acute injuries, overuse injuries, and illnesses) weekly (31 weeks) using the Oslo Sports Trauma Research Center Questionnaire on Health Problems. Results: Overall, the players reported 191 acute injuries, 82 overuse injuries, and 132 illnesses. The least-fit tercile of players did not report more health problems (mean, 3.0; 95% CI, 2.2-3.8) compared with the most-fit (mean, 3.4; 95% CI, 2.6-4.2) or the medium-fit (mean, 2.7; 95% CI, 1.9-3.5) players. The most-fit players reported more substantial health problems (mean, 2.0; 95% CI, 1.6-2.5) compared with the medium-fit (mean, 1.3; 95% CI, 0.8 -1.8) and least-fit (mean, 1.8; 95% CI, 1.3-2.3) (P = .02) players. There was no association between low physical fitness and number of health problems when comparing the least-fit tercile of the players with the rest of the cohort (P > .05); however, there was an association between low physical fitness and greater severity of all health problems when comparing the least-fit tercile of players to the rest of the cohort after adjusting for time on ice per game, playing position, and age (P = .02). Conclusion: Low physical fitness was not associated with increased rate of injury or illness but was associated with greater severity of all health problems after adjusting for time on ice per game, playing position, and age.

• Hilska, Matias; Leppänen, Mari; Vasankari, Tommi; Clarsen, Benjamin Matthew; Aaltonen, Sari & Bahr, Roald [Show all 10 contributors for this article] (2021). Neuromuscular training warm-up in the prevention of overuse lower extremity injuries in children's football: A cluster-randomized controlled trial. Translational Sports Medicine (TSM). ISSN 2573-8488. 4(6), p. 849–858. doi: 10.1002/tsm2.289.
• Koerte, Inga K.; Bahr, Roald; Filipcik, Peter; Gooijers, Jolien; Leemans, Alexander & Lin, Alexander P. [Show all 11 contributors for this article] (2021). REPIMPACT - a prospective longitudinal multisite study on the effects of repetitive head impacts in youth soccer. Brain Imaging and Behavior. ISSN 1931-7557. doi: 10.1007/s11682-021-00484-x. Full text in Research Archive Show summary

  Repetitive head impacts (RHI) are common in youth athletes participating in contact sports. RHI differ from concussions; they are considered hits to the head that usually do not result in acute symptoms and are therefore also referred to as “subconcussive” head impacts. RHI occur e.g., when heading the ball or during contact with another player. Evidence suggests that exposure to RHI may have cumulative effects on brain structure and function. However, little is known about brain alterations associated with RHI, or about the risk factors that may lead to clinical or behavioral sequelae. REPIMPACT is a prospective longitudinal study of competitive youth soccer players and non-contact sport controls aged 14 to 16 years. The study aims to characterize consequences of exposure to RHI with regard to behavior (i.e., cognition, and motor function), clinical sequelae (i.e., psychiatric and neurological symptoms), brain structure, function, diffusion and biochemistry, as well as blood- and saliva-derived measures of molecular processes associated with exposure to RHI (e.g., circulating microRNAs, neuroproteins and cytokines). Here we present the structure of the REPIMPACT Consortium which consists of six teams of clinicians and scientists in six countries. We further provide detailed information on the specific aims and the design of the REPIMPACT study. The manuscript also describes the progress made in the study thus far. Finally, we discuss important challenges and approaches taken to overcome these challenges.

• Kotsifaki, Argyro; van Rossom, Sam; Whiteley, Rodney; Korakakis, Vasileios; Bahr, Roald & Sideris, Vasileios [Show all 8 contributors for this article] (2021). Symmetry in Triple Hop Distance Hides Asymmetries in Knee Function After ACL Reconstruction in Athletes at Return to Sports. American Journal of Sports Medicine. ISSN 0363-5465. doi: 10.1177/03635465211063192. Full text in Research Archive Show summary

  Background: After anterior cruciate ligament reconstruction (ACLR), a battery of strength and hop tests is frequently used to determine the readiness of an athlete to successfully return to sports. However, the anterior cruciate ligament reinjury rate remains alarmingly high. Purpose: To evaluate the lower limb function of athletes after ACLR at the time when they had been cleared to return to sports (RTS). We aimed to evaluate if passing discharge criteria ensures restoration of normal lower limb biomechanics in terms of kinematics, kinetics, work, and percentage work contribution during a triple hop for distance. Study Design: Controlled laboratory study. Methods: Integrated 3-dimensional motion analysis was performed in 24 male athletes after ACLR when cleared to RTS and 23 healthy male controls during the triple-hop test. The criteria for RTS were (1) clearance by the surgeon and the physical therapist, (2) completion of a sports-specific on-field rehabilitation program, and (3) limb symmetry index >90% after quadriceps strength and hop battery tests. Lower limb and trunk kinematics, as well as knee joint moments and work, were calculated. Between-limb differences (within athletes after ACLR) and between-group differences (between ACLR and control groups) were evaluated using mixed linear models. Results: Although achieving 97% limb symmetry in distance hopped and displaying almost 80% symmetry for knee work absorption in the second rebound and third landing, the ACLR cohorts demonstrated only 51% and 66% limb symmetry for knee work generation in the first and second rebound phases, respectively. During both work generation phases of the triple hop, the relative contribution of the involved knee was significantly smaller, with a prominent compensation from the hip joint (P < .001, for all phases) as compared with the uninvolved limb and the controls. In addition, patients deployed a whole body compensatory strategy to account for the between-limb differences in knee function, mainly at the hip, pelvis, and trunk. Conclusion: Symmetry in the triple hop for distance masked important deficits in the knee joint work. These differences were more prominent during work generation (concentric-propulsive) than work absorption (eccentric-landing).

• Nordstrøm, Anine; Bahr, Roald; Clarsen, Benjamin Matthew & Talsnes, Ove (2021). Sammenhengen mellom fysisk form og risiko for skader og sykdom blant senior elite ishockeyspillere. In Nyheim, Kurt Tomas (Eds.), Book of Abstract - Idrettsmedisinsk høstkongress 2021. NIMF.
• Nordstrøm, Anine; Bahr, Roald; Clarsen, Benjamin Matthew & Talsnes, Ove (2021). Prevalens og belastning av helseproblem blant junior elite ishockeyspillere. En 44-uker prospektiv kohortstudie . In Nyheim, Kurt Tomas (Eds.), Book of Abstract - Idrettsmedisinsk høstkongress 2021. NIMF.
• Materne, Olivier; Chamari, Karim; Farooq, Abdulaziz; Tabben, Montassar; Weir, Adam & Holmich, Per [Show all 9 contributors for this article] (2021). Shedding light on incidence and burden of physeal injuries in a youth elite football academy: A 4-season prospective study. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 32(1), p. 165–176. doi: 10.1111/sms.14059. Full text in Research Archive Show summary

  Introduction: Physeal injuries have been overlooked in epidemiological research in youth sports. Our prospective study investigated the incidence, severity, and burden of physeal injuries in a youth elite football academy. Methods: In total, 551 youth male football players from under-9 to under-19 were included and observed over four consecutive seasons. Injuries involving the physis were diagnosed and recorded according to type, location, and diagnosis. Injury incidence (II), severity (days lost), and injury burden (IB) were calculated per squad per season (25 players/squad). Results: There were 307 physeal injuries: 262 apophyseal (85%), 26 physeal (9%), 2 epiphyseal (1%), and 17 other physeal injuries (5%) with 80% (n=245) causing time-loss. The overall mean incidence of time-loss physeal injuries was 6 injuries/squad-season, leading to a total of 157 days lost/squad-season. The U-16s had the highest burden with 444 days lost per squad-season [median: 20 (95% CI: 12–30) days; II: 10 (95% CI: 7.3.1–13.4)]. Apophyseal injuries of the hip–pelvis resulted in the greatest burden [median: 13 (95% CI: 10–17); II: 2.5 (95% CI: 2.1–3.0)]. Peak apophyseal injury incidence per body parts occurred in U-11 for foot–ankle (II: 2.4; 95% CI: 1.0–4.9), U-14 for knee (II: 4.5; 95% CI: 2.7–7.1), and U-17 for hip–pelvis (II: 6.4; 95% CI: 4.2–9.3). Conclusion: Physeal injuries accounted for a quarter of all-time loss with the largest injury burden in U-16. Most physeal injuries involved the lower limb and affected the apophysis. Physeal and apophyseal injuries incidence, burden, and pattern vary substantially depending on age. Hip–pelvic apophyseal injuries accounted for the largest injury burden.

• Steffen, Kathrin; Clarsen, Benjamin Matthew; Gjelsvik, Hilde; Haugvad, Lars; Koivisto-Mørk, Anu & Bahr, Roald [Show all 7 contributors for this article] (2021). Illness and injury among Norwegian Para athletes over five consecutive Paralympic Summer and Winter Games cycles: prevailing high illness burden on the road from 2012 to 2020. British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2021-104489. Full text in Research Archive Show summary

  Objective: To describe the illness and injury pattern of Norwegian Para athletes over five consecutive Paralympic Summer and Winter Games cycles and to identify which health problems should be targeted in risk management plans with respect to impairment types. Methods: We monitored athletes from 12 to 18 months prior to each Game using a weekly online questionnaire (Oslo Sports Trauma Research Center-H2 (OSTRC-H2)). We asked them to report all health problems they had experienced in the preceding 7 days, irrespective of their consequences on their sports participation or performance and whether they had sought medical attention. Results: Between 2011 and 2020, 94 candidate athletes were included in this monitoring programme and prepared to represent Norway; of these, 66 (71%) were finally selected for multiple Paralympic Games. The overall response rate to the weekly questionnaires was 87%. At any given time during the five observation cycles, 37% of the athletes (95% CI 36% to 38%) reported having at least one health problem. Athletes with neurological impairments (n=51) lost 10 days per year due to respiratory problems (95% CI 9 to 11) compared with 9 days (8-10) among those with musculoskeletal impairments (n=37). Gastrointestinal problems caused a time loss of on average 4 days per year in athletes with neurological impairments versus 1 day in athletes with musculoskeletal impairments (mean difference 2.7 days, 2.1–3.3). Musculoskeletal injuries generated a high burden for both athlete groups, in particular, to the elbow, shoulder and lumbosacral regions. Conclusion: At any given time, nearly two out of five elite Norwegian Para athletes reported at least one health problem. Respiratory tract and other infections; gastrointestinal problems, injuries to the shoulder, elbow and lumbosacral regions represented the greatest health burden. Our findings can help guide the allocation of clinical resources, which should include a broad network of medical specialists, together with dieticians and physiotherapists, to meet the health challenges in Para athletes.

• Richter, Chris; Petushek, Erich; Grindem, Hege; Franklyn-Miller, Andrew; Bahr, Roald & Krosshaug, Tron (2021). Cross-validation of a machine learning algorithm that determines anterior cruciate ligament rehabilitation status and evaluation of its ability to predict future injury. Sports Biomechanics. ISSN 1476-3141. doi: 10.1080/14763141.2021.1947358. Full text in Research Archive Show summary

  Classification algorithms determine the similarity of an observation to defined classes, e.g., injured or healthy athletes, and can highlight treatment targets or assess progress of a treatment. The primary aim was to cross-validate a previously developed classification algorithm using a different sample, while a secondary aim was to examine its ability to predict future ACL injuries. The examined outcome measure was ‘healthy-limb’ class membership probability, which was compared between a cohort of athletes without previous or future (No Injury) previous (PACL) and future ACL injury (FACL). The No Injury group had significantly higher probabilities than the PACL (p < 0.001; medium effect) and FACL group (p ≤ 0.045; small effect). The ability to predict group membership was poor for the PACL (area under curve [AUC]; 0.61<AUC<0.62) and FACL group (0.57<AUC<0.59). The ACL injury incidence proportion was highest in athletes with probabilities below 0.20 (9.4%; +2.7% to baseline), while athletes with probabilities above 0.80 had an incidence proportion of 4.1% (−2.6%). While findings that a low probability might represent an increase in injury risk on a group level, it is not sensitive enough for injury screening to predict a future injury on the individual level.

• Nordstrøm, Anine; Bahr, Roald; Clarsen, Benjamin Matthew & Talsnes, Ove (2021). Prevalence and Burden of Self-Reported Health Problems in Junior Male Elite Ice Hockey Players: A 44-Week Prospective Cohort Study. American Journal of Sports Medicine. ISSN 0363-5465. 49(12), p. 3379–3385. doi: 10.1177/03635465211032979. Full text in Research Archive Show summary

  Background: Little is known about the burden of overuse injuries and illnesses in junior elite ice hockey. Purpose: To describe the prevalence and burden of all health problems in junior male elite ice hockey players in Norway during 1 school year. Study Design: Descriptive epidemiological study. Methods: A total of 206 junior male ice hockey players (mean age, 17 years; range, 15-20 years) attending specialized sports academy high schools in Norway reported all health problems, acute injuries, overuse injuries, and illnesses, weekly during the 2018-2019 school year (44 weeks). The players self-reported injuries and illnesses using the Oslo Sports Trauma Research Center Questionnaire on Health Problems. Results: Of the players included, 25% (95% CI, 23%-27%) reported at least 1 health problem at any given time, while 16% (95% CI, 14%-17%) experienced health problems with a substantial negative effect on training and performance. Of the total burden of health problems, acute injuries accounted for 44%, overuse injuries 31%, and illnesses 25%. For acute injuries, the greatest burden was caused by injuries to the ankle, knee, and hand, whereas for overuse injuries the most burdensome location was the hip/groin and knee. Conclusion: This study documented that while acute injuries did represent the greatest problem among junior elite ice hockey players, overuse injuries, especially to the knee and hip/groin, also had a substantial effect.

• Smith, Michelle D.; Vicenzino, Bill; Bahr, Roald; Bandholm, Thomas; Cooke, Rosalyn & Mendonça, Luciana De Michelis [Show all 25 contributors for this article] (2021). Return to sport decisions after an acute lateral ankle sprain injury: Introducing the PAASS framework - An international multidisciplinary consensus. British Journal of Sports Medicine. ISSN 0306-3674. 55(22), p. 1270–1276. doi: 10.1136/bjsports-2021-104087.
• Petushek, Erich; Nilstad, Agnethe; Bahr, Roald & Krosshaug, Tron (2021). Drop Jump? Single-Leg Squat? Not if You Aim to Predict Anterior Cruciate Ligament Injury From Real-Time Clinical Assessment: A Prospective Cohort Study Involving 880 Elite Female Athletes. Journal of Orthopaedic and Sports Physical Therapy. ISSN 0190-6011. 51(7), p. 372–378. doi: 10.2519/jospt.2021.10170. Show summary

  Objective: To determine whether visually assessed performances of the single-leg squat (SLS) and vertical drop jump (VDJ) were associated with future noncontact anterior cruciate ligament (ACL) injury. Design: Prognostic accuracy cohort study. Methods: Elite female handball and football (soccer) athletes (n = 880) were tested from 2007 to 2014 and tracked through 2015. Trained physical therapists visually rated each leg during a SLS and overall control during a VDJ. Receiver operating characteristic curve, Pearson chi-square, and logistic regression analyses were used to determine the prognostic accuracy of the 2 screening tests. Results: Sixty-five noncontact ACL injuries occurred during the follow-up period. Fourteen percent of athletes who sustained an ACL injury had poor SLS performance, compared to 17% of the noninjured athletes (P = .52 and .67 for hip and knee ratings, respectively). Side-to-side asymmetry in the SLS was not different between injured and noninjured athletes (P = .10 and .99 for hip and knee asymmetry, respectively). Twenty-one percent of athletes who sustained an ACL injury had a poor VDJ rating, compared to 27% of the noninjured athletes (P = .09). Furthermore, area under the curve values ranged from 0.43 to 0.54 for the SLS and VDJ, demonstrating no to poor prognostic accuracy. Conclusion: Neither SLS nor VDJ test performance distinguished between athletes who sustained a subsequent noncontact ACL injury and those who did not.

• Materne, Olivier; Chamari, Karim; Farooq, Abdulaziz; Weir, Adam; Hölmich, Per & Bahr, Roald [Show all 8 contributors for this article] (2021). Association of Skeletal Maturity and Injury Risk in Elite Youth Soccer Players: A 4-Season Prospective Study With Survival Analysis. Orthopaedic Journal of Sports Medicine (OJSM). ISSN 2325-9671. 9(3). doi: 10.1177/2325967121999113. Full text in Research Archive Show summary

  Background: The association between injury risk and skeletal maturity in youth soccer has received little attention. Purpose: To prospectively investigate injury patterns and incidence in relation to skeletal maturity in elite youth academy soccer players and to determine the injury risks associated with the skeletal maturity status, both overall and to the lower limb apophysis. Study Design: Descriptive epidemiology study. Methods: All injuries that required medical attention and led to time loss were recorded prospectively during 4 consecutive seasons in 283 unique soccer players from U-13 (12 years of age) to U-19 (18 years). The skeletal age (SA) was assessed in 454 player-seasons using the Fels method, and skeletal maturity status (SA minus chronological age) was classified as follows: late, SA >1 year behind chronological age; normal, SA ±1 year of chronological age; early, SA >1 year ahead of chronological age; and mature, SA = 18 years. An adjusted Cox regression model was used to analyze the injury risk. Results: A total of 1565 injuries were recorded; 60% were time-loss injuries, resulting in 17,772 days lost. Adjusted injury-free survival analysis showed a significantly greater hazard ratio (HR) for different status of skeletal maturity: early vs normal (HR = 1.26 [95% CI, 1.11-1.42]; P < .001) and early vs mature (HR = 1.35 [95% CI, 1.17-1.56]; P < .001). Players who were skeletally mature at the wrist had a substantially decreased risk of lower extremity apophyseal injuries (by 45%-61%) compared with late (P < .05), normal (P < .05), and early (P < .001) maturers. Conclusion: Musculoskeletal injury patterns and injury risks varied depending on the players’ skeletal maturity status. Early maturers had the greatest overall adjusted injury risk. Players who were already skeletally mature at the wrist had the lowest risk of lower extremity apophyseal injuries but were still vulnerable for hip and pelvis apophyseal injuries.

• Ekstrand, Jan; Spreco, Armin; Bengtsson, Håkan & Bahr, Roald (2021). Injury rates decreased in men’s professional football: an 18-year prospective cohort study of almost 12 000 injuries sustained during 1.8 million hours of play. British Journal of Sports Medicine. ISSN 0306-3674. p. 1–9. doi: 10.1136/bjsports-2020-103159. Full text in Research Archive Show summary

  Background: The UEFA Elite Club Injury Study is the largest and longest running injury surveillance programme in football. Objective: To analyse the 18-season time trends in injury rates among male professional football players. Methods: 3302 players comprising 49 teams (19 countries) were followed from 2000–2001 through 2018–2019. Team medical staff recorded individual player exposure and time-loss injuries. Results: A total of 11 820 time-loss injuries were recorded during 1 784 281 hours of exposure. Injury incidence fell gradually during the 18-year study period, 3% per season for both training injuries (95% CI 1% to 4% decrease, p=0.002) and match injuries (95% CI 2% to 3% decrease, p<0.001). Ligament injury incidence decreased 5% per season during training (95% CI 3% to 7% decrease, p<0.001) and 4% per season during match play (95% CI 3% to 6% decrease, p<0.001), while the rate of muscle injuries remained constant. The incidence of reinjuries decreased by 5% per season during both training (95% CI 2% to 8% decrease, p=0.001) and matches (95% CI 3% to 7% decrease, p<0.001). Squad availability increased by 0.7% per season for training sessions (95% CI 0.5% to 0.8% increase, p<0.001) and 0.2% per season for matches (95% CI 0.1% to 0.3% increase, p=0.001). Conclusions: Over 18 years: (1) injury incidence decreased in training and matches, (2) reinjury rates decreased, and (3) player availability for training and match play increased.

• Kotsifaki, Argyro; Whiteley, Rod; van Rossom, Sam; Korakakis, Vasileios; Bahr, Roald & Sideris, Vasileios [Show all 8 contributors for this article] (2021). Single leg hop for distance symmetry masks lower limb biomechanics: time to discuss hop distance as decision criterion for return to sport after ACL reconstruction? British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2020-103677. Full text in Research Archive Show summary

  Background: We evaluated the lower limb status of athletes after anterior cruciate ligament reconstruction (ACLR) during the propulsion and landing phases of a single leg hop for distance (SLHD) task after they had been cleared to return to sport. We wanted to evaluate the biomechanical components of the involved (operated) and uninvolved legs of athletes with ACLR and compare these legs with those of uninjured athletes (controls). Methods: We captured standard video-based three-dimensional motion and electromyography (EMG) in 26 athletes after ACLR and 23 healthy controls during SLHD and calculated lower limb and trunk kinematics. We calculated lower limb joint moments and work using inverse dynamics and computed lower limb muscle forces using an EMG-constrained musculoskeletal modelling approach. Between-limb (within ACLR athletes) and between-group differences (between ACLR athletes and controls) were evaluated using paired and independent sample t-tests, respectively. Results: Significant differences in kinematics (effect sizes ranging from 0.42 to 1.56), moments (0.39 to 1.08), and joint work contribution (0.55 to 1.04) were seen between the involved and uninvolved legs, as well as between groups. Athletes after ACLR achieved a 97%±4% limb symmetry index in hop distance but the symmetry in work done by the knee during propulsion was only 69%. During landing, the involved knee absorbed less work than the uninvolved, while the uninvolved knee absorbed more work than the control group. Athletes after ACLR compensated for lower knee work with greater hip work contribution and by landing with more hip flexion, anterior pelvis tilt, and trunk flexion. Conclusion: Symmetry in performance on a SLHD test does not ensure symmetry in lower limb biomechanics. The distance hopped is a poor measure of knee function, and largely reflects hip and ankle function. Male athletes after ACLR selectively unload the involved limb but outperform controls on the uninvolved knee.

• Nabhan, Dustin; Taylor, David; Lewis, Melie & Bahr, Roald (2021). Protecting the world’s finest athletes: periodic health evaluation practices of the top performing National Olympic Committees from the 2016 Rio or 2018 PyeongChang Olympic Games. British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2020-103481. Show summary

  Aim: To describe the periodic health evaluation (PHE) practices of the top performing National Olympic Committees (NOCs). Methods: We sent a survey to NOCs finishing in the top 8 for medal count at the 2016 Rio Olympic Games or 2018 PyeongChang Olympic Games. The survey included four sections: (1) PHE staff composition and roles, (2) beliefs regarding the PHE, (3) a ranking of risk factors for future injury and (4) details on the elements of the PHE. Results: All 14 NOCs with top 8 finishes at the 2016 Rio Olympic Games or 2018 PyeongChang Olympic Games completed the survey. NOCs included a median of seven staff specialties in the PHE, with physicians and physiotherapists having the highest level of involvement. There was agreement that PHEs are effective in identifying current health conditions (13/14) and that athletes should receive individualised action plans after their PHE (14/14), but less agreement (6/14) that PHEs can predict future injury. The practices of NOCs were diverse and often specific to the athlete population being tested, but always included the patient’s health history, laboratory studies, cardiovascular screening and assessments of movement capacity. The top three risk factors for future injury were thought to be previous injury, age and training experience. Conclusions: Among the top performing NOCs, the PHE is a comprehensive, multidisciplinary process aimed to identify existing conditions and provide baseline health and performance profiles in the event of future injury. Research linking PHEs to injury prevention is needed.

• Nilstad, Agnethe; Petushek, Erich; Mok, Kam-Ming; Bahr, Roald & Krosshaug, Tron (2021). Kiss goodbye to the ‘kissing knees’: no association between frontal plane inward knee motion and risk of future non-contact ACL injury in elite female athletes. Sports Biomechanics. ISSN 1476-3141. doi: 10.1080/14763141.2021.1903541. Full text in Research Archive Show summary

  he aim of this study was to investigate if frontal plane knee and hip control in single-leg squats or vertical drop jumps with an overhead target were associated with future non-contact anterior cruciate ligament (ACL) injury in elite female athletes. Of the 429 handball and 451 football athletes (age 21.5 ± 4.0 years, height 169.6 ± 6.4 cm, body weight 67.1 ± 8.0 kg), 722 non-injured and 56 non-contact ACL injured participants were eligible for analysis. We calculated lateral pelvic tilt, frontal plane knee projection angle, medial knee position, and side-to-side asymmetry in these from 2D videos recorded at baseline, and recorded any new ACL injuries prospectively. None of the aforementioned variables in either screening task were different or could discriminate between injured and non-injured athletes (all p values >.05 and Cohen’s d values < .27). Two-dimensional video assessment of frontal plane knee and hip control during both a single-leg squat and vertical drop jump was unable to identify individuals at increased risk of non-contact ACL injury, thus should not be used for screening.

• Clarsen, Benjamin Matthew; Steffen, Kathrin; Berge, Hilde Moseby; Bendiksen, Fredrik; Fossan, Bjørn & Fredriksen, Hilde [Show all 13 contributors for this article] (2021). Methods, challenges and benefits of a health monitoring programme for Norwegian Olympic and Paralympic athletes: the road from London 2012 to Tokyo 2020. British Journal of Sports Medicine. ISSN 0306-3674. 55, p. 1342–1349. doi: 10.1136/bjsports-2020-103717. Full text in Research Archive
• Rafnsson, Elis Thor; Myklebust, Grethe; Bahr, Roald & Arnason, Arni (2021). No relationship between a movement screening test and risk of overuse problems in low back, shoulder, and knee in elite handball players - A prospective cohort study. Translational Sports Medicine (TSM). ISSN 2573-8488. doi: 10.1002/tsm2.245. Full text in Research Archive Show summary

  Many handball studies have reported injuries that cause absence from participation. In this prospective cohort study on elite Icelandic male players, the aim was to examine the prevalence of overuse problems in low back, knee, and shoulder. Sixteen Icelandic teams were invited. Thirteen teams agreed to participate. The OSTRC overuse questionnaire was distributed every second week during 32-week period. In addition, the 9+ Screening Test was performed on 130 players. In total, 229 players participated with a weekly average response rate of 72%. The average weekly prevalence for shoulder was 28% (95% CI 25% to 31%), for knee 33% (95% CI 30% to 36%), and for low back 32% (95% CI 29% to 35%). Substantial problems were 10% (95% CI 9% to 11%) in shoulder and knee and 11% (95%CI 10% to 12%) in low back. Only 1% (95% CI 1% to 2%) of the overuse problems caused time loss from participation. In total, 61% of the players played with at least one overuse problem and 25% with one affecting their performance. There was no association between the 9+ Screening Test score and overuse problems among Icelandic male handball players.

• Geertsema, Celeste; Geertsema, Liesel; Farooq, Abdulaziz; Harøy, Joar; Oester, Chelsea & Weber, Alexis [Show all 7 contributors for this article] (2021). Injury prevention knowledge, beliefs and strategies in elite female footballers at the FIFA Women’s World Cup France 2019. British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2020-103131. Show summary

  Objectives: This study assessed knowledge, beliefs and practices of elite female footballers regarding injury prevention. Methods: A survey was sent to players participating in the FIFA Women’s World Cup France 2019. Questions covered three injury prevention domains: (1) knowledge; (2) attitudes and beliefs; (3) prevention practices in domestic clubs. Additionally, ACL injury history was assessed. Results: Out of 552 players, 196 women responded (35.5%). More than 80% of these considered injury risk to be moderate or high. Players listed knee, ankle, thigh, head and groin as the most important injuries in women’s football. The most important risk factors identified were low muscle strength, followed by poor pitch quality, playing on artificial turf, too much training, reduced recovery and hard tackles. In these elite players, 15% did not have any permanent medical staff in their domestic clubs, yet more than 75% had received injury prevention advice and more than 80% performed injury prevention exercises in their clubs. Players identified the two most important implementation barriers as player motivation and coach attitude. Two-thirds of players used the FIFA 11+ programme in their clubs. Conclusions: This diverse group of elite players demonstrated good knowledge of risk level and injury types in women’s football. Of the risk factors emphasised by players, there was only one intrinsic risk factor (strength), but several factors out of their control (pitch quality and type, training volume and hard tackles). Still players had positive attitudes and beliefs regarding injury prevention exercises and indicated a high level of implementation, despite a lack of medical support.

• Tabben, Montassar; Eirale, Cristiano; Singh, Gurcharan Dato; Al-Kuwari, Abdulaziz; Ekstrand, Jan & Chalabi, Hakim [Show all 8 contributors for this article] (2021). Injury and illness epidemiology in professional Asian football: lower general incidence and burden but higher ACL and hamstring injury burden compared with Europe. British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2020-102945. Full text in Research Archive Show summary

  Background: While football injury and illness epidemiology surveillance at professional club level in Europe is available, epidemiological data from other continents are lacking. Purpose: Investigating injury and illness epidemiology in professional Asian football. Study design: Descriptive prospective study. Methods: Professional teams from the Asian Football Confederation (AFC) league were followed prospectively for three consecutive AFC seasons (2017 through 2019, 13 teams per season, 322 team months). Time-loss injuries and illnesses in addition to individual match and training exposure were recorded using standardised digital tools in accordance with international consensus procedures. Results: In total, 232 665 hours of exposure (88.6% training and 11.4% matches) and 1159 injuries were recorded; 496 (42.8%) occurred during matches, 610 (52.6%) during training; 32 (2.8%) were reported as ‘not applicable’ and for 21 injuries (1.8%) information was missing. Injury incidence was significantly greater during match play (19.2±8.6 injuries per 1000 hours) than training (2.8±1.4, p<0.0001), resulting in a low overall incidence of 5.1±2.2. The injury burden for match injuries was greater than from training injuries (456±336 days per 1000 hours vs 54±34 days, p<0.0001). The two specific injuries causing the greatest burden were complete ACL ruptures (0.14 injuries (95% CI 0.9 to 0.19) and 29.8 days lost (29.1 to 30.5) per 1000 hours) and hamstring strains (0.86 injuries (0.74 to 0.99) and 17.5 days (17.0 to 18.1) lost per 1000 hours). Reinjuries constituted 9.9% of all injuries. Index injuries caused 22.6±40.8 days of absence compared with 25.1±39 for reinjuries (p=0.62). The 175 illnesses recorded resulted in 1.4±2.9 days of time loss per team per month. Conclusion: Professional Asian football is characterised by an overall injury incidence similar to that reported from Europe, but with a high rate of ACL ruptures and hamstring injury, warranting further investigations.

• Nabhan, Dustin; Taylor, David; Hedges, Andrew & Bahr, Roald (2021). The Value of the Patient History in the Periodic Health Evaluation: Patient Interviews Capture 4 Times More Injuries Than Electronic Questionnaires. Journal of Orthopaedic and Sports Physical Therapy. ISSN 0190-6011. 51(1), p. 46–51. doi: 10.2519/jospt.2021.9821. Show summary

  Objective: To assess the value of the patient interview and electronic questionnaire methods of health history data collection in elite athletes. Design: Cohort study. Methods: A retrospective chart review compared health history data collected by questionnaire and by interview in a cohort of 142 athletes who participated in a periodic health evaluation at the US Olympic & Paralympic Training Center sports medicine clinic. The main outcome measure was number of injuries reported by either interview or written questionnaire. Results: Six hundred twenty-six injuries were reported by interview and 157 by questionnaire. The mean ± SD number of injuries reported per participant was 4.4 ± 4.2 by interview and 1.1 ± 1.3 by questionnaire (difference, 3.3; P<.001). Capture rate by method was similar across sexes and for both Olympic and Paralympic athletes. More injuries were reported by interview than by questionnaire for all injury categories, except for concussions and surgeries. Conclusion: Patient interviews capture 4 times as many past or current injuries than electronic questionnaires in athletes training for the Olympic and Paralympic Games. Questionnaires provide incomplete health history information in this patient population.

• Materne, Olivier; Chamari, Karim; Farooq, Abdulaziz; Weir, Adam; Hölmich, Per & Bahr, Roald [Show all 8 contributors for this article] (2020). Injury incidence and burden in a youth elite football academy: a four-season prospective study of 551 players aged from under 9 to under 19 years. British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2020-102859. Show summary

  Objective: Investigate the incidence and burden of injuries by age group in youth football (soccer) academy players during four consecutive seasons. Methods: All injuries that caused time-loss or required medical attention (as per consensus definitions) were prospectively recorded in 551 youth football players from under 9 years to under 19 years. Injury incidence (II) and burden (IB) were calculated as number of injuries per squad season (s-s), as well as for type, location and age groups. Results: A total of 2204 injuries were recorded. 40% (n=882) required medical attention and 60% (n=1322) caused time-loss. The total time-loss was 25 034 days. A squad of 25 players sustained an average of 30 time-loss injuries (TLI) per s-s with an IB of 574 days lost per s-s. Compared with the other age groups, U-16 players had the highest TLI incidence per s-s (95% CI lower-upper): II= 59 (52 to 67); IB=992 days; (963 to 1022) and U-18 players had the greatest burden per s-s: II= 42.1 (36.1 to 49.1); IB= 1408 days (1373 to 1444). Across the cohort of players, contusions (II=7.7/s-s), sprains (II=4.9/s-s) and growth-related injuries (II=4.3/s-s) were the most common TLI. Meniscus/cartilage injuries had the greatest injury severity (95% CI lower-upper): II= 0.4 (0.3 to 0.7), IB= 73 days (22 to 181). The burden (95% CI lower-upper) of physeal fractures (II= 0.8; 0.6 to 1.2; IB= 58 days; 33 to 78) was double than non-physeal fractures. Summary: At this youth football academy, each squad of 25 players averaged 30 injuries per season which resulted in 574 days lost. The highest incidence of TLI occurred in under-16 players, while the highest IB occurred in under-18 players.

• Wik, Eirik Halvorsen; Lolli, Lorenzo; Chamari, Karim; Materne, Olivier; Di Salvo, Valter & Gregson, Warren [Show all 7 contributors for this article] (2020). Injury patterns differ with age in male youth football: a four-season prospective study of 1111 time-loss injuries in an elite national academy. British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2020-103430. Show summary

  Objectives: To describe age group patterns for injury incidence, severity and burden in elite male youth football. Methods: Prospective cohort study capturing data on individual exposure and time-loss injuries from training and matches over four seasons (2016/2017 through 2019/2020) at a national football academy (U13–U18; age range: 11–18 years). Injury incidence was calculated as the number of injuries per 1000 hours, injury severity as the median number of days lost and injury burden as the number of days lost per 1000 hours. Results: We included 301 players (591 player-seasons) and recorded 1111 time-loss injuries. Overall incidence was 12.0 per 1000 hours (95% CI 11.3 to 12.7) and burden was 255 days lost per 1000 hours (252 to 259). The mean incidence for overall injuries was higher in the older age groups (7.8 to 18.6 injuries per 1000 hours), while the greatest burden was observed in the U16 age group (425 days; 415 to 435). In older age groups, incidence and burden were higher for muscle injuries and lower for physis injuries. Incidence of joint sprains and bone stress injuries was greatest for players in the U16, U17 and U18 age groups, with the largest burden observed for U16 players. No clear age group trend was observed for fractures. Conclusion: Injury patterns differed with age; tailoring prevention programmes may be possible.

• Sandmo, Stian Bahr; Gooijers, Jolien; Seer, Caroline; Kaufmann, David; Bahr, Roald & Pasternak, Ofer [Show all 9 contributors for this article] (2020). Evaluating the validity of self-report as a method for quantifying heading exposure in male youth soccer. Research in Sports Medicine: An International Journal. ISSN 1543-8627. doi: 10.1080/15438627.2020.1853541. Show summary

  Assessing heading exposure in football is important when exploring the association between heading and brain alterations. To this end, questionnaires have been developed for use in adult populations. However, the validity of self-report in adolescents remains to be elucidated. Male youth soccer players (n = 34) completed a questionnaire on heading exposure after a two-week period, which included matches and training sessions. Self-reported numbers were compared to observation (considered reference). In total, we observed 157 training sessions and 64 matches. Self-reported heading exposure correlated with observed heading exposure (Spearman’s rho 0.68; p < 0.001). Players systematically overestimated their heading exposure by a factor of 3 with the random error of 46%. Area under the curve was 0.87 (95% CI 0.67–1) utilizing self-report for identifying players from high- and low-exposure groups. Thus, in this study, self-reported data could be used to group youth players into high and low heading exposure groups, but not to quantify individual heading exposure.

• Nabhan, Dustin; Lewis, Melie; Taylor, David & Bahr, Roald (2020). Expanding the screening toolbox to promote athlete health: how the US Olympic & Paralympic Committee screened for health problems in 940 elite athletes. British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2020-102756. Full text in Research Archive Show summary

  Aim: To assess the value of including validated screening tools for allergies, anxiety, depression, sleep apnoea and sleep quality into an electronic patient health history questionnaire. Methods: In this descriptive study, we reviewed electronic medical records of Olympic and Paralympic athletes who completed health screenings, which included validated screens for allergies (Allergy Questionnaire for Athletes), anxiety (General Anxiety Disorder-2), depression (Patient Health Questionaire-2), sleep apnoea (Berlin Questionnaire) and sleep quality (Pittsburgh Sleep Quality Index), using established criteria for a positive screen. We report the prevalence of positive tests and the associations between positive screening tools. Results: A total of 683 Olympic and 257 Paralympic athletes (462 male, 478 female) completed the health history between May and September of 2019. At least one positive screen was reported by 37% of athletes training for the Olympics and 48% of athletes training for the Paralympics. More than 20% of all athletes screened positive for allergies and poor sleep quality. Athletes training for the Paralympics had a significantly higher percentage of positive screens for anxiety, depression, poor sleep quality and sleep apnoea risk. Females had significantly more positive screens for allergy and poor sleep quality. Conclusions: The addition of standardised screening tools to an electronic health history resulted in the identification of potential mental health, sleep and allergy problems in both Olympic and Paralympic athletes. Strong associations between mental health and sleep disorders suggest these problems should be considered together in health screening programmes.

• Racinais, Sebastien; Alhammoud, Marine; Nasir, Nada & Bahr, Roald (2020). Epidemiology and risk factors for heat illness: 11 years of Heat Stress Monitoring Programme data from the FIVB Beach Volleyball World Tour. British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2020-103048. Full text in Research Archive Show summary

  Objectives: To analyse 11 years of FIVB heat stress-monitoring data to determine the relative influence of the different environmental parameters in increasing the likelihood of a heat-related medical time-out (MTOheat). Methods: A total of 8530 matches were recorded. The referee measured air temperature, black globe temperature, relative humidity and wet-bulb globe temperature (WBGT) before the matches, and registered the MTOheat. The absolute humidity was computed at posteriori. Results: There were 20 MTOheat cases, but only 3 resulted in forfeiting the match. MTOheat incidence was not statistically impacted by sex (p=0.59). MTOheat cases were more prevalent during the games played in Asia during the 4th quarter of the year (p<0.001). Two cases of MTOheat experienced diarrhoea or gastroenteritis during the 5 preceding days; both of them forfeited the match. A principal component analysis showed a specific environmental profile for the matches with MTOheat. They occurred at higher WBGT, temperatures and absolute humidity (p<0.001), but with a lower relative humidity (p=0.027). Conclusions: The current data showed that an increase in ambient or black globe temperature, but not relative humidity, increased the risk of a MTOheat; but that the absolute risk remained low in elite beach volleyball players. However, suffering or recovering from a recent illness may represent a risk factor for a MTOheat to lead to player forfeit.

• Nielsen, Rasmus Oestergaard; Shrier, Ian; Casals, Marti; Nettel-Aguirre, Alberto; Møller, Merete & Bolling, Caroline [Show all 24 contributors for this article] (2020). Statement on methods in sport injury research from the 1st METHODS MATTER Meeting, Copenhagen, 2019. British Journal of Sports Medicine. ISSN 0306-3674. 54(15), p. 941–947. doi: 10.1136/bjsports-2019-101323. Show summary

  High quality sports injury research can facilitate sports injury prevention and treatment. There is scope to improve how our field applies best practice methods—methods matter (greatly!). The 1st METHODS MATTER Meeting, held in January 2019 in Copenhagen, Denmark, was the forum for an international group of researchers with expertise in research methods to discuss sports injury methods. We discussed important epidemiological and statistical topics within the field of sports injury research. With this opinion document, we provide the main take-home messages that emerged from the meeting.

• Fredriksen, Hilde; Cools, Ann; Bahr, Roald & Myklebust, Grethe (2020). Does an effective shoulder injury prevention program affect risk factors in handball? A randomized controlled study. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 30(8), p. 1423–1433. doi: 10.1111/sms.13674. Show summary

  Background: Shoulder problems are common in handball, but injury risk reduction is possible by implementing a prevention program. However, player compliance to the program remains a challenge, with feedback from players that the program is too time consuming. Aim: To develop a more efficient program, we aimed to assess the effect of the Oslo Sports Trauma Research Center shoulder injury prevention program on external rotation (ER) strength and internal rotation (IR) range of motion (ROM), considered to represent key risk factors for injury. Methods: Four youth handball teams (three females, one males, 57 players, mean age 17.1 years) were randomized to an intervention or control group. The intervention program was conducted three times per week as a part of handball warm‐up for 18 weeks, supervised by physical therapists. The main outcome variables were the between‐group differences in ER strength and IR ROM change from baseline to postintervention. Isometric ER strength was measured with a handheld dynamometer and IR ROM with a digital goniometer. Results: Mean dominant shoulder isometric ER strength increased both in the intervention (10%) and the control group (6%) during the intervention, but there was no significant group by time interaction (group difference: 0.06 N/kg (95% CI: −0.04 to 0.17). IR ROM did not change in either group during the intervention. Conclusion: The Oslo Sports Trauma Research Center shoulder injury prevention program did not affect the risk factors ER strength and IR ROM. The preventive effect of the program must therefore be due to other factors.

• Skazalski, Christopher M.; Bahr, Roald & Whiteley, Rod (2020). Shoulder complaints more likely in volleyball players with a thickened bursa or supraspinatus tendon neovessels. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. doi: 10.1111/sms.13831. Full text in Research Archive Show summary

  Shoulder problems are common in volleyball and greatly impede both training and player performance. Subacromial bursa (SAB) thickening and tendon neovascularity have shown relevance in other populations, but their relationship with the development of shoulder complaints has not been investigated in volleyball players or overhead‐throwing athletes. The study aim was to examine the role of SAB thickness, neovascularization of the supraspinatus tendon, shoulder strength, range of motion (ROM), player position, and age in the development of shoulder complaints in professional volleyball players. Players underwent preseason baseline testing (n = 86) and reported shoulder complaints during the subsequent 12‐week period. Generalized estimating equations were used to model for probabilities of complaints after adjusting for player position, SAB side‐to‐side difference, neovessel presence, shoulder external rotation (ER) ROM, and age. Outside hitters and opposites were 12.2‐fold more likely to develop complaints, and greater shoulder ER ROM increased risk by 8% for each additional degree. A side‐to‐side difference in SAB thickness ≥0.3 mm in the dominant compared with the non‐dominant arm was associated with a 10.2‐fold increased risk. Those with neovessels were 6.5 times more likely to develop complaints. Players without neovessels and with normal SAB thickness were very unlikely to develop complaints. This stark contrast to players with neovessels or increased SAB thickness, where nearly half of the players developed complaints, is of interest. Players with current complaints at baseline presented with greater IR:ER strength ratios; however, neither strength nor IR ROM at baseline was associated with an increased risk of developing complaints.

• Nielsen, Rasmus Østergaard; Shrier, Ian; Casals, Martí; Nettel-Aguirre, Alberto; Møller, Merete & Bolling, Caroline [Show all 24 contributors for this article] (2020). Statement on methods in sport injury research from the first methods matter meeting, Copenhagen, 2019. Journal of Orthopaedic and Sports Physical Therapy. ISSN 0190-6011. 50(5), p. 226–233. doi: 10.2519/jospt.2020.9876.
• Sandmo, Stian Bahr; Filipcik, Peter; Cente, Martin; Hanes, Jozef; Andersen, Thor Einar & Straume-Næsheim, Truls Martin [Show all 7 contributors for this article] (2020). Neurofilament light and tau in serum after head-impact exposure in soccer. Brain Injury. ISSN 0269-9052. 34(5), p. 602–609. doi: 10.1080/02699052.2020.1725129. Full text in Research Archive Show summary

  Introduction: Blood-based biomarkers can provide valuable information on the effects of repetitive head impacts in sports. This study investigated if repetitive headers or accidental head impacts in soccer could cause structural brain injury, detected as an increase in serum neurofilament light (NfL) or tau. Methods: NfL and tau were measured in professional soccer players in pre-season. Then, the effect of three short-term exposures on biomarker levels was assessed: (1) high-intensity exercise, (2) repetitive headers, and (3) head impacts in a match. Results: We analyzed 354 samples and observed no effects on NfL from any of the three short-term exposures. Tau levels rose significantly from baseline to 1 h after (1) high-intensity exercise (Δ0.50 pg/ mL, 95% CI 0.19–0.81, p < .01); the same was observed after (2) repetitive headers (Δ0.29 pg/mL, 95% CI 0.10–0.48, p < .01), but not after (3) accidental head-impact incidents (Δ0.36 pg/mL, 95% CI −0.02–0.74, p = .06). The highest absolute values were seen 1 h after high-intensity exercise (mean±SD, 1.92 ± 0.83 pg/mL). Conclusion: NfL and tau in serum were unaffected by head impacts in soccer. Importantly, tau levels seem to rise in response to exercise, emphasizing the need for control groups. Our findings highlight important characteristics and limitations when using these biomarkers in sports.

• Orchard, John W.; Meeuwisse, Willem; Derman, Wayne; Hägglund, Martin; Soligard, Torbjørn & Schwellnus, Martin [Show all 7 contributors for this article] (2020). Sport Medicine Diagnostic Coding System (SMDCS) and the Orchard Sports Injury and Illness Classification System (OSIICS): Revised 2020 Consensus Versions. British Journal of Sports Medicine. ISSN 0306-3674. 54(7), p. 397–401. doi: 10.1136/bjsports-2019-101921. Full text in Research Archive Show summary

  Coding in sports medicine generally uses sports-specific coding systems rather than the International Classification of Diseases (ICD), because of superior applicability to the profile of injury and illness presentations in sport. New categories for coding were agreed on in the 'International Olympic Committee (IOC) consensus statement: Methods for recording and reporting of epidemiological data on injury and illness in sports 2020.' We explain the process for determining the new categories and update both the Sport Medicine Diagnostic Coding System (SMDCS) and the Orchard Sports Injury and Illness Classification System (OSIICS) with new versions that operationalise the new consensus categories. The author group included members from an expert group attending the IOC consensus conference. The primary authors of the SMDCS (WM) and OSIICS (JO) produced new versions that were then agreed on by the remaining authors using expert consensus methodology. The SMDCS and OSIICS systems have been adjusted and confirmed through a consensus process to align with the IOC consensus statement to facilitate translation between the two systems. Problematic areas for defining body part categories included the groin and ankle regions. For illness codes, in contrast to the ICD, we elected to have a taxonomy of 'organ system/region' (eg, cardiovascular and respiratory), followed by an 'aetiology/pathology' (eg, environmental, infectious disease and allergy). Companion data files have been produced that provide translations between the coding systems. The similar structure of coding underpinning the OSIICS and SMDCS systems aligns the new versions of these systems with the IOC consensus statement and also facilitates easier translation between the two systems. These coding systems are freely available to the sport and exercise research community.

• Clarsen, Benjamin Matthew; Bahr, Roald; Myklebust, Grethe; Andersson, Stig Haugsbø; Docking, Sean & Drew, Michael [Show all 19 contributors for this article] (2020). Improved reporting of overuse injuries and health problems in sport: an update of the Oslo Sport Trauma Research Center questionnaires. British Journal of Sports Medicine. ISSN 0306-3674. 54(7), p. 390–396. doi: 10.1136/bjsports-2019-101337. Full text in Research Archive Show summary

  In 2013, the Oslo Sports Trauma Research Center Overuse Injury Questionnaire (OSTRC-O) was developed to record the magnitude, symptoms and consequences of overuse injuries in sport. Shortly afterwards, a modified version of the OSTRC-O was developed to capture all types of injuries and illnesses—The Oslo Sports Trauma Research Center Questionnaire on Health Problems (OSTRC-H). Since then, users from a range of research and clinical environments have identified areas in which these questionnaires may be improved. Therefore, the structure and content of the questionnaires was reviewed by an international panel consisting of the original developers, other user groups and experts in sports epidemiology and applied statistical methodology. Following a review panel meeting in October 2017, several changes were made to the questionnaires, including minor wording alterations, changes to the content of one question and the addition of questionnaire logic. In this paper, we present the updated versions of the questionnaires (OSTRC-O2 and OSTRC-H2), assess the likely impact of the updates on future data collection and discuss practical issues related to application of the questionnaires. We believe this update will improve respondent adherence and improve the quality of collected data.

• Wik, Eirik Halvorsen; Martínez-Silván, Daniel; Farooq, Abdulaziz; Cardinale, Marco; Johnson, Amanda & Bahr, Roald (2020). Skeletal maturation and growth rates are related to bone and growth plate injuries in adolescent athletics. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 30(5), p. 894–903. doi: 10.1111/sms.13635. Show summary

  Injuries are common in elite adolescent athletics, but few studies have addressed risk factors for injury. Growth and maturation are potential risk factors in this population; however, the current body of literature is both inconclusive and considered at high risk of bias. The aim of this study was therefore to examine whether growth rate, maturity status, and maturity tempo are associated with injury risk in an elite sports academy. Anthropometric, skeletal maturity and injury data collected prospectively over four seasons (117 athlete‐seasons) were included in the analyses. Growth rate for stature was associated with greater risk of bone (incidence rate ratio (IRR): 1.5 per one standard deviation increase above the mean; 95% CI: 1.1‐1.9) and growth plate injuries (IRR: 2.1; 1.5‐3.1). Growth rate for leg length was associated with greater overall injury risk (IRR: 1.3; 1.0‐1.7) as well as the risk of bone (IRR: 1.4; 1.0‐1.9) and growth plate injuries (IRR: 2.1; 1.4‐3.0). Athletes with greater skeletal maturity, expressed as skeletal age (IRR: 0.6 per year; 0.5‐0.9) and percentage of predicted mature height (IRR: 0.8 per percent increase; 0.7‐1.0), were less prone to growth plate injuries. Rate of change in skeletal age was associated with an increased risk of bone injuries (IRR: 1.5; 1.0‐2.3). The results of this study suggest that rapid growth in stature and leg length, skeletal maturity status, and maturity tempo represent risk factors for certain injury types in adolescent athletics.

• Nordstrøm, Anine; Bahr, Roald; Talsnes, Ove & Clarsen, Benjamin Matthew (2020). Prevalence and Burden of Health Problems in Male Elite Ice Hockey Players: A Prospective Study in the Norwegian Professional League. Orthopaedic Journal of Sports Medicine (OJSM). ISSN 2325-9671. 8(2). doi: 10.1177/2325967120902407. Full text in Research Archive Show summary

  Background: As previous epidemiological studies in elite ice hockey have focused on acute time-loss injuries, little is known about the burden of overuse injuries and illnesses in ice hockey. Purpose: To report the prevalence and burden of all health problems in male professional ice hockey players in Norway during a single competitive season. Study Design: Descriptive epidemiological study. Methods: A total of 225 male ice hockey players in the GET League (the premier professional league) in Norway reported all health problems (acute injuries, overuse injuries, and illnesses) during the 2017-2018 competitive season. Players reported all injuries and illnesses for 31 weeks using the Oslo Sports Trauma Research Center Questionnaire on Health Problems. Results: At any given time, 40% (95% CI, 37%-43%) of players reported symptoms from an injury or illness, and 20% (95% CI, 19%-22%) experienced health problems with a substantial negative impact on training and performance. Acute injuries represented the greatest incidence, prevalence, and burden (defined as the cross-product of severity and incidence). The most burdensome acute injuries were to the head/face, shoulder/clavicle, knee, and ankle. The most burdensome overuse injuries were to the knee, lumbar spine, and hip/groin. Conclusion: This registration captured a greater burden from overuse injuries than traditional injury registration, but acute injuries did represent a major problem. These data provide guidance in the development of prevention programs for both acute and overuse injuries, which should focus on the lumbar spine, hip/groin, and knee.

• Bahr, Roald; Clarsen, Benjamin Matthew; Derman, Wayne; Dvorak, Jiří; Emery, Carolyn A. & Finch, Caroline F. [Show all 27 contributors for this article] (2020). International Olympic Committee consensus statement: methods for recording and reporting of epidemiological data on injury and illness in sport 2020 (including STROBE Extension for Sport Injury and Illness Surveillance (STROBE-SIIS)). British Journal of Sports Medicine. ISSN 0306-3674. 54(7), p. 372–389. doi: 10.1136/bjsports-2019-101969. Full text in Research Archive Show summary

  Injury and illness surveillance, and epidemiological studies, are fundamental elements of concerted efforts to protect the health of the athlete. To encourage consistency in the definitions and methodology used, and to enable data across studies to be compared, research groups have published 11 sport-specific or setting-specific consensus statements on sports injury (and, eventually, illness) epidemiology to date. Our objective was to further strengthen consistency in data collection, injury definitions and research reporting through an updated set of recommendations for sports injury and illness studies, including a new Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist extension. The IOC invited a working group of international experts to review relevant literature and provide recommendations. The procedure included an open online survey, several stages of text drafting and consultation by working groups and a 3-day consensus meeting in October 2019. This statement includes recommendations for data collection and research reporting covering key components: defining and classifying health problems; severity of health problems; capturing and reporting athlete exposure; expressing risk; burden of health problems; study population characteristics and data collection methods. Based on these, we also developed a new reporting guideline as a STROBE Extension—the STROBE Sports Injury and Illness Surveillance (STROBE-SIIS). The IOC encourages ongoing in- and out-of-competition surveillance programmes and studies to describe injury and illness trends and patterns, understand their causes and develop measures to protect the health of the athlete. Implementation of the methods outlined in this statement will advance consistency in data collection and research reporting.

• Bahr, Roald; Clarsen, Benjamin Matthew; Derman, Wayne; Dvorak, Jiří; Emery, Carolyn A. & Finch, Caroline F. [Show all 27 contributors for this article] (2020). International Olympic Committee Consensus Statement: Methods for Recording and Reporting of Epidemiological Data on Injury and Illness in Sports 2020 (Including the STROBE Extension for Sports Injury and Illness Surveillance (STROBE-SIIS)). Orthopaedic Journal of Sports Medicine (OJSM). ISSN 2325-9671. doi: 10.1177/2325967120902908. Show summary

  Background: Injury and illness surveillance, and epidemiological studies, are fundamental elements of concerted efforts to protect the health of the athlete. To encourage consistency in the definitions and methodology used, and to enable data across studies to be compared, research groups have published 11 sport- or setting-specific consensus statements on sports injury (and, eventually, illnesses) epidemiology to date. Objective: To further strengthen consistency in data collection, injury definitions, and research reporting through an updated set of recommendations for sports injury and illness studies, including a new Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist extension. Study Design: Consensus statement of the International Olympic Committee (IOC). Methods: The IOC invited a working group of international experts to review relevant literature and provide recommendations. The procedure included an open online survey, several stages of text drafting and consultation by working groups, and a 3-day consensus meeting in October 2019. Results: This statement includes recommendations for data collection and research reporting covering key components: defining and classifying health problems, severity of health problems, capturing and reporting athlete exposure, expressing risk, burden of health problems, study population characteristics, and data collection methods. Based on these, we also developed a new reporting guideline as a STROBE extension—the STROBE Sports Injury and Illness Surveillance (STROBE-SIIS). Conclusion: The IOC encourages ongoing in- and out-of-competition surveillance programs and studies to describe injury and illness trends and patterns, understand their causes, and develop measures to protect the health of the athlete. The implementation of the methods outlined in this statement will advance consistency in data collection and research reporting.

• Rio, Ebonie Kendra; Mc Auliffe, Seán; Kuipers, Irene; Girdwood, Michael; Alfredson, Håkan & Bahr, Roald [Show all 26 contributors for this article] (2019). ICON PART-T 2019–International Scientific Tendinopathy Symposium Consensus: recommended standards for reporting participant characteristics in tendinopathy research (PART-T). British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2019-100957. Show summary

  We aimed to establish consensus for reporting recommendations relating to participant characteristics in tendon research. A scoping literature review of tendinopathy studies (Achilles, patellar, hamstring, gluteal and elbow) was followed by an online survey and face-to-face consensus meeting with expert healthcare professionals (HCPs) at the International Scientific Tendon Symposium, Groningen 2018. We reviewed 263 papers to form statements for consensus and invited 30 HCPs from different disciplines and geographical locations; 28 completed the survey and 15 attended the meeting. There was consensus that the following data should be reported for cases and controls: sex, age, standing height, body mass, history of tendinopathy, whether imaging was used to confirm pathology, loading tests, pain location, symptom duration and severity, level of disability, comorbidities, physical activity level, recruitment source and strategies, and medication use history. Standardised reporting of participant characteristics aims to benefit patients and clinicians by guiding researchers in the conduct of their studies. We provide free resources to facilitate researchers adopting our recommendations.

• Lolli, Lorenzo; Bahr, Roald; Weston, Matthew; Whiteley, Rodney; Tabben, Montassar & Bonanno, Daniele [Show all 10 contributors for this article] (2019). No association between perceived exertion and session duration with hamstring injury occurrence in professional football. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. doi: 10.1111/sms.13591. Full text in Research Archive Show summary

  Training and competition loads have emerged as modifiable composite risk factors of non‐contact injury. Hamstring strains are the most common injuries in football with substantial burden on the individual player and club. Nevertheless, robust evidence of a consistent load‐hamstring injury relationship in professional football is lacking. Using available data from the Qatar Stars League over three competitive seasons, this study investigated the separate and combined effects of perceived exertion and session duration on hamstring injury occurrence in a sample of 30 outfield football players. Load variables were calculated into 7‐day, 14‐day, 21‐day, 28‐day periods of data, and week‐to‐week changes for average ratings of perceived exertion (RPE; au) score and session‐RPE (s‐RPE; session‐duration urn:x-wiley:09057188:media:sms13591:sms13591-math-0001 score), plus the cumulative training and match minutes and s‐RPE, respectively. Conditional logistic regression models estimated load‐injury relationships per 2‐within‐subject standard deviation increments in each candidate variable. Associations were declared practically important based on the location of the confidence interval in relation to thresholds of 0.90 and 1.11 defining small beneficial and harmful effects, respectively. The uncertainty for the corrected odds ratios show that typically high within‐subject increments in each candidate variable were not practically important for training‐ and match‐related hamstring injury (95% confidence intervals range: 0.85 to 1.16). We found limited exploratory evidence regarding the value of perceived exertion and session duration as etiological factors of hamstring injury in Middle‐East professional football. Monitoring remains valuable to inform player load management strategies, but our exploratory findings suggest its role for type‐specific injury risk determination appears empirically unsupported.

• Vicenzino, Bill; de Vos, Robert-Jan; Alfredson, Håkan; Bahr, Roald; Cook, Jill L. & Coombes, Brooke K. [Show all 24 contributors for this article] (2019). ICON 2019—International Scientific Tendinopathy Symposium Consensus: There are nine core health-related domains for tendinopathy (CORE DOMAINS): Delphi study of healthcare professionals and patients. British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2019-100894. Full text in Research Archive Show summary

  Background: The absence of any agreed-upon tendon health-related domains hampers advances in clinical tendinopathy research. This void means that researchers report a very wide range of outcome measures inconsistently. As a result, substantial synthesis/meta-analysis of tendon research findings is almost futile despite researchers publishing busily. We aimed to determine options for, and then define, core health-related domains for tendinopathy. Methods: We conducted a Delphi study of healthcare professionals (HCP) and patients in a three-stage process. In stage 1, we extracted candidate domains from clinical trial reports and developed an online survey. Survey items took the form: ‘The ‘candidate domain’ is important enough to be included as a core health-related domain of tendinopathy’; response options were: agree, disagree, or unsure. In stage 2, we administered the online survey and reported the findings. Stage 3 consisted of discussions of the findings of the survey at the ICON (International Scientific Tendinopathy Symposium Consensus) meeting. We set 70% participant agreement as the level required for a domain to be considered ‘core’; similarly, 70% agreement was required for a domain to be relegated to ‘not core’ (see Results next). Results: Twenty-eight HCP (92% of whom had >10 years of tendinopathy experience, 71% consulted >10 cases per month) and 32 patients completed the online survey. Fifteen HCP and two patients attended the consensus meeting. Of an original set of 24 candidate domains, the ICON group deemed nine domains to be core. These were: (1) patient rating of condition, (2) participation in life activities (day to day, work, sport), (3) pain on activity/loading, (4) function, (5) psychological factors, (6) physical function capacity, (7) disability, (8) quality of life and (9) pain over a specified time. Two of these (2, 6) were an amalgamation of five candidate domains. We agreed that seven other candidate domains were not core domains: range of motion, pain on clinician applied test, clinical examination, palpation, drop out, sensory modality pain and pain without other specification. We were undecided on the other five candidate domains of physical activity, structure, medication use, adverse effects and economic impact. Conclusion: Nine core domains for tendon research should guide reporting of outcomes in clinical trials. Further research should determine the best outcome measures for each specific tendinopathy (ie, core outcome sets).

• Nabhan, Dustin; Bielko, Shane; Sinex, Jacob A.; Surhoff, Kendall; Moreau, William J. & Schumacher, Yorch Olaf [Show all 8 contributors for this article] (2019). Serum ferritin distribution in elite athletes. Journal of Science and Medicine in Sport. ISSN 1440-2440. 23(6), p. 554–558. doi: 10.1016/j.jsams.2019.12.027. Full text in Research Archive Show summary

  Objectives: It is not uncommon for athletes to be diagnosed with iron deficiency, yet there remains uncertainty whether the prevalence of suboptimal iron status in elite athletes differs from the normal population or warrants routine screening. The purpose of this study is to describe the distribution of serum ferritin (SF) in a cohort of elite athletes. Design: Retrospective cohort study. Methods: Electronic health records of 1085 elite adult athletes (570 women, 515 men) from 2012–2017 were examined retrospectively. SF values were compared to published normal population data. The proportion of athletes meeting criterion values for iron deficiency or initiation of treatment was examined. Results: SF distributions in male athletes were significantly lower than normal males aged 20 to <24 yrs. (χ2 28.8, p < 0.001) and aged 24 to <28 yrs. (χ2 91.9, p < 0.001). SF status was similar in female athletes and normal women aged 20 to <24 yrs. (χ2 9.5, p > 0.05) or aged 24 to <28 yrs. (χ2 11.5, p > 0.05). Using 35 ng/ml as the criterion value for stage one iron deficiency, 15% of male athletes and 52% of female athletes displayed suboptimal iron status. Conclusions: Male athletes have a significantly lower population distribution of SF values as compared to normative data on healthy males, with 15% of male athletes having suboptimal SF status. The distribution of SF values in elite female athletes did not differ from population values, however approximately half women athletes were iron deficient. These data suggest that iron screening should be considered in both male and female athlete populations.

• Mørtvedt, Anne Inger; Krosshaug, Tron; Bahr, Roald & Petushek, Erich (2019). I spy with my little eye … a knee about to go ‘pop’? Can coaches and sports medicine professionals predict who is at greater risk of ACL rupture? British Journal of Sports Medicine. ISSN 0306-3674. 54(3). doi: 10.1136/bjsports-2019-100602. Full text in Research Archive Show summary

  Background: The vertical drop jump (VDJ) test is widely used for clinical assessment of ACL injury risk, but it is not clear whether such assessments are valid. Aim: To examine if sports medicine professionals and coaches are able to identify players at risk of sustaining an ACL injury by visually assessing player performance during a VDJ test. Methods: 102 video clips of elite female handball and football players performing a baseline VDJ test were randomly extracted from a 738-person prospective cohort study that tracked ACL injuries. Of the sample, 20 of 102 went on to suffer an ACL injury. These 102 videos were uploaded to an online survey. Sports medicine professionals and coaches were invited to assess athlete performance and rate each clip with a number between 1 and 10 (1 representing low risk of sustaining an ACL injury and 10 representing high risk). Receiver operating characteristic analyses were used to assess classification accuracy and between-group differences were analysed using one-way analysis of variance. Results: 237 assessors completed the survey. Area under the curve values ranged from 0.36 to 0.60, with a mean score of 0.47, which is similar to random guessing. There were no significant differences in classification accuracy between groups (physicians, coaches, certified athletic trainers, researchers or physical therapists). Conclusion: Assessors have poor predictive ability (no better than chance), indicating that visual assessment of a VDJ test is a poor test for assessing ACL injury risk in elite female handball and football players.

• Sandmo, Stian Bahr; Andersen, Thor Einar; Koerte, Inga Katharina & Bahr, Roald (2019). Head impact exposure in youth football-Are current interventions hitting the target? Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 30(1), p. 193–198. doi: 10.1111/sms.13562. Full text in Research Archive Show summary

  Restrictions on heading in youth football have been implemented in some countries to limit head impact exposure. However, current interventions remain poorly guided by evidence. Our objective was to quantify heading exposure in youth football, assessing the effects of sex and age. Football matches played during an international youth football tournament with no heading restrictions were directly observed, including players from both sexes (11‐19 years). The elite senior level was included for comparison, using video analysis. All heading events were registered, classified, and assigned to individual players. Heading rates were calculated for each sex and age group. We observed a total of 267 matches, corresponding to 4011 player hours (1927 player hours for females, 2083 player hours for males). Males headed more frequently than females (2.7 vs 1.8 headers/player hour; P < .001). Heading rates increased with age (ANOVA, P < .001), approaching the elite senior level for players 16 years and older. There was substantial variation within teams for all age and sex groups, with the widest range (1‐18 headers) observed for girls aged 19. Girls younger than 12 years had the lowest exposure, with an average of <2 players per team heading the ball, each with 1‐2 headers. In conclusion, age and sex influence head impact exposure in youth football, and warrants careful consideration when introducing injury prevention measures. Males are more frequently exposed than females, heading rates increase with age, and there is substantial variation between players. Heading is a rare event in the youngest age groups, especially among females.

• Andersson, Stig Haugsbø; Bahr, Roald; Olsen, Magnus Johnsen & Myklebust, Grethe (2019). Attitudes, beliefs, and behavior toward shoulder injury prevention in elite handball: Fertile ground for implementation. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. doi: 10.1111/sms.13522. Full text in Research Archive Show summary

  We aimed to examine attitudes, beliefs, and current behavior toward risk factors and prevention of shoulder injuries, and to investigate the application of an exercise program during a cluster‐randomized controlled trial aiming to prevent shoulder injuries in elite handball. All captains and coaches of 44 elite handball teams (22 male and 22 female) constituting the intervention (21 teams) and control arm (n = 23 teams) in the trial were invited to take part in a survey. A questionnaire, based on the Reach, Efficacy, Adoption, Implementation, and Maintenance framework, addressing the end user perspective on risk factors and prevention of shoulder injuries, as well as key issues related to the application of the Oslo Sports Trauma Research Center (OSTRC) Shoulder Injury Prevention Programme, was distributed using electronic survey software. The response rate was 100%. Overall, the majority of coaches (84%) and captains (89%) believed that handball players are at high risk for shoulder injuries. All delivery agents in the trial reported to be familiar with the exercise program and the majority believed in a preventative effect (coaches 90% and captains 81%). Only a minority reported full compliance with the recommended frequency (coaches 29%, captains 14%), with program being too time‐consuming (coaches 67%, captains 81%) and lack of player motivation (coaches 76%, captains 62%) as the main barriers. Our results suggest that there is fertile ground for implementation of the OSTRC Shoulder Injury Prevention Programme in elite handball, with program length and lack of player motivation as the main barriers to overcome.

• Harøy, Joar; Wiger, Espen Guldahl; Bahr, Roald & Andersen, Thor Einar (2019). Implementation of the Adductor Strengthening Programme: Players primed for adoption but reluctant to maintain ? A cross-sectional study. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 29(8), p. 1092–1100. doi: 10.1111/sms.13444. Full text in Research Archive Show summary

  Groin injuries represent a considerable problem in male football, accounting for 4%‐19% of all time‐loss injuries. The Adductor Strengthening Programme is the first groin‐specific prevention program shown to reduce the risk of groin problems. We aimed to use the RE‐AIM framework to examine the players’ experiences with the implementation of the program and player attitude toward groin injury prevention in football. Of the 632 players involved in the trial examining the effect of the Adductor Strengthening Programme, 501 agreed to participate in a survey at the end of the season. Most players thought that footballers are at moderate to high risk for groin injuries (87%) and that there is a need for preventive measures (96%). They also believed that a preventive program with strengthening exercises would reduce the risk of groin injuries (91%). Majority of the players reported using <5 minutes to complete the program (73%), and only 11% wanted additional exercises. However, only 46% reported to have performed the program as recommended, and an even smaller proportion (31%) planned to continue using it as recommended the next season. Our results suggest that footballers believe that prevention of groin injuries is needed. Attitude toward implementation of the Adductor Strengthening Programme was positive, and the single‐exercise approach was considered an important facilitator. However, in future dissemination of the program, the players’ reluctance to maintain the exercise protocol may be a potential barrier to implementation that should be addressed.

• Moseid, Christine Holm; Myklebust, Grethe; Slåstuen, Marit Kyte; Bar-Yaacov, Jonathan Brun; Kristiansen, Åse & Fagerland, Morten [Show all 7 contributors for this article] (2019). The association between physical fitness level and number and severity of injury and illness in youth elite athletes. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. doi: 10.1111/sms.13498. Show summary

  Youth elite athletes often double their training and competition load after enrollment into specialized sport academy high school programs. The least fit athletes may be exposed to an excessive and too rapid increase in training load, with negative adaptations such as injury and illness as a consequence. In this study, our aim was to determine whether these least fit athletes were at greater risk of injury or illness during their first school year. Participants were 166 youth elite athletes (72% boys) from a variety of team, technical, and endurance sports newly enrolled into specialized sport academy high schools. The Oslo Sports Trauma Research Center Questionnaire on Health Problems was used to self‐report injuries and illnesses weekly for 26 weeks. Athletes completed the Ironman Jr physical fitness test battery at baseline, evaluating endurance, strength, agility, and speed properties. We ranked the athletes based on their combined test scores and identified the least fit quartile. The main outcome was the number and severity of health problems, comparing the least fit quartile of athletes to the rest of the cohort. Overall, the least fit quartile of athletes did not report more health problems (mean 3.7, 95% CI 3.0‐4.4) compared with the rest of the cohort (3.6, 3.2‐3.9). In conclusion, we demonstrated no association between low physical fitness level and number and severity of injury and illness in youth elite athletes after enrollment into a specialized sport academy high school program.

• Rafnsson, ET; Myklebust, Grethe; Bahr, Roald; Valdimarsson, Ö; Frohm, A & Arnason, A (2019). Characteristics of functional movement screening testing in elite handball players: Indicative data from the 9+. Physical Therapy in Sport. ISSN 1466-853X. 37, p. 15–20. doi: 10.1016/j.ptsp.2019.02.001. Full text in Research Archive Show summary

  Objectives: To test 9 + screening batterie's intra-rater reliability, to provide indicative data of elite handball players, and to analyze difference between age, playing positions and level of play. Design: Descriptive study. Setting: Icelandic elite male handball players. Participants: 182 elite male handball players. Main outcome measures: Nine + screening battery. Results: Reliability test: Intra-class correlation for the total score was 0.95. The correlation of each of the test factors varied from 0.63 to 0.91. The mean total score was 22.3 ± 2.9 (95%CI 16.7–28.1), with no difference in total score comparing players age or level of play. Goalkeepers displayed a higher total score than other players (F3,151 = 5.75, p = 0.001). Junior players had a lower score than senior players in tests measuring abdominal strength and core stability; Test 5; │2(3, 182) = 41.5, p < 0.0001, Test 6; │2(3, 182) = 55.7, p < 0.0001, Test 7; │2(3, 182) = 11.8, p < 0.005, but higher scores in tests measuring trunk and shoulder mobility Test 8; │2(3, 182) = 18.2, p < 0.0001, Test 9; │2(3, 182) = 22.2, p = 0.006. Conclusions: The 9+ intra-rater reliability was acceptable for the total score and individual tests. Age-related differences were provided in many individual tests.

• Scott, Alex; LaPrade, Robert F.; Harmon, Kimberly G.; Filardo, Giuseppe; Kon, Elizaveta & Villa, Stefano Della [Show all 12 contributors for this article] (2019). Platelet-Rich Plasma for Patellar Tendinopathy: A Randomized Controlled Trial of Leukocyte-Rich PRP or Leukocyte-Poor PRP Versus Saline. American Journal of Sports Medicine. ISSN 0363-5465. 47(7), p. 1654–1661. doi: 10.1177/0363546519837954. Show summary

  Background: A small number of randomized controlled trials have found ultrasound-guided injection of platelet-rich plasma (PRP) to be no more effective than saline for several tendinopathies; limited information exists for patellar tendinopathy. In addition, different PRP formulations that produce varying concentrations of leukocytes have not been directly compared for patellar tendinopathy. Purpose/Hypothesis: To determine if a single ultrasound-guided PRP injection, either leukocyte-rich PRP (LR-PRP) or leukocyte-poor PRP (LP-PRP), was superior to saline injection for the treatment of patellar tendinopathy. The null hypothesis was that no treatment would be superior to another for the treatment of patellar tendinopathy. Study Design: Randomized controlled trial; Level of evidence, 1. Methods: Athletes with patellar tendinopathy for ≥6 months (Blazina stage IIIB) were assessed for eligibility in a multisite single-blind controlled trial. There were 3 injection arms: LR-PRP, LP-PRP, and saline. Patients received a single ultrasound-guided injection, followed by 6 weeks of supervised rehabilitation (heavy slow resistance training, concentric and eccentric, 3 times per week). Outcome measures—Victorian Institute of Sport Assessment (patellar; VISA-P), pain during activity, and global rating of change—were assessed at 6 and 12 weeks and 6 and 12 months. VISA-P score at 12 weeks was the primary outcome. Fifty-seven patients (19 in each group) were included in an intention-to-treat analysis. Secondary outcome measures included pain during activity and patients’ global rating of change. Results: Study retention was 93% at 12 weeks and 79% after 1 year. There was no significant difference in mean change in VISA-P score, pain, or global rating of change among the 3 treatment groups at 12 weeks or any other time point. After 1 year, the mean (SD) outcomes for the LR-PRP, LP-PRP, and saline groups were as follows, respectively: VISA-P—58 (29), 71 (20), and 80 (18); pain—4.0 (2.4), 2.4 (2.3), and 2.0 (1.9); global rating of change—4.7 (1.6), 5.6 (1.0), and 5.7 (1.2) (P > .05 for all outcomes). Conclusion: Combined with an exercise-based rehabilitation program, a single injection of LR-PRP or LP-PRP was no more effective than saline for the improvement of patellar tendinopathy symptoms.

• Wik, Eirik Halvorsen; Materne, Olivier; Chamari, Karim; Duque, Juan David Peña; Horobeanu, Cosmin & Salcinovic, Benjamin [Show all 8 contributors for this article] (2019). Involving research‐invested clinicians in data collection affects injury incidence in youth football. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 29(7), p. 1031–1039. doi: 10.1111/sms.13427. Full text in Research Archive Show summary

  It is well established that differences in injury definition and recording methodology restrict comparisons between injury surveillance programmes. There is, however, little documentation of the variation that can exist between data recorders. The aim of this study was, therefore, to explore the effect on reported injuries when team recorders or supervisors are involved in research. Injury data collected prospectively over five seasons for the U16, U17, and U18 age groups in a youth football (soccer) academy were used to compare different recording settings based on the research involvement of the clinicians. A research‐invested team physiotherapist reported an 8.8 times greater incidence (P < 0.001) of non‐time‐loss injuries and a 2.5 times greater incidence (P < 0.001) of minimal injuries (1‐3 days lost) compared to a setting where neither the team physiotherapists nor the supervisor relied on the collected data for research purposes. When team physiotherapists were not invested in research themselves but were supervised by a researcher, the incidence of non‐time‐loss injuries and minimal injuries was 2.5 times (P < 0.001) and 2.0 times greater (P < 0.01) than in the non‐invested setting, respectively. However, there were no differences between recording settings for overall incidence of time‐loss injuries. The results from this study demonstrate that involving clinicians that are relying on the collected data for research purposes can significantly affect the reported rates of non‐time‐loss and minimal injuries. Time‐loss injuries overall were not affected by research investment, and should therefore be preferred for comparisons between teams and seasons.

• Sandmo, Stian Bahr; McIntosh, Andrew S.; Andersen, Thor Einar; Koerte, Inga & Bahr, Roald (2019). Evaluation of an In-Ear Sensor for Quantifying Head Impacts in Youth Soccer. American Journal of Sports Medicine. ISSN 0363-5465. 47(4), p. 974–981. doi: 10.1177/0363546519826953. Full text in Research Archive Show summary

  Background: Wearable sensor systems have the potential to quantify head kinematic responses of head impacts in soccer. However, on-field use of sensors (eg, accelerometers) remains challenging, owing to poor coupling to the head and difficulties discriminating low-severity direct head impacts from inertial loading of the head from human movements, such as jumping and landing. Purpose: To test the validity of an in-ear sensor for quantifying head impacts in youth soccer. Study Design: Descriptive laboratory study. Methods: First, the sensor was mounted to a Hybrid III headform and impacted with a linear impactor or a soccer ball. Peak linear acceleration (PLA), peak rotational acceleration (PRA), and peak rotational velocity (PRV) were obtained from both systems; random and systematic errors were calculated with Hybrid III as reference. Then, 6 youth soccer players wore sensors and performed a structured training protocol, including heading and nonheading exercises; they also completed 2 regular soccer sessions. For each accelerative event recorded, PLA, PRA, and PRV outputs were compared with video recordings. Receiver operating characteristic curves were used to determine the sensor’s discriminatory capacity in both on-field settings, establishing cutoff values for predicting outcomes. Results: For the laboratory tests, the random error was 11% for PLA, 20% for PRA, and 5% for PRV; the systematic error was 11%, 19%, and 5%, respectively. For the structured training protocol, heading events resulted in higher absolute values (PLA = 15.6g 6 11.8g) than nonheading events (PLA = 4.6g 6 1.2g); the area under the curve was 0.98 for PLA. In regular training sessions, the area under the curve was .0.99 for PLA. A 9g cutoff value yielded a positive predictive value of 100% in the structured training protocol versus 65% in the regular soccer sessions. Conclusion: The in-ear sensor displayed considerable random error and substantially overestimated head impact exposure. Despite the sensor’s excellent on-field accuracy for discriminating headings from other accelerative events in youth soccer, absolute values must be interpreted with caution, and there is a need for secondary means of verification (eg, video analysis) in real-life settings.

• van Dyk, Nicol; Wangensteen, Arnlaug; Vermeulen, Robin; Whiteley, Rod; Bahr, Roald & Tol, Johannes [Show all 7 contributors for this article] (2019). Similar Isokinetic Strength Preinjury and at Return to Sport after Hamstring Injury. Medicine & Science in Sports & Exercise. ISSN 0195-9131. 51(6), p. 1091–1098. doi: 10.1249/MSS.0000000000001900. Show summary

  Introduction: Side-to-side strength differences are often used in return to sport (RTS) decision making following hamstring injury. In football (soccer), there is little consensus, and a side-toside difference of <10% is often suggested as a criterion. To date, no study has determined whether differences exist when comparing the strength of the injured limb at RTS to the preinjury level. Purpose: The aim of this study was to compare the isokinetic strength at RTS to preinjury strength in the injured limb, and to investigate the side-to-side differences at RTS. Methods: This study was based on a pooled group of patients participating in two single-site randomized controlled trials. All eligible professional male soccer players who suffered an MRIpositive hamstring injury were included. The isokinetic strength of the injured limb at RTS was compared to pre-injury screening tests, and the side-to-side difference was determined at both time points. Results: In total, 41 hamstring injuries were included in the analyses. Side-to-side differences in isokinetic strength at RTS were similar to pre-injury levels. At RTS, the average strength of the injured limb was >95% compared to pre-injury strength. Overall, 63.4% of the players had a >10% negative strength difference (i.e. the injured limb being weaker) and 57.9% of the players had a >10% positive strength difference (i.e. the injured limb being stronger) in at least one of the five isokinetic variables. Conclusion: The distribution of isokinetic strength differences when comparing strength at RTS to pre-injury measures were similar, urging clinical caution when interpreting these results. Small changes in isokinetic strength of the injured limb at RTS compared to pre-injury strength suggest that isokinetic cut-off values are not useful to guide restoration of strength as a criterion for RTS after hamstring injury.

• Sivertsen, Einar; Foss, Kari Bente; Kristianslund, Eirik; Siebke, Anne-Marie; Parkkari, Jari & Lehtimäki, Terho [Show all 9 contributors for this article] (2019). No Association Between Risk of Anterior Cruciate Ligament Rupture and Selected Candidate Collagen Gene Variants in Female Elite Athletes From High-Risk Team Sports. American Journal of Sports Medicine. ISSN 0363-5465. 47(1), p. 52–58. doi: 10.1177/0363546518808467. Full text in Research Archive
• Foss, Kari Bente; Visnes, Håvard; Sivertsen, Einar & Bahr, Roald (2018). Genetic variation in candidate genes and patellar tendinopathy: Prospective cohort study of 126 elite volleyball players. Translational Sports Medicine (TSM). ISSN 2573-8488. 1(2), p. 73–78. doi: 10.1002/tsm2.13. Full text in Research Archive Show summary

  Variation in genes coding for structural proteins may represent risk factors for developing tendinopathy among athletes. The purpose of this prospective cohort study of elite volleyball students was to investigate whether specific single nucleotide variants (SNVs) in selected candidate genes, known to be associated with Achilles tendinopathy, were associated with the risk for developing patellar tendinopathy (jumper′s knee). Of 126 Caucasian athletes (64 females and 62 males), 33 cases (athletes developing jumper′s knee) were compared to 93 healthy controls. Six SNVs, distributed in the candidate genes COL1A1, COL5A1, MMP3, and GDF3, were genotyped. Baseline characteristics, genotypes, and minor allele frequencies (MAF) were compared between groups. Neither genotype nor minor allele frequencies differed significantly between the jumper′s knee group and the healthy controls. However, the low‐frequency homozygous T/T genotype of the COL1A1 gene (rs1800012) was absent in the jumper′s knee group (P = .075). Separating the two study groups by gender suggested that there may be a female‐specific genotype pattern, although the sample was too small for statistical calculations. In this study, although limited by sample size, we could not detect any clear relationship between six selected SNVs located in candidate genes and the risk for the development of jumper′s knee in elite volleyball students.

• Dyk, Nicole van; McCunn, Robert; Coles, Phil & Bahr, Roald (2018). Musculoskeletal screening in football. In McCall, Alan; Andersen, Thor Einar; Clarsen, Benjamin & Pruna, Ricard (Ed.), Muscle injury guide: Prevention of and Return to Play from Muscle Injuries. Barca innovation hub. p. 34–36.
• Rekik, Raouf Nader; Tabben, Montassar; Eirale, Christiano; Landreau, Philippe; Bouras, Rachid & Wilson, Mathew G [Show all 9 contributors for this article] (2018). ACL injury incidence, severity and patterns in professional male soccer players in a Middle Eastern league. BMJ Open sport & exercise medicine. ISSN 2055-7647. 4(1), p. 1–5. doi: 10.1136/bmjsem-2018-000461. Full text in Research Archive Show summary

  Aim: To ascertain ACL injury incidence, severity (injury burden) and patterns (contact/non-contact and reinjuries) in a professional male football league in the Middle East over five consecutive seasons. Methods: Prospective epidemiological study reporting ACL injuries in professional male soccer players in the Qatar Stars League, with complete matches/training exposure over five seasons (2013–2014 to 2017–2018), corresponding to 2243 player seasons and 729 team months. Results: 37 complete ACL ruptures occurred in 37 players during 486 951  hours of player exposure. The overall ACL injury rate was 0.076 injuries/1000  hours of exposure (season range 0.045–0.098). Injury incidence during matches and training was 0.41 and 0.04 injuries/1000  hours of exposure, respectively. Match injury incidence was greater than that of training (OR 11.8, 95%  CI 6.21 to 23.23, p<0.001). Average injury-related time-loss following ACL injury was 225 days±65 (range 116–360). Overall injury burden was 16.3 days lost/1000  hours of exposure. Conclusion: The overall ACL injury rate in professional male soccer players competing in the Middle East was 0.076 injuries/1000  hours of exposure, match injury incidence was greater than training, while the average ACL time-loss was 225 days.

• Serner, Andreas; Mosler, Andrea Britt; Tol, Johannes L.; Bahr, Roald & Weir, Adam (2018). Infographic. Mechanisms of acute adductor longus injuries in male football players. British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2018-099872.
• Moseid, Christine Holm; Myklebust, Grethe; Fagerland, Morten & Bahr, Roald (2018). The Association between Early Specialization and Performance Level with Injury and Illness Risk in Youth Elite Athletes. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 29(3), p. 460–468. doi: 10.1111/sms.13338. Full text in Research Archive Show summary

  A trend is observed towards more specialized training and selection into talent programs at an early age for youth athletes. Little is known how this might influence the risk of illness and injury. The aim of the study was to assess whether, in a group of youth elite athletes, those specializing early or performing best were at increased risk of incurring injury or illness after entering a specialized Sport Academy High School program. We enrolled 259 16‐year old elite athletes. They completed a baseline web‐based questionnaire covering their age at specialization, single‐ versus multi‐sport involvement during the previous 2 years and current performance level (rated by themselves and their coach). Subsequently, the Oslo Sports Trauma Research Centre (OSTRC) questionnaire on health problems was used to self‐report injuries and illnesses weekly for 26 weeks from October to May. In this specialized Sport Academy High School program, 39% of the athletes reported early specialization (at 12 years or younger). However, early specialization did not increase the risk of injury or illness during the 26 weeks, nor did being a single‐sport athlete the previous two years increase this risk. The best performing athletes at the time of enrollment were not at greater risk of becoming injured or ill during the 26 weeks. In conclusion, in a group of youth elite athletes entering a specialized Sport Academy High School program neither early single‐sport specialization nor performance level appears to represent risk factors for injury or illness after enrollment.

• Berge, Hilde Moseby; Andersen, Thor Einar & Bahr, Roald (2018). Cardiovascular incidents in male professional football players with negative preparticipation cardiac screening results: an 8-year follow-up. British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2018-099845. Show summary

  Background: Preparticipation cardiac screening of athletes aims to detect cardiovascular disease at an early stage to prevent sudden cardiac arrests and deaths. Few studies have described the cardiovascular outcomes in athletes classified as negative on screening. Objective: To identify cardiovascular incidents in a cohort of male professional football players who were cleared to play after a negative screening result. Methods: This is a retrospective 8-year follow-up study of 595 professional male football players in Norway who underwent preparticipation cardiac screening by experienced cardiologists, including electrocardiography (ECG) and echocardiography, in 2008. We performed a media search to identify sudden cardiovascular incidents between January 2008 and February 2016. Incidents were cross-checked with medical records. Results: Six of the 595 players (1%), all classified as negative on cardiac screening, experienced severe cardiovascular incidents during follow-up. Retrospective review revealed abnormal ECG findings in one case, not recognised at the time of screening. Three players suffered a sudden cardiac arrest (all resuscitated successfully), one a myocardial infarction, one a transient ischaemic attack and one atrial flutter. Three of the players ignored chest pain, paresis, dyspnoea or near-syncope, two completed a match with symptoms before seeking medical assistance, one player’s symptoms were misinterpreted and received inappropriate treatment initially, and two players were discharged from hospital without proper follow-up, despite having serious cardiovascular symptoms. Conclusions: A comprehensive preparticipation cardiac screening did not identify a subset of 6 of 595 players who experienced subsequent cardiovascular incidents as being at risk. It is important to remind athletes that a normal cardiac screening exam does not protect against all cardiac diseases. Timely reporting of symptoms is essential.

• Sivertsen, Einar Andreas; Haug, Kari Bente Foss; Kristianslund, Eirik Klami; Trøseid, Anne-Marie Siebke; Parkkari, Jari & Lehtimäki, Terho [Show all 9 contributors for this article] (2018). Ingen assosiasjon mellom fremre korsbåndsruptur og utvalgte kollagen genvarianter hos kvinnelige toppidrettsutøvere, Høstmøteboken 2018 - Vitenskapelig program og abstrakter. Norsk ortopedisk forening.
• Serner, Andreas; Mosler, Andrea Britt; Tol, Johannes L.; Bahr, Roald & Weir, Adam (2018). Mechanisms of acute adductor longus injuries in male football players: A systematic visual video analysis. British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2018-099246. Full text in Research Archive Show summary

  Background: Change of direction and kicking have been described as the main actions resulting in adductor longus injury. Video descriptions of inciting events are lacking. Objective: Perform a standardised visual video analysis of a series of acute adductor longus injuries in football. Study design: Cross-sectional. Methods: Video footage was reviewed by players, and assessed independently by five sports medicine professionals. Inciting events were described and categorised using standardised scoring, including playing situation, player/opponent behaviour, movement and body positions. Results: Videos of acute adductor longus injuries in 17 professional male football players were analysed. Most injuries occurred in non-contact situations (71%), following a quick reaction to a change in play (53%). Injury actions were: change of direction (35%), kicking (29%), reaching (24%) and jumping (12%). Change of direction and reaching injuries were categorised as closed chain movements (59%), characterised by hip extension and abduction with external rotation. Kicking and jumping injuries were categorised as open chain (41%), characterised by a change from hip extension to hip flexion, and hip abduction to adduction, with external rotation. Conclusion: Acute adductor longus injuries in football occur in a variety of situations. Player actions can be categorised into closed (change of direction and reaching) and open (kicking and jumping) chain movements involving triplanar hip motion. A rapid muscle activation during a rapid muscle lengthening appears to be the fundamental injury mechanism for acute adductor longus injuries.

• Tabben, Montassar; Landreau, Philippe; Chamari, Karim; Juin, Gerard; Ahmed, Hosny & Farooq, Abdulaziz [Show all 8 contributors for this article] (2018). Age, player position and 2 min suspensions were associated with match injuries during the 2017 Men's Handball World Championship (France). British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2018-099350. Full text in Research Archive Show summary

  Aim: To study the association between player characteristics, technical components of the game and the risk of match injuries during the 2017 Men’s Handball World Championship. Methods: Team physicians of the participating teams (n=24) were requested to provide injury report forms throughout the Men’s Handball World Championship (France, January 2017). The individual time played, age, number of international matches played and all technical and penalty variables for each player were extracted from the official International Handball Federation (IHF) online database and used as risk factors in a general logistic linear model analysis. Results: Of 387 players, 49 sustained one or more injuries (93 injuries in total). The total incidence of match injuries was 82.1 injuries per 1000 hours (95% CI 66.2 to 100.5), non-time-loss injury incidence was 40.6 injuries per 1000 hours (95% CI 29.3 to 54.9), while time-loss injury incidence was 30.9 injuries per 1000 hours (95% CI 21.5 to 42.9). Multivariate analysis showed that age (OR 1.1, 95% CI 1.02 to 1.18, p=0.011), player position (backs: OR 6.79, 95% CI 2.25 to 20.54, p=0.001; goalkeepers: OR 5.03, 95% CI 1.15 to 21.94, p=0.031) and 2 min suspensions (1–2 times: OR 2.77, 95% CI 1.27 to 6.04, p=0.011; 3 or more times: OR 2.66, 95% CI 1.18 to 6.38, p=0.029) were significant risk factors for getting injured during competition matches. Conclusion: Age, player position (backs, goalkeepers) and 2 min suspensions were associated with match injury. Stricter rule enforcement should be considered to prevent match injuries in elite handball.

• Leppänen, Mari; Pasanen, Kati; Clarsen, Benjamin; Kannus, Pekka; Bahr, Roald & Parkkari, Jari [Show all 8 contributors for this article] (2018). Overuse injuries are prevalent in children’s competitive football: a prospective study using the OSTRC Overuse Injury Questionnaire. British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2018-099218. Show summary

  Objectives: To investigate the prevalence and burden of overuse injuries in children’s football as well as player characteristics and their association with overuse injury risk. Methods: This investigation is based on the control arm (10 clubs) of a randomised controlled trial investigating prevention of injuries in youth football. We conducted a prospective 20-week follow-up study on overuse injuries among Finnish football players (n=733, aged 9–14 years). Each week, we sent a text message to players’ parents to ask if the player had sustained any injury during the past week. Players with overuse problem were interviewed over the phone using an overuse injury questionnaire. The main outcome measures were prevalence of all overuse injuries and substantial overuse injuries (those leading to moderate or severe reductions in participation or performance) and injury severity. Results: The average response rate was 95%. In total, 343 players (46.8%) reported an overuse problem while in the study. The average weekly prevalence of all overuse problems and substantial overuse problems was 12.8% and 6.0%, respectively. Injuries affecting the knee had the highest weekly prevalence (5.7% and 2.4% for all and substantial knee problems, respectively). Girls had a higher likelihood of knee problems (OR 2.70; 95% CI 1.69 to 4.17), whereas boys had a higher likelihood of heel problems (OR 2.82; 95% CI 1.07 to 7.44). The likelihood of reporting an overuse problem increased with age (OR 1.21; 95% CI 1.00 to 1.47). Conclusion: Overuse injuries are prevalent in children’s competitive football. Knee overuse injuries represent the greatest burden on participation and performance.

• Guermazi, Ali; Hayashi, Daichi; Jarraya, Mohamed; Crema, Michel D.; Bahr, Roald & Roemer, Frank W. [Show all 12 contributors for this article] (2018). Sports Injuries at the Rio de Janeiro 2016 Summer Olympics: Use of Diagnostic Imaging Services. Radiology. ISSN 0033-8419. 287(3), p. 922–932. doi: 10.1148/radiol.2018171510. Full text in Research Archive Show summary

  Purpose: To describe the occurrence of imaging-depicted sports-related stress injuries, fractures, and muscle and tendon disorders during the 2016 Summer Olympic Games in Rio de Janeiro, Brazil. Materials and Methods: Data on radiologic examinations were collected and retrospectively analyzed centrally by two board-certified musculoskeletal radiologists (with a third musculoskeletal radiologist acting as an adjudicator in case of discrepancies). Descriptive data on all imaging examinations by using radiography, ultrasonography (US), and magnetic resonance (MR) imaging were collected and analyzed according to imaging modality, country of origin of the athletes, type of sport, and type and location of injury. Results: There were 1101 injuries that occurred in 11 274 (9.8%) athletes. A total of 1015 radiologic examinations were performed, including 304 (30.0%) radiographic, 104 (10.2%) US, and 607 (59.8%) MR examinations. Excluding 10 athletes categorized as refugees, athletes from Africa had the highest utilization rate (14.8%, 148 of 1001). Athletes from Europe underwent the most examinations with 103 radiographic, 39 US, and 254 MR examinations. Gymnastics (artistic) had the highest percentage of athletes who underwent imaging (15.5%, 30 of 194). Athletics (track and field) had the most examinations (293, including 53 radiographic, 50 US, and 190 MR examinations). Conclusion: The overall occurrence of imaging used to help diagnose sports-related injuries at the Rio de Janeiro 2016 Summer Olympics was 6.4% of athletes. In these cases, MR imaging comprised 60% of imaging utilization.

• Wangensteen, Arnlaug; Guermazi, Ali; Tol, Johannes L.; Roemer, Frank W.; Hamilton, Bruce & Alonso, Juan-Manuel [Show all 8 contributors for this article] (2018). New MRI muscle classification systems and associations with return to sport after acute hamstring injuries: a prospective study. European Radiology. ISSN 0938-7994. 28(8), p. 3532–3541. doi: 10.1007/s00330-017-5125-0. Show summary

  Objectives: To determine agreement between modified Peetrons, Chan acute muscle strain injury classification and British Athletics Muscle Injury Classification (BAMIC) and to investigate their associations and ability to predict time to return to sport (RTS). Methods: Male athletes (n=176) with acute hamstring injury and MRI (1.5T) ≤5 days were followed until RTS. MRIs were scored using standardised forms. Results: For MRI-positive injuries there was moderate agreement in severity grading (κ = 0.50–0.56). Substantial variance in RTS was demonstrated within and between MRI categories. Mean differences showed an overall main effect for severity grading (p < 0.001), but post hoc pairwise comparisons for BAMIC (grade 0a/b vs. 1, p = 0.312; 1 vs 2, p = 0.054; 0a/b vs 2, p < 0.001; 1 vs 3, p < 0.001) and mean differences for anatomical sites (BAMIC a–c, p < 0.001 [a vs b, p = 0.974; a vs c, p = 0.065; b vs c, p = 0.007]; Chan anatomical sites 1–5, p < 0.077; 2A–C, p = 0.373; 2a–e, p = 0.008; combined BAMIC, p < 0.001) varied. For MRI-positive injuries, total explained RTS variance was 7.6–11.9% for severity grading and BAMIC anatomical sites. Conclusions: There was wide overlap between/variation within the grading/classification categories. Therefore, none of the classification systems could be used to predict RTS in our sample of MRI-positive hamstring injuries.

• Harøy, Joar; Clarsen, Benjamin; Wiger, Espen Guldahl; Øyen, Mari Glomnes; Serner, Andreas & Thorborg, Kristian [Show all 9 contributors for this article] (2018). The Adductor Strengthening Programme prevents groin problems among male football players: a cluster-randomised controlled trial. British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2017-098937. Show summary

  Background: Groin injuries represent a considerable problem in male football. Previous groin-specific prevention programmes have not shown a significant reduction in groin injury rates. An exercise programme using the Copenhagen Adduction exercise increases hip adduction strength, a key risk factor for groin injuries. However, its preventive effect is yet to be tested. Aim: To evaluate the effect of a single-exercise approach, based on the Copenhagen Adduction exercise, on the prevalence of groin problems in male football players. Methods: 35 semiprofessional Norwegian football teams were cluster-randomised into an intervention group (18 teams, 339 players) and a control group (17 teams, 313 players). The intervention group performed an Adductor Strengthening Programme using one exercise, with three progression levels, three times per week during the preseason (6–8 weeks), and once per week during the competitive season (28 weeks). The control group were instructed to train as normal. The prevalence of groin problems was measured weekly in both groups during the competitive season using the Oslo Sports Trauma Research Center Overuse Injury Questionnaire. Results: The average prevalence of groin problems during the season was 13.5% (95% CI 12.3% to 14.7%) in the intervention group and 21.3% (95% CI 20.0% to 22.6%) in the control group. The risk of reporting groin problems was 41% lower in the intervention group (OR 0.59, 95% CI 0.40 to 0.86, p=0.008). Conclusion: The simple Adductor Strengthening Programme substantially reduced the self-reported prevalence and risk of groin problems in male football players.

• Skazalski, Christopher Mitchell; Whiteley, Rod & Bahr, Roald (2018). High jump demands in professional volleyball – large variability exists between players and player positions. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 28(11), p. 2293–2298. doi: 10.1111/sms.13255. Full text in Research Archive Show summary

  Purpose: Training volume has been associated with jumper's knee in volleyball players, but jump variability among professionals has not been investigated and individual jump demands are unknown. The purpose of this study was to examine position‐specific jump demands required for training and competition during a professional volleyball season and to investigate the individual variability associated with jump load. Methods: Jumps performed by 14 professional players during one season of training and competition were timestamped, individually assigned, and recorded for jump height. Jump counts, heights, and frequency were analyzed to determine the specific jump load performed by players at each position during training and match play. Results: A total of 129,173 jumps were performed during 142 sessions (108 practices, 27 matches, 7 friendly matches). Setters performed the greatest volume of jumps (121 jumps/training session). Opposites performed more high intensity jumps than their teammates (median season jump height: 69% of maximum). Substantial weekly jump count variability was observed, 18 of 28 weeks included at least one player with a 2‐fold increase in jump load or a player returning to volleyball after performing no jumps the previous week. Additionally, each player had at least one week with a 2‐fold increase in jumps. Conclusion: Jump demands are high in professional volleyball and performance programs should be tailored to the match and training demands required at each position. Jump loads are highly variable – substantial week‐to‐week increases were observed for both the team and individual players. As a result, monitoring individual jump load seems necessary.

• Andersson, Stig Haugsbø; Cardinale, Marco; Whiteley, Rod; Popovic, Nebojsa; Hansen, Clint & Lopez, Fernando Sanz [Show all 9 contributors for this article] (2018). Video analysis of acute injuries and referee decisions during the 24th Men's Handball World Championship 2015 in Qatar. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 28(7), p. 1837–1846. doi: 10.1111/sms.13090. Show summary

  Although handball is a contact sport with a high risk of acute match injuries, their mechanisms have not yet been investigated. We aimed to describe the mechanisms of acute match injuries in elite male handball and evaluate referee performance in injury situations. Based on injury surveillance from the 24th Men′s Handball World Championship 2015 in Qatar, injury situations and the referee decisions were identified on video footage. A total of 55 injury situations and 37 referee decisions were included for analysis. The injury situations were analyzed individually by five handball experts, followed by a consensus meeting. An expert referee panel performed individual blinded evaluation of the referee decisions, followed by an online consensus meeting. Injuries were evenly distributed among attackers (n = 29) and defenders (n = 26). The most frequent injury cause was contact trauma due to a tackle (n = 27). At the time of injury, attackers were most frequently performing a jump shot (n = 9), while defenders were completing a tackle (n = 10). Defenders most commonly tackled the throwing arm (n = 7) or toward the head/face region (n = 6) of injured attackers, while attackers most frequently hit injured defenders with the knee during jump shots (n = 5). Agreement between the referees and the expert panel was weak (kappa: 0.22, 95% CI 0.07 to 0.36), with substantially more lenient rule interpretation by the referees. Our results suggest that stricter refereeing and rule amendments should be considered to prevent acute match injuries in elite handball, especially in relation to tackling episodes when an attacker is performing a jump shot.

• van Dyk, Nicol; Bahr, Roald; Burnett, Angus F.; Verhagen, Evert; von Tiggelen, Damien & Witvrouw, Erik (2018). No association between rate of torque development and onset of muscle activity with increased risk of hamstring injury in elite football. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 28(10), p. 2153–2163. doi: 10.1111/sms.13224. Full text in Research Archive Show summary

  Introduction: Hamstring injuries remain a significant burden in sports that involve high speed running. In elite male football, hamstring injury has repeatedly been identified as the most common noncontact injury, representing 12% of all injuries. As the incidence remains high, investigations are aimed at better understanding how to improve prevention efforts. Intrinsic risk factors such as strength have been investigated extensively in a cohort of professional football players; however, other intrinsic measures of neuromuscular function have not been studied in this cohort. This study aims to investigate the association between timing of hamstring muscle activity onset and the rate of torque development during the early phase of isokinetic strength testing with risk of hamstring injury in professional football players in a prospective cohort study. Methods: All teams (n=18) eligible to compete in the premier football league in Qatar underwent a comprehensive strength assessment during their annual periodic health evaluation at Aspetar Orthopaedic and Sports Medicine Hospital in Doha, Qatar. Variables included rate of torque development and timing of muscle activity onset. Results: A total of 367 unique players (60.6% of all QSL players) competed for 514 player seasons (103 players competed both seasons) and sustained 65 hamstring injuries. There was no difference in the onset of muscle activity between the biceps femoris and medial hamstrings comparing the injured to uninjured players. For both onset of muscle activity and rate of torque development, there were no significant differences between any of the variables (p>0.05), with small effect sizes detected across all the different variables (d<0.3). Conclusion: Rate of torque development and onset of muscle activity were not associated with a risk of future hamstring injury. The use of these measures as part of a periodic health evaluation to identify risk of hamstring injury is unsupported.

• van Dyk, Nicol; Farooq, Abdulaziz; Bahr, Roald & Witvrouw, Erik (2018). Hamstring and Ankle Flexibility Deficits Are Weak Risk Factors for Hamstring Injury in Professional Soccer Players: A Prospective Cohort Study of 438 Players Including 78 Injuries. American Journal of Sports Medicine. ISSN 0363-5465. 46(9), p. 2203–2210. doi: 10.1177/0363546518773057. Full text in Research Archive Show summary

  Background: Hamstring injuries remain a significant injury burden in sports such as soccer that involve high-speed running. It has repeatedly been identified as the most common noncontact injury in elite male soccer, representing 12% of all injuries. As the incidence of hamstring injuries remains high, investigations are aimed at better understanding how to prevent hamstring injuries. Stretching to improve flexibility is commonly used in elite-level sports, but risk factor studies have reported contradicting results, leading to unclear conclusions regarding flexibility as a risk factor for hamstring injuries. Purpose: To investigate the association of lower limb flexibility with the risk of hamstring injuries in professional soccer players. Study Design: Cohort study; Level of evidence, 2. Methods: All teams (n = 18) eligible to compete in the premier soccer league in Qatar (Qatar Stars League [QSL]) underwent a comprehensive musculoskeletal assessment during their annual periodic health evaluation at Aspetar Orthopaedic and Sports Medicine Hospital in Doha, Qatar. Variables included passive knee extension and ankle dorsiflexion range of motion. A clustered multivariate Cox regression analysis was used to identify associations with the risk of hamstring injuries. Receiver operating characteristic (ROC) curves were calculated to determine sensitivity and specificity. Results: A total of 438 unique players (72.4% of all QSL players) competed for 601 player-seasons (148 players competed both seasons) and sustained 78 hamstring injuries. Passive knee extension range of motion (hazard ratio [HR], 0.97 [95% CI, 0.95-0.99]; P = .008) and ankle dorsiflexion range of motion (HR, 0.93 [95% CI, 0.88-0.99]; P = .02) were independently associated with the injury risk. The absolute differences between the injured and uninjured players were 1.8° and 1.4 cm, respectively, with small effect sizes (d < 0.2). The ROC curve analyses showed an area under the curve of 0.52 for passive knee extension and 0.61 for ankle dorsiflexion, indicating failed to poor combined sensitivity and specificity of the 2 strength variables identified in the multivariate Cox regression analysis. Conclusion: This study identified deficits in passive hamstring and ankle dorsiflexion range of motion as weak risk factors for a hamstring injury. These findings have little clinical value in predicting the risk of future hamstring injuries, and test results must therefore be interpreted cautiously in athletic screening.

• van Dyk, Nicol; Witvrouw, Erik & Bahr, Roald (2018). Interseason variability in isokinetic strength and poor correlation with Nordic hamstring eccentric strength in football players. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 28(8), p. 1878–1887. doi: 10.1111/sms.13201. Full text in Research Archive Show summary

  In elite sport, the use of strength testing to establish muscle function and performance is common. Traditionally, isokinetic strength tests have been used, measuring torque during concentric and eccentric muscle action. A device that measures eccentric hamstring muscle strength while performing the Nordic hamstring exercise is now also frequently used. The study aimed to investigate the variability of isokinetic muscle strength over time, for example, between seasons, and the relationship between isokinetic testing and the new Nordic hamstring exercise device. All teams (n = 18) eligible to compete in the premier football league in Qatar underwent a comprehensive strength assessment during their periodic health evaluation at Aspetar Orthopaedic and Sports Medicine Hospital in Qatar. Isokinetic strength was investigated for measurement error, and correlated to Nordic hamstring exercise strength. Of the 529 players included, 288 players had repeated tests with 1/2 seasons between test occasions. Variability (measurement error) between test occasions was substantial, as demonstrated by the measurement error (approximately 25 Nm, 15%), whether separated by 1 or 2 seasons. Considering hamstring injuries, the same pattern was observed among injured (n = 60) and uninjured (n = 228) players. A poor correlation (r = .35) was observed between peak isokinetic hamstring eccentric torque and Nordic hamstring exercise peak force. The strength imbalance between limbs calculated for both test modes was not correlated (r = .037). There is substantial intraindividual variability in all isokinetic test measures, whether separated by 1 or 2 seasons, irrespective of injury. Also, eccentric hamstring strength and limb‐to‐limb imbalance were poorly correlated between the isokinetic and Nordic hamstring exercise tests.

• Bakken, Arnhild; Targett, Stephen; Bere, Tone Tufte; Eirale, Cristiano; Farooq, Abdulaziz & Mosler, Andrea [Show all 10 contributors for this article] (2018). Muscle Strength Is a Poor Screening Test for Predicting Lower Extremity Injuries in Professional Male Soccer Players: A 2-Year Prospective Cohort Study. American Journal of Sports Medicine. ISSN 0363-5465. 46(6), p. 1481–1491. doi: 10.1177/0363546518756028. Show summary

  Background: Lower extremity muscle strength tests are commonly used to screen for injury risk in professional soccer. However, there is limited evidence on the ability of such tests in predicting future injuries. Purpose: To examine the association between hip and thigh muscle strength and the risk of lower extremity injuries in professional male soccer players. Study Design: Case-control study; Level of evidence, 3. Methods: Professional male soccer players from 14 teams in Qatar underwent a comprehensive strength assessment at the beginning of the 2013/2014 and 2014/2015 seasons. Testing consisted of concentric and eccentric quadriceps and hamstring isokinetic peak torques, eccentric hip adduction and abduction forces, and bilateral isometric adductor force (squeeze test at 45°). Time-loss injuries and exposure in training and matches were registered prospectively by club medical staff throughout each season. Univariate and multivariate Cox regression analyses were used to calculate hazard ratios (HRs) with 95% CIs. Results: In total, 369 players completed all strength tests and had registered injury and exposure data. Of these, 206 players (55.8%) suffered 538 lower extremity injuries during the 2 seasons; acute muscle injuries were the most frequent. Of the 20 strength measures examined, greater quadriceps concentric peak torque at 300 deg/s (HR, 1.005 [95% CI, 1.00-1.01]; P = .037) was the only strength measure identified as significantly associated with a risk of lower extremity injuries in multivariate analysis. Greater quadriceps concentric peak torque at 60 deg/s (HR, 1.004 [95% CI, 1.00-1.01]; P = .026) was associated with the risk of overuse injuries, and greater bilateral adductor strength adjusted for body weight (HR, 0.75 [95% CI, 0.57-0.97; P = .032) was associated with a lower risk for any knee injury. Receiver operating characteristic curve analyses indicated poor predictive ability of the significant strength variables (area under the curve, 0.45-0.56). Conclusion: There was a weak association with the risk of lower extremity injuries for 2 strength variables: greater quadriceps concentric muscle strength at (1) high and (2) low speeds. These associations were too small to identify an “at-risk” player. Therefore, strength testing, as performed in the present study, cannot be recommended as a screening test to predict injuries in professional male soccer.

• Mosler, Andrea Britt; Weir, Adam; Serner, Andreas; Agricola, Rintje; Eirale, Cristiano & Farooq, Abdulaziz [Show all 12 contributors for this article] (2018). Musculoskeletal Screening Tests and Bony Hip Morphology Cannot Identify Male Professional Soccer Players at Risk of Groin Injuries: A 2-Year Prospective Cohort Study. American Journal of Sports Medicine. ISSN 0363-5465. 46(6), p. 1294–1305. doi: 10.1177/0363546518763373. Full text in Research Archive Show summary

  Background: Musculoskeletal hip/groin screening tests are commonly performed to detect at-risk individuals. Bony hip morphology is considered a potential intrinsic risk factor but has not been examined prospectively. Purpose: To evaluate the association between intrinsic risk factors identified from musculoskeletal and radiographic screening tests and hip/groin injuries leading to time loss from training and/or match play in professional male soccer players. Study Design: Prospective cohort study; Level of evidence, 2. Methods: Male professional soccer players, aged ≥18 years, underwent screening specific for hip/groin pain during 2 consecutive seasons of the Qatar Stars League. The screening battery included pain provocation, range of motion, and strength tests as well as a hip radiographic examination. The radiographic examination included an anteroposterior pelvic view and 45° Dunn view, with bony hip morphology determined using quantitative methods. Time-loss (≥1 day) hip/groin injuries and individual player exposure (training and match play) were recorded prospectively, and injuries were categorized as adductor-related, inguinal-related, iliopsoas-related, pubic-related, or hip-related groin pain, or “other,” as recommended in the Doha agreement. We calculated hazard ratios (HRs) from univariate and multivariate Cox regression models to assess the relationship between potential risk factors and hip/groin injuries. Results: There were 438 players, completing 609 player seasons, and 113 hip/groin injuries that met the criteria for inclusion, with 85 injuries categorized as adductor-related. The proportion of players with bony morphological variants was the following: cam, 71%; pincer, 5%; and acetabular dysplasia, 13%. Previous hip/groin injuries (HR, 1.8; 95% CI, 1.2-2.7) and eccentric adduction strength were associated with the risk of hip/groin injuries. Higher (>1 SD above the mean) than normal eccentric adduction strength was associated with an increased risk for all hip/groin injuries (HR, 1.6; 95% CI, 1.0-2.5). Lower (<1 SD below the mean) than normal eccentric adduction strength was associated with an increased risk for adductor-related injuries (HR, 1.7; 95% CI, 1.0-3.0). No other musculoskeletal screening test or bony hip morphology variables were associated with the injury risk. Conclusion: Previous groin injuries and eccentric adduction strength were associated with the risk of groin injuries. However, these associations were not strong enough to identify an “at-risk” individual, and therefore, musculoskeletal screening tests were not useful to dictate individualized prevention strategies. Bony hip morphology was not associated with the risk of groin injuries.

• Skazalski, Christopher Mitchell; Whiteley, Rod; Hansen, Clint & Bahr, Roald (2018). A valid and reliable method to measure jump-specific training and competition load in elite volleyball players. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 28(5), p. 1578–1585. doi: 10.1111/sms.13052. Full text in Research Archive Show summary

  Purpose: Use of a commercially available wearable device to monitor jump load with elite volleyball players has become common practice. The purpose of this study was to evaluate the validity and reliability of this device, the Vert, to count jumps and measure jump height with professional volleyball players. Methods: Jump count accuracy was determined by comparing jumps recorded by the device to jumps observed through systematic video analysis of three practice sessions and two league matches performed by a men's professional volleyball team. Jumps performed by 14 players were each coded for time and jump type and individually matched to device recorded jumps. Jump height validity of the device was examined against reference standards as participants performed countermovement jumps on a force plate and volleyball-specific jumps with a Vertec. Results: The Vert device accurately counted 99.3% of the 3637 jumps performed during practice and match play. The device showed excellent jump height inter-device reliability for two devices placed in the same pouch during volleyball jumps (r = 0.99, 95% CI 0.98 to 0.99). The device had a minimum detectable change (MDC) of 9.7 cm and overestimated jump height by an average of 5.5 cm (95% CI 4.5 to 6.5) across all volleyball jumps. Conclusion: The Vert device demonstrates excellent accuracy counting volleyball-specific jumps during training and competition. While the device is not recommended to measure maximal jumping ability when precision is needed, it provides an acceptable measure of on-court jump height that can be used to monitor athlete jump load.

• Steenstrup, Sophie E.; Bakken, Arnhild; Bere, Tone Tufte; Patton, Declan A. & Bahr, Roald (2018). Head injury mechanisms in FIS World Cup alpine and freestyle skiers and snowboarders. British Journal of Sports Medicine. ISSN 0306-3674. 52(1), p. 61–69. doi: 10.1136/bjsports-2017-098240. Show summary

  INTRODUCTION: Head injuries represent a concern in skiing and snowboarding, with traumatic brain injuries being the most common cause of death. AIM: To describe the mechanisms of head and face injuries among World Cup alpine and freestyle skiers and snowboarders. METHODS: We performed a qualitative analysis of videos obtained of head and face injuries reported through the International Ski Federation Injury Surveillance System during 10 World Cup seasons (2006-2016). We analysed 57 head impact injury videos (alpine n=29, snowboard n=13, freestyle n=15), first independently and subsequently in a consensus meeting. RESULTS: During the crash sequence, most athletes (84%) impacted the snow with the skis or board first, followed by the upper or lower extremities, buttocks/pelvis, back and, finally, the head. Alpine skiers had sideways (45%) and backwards pitching falls (35%), with impacts to the rear (38%) and side (35%) of the helmet. Freestyle skiers and snowboarders had backwards pitching falls (snowboard 77%, freestyle 53%), mainly with impacts to the rear of the helmet (snowboard 69%, freestyle 40%). There were three helmet ejections among alpine skiers (10% of cases), and 41% of alpine skiing injuries occurred due to inappropriate gate contact prior to falling. Athletes had one (47%) or two (28%) head impacts, and the first impact was the most severe (71%). Head impacts were mainly on snow (83%) on a downward slope (63%). CONCLUSION: This study has identified several characteristics of the mechanisms of head injuries, which may be addressed to reduce risk.

• Steenstrup, Sophie E.; Mok, Kam-Ming; McIntosh, Andrew S.; Bahr, Roald & Krosshaug, Tron (2018). Reconstruction of head impacts in FIS World Cup alpine skiing. British Journal of Sports Medicine. ISSN 0306-3674. 52(11), p. 709–715. doi: 10.1136/bjsports-2017-098050. Show summary

  Introduction: Prior to the 2013/2014 season, the International Ski Federation (FIS) increased the helmet testing speed from 5.4 to 6.8m/s for alpine downhill, super-G and giant slalom. Whether this increased testing speed reflects head impact velocities in real head injury situations on snow is unclear. We therefore investigated the injury mechanisms and gross head impact biomechanics in seven real head injury situations among World Cup (WC) alpine skiers. Methods: We analysed nine head impacts from seven head injury videos from the FIS Injury Surveillance System, throughout nine WC seasons (2006–2015) in detail. We used commercial video-based motion analysis software to estimate head impact kinematics in two dimensions, including directly preimpact and postimpact, from broadcast video. The sagittal plane angular movement of the head was also measured using angle measurement software. Results: In seven of nine head impacts, the estimated normal to slope preimpact velocity was higher than the current FIS helmet rule of 6.8m/s (mean 8.1 (±SD 0.6) m/s, range 1.9±0.8 to 12.1±0.4m/s). The nine head impacts had a mean normal to slope velocity change of 9.3±1.0m/s, range 5.2±1.1 to 13.5±1.3m/s. There was a large change in sagittal plane angular velocity (mean 43.3±2.9 rad/s (range 21.2±1.5 to 64.2±3.0 rad/s)) during impact. Conclusion: The estimated normal to slope preimpact velocity was higher than the current FIS helmet rule of 6.8m/s in seven of nine head impacts.

• Moseid, Christine Holm; Myklebust, Grethe; Fagerland, Morten; Clarsen, Benjamin & Bahr, Roald (2018). The prevalence and severity of health problems in youth elite sports: a 6-month prospective cohort study of 320 athletes. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 28(4), p. 1412–1423. doi: 10.1111/sms.13047. Show summary

  Little is known regarding the overall health of youth elite athletes. Our aim was to describe the prevalence and severity of health problems in a cohort of youth elite athletes representing a variety of endurance, team and technical sports. Elite sport athletes (N=260, 16.2 yrs) from different Sport Academy High Schools in Norway, and a group of their teammates (N=60, 16.4 yrs) attending regular high schools, were included in the study. The Oslo Sports Trauma Research Centre (OSTRC) questionnaire on health problems was used to self report injuries and illnesses for 26 weeks. At any given time, an average of 43% [95% CI: 37-49%] of the elite sport athletes had some form of health problem and 25% [20-31%] had substantial health problems. The prevalence of health problems was similar between the elite team sport athletes versus their teammates, except for substantial injuries (22% [16-30%] vs. 10% [5-20%]). Endurance sport athletes reported more illnesses (23% [15-35%]) than technical and team sport athletes (10% [5-20%] and 8% [4-14%]). In contrast, technical and team sport athletes reported more injuries (36% [95% CI: 25-48] and 37% [95% CI 29-45]) compared to endurance sport athletes (15% [8-25%]). The total impact of health problems was roughly split in thirds between overuse injuries (37%), acute injuries (34%) and illnesses (30%). This is the first prospective study to present self-reported injury and illness data in a large heterogeneous group of youth elite athletes, documenting a substantial impact of both injuries and illnesses on the health of this population.

• Mok, Kam-Ming; Bahr, Roald & Krosshaug, Tron (2018). Reliability of lower limb biomechanics in two sport-specific sidestep cutting tasks. Sports Biomechanics. ISSN 1476-3141. 17(2), p. 157–167. doi: 10.1080/14763141.2016.1260766. Full text in Research Archive Show summary

  The purpose of this study was to assess the within- and between-session reliability of lower limb biomechanics in two sport-specific sidestep cutting tasks performed by elite female handball and football (soccer) athletes. Moreover, we aimed at determining the minimum number of trials necessary to obtain a reliable measure. Nineteen elite female handball and 22 elite female football (soccer) athletes (M ± SD: 22 ± 4 yrs old, 168 ± 5 cm, 66 ± 8 kg) were tested. The reliability was quantified by intra-class correlations (ICCs), typical error and Spearman’s rank correlation. Only minor improvements in ICC values were seen when increasing the number of trials from 3 to 5. Based on trials 1–3, all variables showed good to excellent within-session reliability (M ICC: 0.91, 95% CI: 0.89–0.93), fair to good between-session reliability (M ICC: 0.73, 95% CI: 0.70–0.76), moderately positive between-session rank correlation coefficients (M: 0.72, 95% CI: 0.69–0.76). A few frontal plane biomechanical variables displayed lower between-session reliability in the football task compared with the handball task. The moderately positive between-session ranking and practically small typical error implies that the measurements could reliably reproduce the ranking of individuals in multiple-session studies. Adequate reliability could be attained from 3 trials, with only minor improvements when adding more trials.

• Andersson, Stig Haugsbø; Bahr, Roald; Clarsen, Benjamin & Myklebust, Grethe (2018). Risk factors for overuse shoulder injuries in a mixedsex cohort of 329 elite handball players: previous findings could not be confirmed. British Journal of Sports Medicine. ISSN 0306-3674. 52(18), p. 1191–1198. doi: 10.1136/bjsports-2017-097648. Show summary

  Background: Shoulder injuries are common among handball players and predominantly characterised by overuse characteristics. Reduced total glenohumeral rotation, external rotation weakness and scapular dyskinesis have been identified as risk factors among elite male handball players. Aim: To assess whether previously identified risk factors are associated with overuse shoulder injuries in a large cohort of elite male and female handball players. Methods: 329 players (168 male, 161 female) from the two upper divisions in Norway were included and tested prior to the 2014–2015 season. Measures included glenohumeral internal and external rotation range of motion, isometric internal and external rotation strength, and assessment of scapular dyskinesis. Players were followed prospectively for one competitive season, with prevalence and severity of shoulder problems registered monthly using the Oslo Sports Trauma Research Center Overuse Injury Questionnaire. A severity score based on players’ questionnaire responses was used as the outcome measure in multivariable logistic regression to investigate associations between candidate risk factors and overuse shoulder injury. Results: No significant associations were found between total rotation (OR 1.05 per 5° change, 95%CI 0.98 to 1.13), external rotation strength (OR 1.05 per 10N change, 95%CI 0.92 to 1.20) or obvious scapular dyskinesis (OR 1.23, 95%CI 0.25 to 5.99) and overuse shoulder injury. A significant positive association was found between greater internal rotation (OR 1.16 per 5° change, 95%CI 1.00 to 1.34) and overuse shoulder injury. Conclusion: None of the previously identified risk factors were associated with overuse shoulder injuries in a mixed-sex cohort of elite handball players.

• Koga, Hideyuki; Nakamae, Atsuo; Shima, Yosuke; Bahr, Roald & Krosshaug, Tron (2018). Hip and Ankle Kinematics in Noncontact Anterior Cruciate Ligament Injury Situations : Video Analysis Using Model-Based Image Matching. American Journal of Sports Medicine. ISSN 0363-5465. 46(2), p. 333–340. doi: 10.1177/0363546517732750. Show summary

  Background: Detailed kinematic descriptions of real anterior cruciate ligament (ACL) injury situations are limited to the knee only. Purpose: To describe hip and ankle kinematics as well as foot position relative to the center of mass (COM) in ACL injury situations through use of a model-based image-matching (MBIM) technique. The distance between the projection of the COM on the ground and the base of support (BOS) (COM_BOS) normalized to the femur length was also evaluated. Study Design: Descriptive laboratory study. Methods: Ten ACL injury video sequences from women’s handball and basketball were analyzed. Hip and ankle joint kinematic values were obtained by use of MBIM. Results: The mean hip flexion angle was 51° (95% CI, 41° to 63°) at initial contact and remained constant over the next 40 milliseconds. The hip was internally rotated 29° (95% CI, 18° to 39°) at initial contact and remained unchanged for the next 40 milliseconds. All of the injured patients landed with a heel strike with a mean dorsiflexion angle of 2° (95% CI, –9° to 14°), before reaching a flatfooted position 20 milliseconds later. The foot position was anterior and lateral to the COM in all cases. However, none of the results showed larger COM_BOS than 1.2, which has been suggested as a criterion for ACL injury risk. Conclusions: Hip kinematic values were consistent among the 10 ACL injury situations analyzed; the hip joint remained unchanged in a flexed and internally rotated position in the phase leading up to injury, suggesting that limited energy absorption took place at the hip. In all cases, the foot contacted the ground with the heel strike. However, relatively small COM_BOS distances were found, indicating that the anterior and lateral foot placement in ACL injury situations was not different from what can be expected in noninjury game situations.

• Swedberg, Aaron M.; Wijdicks, Coen A.; LaPrade, Robert F. & Bahr, Roald (2017). Alpine skiing and snowboarding : current trends and future directions. In Feletti, Francesco (Eds.), Extreme sports medicine. Springer. ISSN 978-3-319-28263-3. p. 123–137. doi: 10.1007/978-3-319-28265-7_11.
• Koga, Hideyuki; Muneta, Takeshi; Bahr, Roald; Engebretsen, Lars & Krosshaug, Tron (2017). ACL injury mechanisms : lessons learned from video analysis. In Musahl, Volker; Karlsson, Jón; Kuroda, Ryosuke & Zaffagnini, Stefano (Ed.), Rotary knee instability : an evidence based approach. Springer. ISSN 978-3-319-32069-4. p. 27–36. doi: 10.1007/978-3-319-32070_3.
• Leppänen, Mari; Pasanen, Kati; Krosshaug, Tron; Kannus, Pekka; Vasankari, Tommi & Kujala, Urho M [Show all 9 contributors for this article] (2017). Sagittal Plane Hip, Knee, and Ankle Biomechanics and the Risk of Anterior Cruciate Ligament Injury :A Prospective Study. Orthopaedic Journal of Sports Medicine (OJSM). ISSN 2325-9671. 5(12). doi: 10.1177/2325967117745487. Full text in Research Archive
• van Dyk, Nicol; Bahr, Roald; Burnett, Angus F.; Whiteley, Rod; Bakken, Arnhild & Mosler, Andrea [Show all 8 contributors for this article] (2017). A comprehensive strength testing protocol offers no clinical value in predicting risk of hamstring injury: a prospective cohort study of 413 professional football players. British Journal of Sports Medicine. ISSN 0306-3674. 51(23), p. 1695–1702. doi: 10.1136/bjsports-2017-097754. Show summary

  Background: Hamstring injuries remain prevalent across a number of professional sports. In football, the incidence has even increased by 4% per year at the Champions League level over the last decade. The role of muscle strength or strength ratios and their association with risk of hamstring injury remain restricted by small sample sizes and inconclusive results. Purpose: The purpose of this study is to identify risk factors for hamstring injury in professional football players in an adequately powered, prospective cohort study. Using both established (isokinetic) and novel (eccentric hamstring test device) measures of muscle strength, we aimed to investigate the relationship between these strength characteristics over the entire range of motion with risk of hamstring injury. Methods: All teams (n=18) eligible to compete in the premier football league in Qatar underwent a comprehensive strength assessment during their annual periodic health evaluation at Aspetar Orthopaedic and Sports Medicine Hospital in Doha, Qatar. Variables included isokinetic strength, Nordic hamstring exercise strength and dynamic hamstring: quadriceps ratios. Results: Of the 413 players included (68.2% of all league players), 66 suffered a hamstring injury over the two seasons. Only isokinetic quadriceps concentric at 300°/s (adjusted for bodyweight) was associated with risk of hamstring injury when considered categorically. Age, body mass and playing position were also associated with risk of hamstring injury. None of the other 23 strength variables examined were found to be associated with hamstring injury. Conclusion: The clinical value of isolated strength testing is limited, and its use in musculoskeletal screening to predict future hamstring injury is unfounded.

• Skazalski, Christopher; Kruczynski, Jacek; Bahr, Martin A.; Bere, Tone Tufte; Whiteley, Rod & Bahr, Roald (2017). Landing-related ankle injuries do not occur in plantarflexion as once thought: a systematic video analysis of ankle injuries in world-class volleyball. British Journal of Sports Medicine. ISSN 0306-3674. 52(2), p. 74–82. doi: 10.1136/bjsports-2016-097155. Full text in Research Archive Show summary

  Background: Ankle injuries are prevalent in elite volleyball and suggested to result from player contact at the net. Traditionally, ankle sprains are thought to happen in a plantarflexed position, but case studies suggest plantarflexion may not be involved. Aim: Describe the injury situations and mechanisms of ankle injuries in world-class volleyball based on systematic video analysis of injuries reported through the Fédération Internationale de Volleyball (FIVB) Injury Surveillance System. Methods: Videos of 24 injuries from major FIVB tournaments were included for analysis (14 men, 10 women). Five analysts reviewed the videos to determine specific situations and mechanisms leading to injuries. Results: The majority of injuries occurred during two volleyball situations, blocking (n=15) and attacking (n=6). Injuries to blockers were the result of landing on an opponent (n=11) or teammate (n=4). Attacking injuries most frequently occurred when a back-row player landed on a front-row teammate (n=4 of 6). When landing on an opponent under the net, the attacker landed into the opponent’s court in 11 of 12 situations but without violating the centre line rule. Injuries mostly resulted from rapid inversion without any substantial plantarflexion. Conclusions: The majority of injuries occur while blocking, often landing on an opponent. The attacker is overwhelmingly to blame for injuries at the net secondary to crossing the centre line. Injuries while attacking often result from a back-row player landing on a front-row teammate. Landing-related injuries mostly result from rapid inversion with the absence of plantarflexion.

• MacDonald, Kerry; Bahr, Roald; Baltich, Jennifer; Whittaker, Jackie L. & Meeuwisse, Willem (2017). Validation of an inertial measurement unit for the measurement of jump count and height. Physical Therapy in Sport. ISSN 1466-853X. 25, p. 15–19. doi: 10.1016/j.ptsp.2016.12.001. Show summary

  Objectives: To validate the use of an inertial measurement unit (IMU) for the collection of total jump count and assess the validity of an IMU for the measurement of jump height against 3-D motion analysis. Design: Cross sectional validation study. Setting: 3D motion-capture laboratory and field based settings. Participants: Thirteen elite adolescent volleyball players. Independent variables: Participants performed structured drills, played a 4 set volleyball match and performed twelve counter movement jumps. Main outcome measures: Jump counts from structured drills and match play were validated against visual count from recorded video. Jump height during the counter movement jumps was validated against concurrent 3-D motion-capture data. Results: The IMU device captured more total jumps (1032) than visual inspection (977) during match play. During structured practice, device jump count sensitivity was strong (96.8%) while specificity was perfect (100%). The IMU underestimated jump height compared to 3D motion-capture with mean differences for maximal and submaximal jumps of 2.5 cm (95%CI: 1.3 to 3.8) and 4.1 cm (3.1–5.1), respectively. Conclusion: The IMU offers a valid measuring tool for jump count. Although the IMU underestimates maximal and submaximal jump height, our findings demonstrate its practical utility for field-based measurement of jump load.

• Harøy, Joar; Thorborg, Kristian; Serner, Andreas; Bjørkheim, Andrè; Rolstad-Martinez, Linn E. & Hölmich, Per [Show all 8 contributors for this article] (2017). Including the Copenhagen Adduction Exercise in the FIFA 11+ Provides Missing Eccentric Hip Adduction Strength Effect in Male Soccer Players: A Randomized Controlled Trial. American Journal of Sports Medicine. ISSN 0363-5465. 45(13), p. 3052–3059. doi: 10.1177/0363546517720194. Show summary

  Background: The FIFA 11+ was developed as a complete warm-up program to prevent injuries in soccer players. Although reduced hip adduction strength is associated with groin injuries, none of the exercises included in the FIFA 11+ seem to specifically target hip adduction strength. Purpose: To investigate the effect on eccentric hip adduction strength of the FIFA 11+ warm-up program with or without the Copenhagen adduction exercise. Study Design: Randomized controlled trial; Level of evidence, 1. Methods: We recruited 45 eligible players from 2 U19 elite male soccer teams. Players were randomized into 2 groups; 1 group carried out the standard FIFA 11+ program, while the other carried out the FIFA 11+ but replaced the Nordic hamstring exercise with the Copenhagen adduction exercise. Both groups performed the intervention 3 times weekly for 8 weeks. Players completed eccentric strength and sprint testing before and after the intervention. Per-protocol analyses were performed, and 12 players were excluded due to low compliance (<67% of sessions completed). The main outcome was eccentric hip adduction strength (N·m/kg). Results: Between-group analyses revealed a significantly greater increase in eccentric hip adduction strength of 0.29 Nm/kg (8.9%; P = .01) in favor of the group performing the Copenhagen adduction exercise, whereas no within-group change was noted in the group that used the standard FIFA 11+ program (–0.02 N·m/kg [–0.7%]; P = .69). Conclusion: Including the Copenhagen adduction exercise in the FIFA 11+ program increases eccentric hip adduction strength, while the standard FIFA 11+ program does not.

• Soligard, Torbjørn; Steffen, Kathrin; Palmer, Debbie; Alonso, Juan Manuel; Bahr, Roald & Lopes, Alexandre Dias [Show all 14 contributors for this article] (2017). Sports injury and illness incidence in the Rio de Janeiro 2016 Olympic Summer Games: A prospective study of 11274 athletes from 207 countries. British Journal of Sports Medicine. ISSN 0306-3674. 51(17), p. 1265–1271. doi: 10.1136/bjsports-2017-097956. Full text in Research Archive
• Bakken, Arnhild; Targett, Stephen; Bere, Tone Tufte; Eirale, Cristiano; Farooq, Abdulaziz & Tol, Johannes L. [Show all 9 contributors for this article] (2017). The functional movement test 9+ is a poor screening test for lower extremity injuries in professional male football players: a 2-year prospective cohort study. British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2016-097307. Show summary

  Background: The 9+ screening battery test consists of 11 tests to assess limitations in functional movement. Aim: To examine the association of the 9+ with lower extremity injuries and to identify a cut-off point to predict injury risk. Methods: Professional male football players in Qatar from 14 teams completed the 9+ at the beginning of the 2013/2014 and 2014/2015 seasons. Time-loss injuries and exposure in training and matches were registered prospectively by club medical staff during these seasons. Univariate and multivariate Cox regression analyses were used to calculate HR and 95% CI. Receiver operating characteristic (ROC) curves were calculated to determine sensitivity and specificity and identify the optimal cut-off point for risk assessment. Results: 362 players completed the 9+ and had injury and exposure registration. There were 526 injuries among 203 players (56.1%) during the two seasons; injuries to the thigh were the most frequent. There was no association between 9+ total score and the risk of lower extremity injuries (HR 1.02, 95% CI 0.99 to 1.05, p=0.13), even after adjusting for other risk factors in a multivariate analysis (HR 1.01, 95% CI 0.98 to 1.04, p=0.37). ROC curve analysis revealed an area under the curve of 0.48, and there was no cut-off point that distinguished injured from non-injured players. Conclusion: The 9+ was not associated with lower extremity injury, and it was no better than chance for distinguishing between injured and uninjured players. Therefore, the 9+ test cannot be recommended as an injury prediction tool in this population.

• Steenstrup, Sophie E.; Mok, Kam-Ming; McIntosh, Andrew S.; Bahr, Roald & Krosshaug, Tron (2017). Head impact velocities in FIS World Cup snowboarders and freestyle skiers: Do real-life impacts exceed helmet testing standards? British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2016-097086. Show summary

  Introduction: Prior to the 2013–2014 season, the International Ski Federation (FIS) increased the helmet testing speed from a minimum requirement of 5.4 to 6.8 m/s for alpine downhill, super-G and giant slalom and for freestyle ski cross, but not for the other freestyle disciplines or snowboarding. Whether this increased testing speed reflects impact velocities in real head injury situations on snow is unclear. We therefore investigated the injury mechanisms and gross head impact biomechanics in four real head injury situations among World Cup (WC) snowboard and freestyle athletes and compared these with helmet homologation laboratory test requirements. The helmets in the four cases complied with at least European Standards (EN) 1077 (Class B) or American Society for Testing and Materials (ASTM) F2040. Methods: We analysed four head injury videos from the FIS Injury Surveillance System throughout eight WC seasons (2006–2014) in detail. We used motion analysis software to digitize the helmet’s trajectory and estimated the head’s kinematics in two dimensions, including directly preimpact and postimpact. Results: All four impacts were to the occiput. In the four cases, the normal-to-slope preimpact velocity ranged from 7.0(±SD 0.2) m/s to 10.5±0.5 m/s and the normal-to-slope velocity change ranged from 8.4±0.6 m/s to 11.7±0.7 m/s. The sagittal plane helmet angular velocity estimates indicated a large change in angular velocity (25.0±2.9 rad/s to 49.1±0.3 rad/s). Conclusion: The estimated normal-to-slope preimpact velocity was higher than the current strictest helmet testing rule of 6.8 m/s in all four cases.

• Wangensteen, Arnlaug; Tol, Johannes L.; Roemer, Frank W.; Bahr, Roald; Dijkstra, H. Paul & Crema, Michel Daoud [Show all 8 contributors for this article] (2017). Intra- and interrater reliability of three different MRI grading and classification systems after acute hamstring injuries. European Journal of Radiology. ISSN 0720-048X. 89, p. 182–190. doi: 10.1016/j.ejrad.2017.02.010. Show summary

  Objective: To assess and compare the intra- and interrater reliability of three different MRI grading and classification systems after acute hamstring injury. Methods: Male athletes (n = 40) with clinical diagnosis of acute hamstring injury and MRI ≤5 days were selected from a prospective cohort. Two radiologists independently evaluated the MRIs using standardised scoring form including the modified Peetrons grading system, the Chan acute muscle strain injury classification and the British Athletics Muscle Injury Classification. Intra-and interrater reliability was assessed with linear weighted kappa (κ) or unweighted Cohen's κ and percentage agreement was calculated. Results: We observed ‘substantial’ to ‘almost perfect’ intra- (κ range 0.65–1.00) and interrater reliability (κ range 0.77–1.00) with percentage agreement 83–100% and 88–100%, respectively, for severity gradings, overall anatomical sites and overall classifications for the three MRI systems. We observed substantial variability (κ range −0.05 to 1.00) for subcategories within the Chan classification and the British Athletics Muscle Injury Classification, however, the prevalence of positive scorings was low for some subcategories. Conclusions: The modified Peetrons grading system, overall Chan classification and overall British Athletics Muscle Injury Classification demonstrated ‘substantial' to ‘almost perfect' intra- and interrater reliability when scored by experienced radiologists. The intra- and interrater reliability for the anatomical subcategories within the classifications remains unclear.

• Bahr, Roald; Clarsen, Benjamin; Myklebust, Grethe; Verhagen, Evert; Gabbett, Tim J. & Orchard, John (2017). Preventing injury, Brukner and Khan's clinical sports medicine : vol. 1 Injuries. McGraw-Hill. ISSN 9781743761380. p. 165–188.
• Harøy, Joar; Clarsen, Benjamin; Thorborg, Kristian; Hölmich, Per; Bahr, Roald & Andersen, Thor Einar (2017). Groin Problems in Male Soccer Players Are More Common Than Previously Reported. American Journal of Sports Medicine. ISSN 0363-5465. 45(6), p. 1304–1308. doi: 10.1177/0363546516687539. Show summary

  Background: The majority of surveillance studies in soccer have used a time-;loss injury definition, and many groin problems result from overuse, leading to gradually increasing pain and/or reduced performance without necessarily causing an absence from soccer training or match play. Thus, the magnitude of groin problems in soccer has probably been underestimated in previous studies based on traditional injury surveillance methods. Purpose: To investigate the prevalence of groin problems among soccer players of both sexes and among male soccer players at different levels of play through a new surveillance method developed to capture acute and overuse problems. Study Design: Descriptive epidemiology study. Methods: We registered groin problems during a 6-;week period of match congestion using the Oslo Sports Trauma Research Center Overuse Injury Questionnaire. A total of 240 players from 15 teams across different levels of play and from both sexes were included, and they responded to the weekly questionnaire. We calculated the average weekly prevalence of all groin problems and substantial groin problems. Results: Of the 240 players, 112 male players (59%) and 20 female players (45%) reported at least 1 episode of groin problems. The average weekly prevalence of any groin problem and substantial groin problem for all male players was 29% (range, 23%-32% across different levels) and 10% (7%-13%), respectively. Elite male players had an increased risk of experiencing groin problems (odds ratio: 3.1, 95% CI: 1.5-6.4, P = .03) compared with elite female players. There was no difference in the risk of experiencing groin problems among elite, subelite, and amateur male players. For substantial problems, there was no difference between elite male and elite female players or among levels of play for senior male soccer players. Conclusion: We found a high prevalence of groin problems among male soccer players during a period with match congestion. Time-loss definition as used in previous injury surveillance studies captured only one-;third of the male groin problems registered with the new method. Elite male players had 3 times’ higher risk of reporting groin problems as compared with elite female players, while playing level did not influence the risk of reporting a groin problem among males.

• Steffen, Kathrin; Nilstad, Agnethe; Krosshaug, Tron; Pasanen, Kati; Killingmo, Aleksander & Bahr, Roald (2017). No association between static and dynamic postural control and ACL injury risk among female elite handball and football players: a prospective study of 838 players. British Journal of Sports Medicine. ISSN 0306-3674. 51(4), p. 253–259. doi: 10.1136/bjsports-2016-097068. Show summary

  Background: Research on balance measures as potential risk factors for ACL injury is limited. Objective: To assess whether postural control was associated with an increased risk for ACL injuries in female elite handball and football players. Method: Premier league players were tested in the preseason and followed prospectively for ACL injury risk from 2007 through 2015. At baseline, we recorded player demographics, playing experience, ACL and ankle injury history. We measured centre of pressure velocity in single-leg stabilisation tests and reach distances in the Star Excursion Balance Test. To examine the stability of postural control measures over time, we examined their short-term and long-term reproducibility. We generated logistic regression models, 1 for each of the proposed risk factors. Results: A total of 55 (6.6%) out of 838 players (age 21±4 years; height 170±6 cm; body mass 66±8 kg) sustained a non-contact ACL injury after baseline testing (1.8±1.8 years). When comparing normalised balance measures between injured and uninjured players in univariate analyses, none of the variables were statistically associated with ACL injury risk. Short-term and long-term reproducibility of the selected variables was poor. Players with a previous ACL injury had a 3-fold higher risk of sustaining a new ACL injury compared with previously uninjured players (OR 2.9, CI 1.4 to 5.7). Conclusions: None of postural control measures examined were associated with increased ACL injury risk among female elite handball and football players. Hence, as measured in the current investigation, the variables included cannot be used to predict ACL injury risk.

• Myklebust, Grethe; Bahr, Roald; Nilstad, Agnethe & Steffen, Kathrin (2017). Knee function among elite handball and football players 1 to 6 years after anterior cruciate ligament injury. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 27(5), p. 545–553. doi: 10.1111/sms.12842. Show summary

  The aim of the study was to describe objective and self-reported knee function for athletes who have returned to elite handball and football play after an ACL injury, comparing these to non-injured players at the same level. A total of 414 handball and 444 football players completed baseline tests from 2007 through 2014, examining lower extremity strength, dynamic balance, knee laxity, and knee function (KOOS questionnaire). Measures were compared between injured and non-injured legs, and between injured legs and legs of controls. Eighty (9.3%) of the 858 players reported a previous ACL injury, 1 to 6 yrs post-injury (3.5±2.5 yrs), 49 handball (61.3%) and, 31 football players (38.7%). We found no difference in strength or dynamic balance between previously ACL-injured (N=80) and non-injured players legs (N=1556). However, lower quadriceps (6.3%, 95% CI: 3.2 to 9.2) and hamstrings muscle strength (6.1%, 95% CI: 3.3 to 8.1) was observed in previously ACL-injured legs compared to the non-injured contralateral side (N=80). ACL-injured knees displayed greater joint laxity than for the contralateral knee (N=80, 17%, 95% CI: 8 to 26) and healthy knees (N=1556, 23%, 95% CI: 14 to 33). KOOS scores were significantly lower for injured knees compared to knees of non-injured players. ACL-injured players who have successfully returned to elite sport have comparable strength and balance measures as their non-injured teammates. Subjective perception of knee function is strongly affected by injury history, with clinically relevant lower scores for the KOOS sub-scores Pain, Function, Sport and Quality Of Life.

• Sulheim, Steinar; Ekeland, Arne Erling; Holme, Ingar Morten K & Bahr, Roald (2017). Helmet use and risk of head injuries in alpine skiers and snowboarders: changes after an interval of one decade. British Journal of Sports Medicine. ISSN 0306-3674. 51(1), p. 44–50. doi: 10.1136/bjsports-2015-095798. Show summary

  Background: In a previous study, we concluded that a safety helmet can reduce the risk for head injury by 60%. Other studies reported similar effects, resulting in a general recommendation to wear a helmet while skiing or snowboarding. Aim: To determine the effect of the expected increased helmet wear on the risk of head injury one decade after the recommendation. Methods: Ski patrols reported injury cases in major Norwegian alpine ski resorts. Injury type, helmet use and other risk factors were recorded. A multiple logistic regression analysis was used to assess the relation between individual risk factors and the risk of head injuries by comparing head injured skiers (cases) with skiers and snowboarders who reported other injuries (controls). Results: Helmet use was associated with improved odds for head injuries (OR: 0.45, 95% CI 0.34 to 0.60; p<0.001) in 2002; this effect was attenuated in 2010 (OR: 0.79, 95% CI 0.63 to 0.98; p=0.02), and not significant in 2011 (OR: 0.80, 95% CI 0.60 to 1.06; p=0.12). For potentially severe head injuries, the protective effect of using a helmet was better sustained over the observation period, from an OR of 0.44 (95% CI 0.28 to 0.68, p<0.001) in 2002 to an OR of 0.74 (95% CI 0.57 to 0.97, p=0.02) in 2010 and 0.67 (95% CI 0.47 to 0.96; p=0.03) in 2011. Conclusions: We observed an unexpected reduction in the protective effect of a skiing helmet. This may be due to new skiing trends in the alpine resorts.

• Bakken, Arnhild; Targett, Stephen; Bere, Tone Tufte; Eirale, Cristiano; Farooq, Abdulaziz & Tol, Johannes [Show all 10 contributors for this article] (2017). Interseason variability of a functional movement test, the 9+ screening battery, in professional male football players. British Journal of Sports Medicine. ISSN 0306-3674. 51(14), p. 1081–1086. doi: 10.1136/bjsports-2016-096570. Show summary

  Background: The Nine Plus screening battery test (9+) is a functional movement test intended to identify limitations in fundamental movement patterns predisposing athletes to injury. However, the interseason variability is unknown. Aim: To examine the variability of the 9+ test between 2 consecutive seasons in professional male football players. Methods: Asymptomatic Qatar Star League players (n=220) completed the 9+ at the beginning of the 2013 and 2014 seasons. Time-loss injuries in training and matches were obtained from the Aspetar Injury and Illness Surveillance Program. No intervention was initiated between test occasions. Results: A significant increase in the mean total score of 1.6 points (95% CI 1.0 to 2.2, p<0.001) was found from season 1 (22.2±4.1 (SD)) to season 2 (23.8±3.3). The variability was large, as shown by an intraclass correlation coefficient (ICC) of 0.24 (95% CI 0.11 to 0.36) and a minimal detectable change (MDC) of 8.7 points. Of the 220 players, 136 (61.8%) suffered a timeloss injury between the 2 tests. There was an improvement in mean total scores in the injured (+2.0 ±0.4 (SE), p<0.001) group but not in the uninjured group (+0.9±0.5, p=0.089). The variability from season 1 to season 2 was large both in the injured (ICC 0.25, 0.09 to 0.40, MDC 8.3) and uninjured (ICC 0.24, 0.02 to 0.43, MDC 9.1) groups. Conclusions: The 9+ demonstrated substantial intraindividual variability in the total score between 2 consecutive seasons, irrespective of injury. A change above 8 points is necessary to represent a real change in the 9+ test between seasons.

• Leppänen, Mari; Pasanen, Kati; Kujala, Urho M; Vasankari, Tommi; Kannus, Pekka & Äyrämö, Sami [Show all 11 contributors for this article] (2017). Stiff Landings Are Associated with Increased ACL Injury Risk in Young Female Basketball and Floorball Players. American Journal of Sports Medicine. ISSN 0363-5465. 45(2), p. 386–393. doi: 10.1177/0363546516665810. Show summary

  Background: Few prospective studies have investigated the biomechanical risk factors of anterior cruciate ligament (ACL) injury. Purpose: To investigate the relationship between biomechanical characteristics of vertical drop jump (VDJ) performance and the risk of ACL injury in young female basketball and floorball players. Study Design: Cohort study; Level of evidence, 3. Methods: At baseline, a total of 171 female basketball and floorball players (age range, 12-21 years) participated in a VDJ test using 3-dimensional motion analysis. The following biomechanical variables were analyzed: (1) knee valgus angle at initial contact (IC), (2) peak knee abduction moment, (3) knee flexion angle at IC, (4) peak knee flexion angle, (5) peak vertical ground-reaction force (vGRF), and (6) medial knee displacement. All new ACL injuries, as well as match and training exposure, were then recorded for 1 to 3 years. Cox regression models were used to calculate hazard ratios (HRs) and 95% CIs. Results: Fifteen new ACL injuries occurred during the study period (0.2 injuries/1000 player-hours). Of the 6 factors considered, lower peak knee flexion angle (HR for each 10 increase in knee flexion angle, 0.55; 95% CI, 0.34-0.88) and higher peak vGRF (HR for each 100-N increase in vGRF, 1.26; 95% CI, 1.09-1.45) were the only factors associated with increased risk of ACL injury. A receiver operating characteristic (ROC) curve analysis showed an area under the curve of 0.6 for peak knee flexion and 0.7 for vGRF, indicating a failed-to-fair combined sensitivity and specificity of the test. Conclusions: Stiff landings, with less knee flexion and greater vGRF, in a VDJ test were associated with increased risk of ACL injury among young female basketball and floorball players. However, although 2 factors (decreased peak knee flexion and increased vGRF) had significant associations with ACL injury risk, the ROC curve analyses revealed that these variables cannot be used for screening of athletes.

• Andersson, Stig Haugsbø; Bahr, Roald; Clarsen, Benjamin & Myklebust, Grethe (2017). Preventing overuse shoulder injuries among throwing athletes: a cluster-randomised controlled trial in 660 elite handball players. British Journal of Sports Medicine. ISSN 0306-3674. 51(14), p. 1073–1080. doi: 10.1136/bjsports-2016-096226. Show summary

  Background: Shoulder problems are highly prevalent among elite handball players. Reduced glenohumeral rotation, external rotation weakness and scapula dyskinesis have been identified as risk factors. Aim: Evaluate the effect of an exercise programme designed to reduce the prevalence of shoulder problems in elite handball. Methods: 45 elite handball teams (22 female teams, 23 male teams, 660 players) were cluster randomised (22 teams, 331 players in the intervention group, 23 teams, 329 players in the control group) and followed for 1 competitive season (7 months). The Oslo Sports Trauma Research Center (OSTRC) Shoulder Injury Prevention Programme, an exercise programme to increase glenohumeral internal rotation, external rotation strength and scapular muscle strength, as well as improve kinetic chain and thoracic mobility, was delivered by coaches and captains 3 times per week as a part of the handball warm-up. The main outcome measures, prevalence of shoulder problems and substantial shoulder problems, were measured monthly. Results: The average prevalence of shoulder problems during the season was 17% (95% CI 16% to 19%) in the intervention group and 23% (95% CI 21% to 26%) in the control group (mean difference 6%). The average prevalence of substantial shoulder problems was 5% (95% CI 4% to 6%) in the intervention group and 8% (95% CI 7% to 9%) in the control group (mean difference 3%). Using generalised estimating equation models, a 28% lower risk of shoulder problems (OR 0.72, 95% CI 0.52 to 0.98, p=0.038) and 22% lower risk of substantial shoulder problems (OR 0.78, 95% CI 0.53 to 1.16, p=0.23) were observed in the intervention group compared with the control group. Conclusions: The OSTRC Shoulder Injury Prevention Programme reduced the prevalence of shoulder problems in elite handball and should be included as a part of the warm-up.

• Mok, Kam-Ming; Bahr, Roald & Krosshaug, Tron (2017). The effect of overhead target on the lower limb biomechanics during a vertical drop jump test in elite female athletes. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 27(2), p. 161–166. doi: 10.1111/sms.12640. Show summary

  The purpose of the study was to investigate the effect of anoverhead target on the jump height and lower limbbiomechanics in all three planes of motion in a verticaldrop jump (VDJ) task among elite female handball andfootball (soccer) players. The hypothesis was that addingan overhead target to the VDJ task improves jump height,increases joint loading, and decreases frontal plane kneecontrol. Five hundred and twenty-three female handballand football players (mean  SD: 21  4 years,168  6 cm, 65  8 kg) completed the test. The overheadtarget increased jumping height by 5.8%. Furthermore, theoverhead target led to statistically significant changes inmany of the lower limb biomechanical variables examined.However, all the changes in kinematics and kinetics wereclinically insignificant, as indicated by the small effectsizes. Strong to moderate positive Spearman’s rankcorrelations were found between the two conditions.Therefore, an overhead target is unlikely to increase therange of responses in biomechanical variables in elitefemale handball and football athletes.

• Wangensteen, Arnlaug; Bahr, Roald; van Linschoten, Robbart; Almusa, Emad; Whiteley, Rodney & Witvrouw, Erik [Show all 7 contributors for this article] (2016). MRI appearance does not change in the first 7 days after acute hamstring injury — a prospective study. British Journal of Sports Medicine. ISSN 0306-3674. 51(14), p. 1087–1092. doi: 10.1136/bjsports-2016-096881. Show summary

  Background: The optimal timing of MRI following acute hamstring injury is not known and is mainly based on expert opinions. Aims: To describe the day-to-day changes in the extent of oedema and investigate the optimal timing for detection of fibre disruption on MRI following acute hamstring injuries. Study design: Prospective, descriptive study. Methods: We performed standardised MRI (1.5T) ≤1 day after injury in male athletes with acute hamstring injury. If initial MRI revealed positive signs of injury (increased signal intensity on fluid sensitive sequences), consecutive MRIs were obtained daily throughout the subsequent week (ie, 7 times). The MRI parameters (day 1–7) were scored by a single radiologist using a standardised scoring form. The day-to-day changes in the extent of oedema (distance from tuber, craniocaudal length, mediolateral width and anteroposterior depth) and the presence and extent of fibre disruption (tear) were assessed with descriptive statistics and repeated measures using analysis of variance of log-transformed data. The overall main effect for time was reported with a significance level set at p<0.05. Results: 13 out of 132 male athletes assessed for eligibility between January 2014 and December 2015 were included. 1 dropped out, while 12 (31 years, range 20–49) completed the study; 11 had 7 MRI scans each and one had 5 MRI scans performed. There were no significant day-to-day changes for any of the extent of oedema measures (p values ranging from 0.12 to 0.81). Fibre disruption (tear), present in 5 of the athletes, was detectable from day 1, with small and insignificant day-to-day changes (p values ranging from 0.45 to 0.95). Conclusions: We observed insignificant day-to-day changes in the extent of oedema throughout the first week following acute hamstring injury. Fibre disruption (tear) was detectable from the first day after injury. These findings indicate that MRI can be performed on any day during the first week following an acute (hamstring) muscle injury.

• Neuville, C.; Tassin, V.; Pesme, D.; Monteil, M. C.; Masson-Laborde, P. E. & Baccou, C. [Show all 14 contributors for this article] (2016). Experimental Evidence of the Collective Brillouin Scattering of Multiple Laser Beams Sharing Acoustic Waves. Physical Review Letters. ISSN 0031-9007. 116(23). doi: 10.1103/PhysRevLett.116.235002.
• van Dyk, Nicol; Bahr, Roald; Whiteley, Rodney; Tol, Johannes; Kumar, Bhavesh D. & Hamilton, Bruce [Show all 8 contributors for this article] (2016). Hamstring and Quadriceps Isokinetic Strength Deficits Are Weak Risk Factors for Hamstring Strain Injuries: A 4-Year Cohort Study. American Journal of Sports Medicine. ISSN 0363-5465. 44(7), p. 1789–1795. doi: 10.1177/0363546516632526. Show summary

  Background: A hamstring strain injury (HSI) has become the most common noncontact injury in soccer. Isokinetic muscle strength deficits are considered a risk factor for HSIs. However, underpowered studies with small sample sizes unable to determine small associations have led to inconclusive results regarding the role of isokinetic strength and strength testing in HSIs. Purpose: To examine whether differences in isokinetic strength measures of knee flexion and extension represent risk factors for hamstring injuries in a large cohort of professional soccer players in an adequately powered study design. Study Design: Cohort study; Level of evidence, 2. Methods: A total of 614 professional soccer players from 14 teams underwent isokinetic strength testing during preseason screening. Testing consisted of concentric knee flexion and extension at 60 deg/s and 300 deg/s and eccentric knee extension at 60 deg/s. A clustered multiple logistic regression analysis was used to identify variables associated with the risk of HSIs. Receiver operating characteristic (ROC) curves were calculated to determine sensitivity and specificity. Results: Of the 614 players, 190 suffered an HSI during the 4 seasons. Quadriceps concentric strength at 60 deg/s (odds ratio [OR], 1.41; 95% CI, 1.03-1.92; P = .03) and hamstring eccentric strength at 60 deg/s (OR, 1.37; 95% CI, 1.01-1.85; P = .04) adjusted for bodyweight were independently associated with the risk of injuries. The absolute differences between the injured and uninjured players were 6.9 Nm and 9.1 Nm, with small effect sizes (d \ 0.2). The ROC analyses showed an area under the curve of 0.54 and 0.56 for quadriceps concentric strength and hamstring eccentric strength, respectively, indicating a failed combined sensitivity and specificity of the 2 strength variables identified in the logistic regression models. Conclusion: This study identified small absolute strength differences and a wide overlap of the absolute strength measurements at the group level. The small associations between lower hamstring eccentric strength and lower quadriceps concentric strength with HSIs can only be considered as weak risk factors. The identification of these risk factors still does not allow the identification of individual players at risk. The use of isokinetic testing to determine the association between strength differences and HSIs is not supported.

• Steffen, Kathrin; Nilstad, Agnethe; Kristianslund, Eirik; Myklebust, Grethe; Bahr, Roald & Krosshaug, Tron (2016). Association between Lower Extremity Muscle Strength and Noncontact ACL Injuries. Medicine & Science in Sports & Exercise. ISSN 0195-9131. 48(11), p. 2082–2089. doi: 10.1249/MSS.0000000000001014. Show summary

  Purpose: This study aimed to prospectively investigate the association between isolated and functional lower extremity muscle strength and the risk for noncontact anterior cruciate ligament (ACL) injury in Norwegian female elite handball and football players. Methods: From 2007 through 2015, premier league players participated in strength testing and were prospectively followed for ACL injury risk. At baseline, we recorded player demographics, playing and ACL injury history, and measured peak concentric isokinetic quadriceps and hamstring torques (60-Isj1), hamstring-to-quadriceps ratio, isometric hip abduction strength, and one-repetition maximum in a seated leg press. We followed a predefined statistical protocol where we generated five separate logistic regression models, one for each of the proposed strength risk factors and adjusted for confounding factors. New ACL injury was the outcome, using the leg as the unit of analysis. Results: A total of 57 (6.6%) of 867 players (age = 21 T 4 yr, height = 170 T 6 cm, body mass = 66 T 8 kg) suffered from a noncontact ACL injury after baseline testing (1.8 T 1.8 yr). The OR of sustaining a new injury among those with an ACL injury history was 3.1 (95% confidence interval = 1.6–6.1). None of the five strength variables selected were statistically associated with an increased risk of ACL rupture when adjusted for sport, dominant leg, ACL injury history, and height. Conclusion: Peak lower extremity strength was not associated with an increased ACL injury risk among female elite handball and football players. Hence, peak strength, as measured in the present study, cannot be used to screen elite female athletes to predict injury risk.

• Kyritsis, Polyvios; Bahr, Roald; Landreau, Philippe; Miladi, Riadh & Witvrouw, Erik (2016). Likelihood of ACL graft rupture: not meeting six clinical discharge criteria before return to sport is associated with a four times greater risk of rupture. British Journal of Sports Medicine. ISSN 0306-3674. 50(15), p. 946–951. doi: 10.1136/bjsports-2015-095908. Show summary

  Background: The decision as to whether or not an athlete is ready to return to sport (RTS) after ACL reconstruction is difficult as the commonly used RTS criteria have not been validated. Purpose: To evaluate whether a set of objective discharge criteria, including muscle strength and functional tests, are associated with risk of ACL graft rupture after RTS. Materials and methods: 158 male professional athletes who underwent an ACL reconstruction and returned to their previous professional level of sport were included. Before players returned to sport they underwent a battery of discharge tests (isokinetic strength testing at 60°, 180° and 300°/s, a running t test, single hop, triple hop and triple crossover hop tests). Athletes were monitored for ACL re-ruptures once they returned to sport (median follow-up 646 days, range 1–2060). Results: Of the 158 athletes, 26 (16.5%) sustained an ACL graft rupture an average of 105 days after RTS. Two factors were associated with increased risk of ACL graft rupture: (1) not meeting all six of the discharge criteria before returning to team training (HR 4.1, 95% CI 1.9 to 9.2, p≤0.001); and (2) decreased hamstring to quadriceps ratio of the involved leg at 60°/s (HR 10.6 per 10% difference, 95% CI 10.2 to 11, p=0.005). Conclusions: Athletes who did not meet the discharge criteria before returning to professional sport had a four times greater risk of sustaining an ACL graft rupture compared with those who met all six RTS criteria. In addition, hamstring to quadriceps strength ratio deficits were associated with an increased risk of an ACL graft rupture.

• Schut, Lotte; Wangensteen, Arnlaug; Maaskant, Jolanda; Tol, Johannes; Bahr, Roald & Moen, Maarten (2016). Can Clinical Evaluation Predict Return to Sport after Acute Hamstring Injuries? A Systematic Review. Sports Medicine. ISSN 0112-1642. doi: 10.1007/s40279-016-0639-1. Show summary

  Background: The current literature on the value of clinical evaluation for predicting time to return to sport (RTS) after acute hamstring injuries has not been systematically summarised. Objectives: The aim of this study was to systematically review the literature on the prognostic value of clinical findings (patient history and physical examination) for time to RTS after acute hamstring injuries in athletes. Data Sources: The databases PubMed, EMBASE, SPORTDiscus and Cochrane Library were searched between October 2014 and August 2015. Study Eligibility Criteria: Studies evaluating patient history and/or physical assessment findings as possible predictors for time to RTS (described in days or weeks) following acute hamstring injuries in athletes were eligible for inclusion. Data Analysis: Two authors independently screened the search results and assessed risk of bias using the modified Quality in Prognosis Studies (QUIPS) tool for quality appraisal of prognosis studies. We used a best-evidence synthesis to determine the level of evidence. Results: Sixteen studies were included, of which one study had a low risk of bias and 15 had a high risk of bias. Moderate evidence for an association with time to RTS was found for three clinical findings (visual analogue scale; pain at time of injury, self-predicted time to RTS and clinician predicted time to RTS). There was limited evidence for an association with time to RTS for seven clinical findings (muscle pain during everyday activities, popping sound at injury, forced to stop within 5 min, visual bruising at the site of injury, width (cm) of tenderness to palpation, pain on trunk flexion and pain on active knee flexion initially after injury). The remaining clinical findings revealed either conflicting evidence or limited evidence for an association with time to RTS. Conclusion: There is at present no strong evidence that any clinical finding at baseline provides a valuable prognosis for time to RTS after an acute hamstring injury. There is moderate evidence that visual analogue scale pain at time of injury and predictions for time to RTS by the patient and the clinician are associated with time to RTS. The methodological quality of the current literature is characterised by a substantial risk of bias and reporting of RTS definitions and criteria for RTS were inconsistent. We provide recommendations that can guide the design of future studies.

• Wangensteen, Arnlaug; Tol, Johannes; Witvrouw, Erik; van Linschoten, Robbart; Almusa, Emad & Hamilton, Bruce [Show all 7 contributors for this article] (2016). Hamstring Reinjuries Occur at the Same Location and Early after Return to Sport. American Journal of Sports Medicine. ISSN 0363-5465. 44(8), p. 2112–2121. doi: 10.1177/0363546516646086. Show summary

  Background: Despite relatively high reinjury rates after acute hamstring injuries, there is a lack of detailed knowledge about where and when hamstring reinjuries occur, and studies including imaging-confirmed reinjuries are scarce. Purpose: To investigate the location, radiological severity, and timing of reinjuries on magnetic resonance imaging (MRI) compared with the index injury. Study Design: Case series; Level of evidence, 4. Methods: A MRI scan was obtained ≤5 days after an acute hamstring index injury in 180 athletes, and time to return to sport (RTS) was registered. Athletes with an MRI-confirmed reinjury in the same leg ≤365 days after RTS were included. Categorical grading and standardized MRI parameters of the index injury and reinjury were scored by a single radiologist (with excellent intraobserver reliability). To determine the location of the reinjury, axial and coronal views of the index injury and reinjury were directly compared on proton density–weighted fat-suppressed images. Results: In the 19 athletes included with reinjury, 79% of these reinjuries occurred in the same location within the muscle as the index injury. The median time to RTS after the index injury was 19 days (range, 5-37 days; interquartile range [IQR], 15 days). The median time between the index injury and reinjury was 60 days (range, 20-316 days; IQR, 131 days) and the median time between RTS after the index injury and the reinjury was 24 days (range, 4-311 days; IQR, 140 days). More than 50% of reinjuries occurred within 25 days (4 weeks) after RTS from the index injury and 50% occurred within 50 days after the index injury. All reinjuries with more severe radiological grading occurred in the same location as the index injury. Conclusion: The majority of the hamstring reinjuries occurred in the same location as the index injury, early after RTS and with a radiologically greater extent, suggesting incomplete biological and/or functional healing of the index injury. Specific exercise programs focusing on reinjury prevention initiated after RTS from the index injury are highly recommended.

• Schwellnus, Martin P.; Soligard, Torbjørn; Alonso, Juan-Manuel; Bahr, Roald; Clarsen, Benjamin & Dijkstra, H. Paul [Show all 17 contributors for this article] (2016). How much is too much? (Part 2) : International Olympic Committee consensusstatement on load in sport and risk of illness. British Journal of Sports Medicine. ISSN 0306-3674. 50(17), p. 1043–1052. doi: 10.1136/bjsports-2016-096572. Show summary

  The modern-day athlete participating in elite sports is exposed to high training loads and increasingly saturated competition calendar. Emerging evidence indicates that inappropriate load management is a significant risk factor for acute illness and the overtraining syndrome. The IOC convened an expert group to review the scientific evidence for the relationship of load—including rapid changes in training and competition load, competition calendar congestion, psychological load and travel—and health outcomes in sport. This paper summarises the results linking load to risk of illness and overtraining in athletes, and provides athletes, coaches and support staff with practical guidelines for appropriate load management to reduce the risk of illness and overtraining in sport. These include guidelines for prescription of training and competition load, as well as for monitoring of training, competition and psychological load, athlete well-being and illness. In the process, urgent research priorities were identified.

• Soligard, Torbjørn; Schwellnus, Martin P.; Alonso, Juan-Manuel; Bahr, Roald; Clarsen, Benjamin & Dijkstra, H. Paul [Show all 18 contributors for this article] (2016). How much is too much? (Part 1) International Olympic Committee consensus statement on load in sport and risk of injury. British Journal of Sports Medicine. ISSN 0306-3674. 50(17), p. 1030–1041. doi: 10.1136/bjsports-2016-096581. Show summary

  Athletes participating in elite sports are exposed to high training loads and increasingly saturated competition calendars. Emerging evidence indicates that poor load management is a major risk factor for injury. The International Olympic Committee convened an expert group to review the scientific evidence for the relationship of load (defined broadly to include rapid changes in training and competition load, competition calendar congestion, psychological load and travel) and health outcomes in sport. We summarise the results linking load to risk of injury in athletes, and provide athletes, coaches and support staff with practical guidelines to manage load in sport. This consensus statement includes guidelines for (1) prescription of training and competition load, as well as for (2) monitoring of training, competition and psychological load, athlete well-being and injury. In the process, we identified research priorities.

• Wangensteen, Arnlaug; Bahr, Roald; Almusa, E; van Linschoten, Robbart; Whiteley, R & Witvrouw, E [Show all 7 contributors for this article] (2016). Which is the optimal day for magnetic resonance imaging after acute hamstring injuries? In Roi, Giulio Sergio & Della Villa, Stefano (Ed.), Football medicine strategies - Return to play. Calzetti Mariucci. ISSN 978-88-6028-466-2. p. 383–384.
• Harøy, Joar; Clarsen, Benjamin; Thorborg, Kristian; Hölmich, Per; Bahr, Roald & Andersen, TE (2016). Groin problems are common at all levels of play in Norwegian male football. In Roi, Giulio Sergio & Della Villa, Stefano (Ed.), Football medicine strategies - Return to play. Calzetti Mariucci. ISSN 978-88-6028-466-2. p. 377–378. doi: 10.1177/0363546517737749.
• Bakken, Arnhild; Targett, Stephen; Bere, Tone Tufte; Eirale, Cristiano; Farooq, a & Tol, JL [Show all 10 contributors for this article] (2016). Inter-season variability of a functional movement test in professional football. In Roi, Giulio Sergio & Della Villa, Stefano (Ed.), Football medicine strategies - Return to play. Calzetti Mariucci. ISSN 978-88-6028-466-2. doi: 10.1136/bjsports-2016-096570.
• van Dyk, N; Bahr, Roald; Whiteley, R; Eirale, Cristiano; Tol, JL & Kumar, BD [Show all 9 contributors for this article] (2016). Substantial inter-season variability in isokinetic strength in professional football. In Roi, Giulio Sergio & Della Villa, Stefano (Ed.), Football medicine strategies - Return to play. Calzetti Mariucci. ISSN 978-88-6028-466-2.
• Bakken, Arnhild; Targett, Stephen; Bere, Tone Tufte; Adamuz, MC; Tol, Johannes & Whiteley, Rod [Show all 10 contributors for this article] (2016). Health conditions detected in a comprehensive periodic health evaluation of 558 professional football players. British Journal of Sports Medicine. ISSN 0306-3674. 50(18), p. 1142–1150. doi: 10.1136/bjsports-2015-095829. Show summary

  Background: Despite the widespread use of periodic health evaluation (PHE) to detect and prevent injury and illness in athletes, its effectiveness in detecting health conditions and relevant risk factors is still debated. Aim: To assess health conditions detected by a comprehensive PHE in professional male football players and evaluate their consequences for participation clearance. Methods: A total of 558 professional football players in Qatar completed a PHE prior to the 2013 or 2014 seasons: history, general medical (including blood test), cardiovascular (12-lead ECG and echocardiography) and a musculoskeletal examination, including a specific test battery targeting lower extremity strength and flexibility. On the basis of the PHE, players were either cleared or not cleared for participation. Results: In 533 players (95.5%), at least one health condition was detected requiring treatment or follow-up. Vitamin D deficiency or insufficiency (≤30 ng/mL) was the most common medical condition (n=499, 89.4%), followed by hepatitis B non-immunity or infection (n=164, 29.4%). Cardiac screening identified 48 players (8.6%) with one or more abnormal findings (ECG (n=19, 3.4%) and echocardiography (n=14, 2.5%)). Musculoskeletal conditions were observed in 180 players (32.3%); injuries to or strength deficits of the hip/groin and thigh accounted for the largest proportion. Medical clearance was temporarily not given in 69 players (12.4%), while further examinations were being conducted. One player was disqualified from competitive football. Conclusions: PHE revealed a high prevalence of health conditions requiring treatment or follow-up in professional footballers; however, only 12.4% of conditions impacted on final clearance for participation.

• Bahr, Roald (2016). Why screening tests to predict injury do not work— and probably never will…: a critical review. British Journal of Sports Medicine. ISSN 0306-3674. 50(13), p. 776–780. doi: 10.1136/bjsports-2016-096256. Show summary

  This paper addresses if and how a periodic health examination to screen for risk factors for injury can be used to mitigate injury risk. The key question asked is whether it is possible to use screening tests to identify who is at risk for a sports injury—in order to address the deficit through a targeted intervention programme. The paper demonstrates that to validate a screening test to predict and prevent sports injuries, at least 3 steps are needed. First, a strong relationship needs to be demonstrated in prospective studies between a marker from a screening test and injury risk (step 1). Second, the test properties need to be examined in relevant populations, using appropriate statistical tools (step 2). Unfortunately, there is currently no example of a screening test for sports injuries with adequate test properties. Given the nature of potential screening tests (where test performance is usually measured on a continuous scale from low to high), substantial overlap is to be expected between players with high and low risk of injury. Therefore, although there are a number of tests demonstrating a statistically significant association with injury risk, and therefore help the understanding of causative factors, such tests are unlikely to be able to predict injury with sufficient accuracy. The final step needed is to document that an intervention programme targeting athletes identified as being at high risk through a screening programme is more beneficial than the same intervention programme given to all athletes (step 3). To date, there is no intervention study providing support for screening for injury risk.

• Shimakawa, Tomoyuki; Shimakawa, Yusuke; Kawasoe, Yoko; Yoshimura, Kouji; Chinen, Yuma & Eimon, Kazuya [Show all 12 contributors for this article] (2016). Beach soccer injuries during the Japanese National Championships. Orthopaedic Journal of Sports Medicine (OJSM). ISSN 2325-9671. 4(1), p. 1–7. doi: 10.1177/2325967115625636. Show summary

  Background: The frequency and severity of injury in beach soccer are unknown. Purpose: To estimate the incidence rates, characteristics, and risk factors for injuries associated with beach soccer. Study Design: Cohort study; Level of evidence, 3. Methods: The same sports physician examined and recorded injuries incurred during the Japanese National Beach Soccer Championships in 2013 and 2014. Posttournament follow-up was made for all injuries. Match exposure for each player was recorded through video review to examine individual risk factors. Results: A total of 58 injuries were recorded during 54 matches. The overall injury rate was 179.0 (95% CI, 138.4-231.6), and the time-loss injury rate was 28.2 (95% CI, 14.7-54.1) per 1000 player-hours. The foot/toe (34.9%) was the most frequently injured area, followed by the lower leg (22.2%) and thigh (11.1%). There was only 1 ankle injury (1.6%). The most frequent injury type was contusions (60.3%), followed by lacerations/abrasions (14.3%) and sprains/ligament injuries (6.3%). Only 4 injuries resulted in ≥30 days of time-loss (7.4%). After adjusting for age, a previous history of severe injury and longer experience of beach soccer were significantly associated with injury risk. Conclusion: The time-loss injury rate in this study was comparable to the rates reported during the matches of soccer or futsal tournaments. However, a greater incidence of foot/toe injury and lacerations/abrasions as well as a lower incidence of ankle injury distinguished beach soccer from soccer and futsal, possibly related to the specific playing conditions of being barefoot on a sand surface.

• Krosshaug, Tron; Steffen, Kathrin; Kristianslund, Eirik; Nilstad, Agnethe; Mok, Kam-Ming & Myklebust, Grethe [Show all 10 contributors for this article] (2016). The Vertical Drop Jump Is a Poor Screening Test for ACL Injuries in Female Elite Soccer and Handball Players : A Prospective Cohort Study of 710 Athletes. American Journal of Sports Medicine. ISSN 0363-5465. 44(4), p. 874–883. doi: 10.1177/0363546515625048. Show summary

  Background: The evidence linking knee kinematics and kinetics during a vertical drop jump (VDJ) to anterior cruciate ligament (ACL) injury risk is restricted to a single small sample. Still, the VDJ test continues to be advocated for clinical screening purposes. Purpose: To test whether 5 selected kinematic and kinetic variables were associated with future ACL injuries in a large cohort of Norwegian female elite soccer and handball players. Furthermore, we wanted to assess whether the VDJ test can be recommended as a screening test to identify players with increased risk. Study Design: Cohort study; Level of evidence, 2. Methods: Elite female soccer and handball players participated in preseason screening tests from 2007 through 2014. The tests included marker-based 3-dimensional motion analysis of a drop-jump landing. We followed a predefined statistical protocol in which we included the following candidate risk factors in 5 separate logistic regression analyses, with new ACL injury as the outcome: (1) knee valgus angle at initial contact, (2) peak knee abduction moment, (3) peak knee flexion angle, (4) peak vertical ground-reaction force, and (5) medial knee displacement. Results: A total of 782 players were tested (age, 21 ± 4 years; height, 170 ± 7 cm; body mass, 67 ± 8 kg), of which 710 were included in the analyses. We registered 42 new noncontact ACL injuries, including 12 in previously ACL-injured players. Previous ACL injury (relative risk, 3.8; 95% CI, 2.1-7.1) and medial knee displacement (odds ratio, 1.40; 95% CI, 1.12-1.74 per 1-SD change) were associated with increased risk for injury. However, among the 643 players without previous injury, we found no association with medial knee displacement. A receiver operating characteristic curve analysis of medial knee displacement showed an area under the curve of 0.6, indicating a poor-to-failed combined sensitivity and specificity of the test, even when including previously injured players. Conclusion: Of the 5 risk factors considered, medial knee displacement was the only factor associated with increased risk for ACL. However, receiver operating characteristic curve analysis indicated a poor combined sensitivity and specificity when medial knee displacement was used as a screening test for predicting ACL injury. For players with no previous injury, none of the VDJ variables were associated with increased injury risk. Clinical Relevance: VDJ tests cannot predict ACL injuries in female elite soccer and handball players.

• Svendsen, Ida S.; Taylor, Ian M.; Tønnessen, Espen; Bahr, Roald & Gleeson, Michael (2016). Training-related and competition-related risk factors for respiratory tract and gastrointestinal infections in elite cross-country skiers. British Journal of Sports Medicine. ISSN 0306-3674. 50(13), p. 809–815. doi: 10.1136/bjsports-2015-095398. Show summary

  Aim: To examine symptoms indicative of respiratory tract and gastrointestinal infections and determine risk factors for such symptoms in elite cross-country skiers. Methods: Self-reported training and symptom data for 37 elite cross-country skiers from 2007 to 2015 were analysed using multilevel logistic regression equations with symptom incidence and duration as outcome variables, and sex, performance level, season, competition, air travel, altitude exposure and training characteristics as independent variables. Results: Data for 7016 person-weeks were analysed, including 464 self-reported infection events and 110 959 h of training. Athletes reported median (range) 3 (1–7) respiratory tract and/or gastrointestinal events per year, with symptoms lasting 5 (1–24) days. During the winter, symptoms occurred more frequently (OR 2.09, p<0.001) and lasted longer (b=0.043, p<0.001) compared with summer. Competition and air travel increased the risk of symptoms, with ORs of 2.93 (95% CI 2.24 to 3.83) and 4.94 (95% CI 3.74 to 6.53), respectively (p<0.001). Athletes with higher training monotony had lower risk of symptoms (OR 0.87 (95% CI 0.73 to 0.99), p<0.05). Other training variables were not associated with symptoms. Athletes who had won an Olympic/World Championship medal reported shorter symptom duration compared with less successful athletes (b=−0.019, p<0.05) resulting in significantly fewer symptomatic days/year (14 (6–29) vs 22 (8–43) days/year). Conclusions: Air travel and competition are major risk factors for acute respiratory tract and gastrointestinal symptoms in this population. Athletes who have large fluctuations in training load experience such symptoms more frequently. Shorter duration of symptoms appears to be associated with success in cross-country skiing.

• James, Evan; Bahr, Roald & LaPrade, Robert F. (2016). Youth sport, health and physical activity. In Green, Kenneth Stanley & Smith, Andy (Ed.), Routledge Handbook of Youth Sport. Routledge. ISSN 978-0-415-84003-3. p. 392–405. Show summary

  The Routledge Handbook of Youth Sport is a comprehensive survey of the latest research into young people’s involvement in sport. Drawing on a wide diversity of disciplines, including sociology, psychology, policy studies, coaching, physical education and physiology, the book examines the importance of sport during a key transitional period of our lives, from the later teenage years into the early twenties, and therefore helps us develop a better understanding of the social construction of young people’s lives. The book covers youth sport in all its forms, from competitive game-contests and conventional sport to recreational activities, exercise and lifestyle sport, and at all levels, from elite competition to leisure time activities and school physical education. It explores youth sport across the world, in developing and developed countries, and touches on some of the most significant themes and issues in contemporary sport studies, including physical activity and health, lifelong participation, talent identification and development, and safeguarding and abuse. No other book brings together in one place such a breadth and depth of material on youth sport or the engagement of young people in physical activity. The Routledge Handbook of Youth Sport is therefore important reading for all advanced students, researchers, practitioners and policy-makers with an interest in youth sport, youth culture, sport studies or physical education

• Pluim, Babette; Loeffen, F.G.J.; Clarsen, Benjamin; Bahr, Roald & Verhagen, Evert ALM (2016). A one-season prospective study of injuries and illness in elite junior tennis. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 26(5), p. 564–571. doi: 10.1111/sms.12471. Show summary

  The objective of this study was to estimate the incidence and prevalence of injury and illness among elite junior tennis players. A cohort of 73 players (11–14 years) in the 2012–2013 Dutch national high-performance program was followed for 32 weeks; all participants completed the study. The OSTRC Questionnaire on Health Problems was used to record self-reported injuries and illnesses and to record training and match exposure. Main outcome measures were average prevalence of overuse injury and illness and incidence density of acute injury. On average, players practiced 9.1 h/week (SD 0.6; range 2.3–12.0) and had 2.2 h of match play (SD 0.6; range 2.3–12.0). During the course of the study, 67 players reported a total of 187 health problems. The average weekly prevalence of all health problems was 21.3% (95% CI: 19.2–22.9), of which 12.1% (95% CI: 10.9–13.3) constituted overuse injuries and 5.8% (95% CI: 4.6–6.9) illnesses. The incidence of acute injuries was 1.2/1000 h of tennis play (95% CI: 0.7–1.7). The high occurrence of overuse injuries among elite junior tennis players suggests that an early focus on preventative measures is warranted, with a particular focus on the monitoring and management of workload.

• Haaland, Bjørnar Øvrum; Steenstrup, Sophie E.; Bere, Tone Tufte; Bahr, Roald & Nordsletten, Lars (2016). Injury rate and injury patterns in FIS World Cup Alpine skiing (2006–2015): have the new ski regulations made an impact? British Journal of Sports Medicine. ISSN 0306-3674. 50(1), p. 32–36. doi: 10.1136/bjsports-2015-095467. Show summary

  Background: New regulations for ski equipment were implemented prior to the 2012/2013 season in the International Ski Federation (FIS) Alpine World Cup (WC). Objective: To investigate the effect of the new ski regulations on the rate and pattern of injuries by comparing data before (2006–2012) and after the implementation (2012–2015). Methods: Injuries were recorded on the basis of the FIS Injury Surveillance System (FIS ISS) through retrospective interviews at the end of each of the nine WC seasons. All acute injuries that required medical attention were registered. Exposure was calculated on the basis of the official result lists. Results: The absolute injury rate (injuries/100 athletes/season) was lower in the three seasons after the new ski regulations compared with the six seasons before (risk ratio (RR) 0.74, 95% CI 0.63 to 0.87). This was also the case for the relative injury rate (injuries/1000 runs) (RR 0.76, 95% CI 0.59 to 0.98). These changes were evident for male skiers, not for female skiers. There was a lower absolute injury rate for upper body injuries (RR 0.56, 95% CI 0.43 to 0.77), while no difference was found for lower extremity injuries (RR 0.84, 95% CI 0.70 to 1.01). Conclusions: We found a lower rate of injuries in the three seasons after the new ski regulation compared with the six seasons before. However, the ability to draw conclusions on the effects of the equipment change in subgroups of sex, discipline or body part is restricted by the limited statistical power.

• Pasanen, Kati; Rossi, Marco T.; Parkkari, Jari; Heinonen, Ari; Steffen, Kathrin & Myklebust, Grethe [Show all 14 contributors for this article] (2015). Predictors of lower extremity injuries in team sports (PROFITS-study): a study protocol. BMJ Open sport & exercise medicine. ISSN 2055-7647. 1(1). doi: 10.1136/bmjsem-2015-000076.
• Costa-Scorse, Brenda A.; Hopkins, Will G. & Bahr, Roald (2015). Evaluation of ski-binding-boot system safety using torque testing. ASTM Special Technical Publication. ISSN 0066-0558. STP 1582, p. 163–170. doi: 10.1520/STP158220130158.
• Costa-Scorse, Brenda; Hopkins, Will G.; Bahr, Roald & Lamont, Mike (2015). Translation of international snow-sports equipment standards into injury-prevention practice. ASTM Special Technical Publication. ISSN 0066-0558. STP 1582, p. 150–159. doi: 10.1520/STP158220140009.
• Wangensteen, Arnlaug; Almusa, Emad; Boukarroum, Sirine; Farooq, Abdulaziz; Hamilton, Bruce & Whiteley, Rodney [Show all 8 contributors for this article] (2015). MRI does not add value over and above patient history and clinical examination in predicting time to return to sport after acute hamstring injuries: a prospective cohort of 180 male athletes. British Journal of Sports Medicine. ISSN 0306-3674. 49(24), p. 1579–1587. doi: 10.1136/bjsports-2015-094892. Show summary

  Background: MRI is frequently used in addition to clinical evaluation for predicting time to return to sport (RTS) after acute hamstring injury. However, the additional value of MRI to patient history taking and clinical examination remains unknown and is debated. Aim: To prospectively investigate the predictive value of patient history and clinical examination at baseline alone and the additional predictive value of MRI findings for time to RTS using multivariate analysis while controlling for treatment confounders. Methods: Male athletes (N=180) with acute onset posterior thigh pain underwent standardised patient history, clinical and MRI examinations within 5 days, and time to RTS was registered. A general linear model was constructed to assess the associations between RTS and the potential baseline predictors. A manual backward stepwise technique was used to keep treatment variables fixed. Results: In the first multiple regression model including only patient history and clinical examination, maximum pain score (visual analogue scale, VAS), forced to stop within 5 min, length of hamstring tenderness and painful resisted knee flexion (90°), showed independent associations with RTS and the final model explained 29% of the total variance in time to RTS. By adding MRI variables in the second multiple regression model, maximum pain score (VAS), forced to stop within 5 min, length of hamstring tenderness and overall radiological grading, showed independent associations and the adjusted R2 increased from 0.290 to 0.318. Thus, additional MRI explained 2.8% of the variance in RTS. Summary: There was a wide variation in time to RTS and the additional predictive value of MRI was negligible compared with baseline patient history taking and clinical examinations alone. Thus, clinicians cannot provide an accurate time to RTS just after an acute hamstring injury. This study provides no rationale for routine MRI after acute hamstring injury.

• Koga, Hideyuki; Muneta, Takeshi; Bahr, Roald; Engebretsen, Lars & Krosshaug, Tron (2015). Video analysis of ACL injury mechanisms using a model-based image-matching technique. In Ogawa, Tetsuya; Fukano, Mako & Fukubayashi, Toru (Ed.), Sports injuries and prevention. Springer. ISSN 978-4-431-55317-5. p. 109–120. doi: 10.1007/978-4-431-55318-2_9.
• Krosshaug, Tron & Bahr, Roald (2015). Video analysis of ACL injuries in sports. In Ogawa, Tetsuya; Fukano, Mako & Fukubayashi, Toru (Ed.), Sports injuries and prevention. Springer. ISSN 978-4-431-55317-5. p. 97–108. doi: 10.1007/978-4-431-55318-2_8.
• Bahr, Roald; Thorborg, Kristian & Ekstrand, Jan (2015). Evidence-based hamstring injury prevention is not adopted by the majority of Champions League or Norwegian Premier League football teams: The Nordic Hamstring survey. British Journal of Sports Medicine. ISSN 0306-3674. 49(22), p. 1466–1471. doi: 10.1136/bjsports-2015-094826. Show summary

  Background: The Nordic hamstring (NH) exercise programme was introduced in 2001 and has been shown to reduce the risk of acute hamstring injuries in football by at least 50%. Despite this, the rate of hamstring injuries has not decreased over the past decade in male elite football. Aim: To examine the implementation of the NH exercise programme at the highest level of male football in Europe, the UEFA Champions League (UCL), and to compare this to the Norwegian Premier League, Tippeligaen, where the pioneer research on the NH programme was conducted. Design: Retrospective survey. Setting/participants: 50 professional football teams, 32 from the UCL and 18 from Tippeligaen. Methods: A questionnaire, based on the Reach, Efficacy, Adoption, Implementation and Maintenance framework, addressing key issues related to the implementation of the NH programme during three seasons from 2012 through 2014, was distributed to team medical staff using electronic survey software. Results: The response rate was 100%. Of the 150 club-seasons covered by the study, the NH programme was completed in full in 16 (10.7%) and in part in an additional 9 (6%) seasons. Consequently, 125 (83.3%) club-seasons were classified as non-compliant. There was no difference in compliance between the UCL and Tippeligaen in any season (χ2: 0.41 to 0.52). Conclusions: Adoption and implementation of the NH exercise programme at the highest levels of male football in Europe is low; too low to expect any overall effect on acute hamstring injury rates.

• Nilstad, Agnethe; Krosshaug, Tron; Mok, Kam-Ming; Bahr, Roald & Andersen, Thor Einar (2015). Association Between Anatomical Characteristics, Knee Laxity, Muscle Strength, and Peak Knee Valgus During Vertical Drop-Jump Landings. Journal of Orthopaedic and Sports Physical Therapy. ISSN 0190-6011. 45(12), p. 998–1005. doi: 10.2519/jospt.2015.5612. Show summary

  Study Design: Controlled laboratory study; cross-sectional. Objectives: To investigate the relationship among anatomical variables, knee laxity, muscle strength, and peak knee valgus angles during a vertical drop-jump landing task. Background: Excessive knee valgus has been associated with anterior cruciate ligament injury in females; however, the influence of anatomical characteristics, knee laxity, and muscle strength on frontal plane knee motion is not completely understood. Methods: Norwegian elite female soccer players (n = 279; mean ± SD age, 21 ± 4 years; height, 167 ± 6 cm; body mass, 63 ± 7 kg) were evaluated from 2009 through 2012. The evaluation included 3-D motion analysis of a vertical drop jump, anatomical measures (height, static knee valgus, leg length, and static foot posture), knee laxity, and muscle strength (quadriceps, hamstrings, and hip abductors). Multiple linear regression analyses were used to investigate the relationships among anatomical characteristics, knee laxity, muscle strength, and peak knee valgus angles. Results: Anatomical characteristics explained 11% of the variance in peak knee valgus angles (P<.001), with height and static knee valgus being significant predictors. Conclusion: Greater body height and static knee valgus were associated with greater peak knee valgus angles during a vertical drop-jump landing task. However, these variables only explained 11% of the variance in peak knee valgus.

• Visnes, Håvard; Haug, KBF; Sivertsen, EA & Bahr, Roald (2015). Kan Genetisk testing forutse risikoen for hopperkne? In Vagstad, Terje (Eds.), Høstmøteboken - Vitenskapelig program og abstrakter 2015. Norsk Ortopedisk Forening.
• Bere, Tone Tufte; Alonso, Juan-Manuel; Wangensteen, Arnlaug; Bakken, Arnhild; Eirale, Cristiano & Dijkstra, H. Paul [Show all 9 contributors for this article] (2015). Injury and illness surveillance during the 24th Men's Handball World Championship 2015 in Qatar. British Journal of Sports Medicine. ISSN 0306-3674. 49(17), p. 1151–1156. doi: 10.1136/bjsports-2015-094972. Show summary

  Background: The IOC encourages international federations to establish systematic athlete injury and illness surveillance programmes. Objective: To describe pattern of injuries and illnesses during the 24th Men's Handball World Championship 2015 by implementing the IOC injury and illness surveillance protocol. Methods: The medical staff of participating teams (n=24) were requested to report all new injuries and illnesses during matches and/or training on a daily basis throughout the event (15 January to 1 February, 2015). Exposure (number of player-hours) during all matches was calculated for all players (n=384) and for each of the 4 player positions (wing, back, line and goalkeeper). Results: Medical staff of all teams submitted 96.7% (n=325) of the daily report forms. In total, 27.1% of the players were injured, and of the 132 injuries reported, 40% were time-loss injuries. The total incidence of injuries was 104.5 per 1000 player-hours. The highest risk of injury was found among line players, and more injuries occurred during the first half of the matches. The most frequent injury location was the ankle, followed by the thigh, knee and head/face. The majority of injuries were contusion, sprain or strain. In total, 10.9% of the players were affected by an illness during the event. Of the 42 cases recorded, 31 (73.8%) were reported as respiratory tract infection. Conclusions: The risk of injury in handball is high among Olympic sports. Preventive measures should focus on contusions, ankle sprains, and thigh muscle strains, as well as measures aimed to reduce upper respiratory tract infections.

• Bere, Tone Tufte; Kruczynski, Jacek; Veintimilla, Nadège; Hamu, Yuichiro & Bahr, Roald (2015). Injury risk is low among world-class volleyball players: 4-year data from the FIVB Injury Surveillance System. British Journal of Sports Medicine. ISSN 0306-3674. 49(17), p. 1132–1137. doi: 10.1136/bjsports-2015-094959. Show summary

  Background: Little is known about the rate and pattern of injuries in international volleyball competition. Objective: To describe the risk and pattern of injuries among world-class players based on data from the The International Volleyball Federation (FIVB) Injury Surveillance System (ISS) (junior and senior, male and female). Methods: The FIVB ISS is based on prospective registration of injuries by team medical staff during all major FIVB tournaments (World Championships, World Cup, World Grand Prix, World League, Olympic Games). This paper is based on 4-year data (September 2010 to November 2014) obtained through the FIVB ISS during 32 major FIVB events (23 senior and 9 junior). Results: The incidence of time-loss injuries during match play was 3.8/1000 player hours (95% CI 3.0 to 4.5); this was greater for senior players than for junior players (relative risk: 2.04, 1.29 to 3.21), while there was no difference between males and females (1.04, 0.70 to 1.55). Across all age and sex groups, the ankle was the most commonly injured body part (25.9%), followed by the knee (15.2%), fingers/thumb (10.7%) and lower back (8.9%). Injury incidence was greater for centre players and lower for liberos than for other player functions; injury patterns also differed between player functions. Conclusions: Volleyball is a very safe sport, even at the highest levels of play. Preventive measures should focus on acute ankle and finger sprains, and overuse injuries in the knee, lower back and shoulder.

• Bahr, Roald (2015). How to develop policies for competing in the heat and reducing heat illness risk? In de Vincenzi, Jean-Pierre (Eds.), World Conference Heat Stress and Sport Performance - Program & abstracts. INSEP. p. 93–94.
• van Dyk, N; Whiteley, R; Eirale, Cristiano; Kumar, BD; Hamilton, B & Tol, JL [Show all 8 contributors for this article] (2015). Muscle strength imbalances and hamstring strain injuries - are we moving forward? In Roi, Giulio Sergio & Della Villa, Stefano (Ed.), Football Medicine Strategies for Player Care. XXIV International Conference on Sports Rehabilitation and Traumatology. Abstract Book.. Calzetti Mariucci Editori. ISSN 978-88-6028-429-7.
• Bakken, Arnhild; Targett, Stephen; Bere, Tone Tufte; Adamuz, MC; Tol, JL & Whiteley, R [Show all 10 contributors for this article] (2015). What does a comprehensive periodic health evaluation in football players detect? In Roi, Giulio Sergio & Della Villa, Stefano (Ed.), Football Medicine Strategies for Player Care. XXIV International Conference on Sports Rehabilitation and Traumatology. Abstract Book.. Calzetti Mariucci Editori. ISSN 978-88-6028-429-7. p. 151–151. doi: 10.1136/bjsports-2015-095829.
• Jarning, Jon Moberg; Mok, Kam-Ming; Hansen, Bjørge Hermann & Bahr, Roald (2015). Application of a tri-axial accelerometer to estimate jump frequency in volleyball. Sports Biomechanics. ISSN 1476-3141. 14(1), p. 95–105. doi: 10.1080/14763141.2015.1027950.
• Johansen, Melissa Woll; Steenstrup, Sophie E.; Bere, Tone Tufte; Bahr, Roald & Nordsletten, Lars (2015). Injuries in World Cup telemark skiing: a 5-year cohort study. British Journal of Sports Medicine. ISSN 0306-3674. 49(7), p. 453–457. doi: 10.1136/bjsports-2014-094211. Show summary

  Background: There are limited data on injuries in World Cup (WC) telemark skiing. Objective: To describe the injury incidence and injury pattern seen among WC telemark skiers during the competitive season. Methods: We interviewed all WC athletes (or their coach, if the athlete was not present) at the end of five winter seasons from 2008 until 2013. All acute injuries occurring in the competitive season that required the attention of medical personnel were registered. Exposure was calculated based on the official International Ski Federation (FIS) results database. Results: 149 acute injuries were registered during 565 WC skier seasons. The absolute injury incidence was 26.4 injuries per 100 athletes per season (95% CI 22.1 to 30.6), higher for females than males (risk ratio (RR) 1.49, 95% CI 1.07 to 2.08). During the FIS WC competitions, 69 injuries were registered, corresponding to a relative incidence of 8.2 injuries per 1000 runs (95% CI 6.3 to 10.1). The most frequently injured body part was the knee (21%) followed by the hand-finger-thumb (20%), ankle (13%) and shoulder/clavicle (13%). The absolute risk of knee and shoulder/clavicle injuries was higher for females versus males (RR for knee injuries 2.72, 95% CI 1.35 to 5.51; RR for shoulder/clavicle injuries 2.55, 95% CI 1.06 to 6.14). No differences were detected in the injury incidence between disciplines. Conclusions: Female telemark skiers are at 1.5 times greater risk of injury than male skiers. The most commonly injured body part was the knee. The risk of knee and shoulder/clavicle injuries was higher for female athletes than for male athletes.

• Visnes, Håvard; Tegnander, Agnar & Bahr, Roald (2015). Ultrasound characteristics of the patellar and quadriceps tendons among young elite athletes. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 25(2), p. 205–215. doi: 10.1111/sms.12191.
• Clarsen, Benjamin; Bahr, Roald; Heymans, Martijn W.; Engedahl, Martin; Midtsundstad, Guri Elisabeth & Rosenlund, Linn [Show all 8 contributors for this article] (2015). The prevalence and impact of overuse injuries in five Norwegian sports: Application of a new surveillance method. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 25(3), p. 323–330. doi: 10.1111/sms.12223. Show summary

  Little is known about the true extent and severity of overuse injuries in sport, largely because of methodological challenges involved in recording them. This study assessed the prevalence of overuse injuries among Norwegian athletes from five sports using a newly developed method designed specifically for this purpose. The Oslo Sports Trauma Research Center Overuse Injury Questionnaire was distributed weekly by e-mail to 45 cross-country skiers, 98 cyclists, 50 floorball players, 55 handball players, and 65 volleyball players for 13 weeks. The prevalence of overuse problems at the shoulder, lower back, knee, and anterior thigh was monitored throughout the study and summary measures of an injury severity score derived from athletes' questionnaire responses were used to gauge the relative impact of overuse problems in each area. The area where overuse injuries had the greatest impact was the knee in volleyball where, on average, 36% of players had some form of complaint (95% CI 32–39%). Other prevalent areas included the shoulder in handball (22%, 95% CI 16–27%) the knee in cycling (23%, 95% CI 17–28%), and the knee and lower back in floorball (27%, 95% CI 24–31% and 29%, 95% CI 25–33%, respectively).

• Yamazaki, Junya; Gilgien, Matthias; Kleiven, Svein; McIntosh, Andrew S.; Nachbauer, Werner & Müller, Erich [Show all 9 contributors for this article] (2015). Analysis of a severe head injury in world cup alpine skiing. Medicine & Science in Sports & Exercise. ISSN 0195-9131. 47(6), p. 1113–1118. doi: 10.1249/MSS.0000000000000511. Show summary

  Traumatic brain injury (TBI) is the leading cause of death in alpine skiing. It has been found that helmet use can reduce the incidence of head injuries between 15％ and 60％. However, knowledge on optimal helmet performance criteria in World Cup alpine skiing is currently limited due to lack of biomechanical data from real crash situations. Purpose: This study aimed to estimate impact velocities in a severe TBI case in World Cup alpine skiing. Methods: Video sequences from a TBI case in World Cup alpine skiing were analyzed using a Model-Based Image Matching (MBIM) technique. Video sequences from four camera views were obtained in full high definition (1080p) format. A 3D model of the course was built based on accurate measurements of piste landmarks and matched to the background video footage using the animation software Poser 4. A trunk-neck-head model was utilized for tracking the skier’s trajectory. Results: Immediately before head impact, the downward velocity component was estimated to be 8 m/s. After impact, the upwards velocity was 3 m/s, whereas the velocity parallel to the slope surface was reduced from 33 m/s to 22 m/s. The frontal plane angular velocity of the head changed from 80 rad/s left tilt immediately before impact to 20 rad/s right tilt immediately after impact. Conclusion: A unique combination of HD video footage and accurate measurements of landmarks in the slope made possible a high quality analysis of head impact velocity in a severe TBI case. The estimates can provide crucial information on how to prevent TBI through helmet performance criteria and design.

• Bjørneboe, John Andreas; Bahr, Roald & Andersen, Thor Einar (2014). Gradual increase in the risk of match injury in Norwegian male professional football: A 6-year prospective study. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 24(1), p. 189–196. doi: 10.1111/j.1600-0838.2012.01476.x. Show summary

  The aim of this study was to monitor injury incidence and pattern in Norwegian male professional football over six consecutive seasons and compare the risk of injury between the preseason and competitive season. All time loss injuries were recorded by the medical staff of each club. In total, 2365 injuries were recorded. The incidence of acute injuries was 15.9/1000 match hours [95% confidence interval (CI): 14.9–16.8], 1.9/1000 training hours (95% CI: 1.7–2.0), and 1.4 (95% CI: 1.3–1.5) overuse injuries/1000 h. A linear regression model found an annual increase of 1.06 acute match injuries/1000 h (95% CI: 0.40–1.73), corresponding to a total increase of 49% during the 6-year study period. When accounting for interteam variation and clustering effects using a general estimating equation model, the increase in injury incidence was 0.92 (95% CI: −0.11–1.95, P = 0.083). No difference in the risk of acute match injuries (rate ratio (RR): 0.86, 95% CI: 0.73–1.01), acute training injuries (RR: 1.16, 95% CI: 0.99–1.36), or overuse injuries (RR: 1.04, 95% CI: 0.89–1.21) was observed between the preseason and competitive season. In conclusion, the overall risk of acute match injuries in Norwegian male professional football increased by 49% during the study period, although this increase was not fully consistent across teams. We detected no change in the risk of training and overuse injuries or any difference between the preseason and competitive season.

• Nilstad, Agnethe; Bahr, Roald & Andersen, Thor Einar (2014). Text messaging as a new method for injury registration in sports: A methodological study in elite female football. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 24(1), p. 243–249. doi: 10.1111/j.1600-0838.2012.01471.x. Show summary

  Methodological differences in epidemiologic studies have led to significant discrepancies in injury incidences reported. The aim of this study was to evaluate text messaging as a new method for injury registration in elite female football players and to compare this method with routine medical staff registration. Twelve teams comprising 228 players prospectively recorded injuries and exposure through one competitive football season. Players reported individually by answering three text messages once a week. A designated member of the medical staff conducted concurrent registrations of injuries and exposure. Injuries and exposure were compared between medical staff registrations from nine teams and their 159 affiliated players. During the football season, a total of 232 time-loss injuries were recorded. Of these, 62% were captured through individual registration only, 10% by the medical staff only, and 28% were reported through both methods. The incidence of training injuries was 3.7 per 1000 player hours when calculated from individual registration vs 2.2 from medical staff registration [rate ratio (RR): 1.7, 1.2-2.4]. For match injuries, the corresponding incidences were 18.6 vs 5.4 (RR: 3.4, 2.4-4.9), respectively. There was moderate agreement for severity classifications in injury cases reported by both methods (kappa correlation coefficient: 0.48, confidence interval: 0.30-0.66).

• Nilstad, Agnethe; Andersen, Thor Einar; Bahr, Roald; Holme, Ingar Morten K & Steffen, Kathrin (2014). Risk Factors for Lower Extremity Injuries in Elite Female Soccer Players. American Journal of Sports Medicine. ISSN 0363-5465. 42(4), p. 940–948. doi: 10.1177/0363546513518741. Show summary

  Background: The incidence of lower extremity injuries in female soccer players is high, but the risk factors for injuries are unknown. Purpose: To investigate risk factors for lower extremity injuries in elite female soccer players. Study Design: Cohort study; Level of evidence, 3. Methods: Players in the Norwegian elite female soccer league (N = 12 teams) participated in baseline screening tests before the 2009 competitive soccer season. The screening included tests assessing maximal lower extremity strength, dynamic balance, knee valgus angles in a drop-jump landing, knee joint laxity, generalized joint laxity, and foot pronation. Also included was a questionnaire to collect information on demographic data, elite-level experience, and injury history. Time-loss injuries and exposure in training and matches were recorded prospectively in the subsequent soccer season using weekly text messaging. Players reporting an injury were contacted to collect data regarding injury circumstances. Univariate and multivariate regression analyses were used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for ±1 standard deviation of change. Results: In total, 173 players underwent complete screening tests and registration of injuries and exposure throughout the season. A total of 171 injuries in 107 players (62%) were recorded; ligament and muscle injuries were the most frequent. Multivariate analyses showed that a greater body mass index (BMI) (OR, 1.51; 95% CI, 1.21-1.90; P = .001) was the only factor significantly associated with new lower extremity injuries. A greater BMI was associated with new thigh injuries (OR, 1.51; 95% CI, 1.08-2.11; P = .01), a lower knee valgus angle in a drop-jump landing was associated with new ankle injuries (OR, 0.64; 95% CI, 0.41-1.00; P = .04), and a previous knee injury was associated with new lower leg and foot injuries (OR, 3.57; 95% CI, 1.27-9.99; P = .02), whereas none of the factors investigated influenced the risk of new knee injuries. Conclusion: A greater BMI was associated with lower extremity injuries in elite female soccer players. Clinical Relevance: Increased knowledge on risk factors for lower extremity injuries enables more targeted prevention strategies with the aim of reducing injury rates in female soccer players.

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• Brukner, Peter; Clarsen, Benjamin; Cook, Jill; Cools, Ann; Crossley, Kay & Hutchinson, Mark R. [Show all 9 contributors for this article] (2017). Brukner and Khan's clinical sports medicine : vol. 1 Injuries. McGraw-Hill. ISBN 9781743761380. 1056 p.

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• Øvrebø, Tore; Bahr, Roald & Lybekk, Else-Marthe Sørlie (2024). The Norwegian Model - Norway's approach from youth sports to elite athletes.
• Bahr, Roald (2024). A decision-based model for return to play in sport.
• Bahr, Roald (2024). Taking care of Olympic and Paralympic athletes - what is different between winter and summer sports?
• Moseid, Nils Fredrik Holm; Lemyre, Nicolas; Roberts, Glyn; Fagerland, Morten Wang; Moseid, Christine Holm & Bahr, Roald (2024). No Pain No Gain: Associations Between Health Problems, Motivation and Coach Relation.
• Bahr, Roald & Andersen, Thor Einar (2024). OSTRC & IHS presentations.
• Myklebust, Grethe; Munkvold, Emilie; Hägglund, Martin; Bahr, Roald; Møller, Merete & Bjørndal, Christian Thue [Show all 7 contributors for this article] (2024). Why does it work? Proposed mechanisms of effect in injury prevention programs in football and handball: a scoping review of 84 studies.
• Bahr, Roald (2023). Can we predict ACL injury and if not what should we do?
• Bahr, Roald (2023). Principles of injury and illness surveillance - guidance from the IOC Consensus statement.
• Visnes, Håvard; Bache-Mathiesen, Lena Kristin; Yamaguchi, Tetsuo; Hisdal, Erling & Bahr, Roald (2023). Hopperkne gir varig redusert knefunksjon hos unge volleyballspillere – en prospektiv kohortstudie med 11 års oppfølging.
• Moen, Christian; Myklebust, Grethe; Munkvold, Emilie; Hägglund, Martin; Bahr, Roald & Møller, Merete [Show all 8 contributors for this article] (2023). Hvorfor virker de? Effektmekanismer i skadeforebyggende programmer i fotball og håndball.
• Visnes, Håvard; Bache-Mathiesen, Lena Kristin; Yamaguchi, Tetsuo; Hisdal, Erling & Bahr, Roald (2023). Hopperkne gir vedvarende redusert knefunksjon hos unge volleyballspillere – en prospektiv kohortstudie med 11 års oppfølging.
• Bahr, Roald & Kåshagen, Ingvild (2023). Risikostyring i praksis.
• Bahr, Roald & Kåshagen, Ingvild (2023). Risikostyring.
• Thorarinsdottir, Solveig; Amundsen, Roar; Larmo, Arne Feilberg; Pedersen, Roar; Andersen, Thor Einar & Bahr, Roald [Show all 7 contributors for this article] (2023). Groin injuries in womens premier league football in Norway.
• Thorarinsdottir, Solveig; Amundsen, Roar; Clarsen, Benjamin Matthew; Andersen, Thor Einar; Møller, Merete & Bahr, Roald (2023). #ReadyToPlay. Health problems in womens premier leage football.
• Bahr, Roald & Myklebust, Grethe (2023). The Oslo Sports Trauma Research Centre (OSTRC).
• Bahr, Roald & Kjær, Michael (2023). Tendinopathy - diagnostics and treatment of early-stage tendinopathy. General discussion: "Where do we go from here?".
• Bahr, Roald (2023). Training intervention and adjustment in early-stage tendinopathy.
• Bahr, Roald & Kjær, Michael (2023). Tendinopathy - why does it happen and can it be prevented?
• Bahr, Roald (2023). The role of the Games group.
• Bahr, Roald (2023). Epidemiology of sport injuries of the foot.
• Bahr, Roald (2023). How big is the problem - epidemiology of anterior knee pain in sport.
• Tabben, Montassar; Nader Rekik, R; Chebbi, S; Chaabane, M; Daoud, Rula Ghandour & Schumacher, Yorch Olaf [Show all 8 contributors for this article] (2023). Effect of Covid-19 lockdown on football injuries in the Qatar stars league.
• Kotsifaki, Roula; Sideris, Vasileios; King, E.; Bahr, Roald & Whiteley, Rodney (2023). Prevention or performance - can we have both? Vertical jump testing after ACLr.
• Amundsen, Roar; Thorarinsdottir, Solveig; Larmo, Arne; Pedersen, R.; Andersen, Thor Einar & Møller, Merete [Show all 7 contributors for this article] (2023). Hamstring injuries in the Norwegian women's Premier League.
• Bahr, Roald (2023). Keynote lecture: Next generation leaders - Innovation in prevention.
• Thorarinsdottir, Solveig; Amundsen, Roar; Bahr, Roald; Andersen, Thor Einar; Larmo, Arne & Pedersen, R. [Show all 7 contributors for this article] (2023). Groin injuries in women's Premier League football in Norway. In Della Villa, F & Susta, D (Ed.), Football Medicine - The Pursuit of Excellence - Abstract book. Calzetti Maricci editori. ISSN 9788860286871.
• Thorarinsdottir, Solveig; Amundsen, Roar; Bahr, Roald; Andersen, Thor Einar; Larmo, Arne & Pedersen, R. [Show all 7 contributors for this article] (2023). Groin injuries in women's Premier League football in Norway.
• Bahr, Roald (2023). Roles and responsibilities of sports medicine professionals.
• Bahr, Roald; Zideman, David; Grant, Marie-Elaine; Forster, Bruce & Zahar, Maher (2023). Games Group Updates: FoP and Emergencies, Polyclinic Services.
• Bahr, Roald (2023). Klinisk workshop - Ankel.
• Rooth, Espen; Borgersen, Bård; Jørgensen, Hege & Bahr, Roald (2023). Innledning og presentasjon av faggruppa.
• Bahr, Roald (2023). How the IOC can support you as a sports medicine professional.
• Bahr, Roald (2023). Preventing injuries in sports from "one size fits all" up to personalize management.
• Thorarinsdottir, Solveig; Amundsen, Roar; Clarsen, Benjamin Matthew; Andersen, Thor Einar; Møller, Merete & Bahr, Roald (2022). INJURIES AND ILLNESS IN ELITE WOMEN’S FOTBALL IN NORWAY – A TWO-YEAR PROSPECTIVE COHORT STUDY .
• Moen, Christian; Myklebust, Grethe; Hagglund, Martin; Bahr, Roald; Møller, Merete & Bjørndal, Christian Thue [Show all 7 contributors for this article] (2022). Biomedisinsk perspektiv på skadeforebygging.
• Nordstrøm, Anine; Bahr, Roald; Bache-Mathiesen, Lena Kristin; Clarsen, Benjamin Matthew & Talsnes, Ove (2022). Sammenhengen mellom trening- og kampbelastning og risiko for skade blant junior elite ishockeyspillere.
• Amundsen, Roar; Thorarinsdottir, Solveig; Clarsen, Benjamin Matthew; Andersen, Thor Einar; Møller, Merete & Bahr, Roald (2022). Health problems in the elite women`s football league in Norway - a prospective cohort study.
• Amundsen, Roar; Thorarinsdottir, Solveig; Pedersen, Roar; Larmo, Arne; Andersen, Thor Einar & Møller, Merete [Show all 7 contributors for this article] (2022). Hamstringsskader i elite kvinnefotball.
• Bahr, Roald (2022). KEYNOTE: Hvordan holde (elite)utøverne friske - fra H & M til skreddersøm?
• Bahr, Roald (2022). From postseason injury analysis through pre-season screening – risk management in the team setting.
• Bahr, Roald (2022). Sideline management of ankle sprains – assessment and initial treatment.
• Bahr, Roald (2022). A decision-based model for return to play in sport.
• Bahr, Roald (2022). Vince Higgins Lecture: Preventing injuries in sports - from "one size fits all" to "made to measure"?
• Mountjoy, Margo; McCloskey, B.; Bahr, Roald; Hull, James H.; Kemp, Joanne & Thornton, Jane S. [Show all 7 contributors for this article] (2022). Hosting international sporting events during the COVID-19 pandemic: Lessons learnt and looking forward. British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2022-106096.
• Bahr, Roald & Andersen, Thor Einar (2022). The Oslo Sports Trauma Research Center (OSTRC), The Norwegian School of Sport Sciences.
• Emery, Carolyn & Bahr, Roald (2022). Concussion prevention - evidence informing future direction in primary prevention of concussion in sport.
• Bahr, Roald (2022). Prevention injuries in sports - from "one size fits all" to "made to measure".
• Bahr, Roald (2022). The new IOC epidemiology methodology.
• Bahr, Roald (2022). Medical and functional assessment.
• Bahr, Roald & Engebretsen, Lars (2022). Outline of the Oslo Sports Trauma Research Center & Olympiatoppen programs .
• Bahr, Roald (2022). Injury prevention - the new IOC epidemiology methodology.
• Bahr, Roald (2022). Overuse injuries - medical and functional assessment.
• Wik, Eirik Halvorsen; Lolli, Lorenzo; Chamari, Karim; Tabben, Montassar; Di Salvo, Valter & Gregson, Warren [Show all 7 contributors for this article] (2021). Hvordan påvirker veksthastighet og skjelettmodning skaderisiko hos unge fotballspillere? In Nyheim, Kurt Tomas (Eds.), Book of Abstract - Idrettsmedisinsk høstkongress 2021. NIMF.
• Bahr, Roald (2021). Epidemiology - is (elite) sports good or bad for cartilage?
• Nordstrøm, Anine; Bahr, Roald; Talsnes, Ove & Clarsen, Benjamin Matthew (2021). The prevalence and burden of health problems in male senior ice hockey - a prospective study in the Norwegian professional league. British Journal of Sports Medicine. ISSN 0306-3674. 55. doi: 10.1136/bjsports-2021-IOC.358.
• Sandmo, Stian Bahr; Filipcik, Peter; Cente, Martin; Hanes, Jozef; Andersen, Thor Einar & Straume-Næsheim, Truls Martin [Show all 7 contributors for this article] (2021). Biomarkers in serum after head impact exposure in football. British Journal of Sports Medicine. ISSN 0306-3674. 55. doi: 10.1136/bjsports-2021-IOC.14.
• Sandmo, Stian Bahr; McIntosh, Andrew S.; Andersen, Thor Einar; Koerte, Inga K. & Bahr, Roald (2021). Evaluation of in-ear sensor systems for quantifying head impacts in youth football . British Journal of Sports Medicine. ISSN 0306-3674. 55. doi: 10.1136/bjsports-2021-IOC.11.
• Sandmo, Stian Bahr; Andersen, Thor Einar; Koerte, Inga K. & Bahr, Roald (2021). Head impact exposure in youth football – are current interventions hitting the target? . British Journal of Sports Medicine. ISSN 0306-3674. 55, p. A5–A6. doi: 10.1136/bjsports-2021-IOC.12.
• Wik, Eirik Halvorsen; Martínez-Silván, Daniel; Farooq, Abdulaziz; Cardinale, Marco; Johnson, Amanda & Bahr, Roald (2021). Increased injury risk in youth athletics when growth rates are high and skeletal maturation is low . British Journal of Sports Medicine. ISSN 0306-3674. 55. doi: 10.1136/bjsports-2021-IOC.3.
• Fredriksen, Hilde; Cools, Ann; Bahr, Roald & Myklebust, Grethe (2021). Does the Oslo Sports Trauma Research Center shoulder injury prevention program affect the risk factors external rotation strength and internal rotation range of motion? A randomized controlled study among adolescent handball players . British Journal of Sports Medicine. ISSN 0306-3674. 55. doi: 10.1136/bjsports-2021-IOC.16.
• Moseid, Nils Fredrik Holm; Moseid, Christine Holm; Lemyre, Nicolas; Fagerland, Morten & Bahr, Roald (2021). Injury, illness and coaching style - associations with burnout in young elite athletes . British Journal of Sports Medicine. ISSN 0306-3674. 55. doi: 10.1136/bjsports-2021-IOC.55.
• Rekik, Raouf Nader; Bahr, Roald; Cruz, Flavio; d'Hooghe, Pieter; Read, Paul & Tabben, Montassar [Show all 7 contributors for this article] (2021). The mechanisms of anterior cruciate ligament injuries in male professional football players in the middle east - a systematic video analysis of 15 cases.
• Rekik, Raouf Nader; Bahr, Roald; Cruz, Flavio; D’Hooghe, Pieter; Read, Paul & Tabben, Montassar [Show all 7 contributors for this article] (2021). The mechanisms of anterior cruciate ligament injuries in male professional football players in the middle east - a systematic video analysis of 15 cases. British Journal of Sports Medicine. ISSN 0306-3674. 55.
• De Luca, Alberto; Karayumak, Suheyla Cetin; Leemans, Alexander; Rathi, Yogesh; Swinnen, Stephan & Gooijers, Jolien [Show all 15 contributors for this article] (2021). Harmonization of diffusion kurtosis imaging metrics with rotational invariant spherical harmonics (RISH) to remove cross-site biases.
• Nordstrøm, Anine; Bahr, Roald; Clarsen, Benjamin Matthew & Talsnes, Ove (2021). Prevalens og belastning av helseproblem blant junior elite ishockeyspillere en 44-uker prospektiv kohortstudie.
• Nordstrøm, Anine; Bahr, Roald; Clarsen, Benjamin Matthew & Talsnes, Ove (2021). Sammenheng mellom fysisk form og risiko for skader og sykdom blant senior elite ishockeyspillere.
• Wik, Eirik Halvorsen; Lolli, Lorenzo; Chamari, Karim; Tabben, Montassar; Di Salvo, Valter & Gregson, Warren [Show all 7 contributors for this article] (2021). Hvordan påvirker veksthastighet og skjelettmodning skaderisiko hos unge fotballspillere?
• Nordstrøm, Anine; Bahr, Roald; Clarsen, Benjamin Matthew & Talsnes, Ove (2021). Prevalence and burden of health problems in male junior elite ice hockey players - A 44-week prospective cohort study.
• Nordstrøm, Anine; Bahr, Roald; Clarsen, Benjamin Matthew & Talsnes, Ove (2021). The association between preseason fitness level and risk of injury or illness – a prospective cohort study in male elite ice hockey.
• Nordstrøm, Anine; Bahr, Roald; Talsnes, Ove & Clarsen, Benjamin Matthew (2021). The prevalence and burden of health problems in male senior ice hockey: a prospective study in the Norwegian professional league.
• Moseid, Nils Fredrik Holm; Moseid, Christine Holm; Bahr, Roald; Lemyre, Nicolas & Fagerland, Morten (2021). Injury, illness and coaching style: associations with burnout in young elite athletes.
• Fredriksen, Hilde; Cools, Ann; Bahr, Roald & Myklebust, Grethe (2021). Does the Oslo Sports Trauma Research Center shoulder injury prevention program affect the risk factors external rotation strength and internal rotation range of motion?
• Sandmo, Stian Bahr; Filipcik, Peter; Cente, Martin; Hanes, Jozef; Andersen, Thor Einar & Straume-Næsheim, Truls Martin [Show all 7 contributors for this article] (2021). Biomarkers in serum after head impact exposure in football.
• Sandmo, Stian Bahr; Andersen, Thor Einar; Koerte, Inga K. & Bahr, Roald (2021). Head impact exposure in youth football – are current interventions hitting the target?
• Sandmo, Stian Bahr; McIntosh, Andrew S.; Andersen, Thor Einar; Koerte, Inga K. & Bahr, Roald (2021). Evaluation of in-ear sensor systems for quantifying head impacts in youth football.
• Wik, Eirik Halvorsen; Martínez-Silván, Daniel; Farooq, Abdulaziz; Cardinale, Marco; Johnson, Amanda & Bahr, Roald (2021). Increased injury risk in youth athletics when growth rates are high and skeletal maturation is low.
• Bahr, Roald (2021). The key elements and changes in the new consensus statement.
• Bahr, Roald (2021). A decision-based model for return to play in sport .
• Bahr, Roald (2021). Sideline management of ankle sprains – assessment and initial treatment.
• Bahr, Roald (2021). Introduction of the session.
• Ziderman, David & Bahr, Roald (2021). Field of Play procedures.
• Bahr, Roald (2021). Sideline concussion recognition.
• Nilstad, Agnethe; Petushek, Erich; Mok, Kam-Ming; Bahr, Roald & Krosshaug, Tron (2021). Response to letter to the editor about ‘kiss goodbye to the “kissing knees”: no association between frontal plane inward knee motion and risk of future non-contact ACL injury in elite female athletes’. Sports Biomechanics. ISSN 1476-3141. doi: 10.1080/14763141.2021.1983637.
• Bahr, Roald (2021). Why the injury predictor screening does not work, while the prevention program does?
• Bahr, Roald & Krosshaug, Tron (2020). The Oslo Sports Trauma Research Center (OSTRC).
• Hoppe, Matthias W.; Bahr, Roald; Besenius, Eric; Brucker, Peter U.; Gokeler, Alli & Klein, Christian [Show all 8 contributors for this article] (2020). Methodologie der Präventionsforschung von Sportverletzungen. In Seil, Romain & Tischer, Thomas (Ed.), Primärprävention von Sportverletzungen. Vopelius Verlag. ISSN 978-3-947303-22-9. p. 17–32.
• Bahr, Roald (2020). Akuttbehandling av akutte skader - ICE, RICE, PRICE, PLOICE eller PEACE & LOVE?
• Tabben, Montassar; Whiteley, Rodney; Wik, Eirik Halvorsen; Bahr, Roald & Chamari, Karim (2020). Methods may matter in injury surveillance: “how” may be more important than “what, when or why”. Biology of Sport. ISSN 0860-021X. 37(1), p. 3–5. doi: 10.5114/biolsport.2020.89935. Show summary

  To examine if and how adjustments in injury surveillance recording methodology may have influenced injury rates. Injury and exposure data were collected among professional male players from the Qatar Stars League from the 2008-2009 season to the 2017-2018 season. There have been four iterations of our data collection methods. In the first five seasons, participation in the programme was voluntary. For seasons 6-7, additional dedicated researchers were tasked with contacting the medical teams every month. At the start of season 8, an electronic recording method was instituted. In the final two seasons, injury surveillance participation was further boosted by reinforced encouragement from institutional management. Overall injury incidence increased from season 5 to season 8. Severe injuries have fallen steadily, but slightly over the ten seasons, whereas mild injuries increased dramatically from seasons 5 to 8. The current data suggest that along with the standard metrics (e.g. injury incidence, injury burden) we also need to clearly report the methods by which data were collected and verified in as much detail as possible. We suggest that sports medicine journals should adopt minimum reporting standards and perhaps checklists could be a useful step forward.

• Bahr, Roald (2020). The Norwegian Olympic & Paralympic Screening and Monitoring Program; what is it, why do we do it and does it help Norway win medals?
• Bahr, Roald (2020). Ethics, funding and impact.
• Bahr, Roald (2020). The Norwegian Olympic & Paralympic Screening and Monitoring Program - what is it, why do we do it and does it help Norway win medals?
• Bahr, Roald (2020). Forskningssentre på NIH, Senter for idrettsskadeforskning.
• Scott, Alex; Squier, Kipling; Alfredson, Håkan; Bahr, Roald; Cook, Jill L. & Coombes, Brooke K. [Show all 25 contributors for this article] (2019). ICON 2019: International Scientific Tendinopathy Symposium Consensus: Clinical Terminology. British Journal of Sports Medicine. ISSN 0306-3674. 54, p. 260–262. doi: 10.1136/bjsports-2019-100885.
• Moseid, Nils Fredrik Holm; Bahr, Roald; Lemyre, Nicolas & Moseid, Christine Holm (2019). Skade, sykdom, trenerstil: Sammenheng med utbrenthet hos unge eliteidrettsutøvere.
• Moseid, Nils Fredrik Holm; Bahr, Roald; Lemyre, Nicolas & Moseid, Christine Holm (2019). Health of the young elite athlete.
• Moseid, Nils Fredrik Holm; Moseid, Christine Holm; Bahr, Roald & Lemyre, Nicolas (2019). Skade, sykdom, trenerstil: Sammenheng med utbrenthet hos unge eliteidrettsutøvere.
• Moseid, Nils Fredrik Holm; Moseid, Christine Holm; Bahr, Roald & Lemyre, Nicolas (2019). Health Problems and Athlete Burnout- a study of 210 Young Elite Athletes.
• Berge, Hilde Moseby; Andersen, Thor Einar & Bahr, Roald (2019). Hjertekarlidelser hos profesjonelle mannlige fotballspillere med negative funn ved hjertescreening - en 8 års oppfølgingsstudie.
• Wik, Eirik Halvorsen; Martínez Silván, Daniel; Cardinale, Marco; Farooq, Abdulaziz; Johnson, Amanda & Bahr, Roald (2019). Økt skaderisiko hos unge friidrettsutøvere med stor veksthastighet og et umodent skjelett .
• Bahr, Roald (2019). Screening athletes for injury prevention and return to play: What, how and why?
• Bahr, Roald & Engebretsen, Lars (2019). 20-års arbeid med forskning på forebygging av skader i idrett - hva har vi oppnådd?
• Bahr, Roald (2019). The past, the present and future of sports medicine - a single-case study.
• Bahr, Roald (2019). Closing and next steps.
• Bahr, Roald (2019). Voting on afternoon session - definitions/recommendations & Second Day Wrap-up.
• Bahr, Roald (2019). Voting on morning session - definitions/recommendations (continuing) .
• Bahr, Roald (2019). Voting on afternoon session - definitions/recommendations & First Day Wrap-up.
• Bahr, Roald (2019). Voting on morning session - definitions/recommendations.
• Bahr, Roald (2019). Goals & Rules of Consensus Meeting.
• Bahr, Roald (2019). The Norwegian Olympic Center.
• Bahr, Roald (2019). Sports Injury Prevention - What have we learned so far?
• Bahr, Roald (2019). Are we destroying our most talented athletes?
• Øvrebø, Tore & Bahr, Roald (2019). The Norwegian elite sports and elite sports medicine model - Olympiatoppen and the Oslo Sports Trauma Research Center.
• Bahr, Roald (2019). IOC Consensus Meeting on the Methodology for recording and reporting of data for injury and illness surveillance.
• Bahr, Roald & Myklebust, Grethe (2019). The Oslo Sports Trauma Research Center (OSTRC), The Norwegian School of Sport Sciences.
• Sandmo, Stian Bahr; McIntosh, Andrew S.; Andersen, Thor Einar; Koerte, Inga Katharina & Bahr, Roald (2019). Evaluation of an in-ear Sensor for quantifiying Head Impacts in Youth Football.
• Gooijers, Jolien; Seer, Caroline; Bahr, Roald; Sandmo, Stian Bahr; Leemans, Alexander & Pasternak, Ofer [Show all 10 contributors for this article] (2019). Potential effects of repetitive heading on postural control in elite youth soccer.
• De Luca, Alberto; Pasternak, O; Kaufmann, David; Muehlmann, Marc; Heinen, Florian & Sochen, Nir [Show all 12 contributors for this article] (2019). Acquisition and automated processing of multi-modal MRI protocol to investigate the effect of repetitive head impacts on the brain.
• Bahr, Roald (2019). Why screening to predict injury does not work - and probably never will.
• Bahr, Roald (2019). Why screening tests to predict injury do not work - But prevention programmes do!
• Bahr, Roald; Engebretsen, Lars; Myklebust, Grethe & Steffen, Kathrin (2019). Halvparten av idrettsskadene kan enkelt forebygges. [Newspaper]. Aftenposten.
• Wik, Eirik Halvorsen; Materne, O; Chamari, Karim; Duque, J.D.P.; Horobeanu, C & Salcinovic, B [Show all 8 contributors for this article] (2019). Involving research-invested clinicians in data collection affect injury incidence in youth football. In Roi, Giulio Sergio & Villa, Stefano Della (Ed.), XXVIII Isokinetic Medical Group International Conference - Football medicine meets the universe of sport - Abstract book. Calzetti & Mariucci Editori. ISSN 9788860285904.
• Wik, Eirik Halvorsen; Materne, O; Chamari, Karim; Duque, J.D.P.; Horobeanu, C & Salcinovic, B [Show all 8 contributors for this article] (2019). Involving research-invested clinicians in data collection affects injury incidence in youth football .
• Bahr, Roald (2019). From athlete screening to injury risk management.
• Koerte, Inga; Swinner, Stephan; Sochen, Nir; Bahr, Roald; Filipcik, Peter & Leemans, Alexander (2019). RepImpact - Repetitive Subconcussive Head Impacts - Brain alterations and clinical consequences.
• Bahr, Roald; Engebretsen, Anders Hauge; Myklebust, Grethe; Holme, Ingar & Engebretsen, Lars (2018). Prevention of injuries among male football players - a prospective randomized intervention study targeting players with previous injuries or reduced function. In Vasli, Lars (Eds.), Vitenskapelige forhandlinger. De Norske Kirurgiske Foreninger. ISSN 0801-5902.
• Berge, Hilde Moseby; Andersen, Thor Einar & Bahr, Roald (2018). Mandatory health screen to rule out risk of sudden death in footballers not fail-safe. [Journal]. British Medical Journal.
• Andersen, Thor Einar; Bahr, Roald & Berge, Hilde Moseby (2018). Hvordan forebygge plutselig hjertedød i idrett? [Newspaper]. Aftenposten.
• Andersen, Thor Einar & Bahr, Roald (2018). Partnership with Oslo Sports Trauma Research Centre. In McCall, Alan; Andersen, Thor Einar; Clarsen, Benjamin & Pruna, Ricard (Ed.), Muscle injury guide: Prevention of and Return to Play from Muscle Injuries. Barca innovation hub.
• Targett, Stephen; Bere, Tone Tufte & Bahr, Roald (2018). The role of pre-participation assessment (PPA) and screening in handball. In Laver, Lior; Landreau, Philippe; Seil, Romain & Popovic, Nebojsa (Ed.), Handball Sports Medicine: Basic Science, Injury Management and Return to Sport . Springer. ISSN 978-3-662-55891-1. p. 115–124. doi: 10.1007/978-3-662-55892-8_9.
• Bahr, Roald & Andersen, Thor Einar (2018). OSTRC - summary of the last year and new research areas.
• Bahr, Roald; Malinen, Lauri & Bender, Erwin (2018). Injury and illness surveillance and prevention .
• Harøy, Joar; Pope, David; Clarsen, Benjamin; Wiger, Espen Guldahl; Øyen, Mari Glomnes & Serner, Andreas [Show all 10 contributors for this article] (2018). Infographic. The Adductor Strengthening Programme prevents groin problems among male football players. British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2018-099993.
• Bahr, Roald (2018). Organizing medical support for Norwegian elite athletes.
• Bahr, Roald & Engebretsen, Lars (2018). Oslo Sports Trauma Research Center - an overview of our program.
• Bahr, Roald (2018). REPIMPACT - presentation of status quo.
• Bahr, Roald (2018). Introduction of the session (online questions): Infective illness in the athletes.
• Bahr, Roald (2018). From postseason injury analysis through pre-season screening – risk management in the team setting.
• Bahr, Roald (2018). A decision-based model for return to play in sport.
• Bahr, Roald (2018). Sideline management of ankle sprains – assessment and initial treatment.
• Bahr, Roald (2018). “Demise of the Fittest?”.
• Bahr, Roald (2018). Organising a national Olympic team - the importance and potential of ongoing surveillance for the provision of health care and the prevention of injury and illness.
• Bahr, Roald (2018). Keynote: Preventing injuries in sport.
• Haugvad, Lars & Bahr, Roald (2018). Patellar tendinopathy.
• Bahr, Roald (2018). Introduction: Prevention - are we winning.
• Bahr, Roald (2018). Roles and responsibilities of sports medicine professionals.
• Bahr, Roald (2018). Diagnosis and management of concussion: practising the Sport Concussion Assessment Tool (SCAT3).
• Bahr, Roald (2018). Practical examinations - Ankle/Foot.
• Bahr, Roald (2018). ACL injury prevention programs - how can they be improved?
• Bahr, Roald (2018). Why screening testes to predict injury do not work - and probably never will...
• Bahr, Roald (2018). Preventing overuse injuries through exercise programs - is it possible?
• Soligard, Torbjørn; Steffen, Kathrin; Palmer, Debbie; Alonso, Juan-Manuel; Bahr, Roald & Lopes, Alexandre Dias [Show all 14 contributors for this article] (2018). Infographic: Injury and illness, the 2016 Olympic Games. British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2018-099090.
• Bahr, Roald (2018). What can we expect from musculoskeletal screening?
• Steenstrup, Sophie; Hisdal, Erling & Bahr, Roald (2017). FIS Injury Surveillance System: Injury statistics from the 2016/17 World Cup season.
• Leppänen, Mari; Pasanen, Kati; Kujala, Urho M; Vasankari, Tommi; Kannus, Pekka & Äyrämö, Sami [Show all 11 contributors for this article] (2017). Stiff Landings Are Associated With Increased ACL Injury Risk in Young Female Basketball and Floorball Players: Response. American Journal of Sports Medicine. ISSN 0363-5465. 45(3), p. np5–np6. doi: 10.1177/0363546517692762.
• Berge, Hilde Moseby; Andersen, Thor Einar & Bahr, Roald (2017). Cardiovascular incidents, including sudden cardiac arrests, in professional male football players with negative preparticipation cardiac screening results: 8-year follow-up. European Heart Journal. ISSN 0195-668X. 38.
• Berge, Hilde Moseby; Andersen, Thor Einar & Bahr, Roald (2017). Cardiovascular incidents, including sudden cardiac arrests, in professional male football players with negative pre-participation cardiac screening results: 8-year follow-up.
• Berge, Hilde Moseby; Andersen, Thor Einar & Bahr, Roald (2017). Cardiovascular incidents, including sudden cardiac arrests, in professional male football players with negative pre-participation cardiac screening results - 8-year follow-up.
• van Dyk, Nicol; Bakken, Arnhild; Targett, Stephen & Bahr, Roald (2017). There are many good reasons to screen your athletes - but predicting future injury is not one of them. ASPETAR Sports Medicine Journal. ISSN 2304-0904. 7(12), p. 12–17.
• Wangensteen, Arnlaug; Guermazi, Ali; Tol, Johannes L.; Roemer, Frank; Hamilton, Bruce & Alonso, Juan-Manuel [Show all 8 contributors for this article] (2017). MR-klassifikasjonssystemer alene kan ikke predikere tid til retur til idrett etter akutte hamstringskader.
• Wiger, Espen Guldahl; Harøy, Joar; Bahr, Roald & Andersen, Thor Einar (2017). Motivasjon og holdninger blant mannlige fotballspillere til forebyggingsprogrammet ”Sterk Lyske”.
• Bjørkheim, André; Harøy, Joar; Andersen, Thor Einar & Bahr, Roald (2017). Effekten av FIFA 11+ på eksentrisk styrke i knefleksorene hos unge mannlige elite fotballspillere.
• Øyen, Mari Glomnes; Harøy, Joar; Andersen, Thor Einar; Clarsen, Benjamin & Bahr, Roald (2017). Assosiasjonen mellom acute:chronic workload ratio og risiko for lyskeproblem blant norske mannlige fotballspillere.
• Steenstrup, Sophie E.; Bakken, Arnhild; Bere, Tone Tufte; Patton, Declan A & Bahr, Roald (2017). Videoanalyse av mekanismer for hodeskader i FIS World Cup alpin, freestyle og snowboard.
• Bakken, Arnhild; Targett, Stephen; Bere, Tone Tufte; Eirale, Cristiano; Farooq, Aziz & Mosler, Andrea Britt [Show all 10 contributors for this article] (2017). Muskelstyrketesting er lite treffsikkert til å predikere underekstremitetsskader blant elitefotballspillere.
• Bahr, Roald (2017). Why screening can't predict injuries and probably never will.
• Bahr, Roald (2017). Presenting research - tips & tricks.
• Bahr, Roald (2017). From postseason injury analysis through pre-season screening - risk management in the team setting.
• Bahr, Roald (2017). A decision-based model for return to play in sport.
• Bahr, Roald (2017). Infective illness in the athletes - Introduction of the session (online questions).
• Bahr, Roald (2017). Diagnosis and management of concussion: practising the Sport Concussion Assessment Tool (SCAT3).
• Bahr, Roald (2017). Practical examinations - Ankle/Foot.
• Bahr, Roald (2017). Roles and responsibilities of sports medicine professionals.
• Soligard, Torbjørn; Steffen, Kathrin; Palmer, Debbie; Alonso, Juan Manuel; Bahr, Roald & Lopes, Alexandre Dias [Show all 14 contributors for this article] (2017). Sports injury and illness incidence in the Rio de Janeiro 2016 Olympic Summer Games - a prospective study of 11274 athletes from 207 countries. In Lorentzen, Karl-Ivar (Eds.), Høstmøteboken - Vitenskapelig program og abstract 2017. Norsk ortopedisk forening.
• Soligard, Torbjørn; Steffen, Kathrin; Palmer, Debbie; Alonso, Juan Manuel; Bahr, Roald & Lopes, Alexandre Dias [Show all 14 contributors for this article] (2017). Sports injury and illness incidence in the Rio de Janeiro 2016 Olympic Summer Games - a prospective study of 11274 athletes from 207 countries.
• Bahr, Roald; Clarsen, Benjamin & Ekstrand, Jan (2017). Why we should focus on the burden of injuries and illnesses, not just their incidence. British Journal of Sports Medicine. ISSN 0306-3674. 52(16), p. 1018–1021. doi: 10.1136/bjsports-2017-098160.
• Visnes, Håvard; Couppé, Christian & Bahr, Roald (2017). Jumpers Knee im Volleyball. Sportphysio. ISSN 2196-5951. 5(4), p. 168–172. doi: 10.1055/s-0043-119009.
• Harøy, Joar; Bahr, Roald & Andersen, Thor Einar (2017). Groin problems in male soccer players are more common than previously reported: response. American Journal of Sports Medicine. ISSN 0363-5465. 45(13), p. np32–np33. doi: 10.1177/0363546517737749.
• Bahr, Roald (2017). New thinking and new tools: A bold move towards injury prevention translation in all Olympic sports.
• Bahr, Roald & Clarsen, Benjamin (2017). The Oslo Sports Trauma Research Centre (OSTRC), The Norwegian School of Sport Sciences.
• Bahr, Roald (2017). It's time to "get real" about injury prevention in our athletes.
• Bahr, Roald (2017). The future of prevention.
• Kröll, Josef; Spörri, Jörg; Steenstrup, Sophie E.; Schwameder, Hermann; Müller, Erich & Bahr, Roald (2017). How can we prove that a preventive measure in elite sport is effective when the prevalence of the injury (eg, ACL tear in alpine ski racing) is low? A case for surrogate outcomes. British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2016-097020.
• Bahr, Roald (2017). Keynote: Why screening to predict injury does not work - and probably never will...
• Rafnsson, Elis Thor; Myklebust, Grethe; Bahr, Roald; Frohm, Anna; Valdimarsson, Örnólfur & Arnason, Arni (2017). Overuse problems in Icelandic male handball. British Journal of Sports Medicine. ISSN 0306-3674. 51(4).
• Rafnsson, Elis Thor; Myklebust, Grethe; Bahr, Roald; Frohm, Anna; Valdimarsson, Örnólfur & Arnason, Arni (2017). Overuse problems in Icelandic male handball.
• Andersson, Stig Haugsbø; Bahr, Roald; Cardinale, Marco; Popovic, Nebojsa; Bere, Tone Tufte & Myklebust, Grethe (2017). Video analysis of acute injuries during the 24th Mens's handball world championship 2015 in Qatar. British Journal of Sports Medicine. ISSN 0306-3674. 51(4).
• Andersson, Stig Haugsbø; Bahr, Roald; Cardinale, Marco; Popovic, Nebojsa; Bere, Tone Tufte & Myklebust, Grethe (2017). Video analysis of acute injuries during the 24th Mens's handball world championship 2015 in Qatar.
• Skazalski, Christopher; Kruczynski, Jacek; Bahr, Martin Aase; Bere, Tone Tufte; Whiteley, Rod & Bahr, Roald (2017). Landing-related ankle injuries do not occur in plantarflexion as once thought: A video analysis of ankle injuries in world-class volleyball from the FIVB Injury Surveillance System. British Journal of Sports Medicine. ISSN 0306-3674. 51(4).
• Skazalski, Christopher; Kruczynski, Jacek; Bahr, Martin Aase; Bere, Tone Tufte; Whiteley, Rod & Bahr, Roald (2017). Landing-related ankle injuries do not occur in plantarflexion as once thought: A video analysis of ankle injuries in world-class volleyball from the FIVB Injury Surveillance System.
• Harøy, Joar; Thorborg, Kristian; Hölmich, Per; Serner, Andreas; Bjørkheim, André & Rolstad, Linn E [Show all 8 contributors for this article] (2017). Including the Copenhagen Adduction exercise in FIFA 11+ provides missing eccentric hip adduction strength effect: A randomised controlled trial. British Journal of Sports Medicine. ISSN 0306-3674. 51(4).
• Harøy, Joar; Thorborg, Kristian; Hölmich, Per; Serner, Andreas; Bjørkheim, André & Rolstad, Linn E [Show all 8 contributors for this article] (2017). Including the Copenhagen Adduction exercise in FIFA 11+ provides missing eccentric hip adduction strength effect: A randomised controlled trial.
• Steffen, Kathrin; Nilstad, Agnethe; Krosshaug, Tron; Pasanen, Kati & Bahr, Roald (2017). No association between static and dynamic postural control and ACL injury risk among female elite handball and football players. British Journal of Sports Medicine. ISSN 0306-3674. 51(4).
• Steffen, Kathrin; Nilstad, Agnethe; Krosshaug, Tron; Pasanen, Kati & Bahr, Roald (2017). No association between static and dynamic postural control and ACL injury risk among female elite handball and football players.
• Andersson, Stig Haugsbø; Bahr, Roald; Clarsen, Benjamin & Myklebust, Grethe (2017). Risk factors for overuse shoulder injuries among 329 elite handball players: a prospective cohort study. British Journal of Sports Medicine. ISSN 0306-3674. 51(4), p. 285–286.
• Andersson, Stig Haugsbø; Bahr, Roald; Clarsen, Benjamin & Myklebust, Grethe (2017). Risk factors for overuse shoulder injuries among 329 elite handball players: a prospective cohort study.
• Bakken, Arnhild; Targett, Stephen; Bere, Tone Tufte; Eirale, Christiano; Aziz, Farooq & Tol, Johannes [Show all 9 contributors for this article] (2017). The functional movement test 9+ is a poor screening test for lower extremity injuries in professional male football. British Journal of Sports Medicine. ISSN 0306-3674. 52(16), p. 1047–1053. doi: 10.1136/bjsports-2016-097307.
• Bakken, Arnhild; Targett, Stephen; Bere, Tone Tufte; Eirale, Christiano; Aziz, Farooq & Tol, Johannes [Show all 9 contributors for this article] (2017). The functional movement test 9+ is a poor screening test for lower extremity injuries in professional male football.
• Berge, Hilde Moseby; Andersen, Thor Einar & Bahr, Roald (2017). Cardiovascular incidents, including sudden cardiac arrests, in professional male football players with negative pre-participating cardiac screening results: an 8-yr follow-up study.
• Berge, Hilde Moseby; Andersen, Thor Einar & Bahr, Roald (2017). Cardiovascular incidents, including sudden cardiac arrests, in professional male football players with negative pre-participating cardiac screening results: an 8-yr follow-up study. British Journal of Sports Medicine. ISSN 0306-3674. 51(4), p. 294–295.
• Bahr, Roald; Bergeron, Michael F; Moseid, Christine Holm; Johnson, Amanda; Jayanthi, Neeru & Pluim, Babette [Show all 7 contributors for this article] (2017). Panel discussion: How can research help to change the game of youth elite sports?
• Muneta, Takeshi; Bahr, Roald; Waldén, Markus; Koga, Hideyuki; Bere, Tone Tufte & Tsuda, Eiichi (2017). Panel discussion: Future strategies for ACL injury prevention based on the mechanisms.
• Bahr, Roald (2017). Should ACL injury prevention be specific to type of sports?
• Bahr, Roald; van Dyk, Nicol; Opar, David; Shield, Anthony; Reurink, Gustaaf & Thorborg, Kristian (2017). Panel discussion: Future directions for hamstring injury prevention and implementation.
• Bahr, Roald (2017). Back to the Future - Summing up 20 years of Scandinavian hamstring injury prevention research.
• Andersson, Stig Haugsbø; Bahr, Roald; Olsen, Magnus J & Myklebust, Grethe (2016). Erfaringer og holdninger til skadeforebyggende trening i norsk elitehåndball - en tverrsnittstudie.
• Finch, Caroline F.; Bahr, Roald; Drezner, Jonathan; Dvorak, Jiri; Engebretsen, Lars & Hewett, Timothy E. [Show all 12 contributors for this article] (2016). Towards the reduction of injury and illness in athletes: defining our research priorities. British Journal of Sports Medicine. ISSN 0306-3674. 51(16), p. 1178–1182. doi: 10.1136/bjsports-2016-097042.
• Schwellnus, Martin P.; Soligard, Torbjørn; Alonso, Juan Manuel; Bahr, Roald; Clarsen, Benjamin & Dijkstra, H. Paul [Show all 17 contributors for this article] (2016). Infographic. General guidance for the prevention of illness in athletes. British Journal of Sports Medicine. ISSN 0306-3674. doi: 10.1136/bjsports-2016-097234.
• Andersson, Stig Haugsbø; Bahr, Roald; Clarsen, Benjamin & Myklebust, Grethe (2016). Preventing overuse shoulder injuries among throwing athletes – a cluster-randomised controlled trial in 660 elite handball players. Award lecture.
• Steenstrup, Sophie E.; Bere, Tone Tufte; Krosshaug, Tron; Nordsletten, Lars & Bahr, Roald (2016). FIS Injury Surveillance System, 2016 Injury Statistics update. FIS Medical Committee.
• Steenstrup, Sophie E.; Bere, Tone Tufte; Krosshaug, Tron; Nordsletten, Lars & Bahr, Roald (2016). FIS Injury Surveillance System, 2016 Injury Statistics update FIS ISS Steering Comittee.
• Steenstrup, Sophie E.; Flørenes, Tonje Wåle; Bere, Tone Tufte; Nordsletten, Lars; Heir, Stig & Krosshaug, Tron [Show all 7 contributors for this article] (2016). FIS Injury Surveillance System 2006-12.
• Krosshaug, Tron; Steffen, Kathrin; Kristianslund, Eirik; Nilstad, Agnethe; Mok, Kam-Ming & Myklebust, Grethe [Show all 10 contributors for this article] (2016). The Vertical Drop Jump Is a Poor Screening Test for ACL Injuries: Response. American Journal of Sports Medicine. ISSN 0363-5465. 44(6), p. np24–np25. doi: 10.1177/0363546516651042.
• Bahr, Roald (2016). An upcoming ATPC where and when?
• Bahr, Roald (2016). The World Conference on Prevention of Injury and Illness in Sports - an update on where we are.
• Engebretsen, Lars; Schwellnus, Martin & Bahr, Roald (2016). How can we get to the overuse problems Surveillance between Games?
• Engebretsen, Lars; Schwellnus, Martin & Bahr, Roald (2016). What are the problems in injury and illness? Surveillance at the Games.
• Engebretsen, Lars; Bahr, Roald & m., fl. (2016). Walk & Talk.
• Andersson, Stig Haugsbø; Bahr, Roald; Clarsen, Benjamin & Myklebust, Grethe (2016). Risk factors for overuse shoulder injuries among 329 elite handball players - a prospective cohort study . Norsk idrettsmedisin. ISSN 0806-9328. 31(3), p. 32–32.
• Andersson, Stig Haugsbø; Bahr, Roald; Cardinale, M; Popovic, Nebojsa; Bere, Tone Tufte & Myklebust, Grethe (2016). Video analysis of acute injuries during the 24th men’s handball world championship 2015 in Qatar . Norsk idrettsmedisin. ISSN 0806-9328. 31(3).
• Bakken, Arnhild; Targett, Stephen; Bere, Tone Tufte; Eirale, Cristiano; Tol, Johannes & Whiteley, Rodney [Show all 8 contributors for this article] (2016). The 9+ is a poor screening test for lower extremity injuries in professional male football. Norsk idrettsmedisin. ISSN 0806-9328. 31(3), p. 33–33.
• Harøy, Joar; Thorborg, Kristian; Hölmich, Per; Serner, Andreas; Bjørkheim, A. & Rolstad, LE [Show all 8 contributors for this article] (2016). Including the Copenhagen adduction exercise in the FIFA 11+ provides missing hip adduction strengt effect. Norsk idrettsmedisin. ISSN 0806-9328. 31(3), p. 34–34.
• Haugvad, Lars; Bendiksen, Fredrik; Bahr, Roald & Clarsen, Benjamin (2016). Injuries and illnesses among Norwegian ski jumpers during their preparations for Sochi 2014. Norsk idrettsmedisin. ISSN 0806-9328. 31(3).
• Wangensteen, Arnlaug; Tol, Johannes; van Linschten, R; Almusa, Emad; Whiteley, Rodney & Witvrouw, Erik [Show all 7 contributors for this article] (2016). Magnetic resonance imaging changes throughout the first week after acute hamstring injury - a prospective, descriptive study. Norsk idrettsmedisin. ISSN 0806-9328. 31(3), p. 39–39.
• Wangensteen, Arnlaug; Tol, Johannes; van Linschten, R; Almusa, Emad; Whiteley, Rodney & Witvrouw, Erik [Show all 7 contributors for this article] (2016). Magnetic resonance imaging changes throughout the first week after acute hamstring injury - a prospective, descriptive study.
• Steffen, Kathrin; Nilstad, Agnethe; Krosshaug, Tron; Pasanen, Kati & Bahr, Roald (2016). Association between postural control and ACL injury risk among female elite handball and football players. Norsk idrettsmedisin. ISSN 0806-9328. 31(3), p. 38–38.
• Steffen, Kathrin; Nilstad, Agnethe; Krosshaug, Tron; Pasanen, Kati & Bahr, Roald (2016). Association between postural control and ACL injury risk among female elite handball and football players.
• Steenstrup, Sophie E.; Mok, Kam-Ming; McIntosh, Andrew; Bahr, Roald & Krosshaug, Tron (2016). Head impact velocities in FIS world cup alpine skiers. Norsk idrettsmedisin. ISSN 0806-9328. 31(3), p. 37–38.
• Steenstrup, Sophie E.; Mok, Kam-Ming; McIntosh, Andrew; Bahr, Roald & Krosshaug, Tron (2016). Head impact velocities in FIS world cup alpine skiers.
• Haugvad, Lars; Bendiksen, Fredrik; Bahr, Roald & Clarsen, Benjamin (2016). Injuries and illnesses among Norwegian ski jumpers during their preparations for Sochi 2014.
• Harøy, Joar; Thorborg, Kristian; Hölmich, Per; Serner, Andreas; Bjørkheim, A. & Rolstad, LE [Show all 8 contributors for this article] (2016). Including the Copenhagen adduction exercise in the FIFA 11+ provides missing hip adduction strengt effect.
• Bakken, Arnhild; Targett, Stephen; Bere, Tone Tufte; Eirale, Cristiano; Tol, Johannes & Whiteley, Rodney [Show all 8 contributors for this article] (2016). The 9+ is a poor screening test for lower extremity injuries in professional male football.
• Andersson, Stig Haugsbø; Bahr, Roald; Cardinale, M; Popovic, Nebojsa; Bere, Tone Tufte & Myklebust, Grethe (2016). Video analysis of acute injuries during the 24th men’s handball world championship 2015 in Qatar .
• Andersson, Stig Haugsbø; Bahr, Roald; Clarsen, Benjamin & Myklebust, Grethe (2016). Risk factors for overuse shoulder injuries among 329 elite handball players - a prospective cohort study .
• Bahr, Roald (2016). From postseason injury analysis through pre-season screening - risk management in the team setting.
• Bahr, Roald (2016). A decision-based model for return to play in sport.
• Bahr, Roald (2016). Do ultrasound-guided sclerosing injections work?
• Bahr, Roald (2016). Preventing hamstring (re)injuries, can it be done?
• Kyritsis, Polyvios; Bahr, Roald; Landreau, Philippe; Miladi, Riadh & Witvrouw, Erik (2016). Infographic. Avoid ACL graft rupture. Meet discharge criteria. British Journal of Sports Medicine. ISSN 0306-3674. 50(15), p. 952–952. doi: 10.1136/bjsports-2016-096410.
• Krosshaug, Tron; Steffen, Kathrin; Kristianslund, Eirik; Nilstad, Agnethe; Mok, Kam-Ming & Myklebust, Grethe [Show all 10 contributors for this article] (2016). Screening Tests for ACL Injury: Response. American Journal of Sports Medicine. ISSN 0363-5465. 44(6), p. NP26–NP27. doi: 10.1177/0363546516651046.
• Bahr, Roald (2016). Response to ‘Screening for risk factors: if you liked it then you should have put a number on it’. British Journal of Sports Medicine. ISSN 0306-3674. 50(21), p. 1354–1354. doi: 10.1136/bjsports-2016-096465.
• Bahr, Roald (2016). Author response to the letter from Dr Hewett. British Journal of Sports Medicine. ISSN 0306-3674. 50(21), p. 1353–1354. doi: 10.1136/bjsports-2016-096499.
• Chamari, Karim & Bahr, Roald (2016). Training for Elite Sport Performance: Injury Risk Management Also Matters! International Journal of Sports Physiology and Performance (IJSPP). ISSN 1555-0265. 11(5), p. 561–562. doi: 10.1123/ijspp.2016-0207.
• Bahr, Roald (2016). Education on Anti-Doping - this is what you need to do as a team doctor.
• Bahr, Roald (2016). The FIVB Injury Surveillance Program - Lessons learned.
• Wangensteen, Arnlaug; Bahr, Roald; Almusa, E; van Linschoten, Robbart; Whiteley, R & Witvrouw, E [Show all 7 contributors for this article] (2016). Which is the optimal day for magnetic resonance imaging after acute hamstring injuries?
• Harøy, Joar; Clarsen, Benjamin; Thorborg, Kristian; Hölmich, Per; Bahr, Roald & Andersen, TE (2016). Groin problems are common at all levels of play in Norwegian male football.
• Bakken, Arnhild; Targett, Stephen; Bere, Tone Tufte; Eirale, Cristiano; Farooq, a & Tol, JL [Show all 10 contributors for this article] (2016). Inter-season variability of a functional movement test in professional football.
• van Dyk, N; Bahr, Roald; Whiteley, R; Eirale, Cristiano; Tol, JL & Kumar, BD [Show all 9 contributors for this article] (2016). Substantial inter-season variability in isokinetic strength in professional football.
• Bahr, Roald (2016). Scientific review of return to play.
• Engebretsen, Lars & Bahr, Roald (2016). Can sports injuries be prevented? Models, mechanisms, and making it happen.
• Visnes, Håvard; Haug, Kari Bente Foss; Sivertsen, Einar & Bahr, Roald (2016). Can genetic testing predict the risk for jumper‘s knee? Knee Surgery, Sports Traumatology, Arthroscopy. ISSN 0942-2056. 24.
• Visnes, Håvard; Haug, Kari Bente Foss; Sivertsen, Einar & Bahr, Roald (2016). Can genetic testing predict the risk for jumper‘s knee?
• Skazalski, Christopher & Bahr, Roald (2016). Load monitoring, tissue response, and injury risk factors in male volleyball athletes.
• Bahr, Roald (2016). Can sports injuries be prevented? Models, mechanisms, and making it happen.
• Bahr, Roald (2016). Young elite athletes - the demise of the fittest.
• Bahr, Roald (2016). Building to Rio. Why screening for injury risk is a waste of time - and why we still are screening our Olympic athletes? The Norwegian Olympic Screening and Monitoring Programme.
• Andersson, Stig Haugsbø; Bahr, Roald; Clarsen, Benjamin & Myklebust, Grethe (2016). Preventing overuse shoulder injuries in elite handball - a cluster randomised controlled trail.
• Ardern, Clare; Bizzini, Mario & Bahr, Roald (2016). It is time for consensus on return to play after injury: Five key questions. British Journal of Sports Medicine. ISSN 0306-3674. 50(9), p. 506–508. doi: 10.1136/bjsports-2015-095475.
• Steenstrup, Sophie E.; Bere, Tone Tufte; Nordsletten, Lars; Krosshaug, Tron & Bahr, Roald (2015). FIS Injury Surveillance System: Methodology of the FIS ISS.
• Steenstrup, Sophie E.; Bere, Tone Tufte; Nordsletten, Lars; Krosshaug, Tron & Bahr, Roald (2015). FIS Injury Surveillance System: Methodology of the FIS ISS.
• Steenstrup, Sophie E.; Bere, Tone Tufte; Nordsletten, Lars; Krosshaug, Tron & Bahr, Roald (2015). FIS Injury Surveillance System: Injury statistics from the 2014/15 World Cup season.
• Steenstrup, Sophie E.; Bere, Tone Tufte; Nordsletten, Lars; Krosshaug, Tron & Bahr, Roald (2015). FIS Injury Surveillance System: Injury statistics from the 2014/15 World Cup season.
• Wangensteen, Arnlaug; Tol, Johannes; Witvrouw, Erik; van Linschoten, Robbart; Almusa, Emad & Hamilton, Bruce [Show all 7 contributors for this article] (2015). Hamstring re-injuries occur at the same location with 50% within 25 days after RTP – a descriptive study of MRI-confirmed re-injuries.
• Wangensteen, Arnlaug; Almusa, Emad; Boukarroum, S; Farooq, Abdulaziz; Hamilton, Bruce & Whiteley, R [Show all 8 contributors for this article] (2015). MRI does not add value to patient history and clinical examination in predicting time to RTP after acute hamstring injuries.
• Wangensteen, Arnlaug; Almusa, Emad; Boukarroum, S; Farooq, Abdulaziz; Hamilton, Bruce & Whiteley, R [Show all 8 contributors for this article] (2015). MRI does not add value to patient history and clinical examination in predicting time to RTP after acute hamstring injuries.
• Harøy, Joar; Clarsen, Benjamin; Bahr, Roald & Andersen, Thor Einar (2015). Stort omfang av lyskeplager blant mannlige spillere på alle nivå i norsk fotball.
• Bahr, Roald (2015). Update on digital platform on injury and illness prevention in sports.
• Haaland, Bjørnar Øvrum; Steenstrup, Sophie E.; Bere, Tone Tufte; Bahr, Roald & Nordsletten, Lars (2015). Skadeforekomst og skademønster i FIS World Cup alpint: En sammenligning av data før og etter nye skiregler. Norsk idrettsmedisin. ISSN 0806-9328. 30(3).
• Haaland, Bjørnar Mæland; Steenstrup, Sophie E.; Bere, Tone Tufte; Bahr, Roald & Nordsletten, Lars (2015). Skadeforekomst og skademønster i FIS World Cup alpint: En sammenligning av data før og etter nye skiregler.
• Bakken, Arnhild; Khan, Karim; Targett, Stephen; Tol, Johannes; Whiteley, Rodney & Witvrouw, Erik [Show all 7 contributors for this article] (2015). Funksjonell screening av idrettsutøvere - sesong til sesong variasjon av NI-PLUSS screening test. Norsk idrettsmedisin. ISSN 0806-9328. 30(3).
• Bakken, Arnhild; Khan, Karim; Targett, Stephen; Tol, Johannes; Whiteley, Rodney & Witvrouw, Erik [Show all 7 contributors for this article] (2015). Funksjonell screening av idrettsutøvere - sesong til sesong variasjon av NI-PLUSS screening test.
• Wangensteen, Arnlaug; Tol, Johannes; Witvrouw, Erik; van Linschoten, Robbart; Almusa, Emad & Hamilton, Bruce [Show all 7 contributors for this article] (2015). Re-skade etter akutte hamstringskader skjer i samme lokalisasjon og tidlig etter retur til idrett. Norsk idrettsmedisin. ISSN 0806-9328. 30(3).
• Wangensteen, Arnlaug; Tol, Johannes; Witvrouw, Erik; van Linschoten, Robbart; Almusa, Emad & Hamilton, B [Show all 7 contributors for this article] (2015). Re-skade etter akutte hamstringskader skjer i samme lokalisasjon og tidlig etter retur til idrett.
• Visnes, Håvard; Haug, Kari Bente Foss; Sivertsen, EA & Bahr, Roald (2015). Kan genetisk testing forutse risikoen for hopperkne? Norsk idrettsmedisin. ISSN 0806-9328. 30(3).
• Visnes, Håvard; Foss, Kari Bente; Sivertsen, Einar Andreas & Bahr, Roald (2015). Kan genetisk testing forutse risikoen for hopperkne?
• Moseid, Christine Holm; Myklebust, Grethe; Slaastuen, Marit Kyte; Bar-yaacov, Jonathan Brun; Kristiansen, Åse & Nordsletten, Lars [Show all 7 contributors for this article] (2015). Den unge eliteutøveren - helse og uhelse hos ungdom som begynner på toppidrettsgymnas. Norsk idrettsmedisin. ISSN 0806-9328. 30(3).
• Moseid, Christine Holm; Myklebust, Grethe; Slaastuen, Marit Kyte; Bar-Yaacov, Jonathan Brun; Kristiansen, Åse & Nordsletten, Lars [Show all 7 contributors for this article] (2015). Den unge eliteutøveren - helse og uhelse hos ungdom som begynner på toppidrettsgymnas.
• Andersson, Stig Haugsbø; Bahr, Roald; Clarsen, Benjamin & Myklebust, Grethe (2015). Forebygging av skulderproblemer i norsk elitehåndball - en randomisert kontrollert studie. Norsk idrettsmedisin. ISSN 0806-9328. 30(3).
• Andersson, Stig Haugsbø; Bahr, Roald; Clarsen, Benjamin & Myklebust, Grethe (2015). Forebygging av skulderproblemer i norsk elitehåndball - en randomisert kontrollert studie.
• Harøy, Joar; Andersen, Thor Einar; Clarsen, Benjamin & Bahr, Roald (2015). Stort omfang av lyskeplager blant mannlige spillere på alle nivå i norsk fotball. Norsk idrettsmedisin. ISSN 0806-9328. 30(3).
• Harøy, Joar; Andersen, Thor Einar; Clarsen, Benjamin & Bahr, Roald (2015). Stort omfang av lyskeplager blant mannlige spillere på alle nivå i norsk fotball.
• Steenstrup, Sophie E.; Mok, Kam-Ming; Krosshaug, Tron & Bahr, Roald (2015). Videoanalyse av krasjhastighet i hodeskadesituasjoner hos FIS World Cup snowboard- og freestylekjørere. Norsk idrettsmedisin. ISSN 0806-9328. 30(3).
• Steenstrup, Sophie E.; Mok, Kam-Ming; Krosshaug, Tron & Bahr, Roald (2015). Videoanalyse av krasjhastighet i hodeskadesituasjoner hos FIS World Cup snowboard- og freestylekjørere.
• Bahr, Roald (2015). Planning of the world conference on prevention of injury and illness in sport.
• Bahr, Roald & Myklebust, Grethe (2015). The Oslo Sports trauma research centre, the Norwegian school of sports science.
• Bahr, Roald (2015). Cutting Edge Sports Medicine: Player Safety, Health and Concussions.
• Bahr, Roald (2015). Training - Monitoring.
• Bahr, Roald (2015). Soft Tissues Injury Prevention (moderator).
• Visnes, Håvard; Haug, KBF; Sivertsen, EA & Bahr, Roald (2015). Kan genetisk testing forutse risikoen for hopperkne? Show summary

  Bakgrunn: Hopperkne er et stort problem blant utøvere i idretter som krever spenst og eksplosivitet. Etiologien til denne kroniske seneplagen er vist å være multifaktoriell, hvor både arv og miljø trolig spiller inn. Tidligere studier har påvist genetiske risikofaktorer for Akillessenetendinopati, mens få tilsvarende undersøkelser er utført for hopperkne. Mål: Å undersøke om utvalgte enkeltnukleotidvarianter (SNVs) innen kandidatgener, med kjent assosiasjon til Akillessenetendinopati, disponerer for utvikling av hopperkne. Materiale og metode: Pasientene ble rekruttert fra en 5-årig prospektiv kohortestudie ved et toppidrettsgymnas, ToppVolley Norge (TVN). Totalt 126 (64 jenter og 62 gutter) ble inkludert i perioden 2006- 2011. Hopperknediagnosen var basert på en standardisert klinisk undersøkelse. Av 126 elever ble 33 diagnostisert med hopperkne (9 jenter og 24 gutter). Genomisk DNA ble ekstrahert fra EDTA-blodprøver av utøverne i løpet av perioden på TVN. Til sammen 6 SNVs i genene COL1A1, COL5A1, MMP3 og GDF ble genotypet for alle atletene. Forskjellen i allelfrekvens mellom gruppene med og uten hopperkne ble testet med kji kvadrattest. Resultater: Det ble ikke funnet noen assosiasjon i minor allelfrekvens mellom friske kontroller og hopperknegruppen. Imidlertid ble det påvist markante kjønnsforskjeller mellom genotypefrekvenser for alle 6 SNVs, både innad i gruppen med hopperkne og mellom hopperknegruppen og friske kontroller. Diskusjon: Fra den samme kohorten er det tidligere blitt publisert at kjønn (menn), belastning i form av trening og kamp, spenst og tilstedeværelse av ultralydendringer er klare risikofaktorer for utvikling av hopperkne. På tross av at det ikke ble funnet noen klar assosiasjon mellom hopperkne og de undersøkte SNVs i denne studien, sees også her en betydelig kjønnsforskjell. Genotyperfrekvensen innad i hopperknegruppen varierer mellom mann og kvinne, og for samtlige gener finnes enkelte genotyper klart underrepresentert hos kvinner i hopperknegruppen. Tilsvarende kjønnsforskjeller er også tidligere rapportert i litteraturen hos pasienter med Akillessenetendinopati, og om dette kan være med på å forklare hvorfor menn er mer utsatt enn kvinner er ukjent. Konklusjon: Denne studien viste ingen klar sammenheng mellom 6 utvalgte SNVs i 4 kandidatgener og utviklingen av hopperkne blant en gruppe unge elitevolleyballspillere. Derimot sees klare kjønnsforskjeller i fordelingen mellom genotypefrekvenser i hopperknegruppen og mellom denne gruppen og kontrollgruppen. Betydningen av disse kjønnsforskjellene må undersøkes videre i en større kohort.

• Bahr, Roald (2015). How to develop policies for competing in the heat and reducing heat illness risk?
• Bahr, Roald (2015). New guidelines for management of concussion.
• Bahr, Roald (2015). Does injury prevention work in real life?
• Bahr, Roald (2015). Periodic Health Examinations.
• Bahr, Roald (2015). Principles of risk management.
• Bahr, Roald (2015). Diagnosis and management of concussion - practising the Sport Concussion Assessment Tool (SCAT3).
• Myklebust, Grethe & Bahr, Roald (2015). Ankle/foot.
• Bahr, Roald (2015). Why knee valgus motion in a drop jump test does not predict ACL injury risk?
• Bahr, Roald (2015). Keynote: Mechanisms for ACL injuries.
• Bahr, Roald (2015). Is there any benefit in musculoskeletal screening to reduce the risk of injuries?
• van Dyk, N; Whiteley, R; Eirale, Cristiano; Kumar, BD; Hamilton, B & Tol, JL [Show all 8 contributors for this article] (2015). Muscle strength imbalances and hamstring strain injuries, are we moving forward?
• Bakken, Arnhild; Targett, Stephen; Bere, Tone Tufte; Adamuz, MC; Tol, JL & Whiteley, R [Show all 10 contributors for this article] (2015). What does a comprehensive periodic health evaluation in football players detect?
• Bahr, Roald (2015). A decision-based model for return to play in sport.
• Bahr, Roald (2015). No strain with daily gain - how to prevent hamstring injuries.
• Bahr, Roald (2015). From post-season injury analysis through pre-season screening - risk management in the team setting.
• Bahr, Roald (2015). Welcome - the history and role of the ATPC.
• Bahr, Roald (2015). Injury prevention - what is the evidence?
• Bahr, Roald (2014). Roles and responsibilities of sports medicine professionals.
• Martinsen, Marianne; Bahr, Roald; Børresen, Runi; Holme, Ingar Morten K; Pensgaard, Anne Marte & Sundgot-Borgen, Jorunn (2014). Preventing eating disorders among young elite athletes - a randomized controlled trial .
• Bahr, Roald (2014). Demise of the fittest: are we destroying our biggest talents? British Journal of Sports Medicine. ISSN 0306-3674. 48(17), p. 1265–1267.
• Bahr, Roald (2014). Optimization of management with injuries in team sports - the Norwegian Olympic team experience in London 2012 and Sotchi 2014.
• Bahr, Roald (2014). Injury risk management in team sprots.
• Bahr, Roald (2014). Introduction.
• Wangensteen, Arnlaug; Almusa, E; Boukarroum, S; Farooq, M; Hamilton, Bruce & Whiteley, R [Show all 8 contributors for this article] (2014). Prediktorer for tid til retur til idrett etter akutte hamstringsskader hos mannlige eliteutøvere. Norsk idrettsmedisin. ISSN 0806-9328.
• Bahr, Roald; Amundsen, Roar & Sæther Heimland, Janita (2021). Effekten av høg og låg dosering av Nordic hamstrings trening på eksentrisk knefleksjonsstyrke - ei randomisert kontrollert studie. Norges idrettshøgskole.
• Bahr, Roald; Amundsen, Roar & Helle, Knut Magnus Bauge (2021). Uke-til-uke reliabilitet for målinger av eksentrisk hamstringsstyrke og isometriskisometriskisometrisk isometrisk adduksjons -, abduksjons, innadrotasjons-, utadrotasjons- og fleksjonsstyrke i hoften blant kvinnelige Toppseriespillere i fotball – en metodestudie. Norges idrettshøgskole.
• Dahl, Magnus Duus & Bahr, Roald (2019). Prevalence of low back pain among adolescent alpine ski racers - A cross-sectional study. Norges idrettshøgskole.
• Slåstuen, Marit Kyte & Bahr, Roald (2016). Den unge elite utøvers helse - forekomst, alvorlighetsgrad og klassifikasjon av helseproblemer blant utholdenhetsutøvere på toppidrettsgymnas. Norges idrettshøgskole.
• Kristiansen, Åse-Helene & Bahr, Roald (2016). Den unge eliteutøvers helse - forekomst av helseplager blant lagidrettsutøvere ved norske toppidrettsgymnas. Norges idrettshøgskole.
• Nilstad, Agnethe; Andersen, Thor Einar & Bahr, Roald (2014). Injuries and risk factors in elite female football - implications for screening and prevention. Norges idrettshøgskole. ISSN 978-82-502-0501-7.
• Bjørneboe, John Andreas; Andersen, Thor Einar & Bahr, Roald (2014). Injury surveillance and prevention in male professional football. Universitetet i Oslo. ISSN 978-82-8264-837-0.

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