Ola Eriksrud

• Westheim, Frederic; Gløersen, Øyvind; Harper, Damian; Laugsand, Håkon Nilsen & Eriksrud, Ola (2023). Reliability of phase-specific outcome measurements in change-of-direction tests using a motorized resistance device. Frontiers in Sports and Active Living. ISSN 2624-9367. 5. doi: 10.3389/fspor.2023.1212414. Full text in Research Archive Show summary

  This study aims to determine test-retest reliability of phase-specific information during initial acceleration, deceleration, and re-acceleration phases of different change-of-direction (CoD) tests using a motorized resistance device (MRD). A total of 21 participants (16 males and five females, with mean age of 22.3 ± 3.9 years, body mass of 75.2 ± 6.9 kg, height of 177.9 ± 6.8 cm) completed the modified 505 (m505), 10-0-5, and 15-0-5 CoD tests on four different test sessions while exposed to an external load (3 kg) provided by the MRD. Outcome variables included overall and phase-specific kinetic (force, power, and impulse) and kinematic (time, distance, velocity, and acceleration/deceleration) data during the initial acceleration, deceleration, and re-acceleration phases. The deceleration and re-acceleration phases were further divided into two subphases, namely, early and late subphases, using 50% of maximum velocity. Reliability was assessed using an intraclass correlation coefficient (ICC), coefficient of variation (CV), typical error (TE), and minimal detectable change (MDC). Good to excellent ICC values (>0.75) and acceptable (<10%) to good (<5%) CV values were observed for most outcome measurements. Specifically, 80.1% (822 out of 1,026) of all variables showed good or better relative reliability (i.e., ICC ≥ 0.75), while 97.0% (995 out of 1,026) of all variables showed acceptable or better absolute reliability (i.e., CV < 10%). In conclusion, the present study demonstrates that the MRD can obtain reliable phase-specific outcome measurements across different CoD tests, providing coaches and researchers with new opportunities to advance our understanding of CoD ability and inform more advanced CoD training prescriptions.

• Johansen, Merethe Lia; Eriksrud, Ola; Thorkildsen, Joachim; Norum, Ole-Jacob Anderssen; Wisløff, Torbjørn & Taksdal, Ingeborg [Show all 7 contributors for this article] (2023). Muscle strength characteristics following megaprosthetic knee reconstruction for bone sarcoma. Surgial oncology. ISSN 0960-7404. 48. doi: 10.1016/j.suronc.2023.101944. Full text in Research Archive Show summary

  Objective: To assess muscle strength characteristics in patients with resection and megaprosthetic reconstruction of the knee for bone sarcoma compared to age- and sex-matched controls. Methods: This was a cross-sectional, case-control study. Muscle strength characteristics for knee extension and -flexion were assessed isokinetically at three different joint velocities: 60, 120 and 180°/s, and by the rate of force development (RDFmax) in knee extension. The Toronto Extremity Salvage Score (TESS) was used in patients. Results: Eighteen patients (91.6 months postop.) and 18 controls were included. Relative to controls, patients generated maximal torques of 19%, 23% and 23% in knee extension at 60, 120 and 180°/s, respectively. For knee flexion, patients generated maximal torques of 58%, 53% and 60% at 60, 120, and 180°/s, relative to the controls. RDFmax of the operated leg was 2.75 ± 2.13 N/ms, 7.16 ± 4.78 N/ms for the non-operated leg, and 7.95 ± 4.29 N/ms for the controls. The mean TESS score was 84.0. Conclusion: Patients reached approximately 20% of the maximal knee extension torque. In isometric assessments, they used double the amount of time to generate one-third of the maximal force compared to the controls despite good TESS scores.

• Mai, Patrick; Bill, Kevin; Glöckler, Katharina; Claramunt-Molet, Mireia; Bartsch, Julia & Eggerud, Mathias M. [Show all 14 contributors for this article] (2022). Unanticipated fake-and-cut maneuvers do not increase knee abduction moments in sport-specific tasks: Implication for ACL injury prevention and risk screening. Frontiers in Sports and Active Living. ISSN 2624-9367. 4. doi: 10.3389/fspor.2022.983888. Full text in Research Archive Show summary

  Non-contact anterior cruciate ligament injuries typically occur during cutting maneuvers and are associated with high peak knee abduction moments (KAM) within early stance. To screen athletes for injury risk or quantify the efficacy of prevention programs, it may be necessary to design tasks that mimic game situations. Thus, this study compared KAMs and ranking consistency of female handball players in three sport-specific fake-and-cut tasks of increasing complexity. The biomechanics of female handball players (n = 51, mean ± SD: 66.9 ± 7.8 kg, 1.74 ± 0.06 m, 19.2 ± 3.4 years) were recorded with a 3D motion capture system and force plates during three standardized fake-and-cut tasks. Task 1 was designed as a simple pre-planned cut, task 2 included catching a ball before a pre-planned cut in front of a static defender, and task 3 was designed as an unanticipated cut with three dynamic defenders involved. Inverse dynamics were used to calculate peak KAM within the first 100 ms of stance. KAM was decomposed into the frontal plane knee joint moment arm and resultant ground reaction force. RANOVAs (α ≤ 0.05) were used to reveal differences in the KAM magnitudes, moment arm, and resultant ground reaction force for the three tasks. Spearman's rank correlations were calculated to test the ranking consistency of the athletes' KAMs. There was a significant task main effect on KAM (p = 0.02; η2p = 0.13). The KAM in the two complex tasks was significantly higher (task 2: 1.73 Nm/kg; task 3: 1.64 Nm/kg) than the KAM in the simplest task (task 1: 1.52 Nm/kg). The ranking of the peak KAM was consistent regardless of the task complexity. Comparing tasks 1 and 2, an increase in KAM resulted from an increased frontal plane moment arm. Comparing tasks 1 and 3, higher KAM in task 3 resulted from an interplay between both moment arm and the resultant ground reaction force. In contrast to previous studies, unanticipated cutting maneuvers did not produce the highest KAMs. These findings indicate that the players have developed an automated sport-specific cutting technique that is utilized in both pre-planned and unanticipated fake-and-cut tasks.

• Harper, Damian J.; McBurnie, Alistair J.; Santos, Thomas Dos’; Eriksrud, Ola; Evans, Martin & Cohen, Daniel D. [Show all 9 contributors for this article] (2022). Biomechanical and Neuromuscular Performance Requirements of Horizontal Deceleration: A Review with Implications for Random Intermittent Multi-Directional Sports. Sports Medicine. ISSN 0112-1642. doi: 10.1007/s40279-022-01693-0. Full text in Research Archive Show summary

  Rapid horizontal accelerations and decelerations are crucial events enabling the changes of velocity and direction integral to sports involving random intermittent multi-directional movements. However, relative to horizontal acceleration, there have been considerably fewer scientific investigations into the biomechanical and neuromuscular demands of horizontal deceleration and the qualities underpinning horizontal deceleration performance. Accordingly, the aims of this review article are to: (1) conduct an evidence-based review of the biomechanical demands of horizontal deceleration and (2) identify biomechanical and neuromuscular performance determinants of horizontal deceleration, with the aim of outlining relevant performance implications for random intermittent multi-directional sports. We highlight that horizontal decelerations have a unique ground reaction force profile, characterised by high-impact peak forces and loading rates. The highest magnitude of these forces occurs during the early stance phase (< 50 ms) and is shown to be up to 2.7 times greater than those seen during the first steps of a maximal horizontal acceleration. As such, inability for either limb to tolerate these forces may result in a diminished ability to brake, subsequently reducing deceleration capacity, and increasing vulnerability to excessive forces that could heighten injury risk and severity of muscle damage. Two factors are highlighted as especially important for enhancing horizontal deceleration ability: (1) braking force control and (2) braking force attenuation. Whilst various eccentric strength qualities have been reported to be important for achieving these purposes, the potential importance of concentric, isometric and reactive strength, in addition to an enhanced technical ability to apply braking force is also highlighted. Last, the review provides recommended research directions to enhance future understanding of horizontal deceleration ability.

• Eriksrud, Ola; Ahlbeck, Fredrik; Harper, Damian & Gløersen, Øyvind Nøstdahl (2022). Validity of Velocity Measurements of a Motorized Resistance Device During Change of Direction. Frontiers in Physiology. ISSN 1664-042X. 13. doi: 10.3389/fphys.2022.824606. Full text in Research Archive Show summary

  The aim of this study was to determine validity of velocity measurements of a motorized resistance device (MRD) during change of direction (CoD). Eight male (age: 22.1 ± 4.2 yrs; weight: 83.3 ± 17.1 kg; height: 181.6 ± 12.6 cm) and three female participants (age: 21.7 ± 1.5 yrs; mass: 69.7 ± 2.4 kg; height: 167.0 ± 3.6 cm) completed the modified 505 CoD test (m505) with turning off the left and right foot while exposed to external loads (3, 6, and 9 kg) provided by the MRD. Three-dimensional kinematic data were measured (200 Hz) for all tests using a full-body marker set with an additional marker placed on the pulley used to attach the carabiner (CAR) at the end of the line from the MRD to the participant. Average velocity of overall center of mass (COMvel), pelvis (COMpelvis_vel), and pulley (CARvel) was then calculated and compared to the velocity measured by MRD (MRDvel) in 0.5 s intervals 1.5 s before and after CoD. Average velocities from these intervals were then compared using correlational, Bland–Altman analysis, coefficient of variation (CV), and statistical parametric mapping (SPM). Mostly, excellent correlations were observed and ranged from 0.93 to 1.00, 0.53 to 1.00 and 0.93 to 1.00 for the 3, 6, and 9 kg load conditions, respectively. CV values ranged from 0.3 to 3.2%, 0.8 to 4.3%, and 1.5 to 7.7% for the CARvel, COMpelvis_vel, and COMvel comparisons, respectively. The biases for CARvel comparisons ranged from −0.027 to 0.05 m/s, −0.246 to 0.128 m/s and −0.486 to 0.082 m/s across all load conditions and time intervals for the CARvel, COMpelvis_vel, and COMvel comparisons, respectively. SPM analysis indicated significant differences between MRDvel and COMvel and COMpelvis_vel over short time periods during the CoD, but no difference between MRDvel and CARvel. The velocity measurements obtained by a MRD during a m505 test are valid as low biases, low CV’s, and high correlations are observed for the MRDvel to CARvel comparison. As single points of measurement (i.e., laser) has been proven useful to assess other athletic tasks (i.e., sprint running), the single point CARvel comparison is an appropriate comparison for validating MRDvel measurements during the m505 test.

• Rakovic, Elvir; Paulsen, Gøran; Helland, Christian; Haugen, Thomas André & Eriksrud, Ola (2022). Validity and Reliability of a Motorized Sprint Resistance Device. Journal of Strength and Conditioning Research. ISSN 1064-8011. 36(8), p. 2335–2338. doi: 10.1519/JSC.0000000000003830. Full text in Research Archive Show summary

  An increasing number of sprint-related studies have used motorized devices to provide resistance while sprinting. The aim of this study was to establish within-session reliability and criterion validity of sprint times obtained from a motorized resistance device. Seventeen elite, female, handball players (22.9 ± 3.0 years; 176.5 ± 6.5 cm; 72.7 ± 5.5 kg; training volume 9.3 ± 0.7 hours per week) performed two 30-m sprints under 3 different resistance loading conditions (50, 80 and 110 N). Sprint times (t0–5m, t5–10m, t10–15m, t15–20m, t20–30m, and t0–30m) were assessed simultaneously by a 1080 Sprint motorized resistance device and a postprocessing timing system. The results showed that 1080 Sprint timing was equivalent to the postprocessing timing system within the limits of precision (±0.01 seconds). A systematic bias of approximately 0.34 ± 0.01 seconds was observed for t0–5m caused by different athlete location and velocity at triggering point between the systems. Coefficient of variation was approximately 2% for t0–5 and approximately 1% for the other time intervals, although standard error of measurement ranged from 0.01 to 0.05 seconds, depending on distance and phase of sprint. Intraclass correlation ranged from 0.86 to 0.95. In conclusion, the present study shows that the 1080 Sprint is valid and reliable for sprint performance monitoring purposes.

• Gonjo, Tomohiro; Njøs, Nikolai; Eriksrud, Ola & Olstad, Bjørn Harald (2021). The Relationship Between Selected Load-Velocity Profile Parameters and 50 m Front Crawl Swimming Performance. Frontiers in Physiology. ISSN 1664-042X. 12. doi: 10.3389/fphys.2021.625411. Full text in Research Archive Show summary

  The purpose of the present study was to establish relationships between sprint front crawl performance and a swimming load-velocity profile. Fourteen male national-level swimmers performed 50 m front crawl and semi-tethered swimming with three progressive loads. The 50 m performance was recorded with a multi-camera system, with which two-dimensional head displacement and the beginning of each arm-stroke motion were quantified. Forward velocity (V50m), stroke length (SL) and frequency (SF) were quantified for each cycle, and the mean value of all cycles, excluding the first and last cycles, was used for the analysis. From the semi-tethered swimming test, the mean velocity during three stroke cycles in mid-pool was calculated and plotted as a function of the external load, and a linear regression line expressing the relationship between the load and velocity was established for each swimmer. The intercepts between the established line and the axes of the plot were defined as theoretical maximum velocity (V0) and load (L0). Large to very large correlations were observed between V50m and all variables derived from the load-velocity profiling; L0 (R = 0.632, p = 0.015), L0 normalized by body mass (R = 0.743, p = 0.002), V0 (R = 0.698, p = 0.006), and the slope (R = 0.541, p < 0.046). No significant relationships of SL and SL with V50m and the load-velocity variables were observed, suggesting that each swimmer has his own strategy to achieve the highest swimming velocity. The findings suggest that load-velocity profiling can be used to assess swimming-specific strength and velocity capabilities related to sprint front crawl performance.

• Carlos-Vivas, Jorge; Perez-Gomez, Jorge; Eriksrud, Ola; Freitas, Tomás; Marín-Cascales, Elena & Alcaraz, Pedro E. (2020). Vertical Versus Horizontal Resisted Sprint Training Applied to Young Soccer Players: Effects on Physical Performance. International Journal of Sports Physiology and Performance (IJSPP). ISSN 1555-0265. 15(5), p. 748–758. doi: 10.1123/ijspp.2019-0355. Full text in Research Archive Show summary

  Purpose: To analyze and compare the effects of 4 different resisted sprint training (RST) modalities on youth soccer players’ performance after 8 weeks of training. Methods: Forty-eight youth soccer players were first randomly assigned to 4 groups and only then completed 8 weeks of RST: horizontal resisted sprint, vertical resisted sprint (VRS), combined resisted sprint, and unresisted sprint. Performance in horizontal and vertical jumps, sprint, and change of direction (COD) ability were assessed 1 week before and after the training intervention. Magnitude-based inference analysis was performed for calculating within-group pre–post differences. In addition, an analysis of covariance test was performed for between-group comparison, using the pretest values as covariates. After that, the analysis of covariance P values and the effect statistic were transformed to magnitude-based inference. Results: Within-group outcomes showed that all resisted training modalities experienced improvements in sprint (small to moderate) and COD (small to large) performance. Moreover, all groups, except unresisted sprint, enhanced the horizontal jump performance. However, only VRS improved on vertical jump. Between-group comparison outcomes revealed that only VRS improved the sprint time compared with horizontal resisted sprint (moderate) and COD performance compared with all groups (moderate to large). In addition, VRS enhanced the countermovement jump performance (small to large) compared with the other groups. Conclusions: Independent of the orientation of the resistance applied, RST is an effective training method for improving sprinting and COD performance. Nevertheless, VRS may promote greater improvements on sprint and COD ability and have a positive additional effect on countermovement jump performance and the reduction of COD deficit.

• Olstad, Bjørn Harald; Gonjo, Tomohiro; Njøs, Nikolai; Abächerli, Kathrin & Eriksrud, Ola (2020). Reliability of Load-Velocity Profiling in Front Crawl Swimming. Frontiers in Physiology. ISSN 1664-042X. 11, p. 1–8. doi: 10.3389/fphys.2020.574306. Full text in Research Archive Show summary

  The purposes of this study were to establish test-retest reliability of calculating load-velocity profiles in front crawl swimming using five and three different external loads, and if outcome results were comparable between calculation methods for monitoring performance over time. Fifteen swimmers at either national or international competition level (seven females and eight males) participated in this study. The subjects performed 25 m of semi-tethered swimming with maximal effort with five progressive loads (females 1, 2, 3, 4, and 5 kg and males 1, 3, 5, 7, and 9 kg) as well as 50 m maximal front crawl on 2 different days. The mean velocity during three stroke cycles in mid-pool was calculated and plotted as a function of the external load. Relationship between the load and velocity was expressed by a linear regression line and established for each swimmer. The intercepts between the axes of the plot and the established regression line were defined as theoretical maximum velocity (V0) and load (L0). In addition, L0 was also expressed as a percentage of body mass (rL0). The coefficient of determination (R2) and the slope (Slv) of the linear load-velocity relationship were calculated. The intra-class correlation coefficient (ICC) showed excellent agreement (ICC ≥0.902) for all variables. The coefficient of variation was ≤3.14% and typical error was rated as “good” in all variables. A difference was found between day 1 and 2 in V0 for three- and five-load calculations and for 50 m front crawl time (p < 0.05). No difference was found between the load-velocity profile outcomes variables compared between the three- and five-trial protocols on neither day 1 nor 2. The Bland-Altman plots showed a small bias across all resistance conditions for five loads, L0: 0.04 kg, rL0: 0.13%, V0: −0.03 m/s, and Slv: 0.003 −m/s/kg and for three loads, L0: −0.24 kg, rL0: −0.27%, V0: −0.04 m/s, Slv: 0.002 −m/s/kg. In conclusion, the load-velocity profile for front crawl swimming can be calculated with high reliability from both five and three external loads and comparable results in outcome variables were established. These methods can be used to monitor performance parameters over time, and to investigate and compare swimmers’ velocity and strength capabilities to allow for individualized training prescription to improve performance.

• Gonjo, Tomohiro; Eriksrud, Ola; Papoutsis, Filip Dimitrios Evje & Olstad, Bjørn Harald (2020). Relationships between a Load-velocity Profile and Sprint Performance in Butterfly Swimming. International Journal of Sports Medicine (IJSM). ISSN 0172-4622. 41(7), p. 461–467. doi: 10.1055/a-1103-2114. Show summary

  The purpose of this study was to establish the relationships between 50 m sprint swimming performance and variables acquired from a swimming load-velocity profile established by semi-tethered butterfly swimming. Twelve male elite swimmers participated in the present study and performed 50 m sprint and semi-tethered butterfly swimming with different loads. The mean velocity among all upper-limb cycles was obtained from the 50 m swimming (race velocity), and maximum load and velocity were predicted from the load-velocity profile established by the semi-tethered swimming test. There was a very large correlation (r=0.885, p<0.01) and a high intra-class correlation (0.844, p<0.001) between the race velocity and the predicted maximum velocity. Significant correlations were also observed between the predicted maximum load and the 50 m time as well as the race velocity (r=− 0.624 and 0.556, respectively, both p<0.05), which imply that an ability to achieve a large tethered swimming force is associated with 50 m butterfly performance. These results indicate that the load-velocity profile is a useful tool for predicting and assessing sprint butterfly swimming performance.

• Eriksrud, Ola; Cabri, Jan Maria Hendrick & Federolf, Peter Andreas (2019). Relationship between stability and variability ofthe core in dynamic reaching tasks. Current Issues in Sport Science. ISSN 2414-6641. 4. doi: 10.15203/CISS_2019.007. Full text in Research Archive Show summary

  Core stability is important to many functional and athletic tasks. Motion variability has been proposed as a measure to characterize core stability. Based on motor learning theories, the current study hypothesized that variability and stability of core movements show a U-shaped relationship and further investigated whether functional range of motion (“mobility”) or speed of motion affect this relationship. Twenty-four healthy subjects performed 20 cycles of two different unilateral hand reaching tasks for both the left and right hand under stable and unstable conditions. Reach targets were positioned to trigger large core movements. Specifically, the anterior target was positioned midsagittal at arm length ́s distance and hip height. Two posterior targets (60 degrees posterior to neutral stance frontal plane) on both the left and right side were high (at arm length distance and height with accrued 10 cm) and low (arm length distance at hip height). Kinematic data were recorded and three-dimensional angles between pelvis and thorax (core) were calculated. Pearson correlation coefficients and paired T-tests were calculated to assess variability, mobility and speed of the core movements. A parabolic function was fitted to the variability data and the quality of the fit was assessed by calculating adjusted R-squared values. In the sagittal plane, variability could be modeled with a U-shaped distribution; in the other planes of motion this was the case in 2 of 4 reaching tests. In two tests, movement speed changed between the stable and unstable conditions. Mobility did not appear to affect variability in the stable condition, but some correlations were observed in the unstable condition. The relationship between mobility and variability, and the change in variability were task-specific.

• Eriksrud, Ola; Ghelem, Ali & Cabri, Jan Maria Hendrick (2019). Isokinetic strength training of kinetic chain exercises of a professional tennis player with a minor partial internal abdominal oblique muscle tear ? A case report. Physical Therapy in Sport. ISSN 1466-853X. 38, p. 23–29. doi: 10.1016/j.ptsp.2019.04.012. Full text in Research Archive
• Eriksrud, Ola; Federolf, Peter Andreas & Cabri, Jan Maria Hendrick (2019). Influence of anthropometry, age, sex, and activity level on the hand reach star excursion balance test. Frontiers in Psychology. ISSN 1664-1078. 10. doi: 10.3389/fpsyg.2019.00756. Show summary

  The influence of anthropometric measurements, age, sex, and activity level have been found to influence tests of dynamic postural control such as the star excursion balance test (SEBT). The hand reach star excursion balance test (HSEBT) measures different aspects of dynamic postural control. The purpose of the present study was to explore the influence of these factors on the HSEBT. A convenience sample of 223 subjects performed four horizontal (L45, R45, L135, and R135) and two rotational (LROT and RROT) reaches. The influence of anthropometric measurements (height, arm length, leg length, and wingspan) on reach measurements were assessed using stepwise multiple linear regression. Influence of age (young: <20 years; adult: >20 years), sex (male; female) and activity level (athletes; recreational) on reach measurements were analyzed using independent samples t-test (p < 0.05) and interpreted using effect size (Cohens d) and established values of minimal detectable change (MDC). Wingspan explained a significant portion of the variance of only R45 (34.6%) and L45 (11.7%) reach measurements and normalized (percentage of wingspan). A medium effect of age, sex, and activity level was observed for normalized L45 and R45 reaches (d = 0.50–72). Group differences greater than MDC values and a medium effect for age (d = 0.55) and activity level (d = 0.75) were observed for the R135 reach. L45 and R45 reaches should be normalized to wingspan, but not the other reaches. Between individual or group comparisons should consider age, activity level and sex as potential covariates.

• Eriksrud, Ola; Sæland, Fredrik; Federolf, Peter Andreas & Cabri, Jan Maria Hendrick (2019). Functional Mobility and Dynamic Postural Control Predict Overhead Handball Throwing Performance in Elite Female Team Handball Players. Journal of Sports Science and Medicine. ISSN 1303-2968. 18(1), p. 91–100. Show summary

  The relationship between dynamic postural control, functional mobility and team handball throwing performance, velocity and accuracy, is largely unknown. The hand reach star excursion balance test (HSEBT) is a full kinetic chain assessment tool of these factors. Specifically, L135 and R135 (extension) reaches elicit joint movement combinations similar to the cocking and acceleration phase, while the L45 and R45 (flexion) reaches elicit joint movement combinations similar to the follow-through. The purpose of this study was to determine if specific HSEBT reach measures correlate with team handball throwing performance. Eleven elite female team handball players (21.7 ± 1.8 years; 71.3 ± 9.6 kg; 1.75 ± 0.07 m) executed selected HSEBT reaches before performing five valid step-up overhead throws (1x1m target) from which throwing velocity (motion capture) and accuracy (mean radial error) were quantified. Significant relationships between HSEBT measures and mean radial error, but not throwing velocity were established. Specifically, extension composite scores (L135+R135) for the dominant (150.7 ± 17.4cm) and non-dominant foot (148.1 ± 17.5 cm) were correlated with mean radial error (p < 0.05). Also, specific reaches on the dominant (L135: 87.4 ± 5.6 cm; R135: 63.4 ± 11.8 cm) and non-dominant (R135: 87.0 ± 6.1 cm) foot were correlated with throwing error (p < 0.05). The lack of significant findings to throwing velocity might be due to a ceiling effect of both L135 and R135 and of throwing velocity. We conclude that while there may be other reasons for handball players to train and test functional mobility and dynamic postural control as measured in the HSEBT, no beneficial effect on throwing performance should be expected in an elite group of handball players.

• Helland, Christian; Haugen, Thomas André; Rakovic, Elvir; Eriksrud, Ola; Seynnes, Olivier R. & Mero, Antti A. [Show all 7 contributors for this article] (2019). Force–velocity profiling of sprinting athletes: single-run vs. multiple-run methods. European Journal of Applied Physiology. ISSN 1439-6319. 119(2), p. 465–473. doi: 10.1007/s00421-018-4045-2. Show summary

  Purpose: This study explored the agreement between a single-run and a multiple-run method for force–velocity (Fv) profiling of sprinting athletes; we evaluated both absolute values and changes over time caused by sprint training. Methods: Seventeen female handball players (23 ± 3 years, 177 ± 7 cm, 73 ± 6 kg) performed 30 m un-resisted and resisted sprints (50, 80 and 110 N resistance) before and after an 8-week sprint training intervention. Two approaches were used to calculate theoretical maximal velocity (v0), horizontal force (F0), power (Pmax), and the force–velocity slope (SFv): (1) the single-run method, based on inverse dynamics applied to the centre-of-mass movement, was calculated from anthropometric and sprint split time data; and (2) the multiple-run method, where peak velocity from un-resisted and resisted sprints were plotted against the horizontal resistances. Results: Trivial differences in v0 (0.7%) were observed between the two calculation methods. Corresponding differences for F0, Pmax and SFv were 16.4, 15.6 and 17.6%, respectively (most likely; very large effect size). F0 showed poor agreement between the methods (r = 0.26 and 0.16 before and after the intervention). No substantial correlation between the changes (from pre- to post-training tests) in SFV calculated with the single-run and the multiple-run methods were observed (r = 0.02). Conclusions: This study revealed poor agreement between the Fv relationships of the investigated calculation methods. In practice, both methods may have a purpose, but the single-run and the multiple-run methods appear to measure somewhat different sprint properties and cannot be used interchangeably.

• Eriksrud, Ola; Federolf, Peter Andreas; Anderson, Patrick Julian & Cabri, Jan Maria Hendrick (2018). Hand reach star excursion balance test: An alternative test for dynamic postural control and functional mobility. PLOS ONE. ISSN 1932-6203. 13(5). doi: 10.1371/journal.pone.0196813. Full text in Research Archive Show summary

  Tests of dynamic postural control eliciting full-body three-dimensional joint movements in a systematic manner are scarce. The well-established star excursion balance test (SEBT) elicits primarily three-dimensional lower extremity joint movements with minimal trunk and no upper extremity joint movements. In response to these shortcomings we created the hand reach star excursion balance test (HSEBT) based on the SEBT reach directions. The aims of the current study were to 1) compare HSEBT and SEBT measurements, 2) compare joint movements elicited by the HSEBT to both SEBT joint movements and normative range of motion values published in the literature. Ten SEBT and HSEBT reaches for each foot were obtained while capturing full-body kinematics in twenty recreationally active healthy male subjects. HSEBT and SEBT areas and composite scores (sum of reaches) for total, anterior and posterior subsections and individual reaches were correlated. Total reach score comparisons showed fair to moderate correlations (r = .393 to .606), while anterior and posterior subsections comparisons had fair to good correlations (r = .269 to .823). Individual reach comparisons had no to good correlations (r = -.182 to .822) where lateral and posterior reaches demonstrated the lowest correlations (r = -.182 to .510). The HSEBT elicited more and significantly greater joint movements than the SEBT, except for hip external rotation, knee extension and plantarflexion. Comparisons to normative range of motion values showed that 3 of 18 for the SEBT and 8 of 22 joint movements for the HSEBT were within normative values. The findings suggest that the HSEBT can be used for the assessment of dynamic postural control and is particularly suitable for examining full-body functional mobility.

• Rakovic, Elvir; Paulsen, Gøran; Helland, Christian; Eriksrud, Ola & Haugen, Thomas (2018). The effect of individualised sprint training in elite female team sport athletes: A pilot study. Journal of Sports Sciences. ISSN 0264-0414. 36(24), p. 2802–2808. doi: 10.1080/02640414.2018.1474536. Full text in Research Archive Show summary

  This study aimed to evaluate whether an individualised sprint-training program was more effective in improving sprint performance in elite team-sport players compared to a generalised sprint-training program. Seventeen elite female handball players (23 ± 3 y, 177 ± 7 cm, 73 ± 6 kg) performed two weekly sprint training sessions over eight weeks in addition to their regular handball practice. An individualised training group (ITG, n = 9) performed a targeted sprint-training program based on their horizontal force-velocity profile from the pre-training test. Within ITG, players displaying the lowest, highest and mid-level force-velocity slope values relative to body mass were assigned to a resisted, an assisted or a mixed sprint-training program (resisted sprinting in the first half and assisted sprinting in the second half of the intervention period), respectively. A control group (CG, n = 8) performed a generalised sprint-training program. Both groups improved 30-m sprint performance by ~1% (small effect) and maximal velocity sprinting by ~2% (moderate effect). Trivial or small effect magnitudes were observed for mechanical outputs related to horizontal force- or power production. All between-group differences were trivial. In conclusion, individualised sprint-training was no more effective in improving sprint performance than a generalised sprint-training program.

• Cross, Matt R.; Lahti, Johan; Brown, Scott; Chedati, Mehdi; Jimenez-Reyes, Pedro & Samozino, Pierre [Show all 8 contributors for this article] (2018). Training at maximal power in resisted sprinting: Optimal load determination methodology and pilot results in team sport athletes. PLOS ONE. ISSN 1932-6203. 13(4). doi: 10.1371/journal.pone.0195477. Full text in Research Archive Show summary

  Aims: In the current study we investigated the effects of resisted sprint training on sprinting performance and underlying mechanical parameters (force-velocity-power profile) based on two different training protocols: (i) loads that represented maximum power output (Lopt) and a 50% decrease in maximum unresisted sprinting velocity and (ii) lighter loads that represented a 10% decrease in maximum unresisted sprinting velocity, as drawn from previous research (L10). Methods: Soccer [n = 15 male] and rugby [n = 21; 9 male and 12 female] club-level athletes were individually assessed for horizontal force-velocity and load-velocity profiles using a battery of resisted sprints, sled or robotic resistance respectively. Athletes then performed a 12-session resisted (10 × 20-m; and pre- post-profiling) sprint training intervention following the L10 or Lopt protocol. Results: Both L10 and Lopt training protocols had minor effects on sprinting performance (average of -1.4 to -2.3% split-times respectively), and provided trivial, small and unclear changes in mechanical sprinting parameters. Unexpectedly, Lopt impacted velocity dominant variables to a greater degree than L10 (trivial benefit in maximum velocity; small increase in slope of the force-velocity relationship), while L10 improved force and power dominant metrics (trivial benefit in maximal power; small benefit in maximal effectiveness of ground force orientation). Conclusions: Both resisted-sprint training protocols were likely to improve performance after a short training intervention in already sprint trained athletes. However, widely varied individualised results indicated that adaptations may be dependent on pre-training force-velocity characteristics.

• Eriksrud, Ola; Federolf, Peter Andreas; Sæland, Fredrik; Litsos, Stavros & Cabri, Jan Maria Hendrick (2017). Reliability and Validity of the Hand Reach Star Excursion Balance Test. Journal of Functional Morphology and Kinesiology. ISSN 2411-5142. 2(3). doi: 10.3390/jfmk2030028.
• Moltubakk, Marie M.; Eriksrud, Ola; Paulsen, Gøran; Seynnes, Olivier R. & Bojsen-Møller, Jens (2016). Hamstrings functional properties in athletes with high musculo-skeletal flexibility. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. 26(6), p. 659–665. doi: 10.1111/sms.12488. Show summary

  The purpose of this study was to examine whether athletes with highly flexible hamstring muscle-tendon units display different passive and contractile mechanical properties compared with controls. Flexibility, passive, and active torque–angle properties were assessed in 21 female elite rhythmic gymnasts and 16 female age-matched athletes. Passive resistance to stretch was measured during knee extension with the hip fixed at 100° of flexion. Concentric isokinetic maximal voluntary knee flexion and extension torques were measured at 60°/s in the same position. Tests of flexibility and passive resistance to stretch indicated a greater flexibility in the gymnasts. Despite no differences between groups in knee flexion and extension peak torque, gymnasts reached knee flexion peak torque at more extended positions (longer muscle lengths) and displayed significantly different torque–angle relations. When active torque was corrected for passive resistance to stretch, differences increased, gymnasts producing more work, and maintaining ≥ 70% of peak torque over a larger range of joint excursion. In conclusion, individuals with a higher flexibility of the hamstrings MTU present a different torque–angle profile, favoring the production of flexion torque toward extended knee positions, displaying larger functional range of motion and a higher mechanical work output during knee flexion.

• Buteau, Josephine L.; Eriksrud, Ola & Hasson, Scott M. (2007). Rehabilitation of a glenohumeral instability utilizing the body blade. Physiotherapy Theory and Practice. ISSN 0959-3985. 23(6), p. 333–349. Show summary

  Traditional rehabilitation for shoulder dislocation has a success rate of only 20%. The body blade has been hypothesized to strengthen the muscles stabilizing the shoulder girdle by training the contractile tissues directly and also indirectly affecting the joint and surrounding noncontractile tissues when responding to rapid positional changes and mechanical energy. Shoulder dislocation negatively affects both the active (musculature) and passive (joint and ligaments) stabilizers of the glenohumeral joint. Therefore, the purpose of this case report was to evaluate the efficacy of therapeutic exercise using the body blade in the conservative management of an individual with glenohumeral instability. The patient, an 18-year-old male, dislocated his left shoulder after a wave crashed on top of him. Intervention included therapeutic exercise using the body blade. Measures were taken at examination, re-evaluation (6th visit), and discharge (11th visit). According to the 11-point numeric pain rating scale, worst pain was reduced from 4 to 0. Glenohumeral ROM measures at discharge were all within normal range except external rotation (deficit of 10 degrees), compared to the initial ROM deficits of 10-35% of noninvolved values. Post intervention strength, as assessed by handheld dynamometry, revealed deficits only in scapular retraction compared to the uninvolved side (21% compared to an initial deficit of 39%). Other muscle groups showing deficits from20% to 40% at initial examination exceeded the comparative strength of the other limb at discharge. The SPADI and WOSI scores were reduced from 13 to 0 and 482 to 46, from initial examination to discharge, respectively. Furthermore 6 months post episode of care the patient reported no recurrent dislocation of the involved shoulder. The success rate of an exercise program with individuals who have dislocated their glenohumeral joint is poor. After 11 visits of physical therapy using the body blade the patient improved in ROM, strength, and function.

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• Gjerset, Asbjørn; Nilsson, Johnny Erik; Helge, Jørn Wulff; Enoksen, Eystein; Raastad, Truls & Meen, Helge Dyre [Show all 17 contributors for this article] (2015). Idrettens Treningslære. Gyldendal Undervisning. ISBN 978-82-05-39194-9. 638 p.

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• Eriksrud, Ola; Krosshaug, Tron; Mai, Patrick; Glørsen, Øyvind & Westheim, Frederic (2024). Deceleration demands in change of direction tests: insights from measurements using a motorized resistance device .
• Mai, Patrick; Bill, Kevin; Kersting, Uwe; Willwacher, Steffen; Eriksrud, Ola & Krosshaug, Tron (2024). A nine-week ACL injury prevention program for female handball players: Effect on knee joint loading and cutting technique during a handball-specific fake-cut.
• Bill, Kevin; Mai, Patrick; Robertz, Leon; Glöckler, Katharina; Claramunt-Molet, Mireia & Bartsch, Julia [Show all 14 contributors for this article] (2022). Knee kinematics and kinetics of sport-specific fake-and-cut maneuvers of varying complexity in female handball players.
• Mai, Patrick; Bill, Kevin; Robertz, Leon; Glöckler, Katharina; Claramunt-Molet, Mireia & Bartsch, Julia [Show all 15 contributors for this article] (2022). Can a simplified knee abduction moment estimation be used for athlete screening? Implications for ACL injury prevention.
• Helland, Christian; Haugen, Tommy; Rakovic, Elvir; Eriksrud, Ola; Seynnes, Olivier R. & Mero, Antti A. [Show all 7 contributors for this article] (2019). Correction to: Force–velocity profiling of sprinting athletes: single-run vs. multiple-run methods (European Journal of Applied Physiology, (2019), 119, 2, (465-473), 10.1007/s00421-018-4045-2). European Journal of Applied Physiology. ISSN 1439-6319. 119(2). doi: 10.1007/s00421-018-04057-7.
• Moltubakk, Marie M.; Eriksrud, Ola; Paulsen, Gøran; Seynnes, Olivier R. & Bojsen-Møller, Jens (2012). Tendon stiffness following years of systematic stretching.
• Eriksrud, Ola; Paulsen, Gøran & Bojsen-Møller, Jens (2011). Tendon strain following years of systematic stretching.
• Eriksrud, Ola (2009). KLINISKE FOTSTILLINGSMÅL OG PRONASJON VED LØP HOS FRISKE UNGE KVINNER. Show summary

  Introduksjon En økt pronasjon av ankel og fot vurderes som en av risikofaktorene for idrettsskader i kne, ankel og fot. Pronasjon har blitt definert som dorsifleksjon, eversjon og abduksjon. Klinisk vurderer man pronasjon ved hjelp av kliniske fotstillingsmål. Dette var en del av en større studie hvor formålet med denne delen var å undersøke sammenhengen mellom kliniske fotstillingsmål og pronasjon ved løp. Metode Tre ulike kliniske fotstillingsmål, calcaneus vinkel, naviculare drop og naviculare drift, ble tatt av to erfarne fysioterapeuter på kvinnelige rekreasjonsløpere (N=9). Deretter løp de på en 20 m løpebane i 3,8 m ? s-1 kontrollert med fotoceller. Tredimensjonale kinematiske data ble tatt opp ved hjelp av refleksive markører på underekstremiteten og 8 Pro-Reflex kamera (Qualisys AB, Sverige) ved 240 Hz, mens tredimensjonale kinetiske data ble tatt opp med tre gulvmonterte kraftplatformer (AMTI, USA). Bevegelsesutslaget og maksimalt bevegelesutslag mellom leggen og bakfoten og bakfoten og forfoten ble kalkulert i Visual 3D (C-Motion Inc. USA). Statistisk analyse ble utført med Pearsons r eller Spearmans rho korrelasjons analyse. Resultat Forsøkspersonene var 24 ± 4 år gamle. Mellom legg og bakfot var det bare naviculare drift som var signifikant for eversjonsutslaget (0,78, p < 0,05). I forholdet mellom bakfot og forfot var det bare naviculare drop som var signifikant for eversjonsutslaget (-0,62, p< 0,05) og maksimalt bevegelsesutslag for dorsifleksjon (0,61, p < 0,05). Diskusjon Resultatene er fra dette studiet viser at de ulike kliniske fotmålstestene samsvarer relativt dårlig med pronasjon i løp. Man skulle anta at naviculare drop og calcaneus vinkel skulle ha en korrelasjon med bevegelsesutslaget og maksimalt bevegelsesutslag i frontalplanet, men her fant man ikke noe konsekvent forhold. Naviculare drift testen har en transversal komponent uten at det førte til noe signifikant forhold til abduksjon. Konklusjon Kliniske fotstillingsmål samsvarer dårlig med pronasjon i løp hos friske kvinner.

• Eriksrud, Ola & eltarvåg, Beate (2009). FOTENS MAKSIMALE PRONASJONSBEVEGELSE FØLGER EN FAST SEKVENS I DE TRE KARDINALE PLANENE VED MODERAT LØPSHASTIGHET. Show summary

  Introduksjon Økt pronasjon av ankel og fot har blitt av mange betraktet som viktig i forhold til ulike belastningsskader. Pronasjon har blitt definert som en dorsifleksjon, eversjon og abduksjon. En analyse av pronasjon bør derfor inneholde bevegelsene med tanke på størrelsesorden, hvor i bevegelsesutslaget de finner sted og sekvensen av disse. Dette var en del av en større studie hvor formålet med denne delen var å undersøke når de ulike bevegelsesutslagene nådde sine maksimale verdier. Metode Kvinnelige rekreasjonsløpere (N=22) løp på en 20 m løpebane i 3,8 m ? s-1 kontrollert med fotoceller. Tredimensjonale kinematiske data ble tatt opp ved hjelp av refleksive markører på underekstremiteten og 8 Pro-Reflex kamera (Qualisys AB, Sverige) ved 240 Hz, mens tredimensjonale kinetiske data ble tatt opp med tre gulvmonterte kraftplatformer (AMTI, USA). Bevegelsesutslag av ankel og fot som ett segment ble kalkulert i Visual 3D (C-Motion Inc. USA). Tid til makismalt bevegelsesutslag ble normalisert til varighet av belastningsfasen. Statistisk analyse ble utført med en parvis t-test. Resultat Forsøkspersonene var 22 ± 3 år gamle Maksimal abduksjon, eversjon og dorsifleksjon fant sted henholdsvis 30±10 %, 50±10 % og 60±0,02 % inn i belastningsfasen. Det var signifikant forskjell på når disse maksimale bevegelsesutslagene inntraff i belastningsfasen (p<0,05). Diskusjon En rekke studier viser at maksimal pronasjon skal finne sted innenfor 40-60% av belastningsfasen. Da har man definert maksimal pronasjon som maksimal eversjon. Dette er noe mangelfullt siden pronasjonen er tredimensjonal. Sekvensen for maksimalt bevegelsesutslag kan være avgjørende for prestasjon. Dette gjelder særlig abduksjon og eversjon siden man ønsker en adduksjon og inversjon for å stive av foten for en effektiv kraftoverføring til underlaget. Konklusjon Maksimalt bevegelsesutslag i de tre ulike planene følger en gitt sekvens i henholdsvis transversal-, frontal- og sagittalplanet ved pronasjon hos friske unge kvinner ved løping.

• Eriksrud, Ola; eltarvåg, Beate & Smith, Gerald A. (2009). Relationship of Rearfoot Angular Velocity to Vertical and Leg Stiffness in Running. Show summary

  The mass-spring model is used to describe the mechanical behavior of the lower extremity during running. At the middle of stance the spring is maximally compressed which is associated with maximal pronation, commonly described by rearfoot eversion. Few have looked at the relationship between foot motion and position to leg stiffness (Viale 1998), but not angular velocity. The current study which focuses on angular velocity was part of a larger project evaluating the influence of lower extremity joint kinematics on leg and vertical stiffness. Methods 15 female subjects were all tested in running along a 20 meter running path at a target speed 3.8m?s-1. Three dimensional kinematic data were obtained from reflective markers on the lower extremity using a pro-reflex motion capture system (Qualisys AB, Sweden). Three-dimensional kinetic data were obtained using three floor mounted force plates (AMTI, USA) in sequence placed midway on the runway. Three or more successful trials within a 5% range of 3.8m?s-1 were analyzed using MatLab and Visual 3D. Vertical and leg stiffness were calculated based on the method by McMahon and Cheng (1990). Rearfoot angle was calculated from tracking markers in Visual3D as the relative angle between the foot and shank segments with 0° taken as the positioning in a static standing trial. Rearfoot eversion (EvROM) was the angular change from heel strike to maximum value. EvROM was then divided by time to maximum value for rearfoot eversion angular velocity (EvAngVel). The relationship between EvAngVel and vertical and leg stiffness were evaluated using Pearsons product moment correlation (r). Results Mean EvAngVel was 148.6±47.55??s-1. EvAngVel was not significantly correlated with vertical stiffness (31.1±5.3kN?m-1) (r = 0.38, p > 0.05), but had a moderate and significant correlation with leg stiffness (10.2±1.5kN?m-1) (r = 0.56, p < 0.05). Discussion The mass-spring model applies to the entire lower extremity as a system which collectively stores and returns elastic energy. This model does not identify which structures, joints or planes of motion that would be responsible for this. Foot kinematics is important in shock absorption during impact with the ground, and the angular velocity of foot motion could partially help explain the elastic properties of the leg-spring in running. EvAngVel was the only angular velocity analyzed, and was found to be significantly correlated with leg stiffness, but not vertical stiffness. Eversion is one of many complex motions in the foot, and only one of several joints that could contribute to leg stiffness. However it helps in explaining one important aspect of leg mechanics. Conclusion EvAngVel was significantly correlated with leg stiffness but not vertical stiffness. References McMahon TA & Cheng GC (1990) The mechanics of running: how does stiffness couple with speed. J Biomech 23:65-78 Viale F et al. (1998). Leg stiffness and foot orientation in running. Foot & Ankle 19:761-765

• Eriksrud, Ola & eltarvåg, Beate (2009). Relationship of Rearfoot Motion to Vertical and Leg Stiffness in Running. Show summary

  Relationship of Rearfoot Motion to Vertical and Leg Stiffness in Running Eltarvåg Beate, Eriksrud Ola, Smith Gerald (Norwegian School of Sport Sciences, Norway) During running, the lower extremities function much like a mass-spring system. Near the middle of stance, the leg spring is maximally compressed. This is approximately the time of maximal pronation, commonly described by rearfoot eversion. Few studies have explored the relationship between rearfoot motion and leg stiffness (Viale, 1998). The current study which focuses on foot motion was part of a larger project evaluating the influence of lower extremity joint kinematics on leg and vertical stiffness. Methods 15 female subjects were all tested while running over a 20 m lab runway at a target speed of 3.8 m·s-1. Three dimensional kinematic data were obtained from reflective markers on the lower extremity using a Pro-Reflex motion capture system (Qualisys AB, Sweden). Three-dimensional kinetic data were measured using three floor mounted force plates (AMTI, USA) in sequence placed midway in the runway. Three or more successful trials within a 5% range of 3.8 m·s-1 were analyzed using MatLab and Visual3D. Vertical and leg stiffness were calculated based on the method by McMahon and Cheng (1990). Rearfoot angle was calculated from tracking markers in Visual3D as the relative angle between the foot and shank segments with 0° taken as the positioning in a static, standing trial. Maximum rearfoot eversion (EvMax) along with eversion range of motion (EvROM: angular change from heelstrike to EvMax) were determined. The relationships of EvMax and EvROM to vertical and leg stiffness were evaluated using Pearson's product moment correlation (r). Results Mean EvROM during early stance of running was 14.4 ± 4.2° while EvMax was 11.5 ± 2.7°. Vertical stiffness for the runners was 31.8 ± 4.7 kN·m-1 while leg stiffness averaged 10.3 ± 1.5 kN·m-1. EvRom and EvMax were not significantly correlated with neither vertical nor leg stiffness. Discussion The mass-spring model applies to the whole running leg as a system which collectively exhibits elastic properties. The model does not attempt to identify which anatomical structures produce these characteristics. However, it is likely that structures surrounding ankle, knee and hip all contribute in some amount to this response. Foot kinematics during stance may help to absorb shock during impact with the ground, but in addition, foot motion provides a mechanism for partially explaining the elastic characteristics of the running leg. EvROM was not found to be significantly related to leg stiffness. This is only one plane of a complex foot motion and only one of several joints which could contribute to leg stiffness. Further analysis of the ankle and foot in other planes of motion as well as other joints needs to be analyzed to better understand this important fraction of leg mechanics. References McMahon TA & Cheng GC (1990) The mechanics of running: how does stiffness couple with speed. J Biomech 23:65-78 Viale F et al. (1998). Leg stiffness and foot orientation in running. Foot & Ankle 19:761-765

• Eriksrud, Ola & Smith, Gerald A. (2008). Asymmetry of unilateral stiffness. Show summary

  Vertical stiffness of the musculoskeletal system has been studied extensively using mass-spring modeling, however most studies involve the investigation of the bilateral stiffness of the lower extremities with only few examining unilateral leg stiffness (Dalleau 1998). The purpose of this study was to determine the relationship between bilateral and unilateral vertical stiffness during hopping. This was a part of a larger study evaluating how parameters such as stiffness during hopping and running are different between three distinct athletic populations. Methods: 13 subjects (11 power lifters and 2 distance runners) were tested in bilateral and unilateral hopping for 15 seconds on a floor mounted force plate (AMTI). The average stiffness of 10 consecutive hopping cycles was used for analysis. Vertical stiffness was determined using the model of Morin et al. (2005) which is based on contact and flight time to predict force and displacement. For statistical analysis, the more stiff and the more compliant leg were identified and compared using paired t-test (N=13). In addition, dominant and non-dominant leg were identified and compared using paired t-test (N=12 as dominance was not identified for one subject). Results: Bilateral stiffness (18.7 ± 3.7 kN¿m-1) was significantly greater than unilateral vertical stiffness (p<0.05). For unilateral stiffness comparisons, the stiff and compliant legs differed by about 14% (14.7 ± 3.6 vs 12.8 ± 3.2 kN¿m-1, p<0.05). Dominant and non-dominant legs were not significantly different (13.7 ± 3.4 vs 12.5 ± 2.1 kN¿m-1 respectively, p=0.10). Within subject variability across 10 hops was similar for each leg grouping (CV of 10-12%) Discussion: Dalleau et al (1998) distinguished leg contributions to running by identifying one leg as propulsive and the other as a stiffer, "stick" leg which had about 17% greater stiffness. Asymmetry for hopping unilateral stiffness (14%) was of similar magnitude to these running data. While mean values were not significantly different, the dominant leg was generally stiffer in unilateral hopping than the non-dominant side. For 75% of subjects the stiffest leg was the dominant leg. Whether this dominant vs. non-dominant stiffness difference continues during bilateral hopping was not examined here as separate force measures were not obtained.

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• Eriksrud, Ola & Smith, Gerald A. (2007). Static Flexibility Measures do not Determine Active Range of Motion during Running. Show summary

  Static measures of range of motion (ROM) are used extensively to determine flexibility. These measures are often used to determine if flexibility training is indicated or not since it is thought that these measures reflect functional performance. The purpose of this study was to determine if static flexibility measures predict ROM during running. This was part of a larger project where the main purpose was to look at the influence of flexibility training on running economy, kinematic characteristics and stiffness. Methods: 17 subjects divided into a training group (TRA, n = 8) and a control group (CON, n = 9) were tested before (PRE) and after (POST) the implementation of a flexibility training program which lasted 6 weeks. All static measures were obtained by one experienced physical therapist using a hand-held goniometer. The measures included ankle dorsiflexion and hip extension (Thomas test). Running kinematics were recorded using an 8 camera Qualisys motion analysis system with body markers during treadmill running at an intensity of 60, 70, 80% of VO2-max. Data were exported and analyzed in Matlab. The minimum and maximum angles during running were determined in the sagittal plane for the ankle and hip. Results: The mean correlation PRE and POST in the CON group for static and dynamic measures was r = 0.81 indicating good repeatability of measurements. Static ROM measures of ankle dorsiflexion and hip extension were not associated with maximum values obtained during a running stride from the kinematic analysis. However the static measures had inconsistent levels of significance with the total ROM in the sagital plane for the same joints. Static hip extension measure in the PRE group was significantly related to total sagital plane ROM of the hip (r = 0.54, p< 0.05) at 80% of VO2-max. The static hip extension measure was associated with total ROM in the ankle for all intensities in the PRE and POST group (r = 0.48 ¿ 0.63, p < 0.05). Discussion: ROM restrictions relative to the demands of running are thought to affect kinematic characteristics. Hip extension was obtained using the Thomas test which is supposed to be sensitive to hip flexor mobility, and might therefore not reflect other factors limiting this motion. Ankle dorsiflexion has been found to be greater active assisted than passively. In this study we obtained this measure passively. What is interesting to note is that these static measures at the end of ROM are more stongly associated with the total ROM rather than the corresponding maximum values. Hip extension and ankle dorsiflexion can interrelate during a running stride since one can influence the other in determining total stride length. This is evident since hip extension correlates well with total ankle ROM at all intensities PRE and POST. Conclusion: Static range of ROM are not associated with maximum active ROM, however static measures of hip extension are significantly correlated with total ankle ROM during running.

• Eriksrud, Ola & Smith, Gerald A. (2007). Flexibility and Stiffness Interactions influencing Running Economy. ?. Show summary

  Abstract: Running economy is the submaximal oxygen uptake at a given speed and has been found to vary considerably for any group of runners. Both flexibility and leg stiffness have been associated with running economy. A stiffer system is perhaps more effective in returning energy stored elastically as part of the stretch¿shortening cycles of running, but increased range of motion (ROM) may enhance a runner¿s stride length capability. The interaction of these factors influencing running economy are poorly understood. PURPOSE: To determine the effect of leg stiffness and joint ranges of motion in the lower extremity on running economy. METHODS: 26 subjects completed ROM, running economy and VO2 max testing. Joint flexibility measures of ankle and hip were obtained using standard hand¿held goniometer measurement procedures. VO2 max was measured with a standard protocol from which running speeds corresponding with 60, 70 and 80% of max were obtained. Running economy measures at these speeds were recorded during the 5¿7th minute of an 8 minute bout. Regression across speeds was used to predict VO2 at common speeds of 3.0 and 3.5 m/s. During each bout prior to VO2 measurement, running kinematic characteristics were determined using an 8 camera Qualisys motion analysis system and body markers. Stance and step times were used to determine vertical and leg stiffness over 20 steps based on a mass¿spring model of the running leg. RESULTS: Variability of running economy (CV) was 7¿9% across subjects. ROM was 24 ± 6.4° (ankle dorsiflexion), 102.4 ± 19.8° (straight leg raise, hamstrings) and ¿5.8 ± 3.4° (hip extension). Vertical stiffness was 20.9 ± 3.7 kN¿m¿1, 22.8 ± 3.8 kN¿m¿1 and 24.8 ± 5.1 kN¿m¿1 at 60%, 70% and 80% speeds. Significant negative correlations (p < 0.05) of ankle ROM to oxygen uptake at the common speeds and vertical stiffness were found. While vertical stiffness and hamstring flexibility were negatively correlated (p < 0.05), neither was Print this Page for Your Records Close Window related to economy. Step time was positively related to VO2 at common speeds (p < 0.05). CONCLUSION: Running economy was not strongly related to vertical stiffness or hip ranges of motion, but was clearly influenced by ankle flexibility.

• Eriksrud, Ola; Moltubakk, Marie & Smith, Gerald A. (2007). Static Flexibility Measures do not Determine Active Range of Motion during Running. Show summary

  Static measures of range of motion (ROM) are used extensively to determine flexibility. These measures are often used to determine if flexibility training is indicated or not since it is thought that these measures reflect functional performance. The purpose of this study was to determine if static flexibility measures predict ROM during running. This was part of a larger project where the main purpose was to look at the influence of flexibility training on running economy, kinematic characteristics and stiffness. Methods: 17 subjects divided into a training group (TRA, n = 8) and a control group (CON, n = 9) were tested before (PRE) and after (POST) the implementation of a flexibility training program which lasted 6 weeks. All static measures were obtained by one experienced physical therapist using a hand-held goniometer. The measures included ankle dorsiflexion and hip extension (Thomas test). Running kinematics were recorded using an 8 camera Qualisys motion analysis system with body markers during treadmill running at an intensity of 60, 70, 80% of VO2-max. Data were exported and analyzed in Matlab. The minimum and maximum angles during running were determined in the sagittal plane for the ankle and hip. Results: The mean correlation PRE and POST in the CON group for static and dynamic measures was r = 0.81 indicating good repeatability of measurements. Static ROM measures of ankle dorsiflexion and hip extension were not associated with maximum values obtained during a running stride from the kinematic analysis. However the static measures had inconsistent levels of significance with the total ROM in the sagital plane for the same joints. Static hip extension measure in the PRE group was significantly related to total sagital plane ROM of the hip (r = 0.54, p< 0.05) at 80% of VO2-max. The static hip extension measure was associated with total ROM in the ankle for all intensities in the PRE and POST group (r = 0.48 ¿ 0.63, p < 0.05). Discussion: ROM restrictions relative to the demands of running are thought to affect kinematic characteristics. Hip extension was obtained using the Thomas test which is supposed to be sensitive to hip flexor mobility, and might therefore not reflect other factors limiting this motion. Ankle dorsiflexion has been found to be greater active assisted than passively. In this study we obtained this measure passively. What is interesting to note is that these static measures at the end of ROM are more stongly associated with the total ROM rather than the corresponding maximum values. Hip extension and ankle dorsiflexion can interrelate during a running stride since one can influence the other in determining total stride length. This is evident since hip extension correlates well with total ankle ROM at all intensities PRE and POST. Conclusion: Static range of ROM are not associated with maximum active ROM, however static measures of hip extension are significantly correlated with total ankle ROM during running.

• Moltubakk, Marie; Eriksrud, Ola & Smith, Gerald A. (2007). Changes in Flexibility do not influence Running Movement Patterns or Economy. Show summary

  Previous studies suggest that one factor contributing to the wide range of running economies observed within a group is runner flexibility. Runners with greater flexibility tend to have poorer economy than runners with more restricted ranges of motion. Flexibility training programs aim to increase joint ranges of motion (ROM). Does this affect running economy at the same time? Methods: 17 active subjects (TRA) participated in 18 ± 2 bouts of stretching across 6 weeks. Each subject performed 1 - 4 exercises, depending on initial flexibility criteria: <25° ankle dorsiflexion, <90° hip flexion (straight leg raise), <0° hip extension (Thomas test), <50° inwards hip rotation as measured by goniometry in supine or sitting positions. Each exercise consisted of 4 x 1 minute passive stretching and 3 x 10 dynamic motions towards end range, all performed in standing positions without support and on both sides. The total load was 4290 ± 391 seconds per exercise/side. Standard measurements of running economy and kinematics (2D sagittal model) during treadmill running at 60, 70, 80% of VO2-max were recorded. Regression across speeds was used to predict VO2 at a common speed of 3.5 m¿s-1. Training group characteristics were compared to a control group of 9 active subjects (CON). Results: The training group had significant increases of passive ROM at the ankle (5.8 ± 1.4°), and hip internal rotation (7.1 ± 4.6°) compared to CON (p < .05), while hip flexion increases (11.5 ± 9.4°) and hip extension increases (1.6 ± 2.9°) were not significantly different from CON. Running economy did not change in TRA compared to the CON group over the training period (p=.30). Kinematic characteristics during running (min and max joint angles, ankle angle at heel strike and heel off, hip angle at toe off, stance time and step length) did not systematically change over the training period for either group. Discussion: Although the stretching program was designed to imitate positions and motions of running, the observed changes in passive ROM were not reflected in running kinematics or economy. In subjects with restricted ROM, stretching might be thought to contribute to a longer running stride with increased hip and ankle ROM. But, though passive ROM increased with flexibility training, running kinematics were unaltered. Factors influencing running economy are complex and include biomechanical, physiological and psychological contributions. From results of the present study, passive joint ROM does not appear to be a major contributor to running economy. Conclusion: A 6-week stretching program did not influence economy or kinematics in runners.

• Smith, Gerald A.; Moltubakk, Marie & Eriksrud, Ola (2007). Relationships between Stiffness, Passive Flexibility, Dynamic Range of Motion and Running Economy. Show summary

  Running economy is a characteristic which varies considerably between runners and which has a substantial influence on performance. In some studies, joint flexibility has been found to be a factor which negatively affects economy, however the influences on economy of related characteristics such as leg stiffness and dynamic range of motion during running are not well understood. Methods: Active university students (N = 26) were recruited for this study in which running economy, kinematic and kinetic characteristics were measured. Based on results from a maximum oxygen uptake test, subjects were tested during treadmill running at speeds corresponding to 60, 70 and 80% of max VO2. During 8 minutes of running at each speed, running kinematics were determined using an 8-camera Qualisys ProReflex system and oxygen uptake was recorded using standard metabolic methods. Based on mass-spring modeling and stance-swing timing, vertical and leg stiffness were determined (Morin et al. 2005). In addition, each runner's flexibility was assessed by an experienced physical therapist using goniometry. Comparisons were made across speeds using repeated measures analysis of variance and inter-relationships of these characteristics were evaluated using Pearson correlation. Results: Running speeds at 60, 70 and 80% of max VO2 were 2.7±0.3, 3.2±0.3 and 3.6±0.3 m/s with oxygen uptakes of 31±3, 36±3 and 41±4 ml O2/kg/min. Vertical stiffness (Kvert) increased systematically with speed (p<.01) while leg stiffness (Kleg) remained constant. Dynamic range of motion (ROM) at hip, knee and ankle increased with speed (p<.01). Both Kvert and Kleg were significantly related to hip dynamic ROM (r = -.77 and -.62) but only weakly to knee and ankle motion. None of the stiffness nor dynamic ROM characteristics were significantly related to economy. Passive flexibility measures were only moderately related to economy (ankle: r = .46 and hip ext rotation: r = .35) but were in some cases more strongly related to Kvert (hip int rotation: r = -.66). Discussion: Based on previous studies (e.g. Craib et al., 1996) a positive relationship between flexibility and economy was expected. Also anticipated was an inverse relationship between flexibility and running stiffness, however this did not result in a clear connection of leg or vertical stiffness to running economy. This is contrary to the findings of Dalleau et al. (1998) where a strong association (r = -.80) was observed between cost of running and leg stiffness. Methodological differences may explain these conflicting results.

• Eriksrud, Ola; Moltubakk, Marie & Smith, Gerald A. (2007). Flexibility and Stiffness Interactions influencing Running Economy. Show summary

  Running economy is the submaximal oxygen uptake at a given speed and has been found to vary considerably for any group of runners. Both flexibility and leg stiffness have been associated with running economy. A stiffer system is perhaps more effective in returning energy stored elastically as part of the stretch-shortening cycles of running, but increased range of motion (ROM) may enhance a runer's stride length capability. The interaction of these factors influencing running economy are poorly understood. PURPOSE: To determine the effect of leg stiffness and joint ranges of motion in the lower extremity on running economy. METHODS: 26 subjects completed ROM, running economy and VO2 max testing. Joint flexibility measures of ankle and hip were obtained using standard hand-held goniometer measurement procedures. VO2 max was measured with a standard protocol from which running speeds corresponding with 60, 70 and 80% of max were obtained. Running economy measures at these speeds were recorded during the 5-7th minute of an 8 minute bout. Regression across speeds was used to predict VO2 at common speeds of 3.0 and 3.5 m/s. During each bout prior to VO2 measurement, running kinematic characteristics were determined using an 8 camera Qualisys motion analysis system and body markers. Stance and step times were used to determine vertical and leg stiffness over 20 steps based on a mass-spring model of the running leg. RESULTS: Variability of running economy (CV) was 7-9% across subjects. ROM was 24 ± 6.4° (ankle dorsiflexion), 102.4 ± 19.8° (straight leg raise, hamstrings) and -5.8 ± 3.4° (hip extension). Vertical stiffness was 20.9 ± 3.7 kN¿m-1, 22.8 ± 3.8 kN¿m-1 and 24.8 ± 5.1 kN¿m-1 at 60%, 70% and 80% speeds. Significant negative correlations (p < 0.05) of ankle ROM to oxygen uptake at the common speeds and vertical stiffness were found. While vertical stiffness and hamstring flexibility were negatively correlated (p < 0.05), neither was related to economy. Step time was positively related to VO2 at common speeds (p < 0.05). CONCLUSION: Running economy was not strongly related to vertical stiffness or hip ranges of motion, but was clearly influenced by ankle flexibility.

• Eriksrud, Ola (2006). Fit for golf - anatomi og biomekanikk. Show summary

  Anatomi og biomekanikk og hvordan det relaterer til golf

• Eriksrud, Ola (2006). Funksjonell trening Funksjonell trening og nye perspektiver. Show summary

  Funksjonell trening og tredimensjonal tankegang. Foredrag for forelesere og faglig ansatte ansvarlige for fitnessutdannelsen ved Norges Idrettshøgskole

• Eriksrud, Ola (2006). Funksjonell magetrening Funksjonell magetrening og magemuskler. Show summary

  Funksjonell magetrening og fotball. Cupfinaleseminaret 2006

• Eriksrud, Ola (2006). Funksjonell trening. Show summary

  Intorduksjon til funksjonell trening og funksjonell tankemåte

• Eriksrud, Ola (2006). Fit for Golf Anatomi, bevegelighet og styrketrening. Show summary

  Sammendrag av viktige ledd og muskler og deres funksjon i forhold til golf. Bevegelighet- og styrketrening i forhold til effekt, metode og belastningsfaktorer

• Eriksrud, Ola (2005). De funksjonelle magemusklene.
• Eriksrud, Ola (2009). Anatomi - basisår idrettsvitenskap. Norges idrettshøgskole. ISSN 9788250204294. Show summary

  Dette kompendiet omhandler en introduksjon til anatomi i form av en beskrivelse av posisjon, bevegelse, den strukturelle oppbygningen av knokler, klassifiseringer av ulike ledd samt en noen mekaniske prinsipper av viktighet for å kunne forstå funksjon av ulike muskler. Beskrivelse av knokler, ledd, leddbånd og muskler for overekstremiteten, truncus og underekstremiteten er videre beskrevet.

• Eriksrud, Ola (2006). Anatomi, Muskler, ledd og leddbånd for hele kroppen. Norges idrettshøgskole. ISSN 8250203917. Show summary

  Beskrivelse av utspring, feste og funksjon til muskler og leddbånd i tre dimensjoner for hele kroppen samt beskrivelse av alle ledd i kroppen.

• Eriksrud, Ola (2005). Anatomi, muskler, ledd og leddbånd for hele kroppen. Norges idrettshøgskole. ISSN 8250203879.

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