Olivier Seynnes

• Andersen, Vidar; Paulsen, Gøran; Stien, Nicolay; Baarholm, Martin; Seynnes, Olivier R. & Sæterbakken, Atle Hole (2024). Resistance Training with Different Velocity Loss Thresholds Induce Similar Changes in Strength and Hypertrophy. Journal of Strength and Conditioning Research. ISSN 1064-8011. 38(3), s. E135–E142. doi: 10.1519/JSC.0000000000004067.
• Ritsche, Paul; Franchi, Martino V.; Faude, Oliver; Finni, Taija; Seynnes, Olivier R. & Cronin, Neil J. (2024). Fully Automated Analysis of Muscle Architecture from B-Mode Ultrasound Images with DL_Track_US. Ultrasound in Medicine and Biology. ISSN 0301-5629. 50(2), s. 258–267. doi: 10.1016/j.ultrasmedbio.2023.10.011. Vis sammendrag

  Objective: B-mode ultrasound can be used to image musculoskeletal tissues, but one major bottleneck is analyses of muscle architectural parameters (i.e., muscle thickness, pennation angle and fascicle length), which are most often performed manually. Methods: In this study we trained two different neural networks (classic U-Net and U-Net with VGG16 pre-trained encoder) to detect muscle fascicles and aponeuroses using a set of labeled musculoskeletal ultrasound images. We determined the best-performing model based on intersection over union and loss metrics. We then compared neural network predictions on an unseen test set with those obtained via manual analysis and two existing semi/automated analysis approaches (simple muscle architecture analysis [SMA] and UltraTrack). DL_Track_US detects the locations of the superficial and deep aponeuroses, as well as multiple fascicle fragments per image. Results: For single images, DL_Track_US yielded results similar to those produced by a non-trainable automated method (SMA; mean difference in fascicle length: 5.1 mm) and human manual analysis (mean difference: –2.4 mm). Between-method differences in pennation angle were within 1.5°, and mean differences in muscle thickness were less than 1 mm. Similarly, for videos, there was overlap between the results produced with UltraTrack and DL_Track_US, with intraclass correlations ranging between 0.19 and 0.88. Conclusion: DL_Track_US is fully automated and open source and can estimate fascicle length, pennation angle and muscle thickness from single images or videos, as well as from multiple superficial muscles. We also provide a user interface and all necessary code and training data for custom model development.

• Ritsche, Paul; Seynnes, Olivier R. & Cronin, Neil J. (2023). DL_Track_US: a python package to analyse muscle ultrasonography images. Journal of Open Source Software (JOSS). ISSN 2475-9066. 8(85). doi: 10.21105/joss.05206. Fulltekst i vitenarkiv Vis sammendrag

  Ultrasonography can be used to assess muscle architectural parameters during static and dynamic conditions. Nevertheless, the analysis of the acquired ultrasonography images presents a major difficulty. Muscle architectural parameters such as muscle thickness, fascicle length and pennation angle are mainly segmented manually. Manual analysis is time expensive, subjective and requires thorough expertise. Within recent years, several algorithms were developed to solve these issues. Yet, these are only partly automated, are not openly available, or lack in user friendliness. The DL_Track_US python package is designed to allow fully automated and rapid analysis of muscle architectural parameters in lower limb ultrasonography images.

• Jerger, Simon; Centner, Christoph; Lauber, Benedikt; Seynnes, Olivier R.; Friedrich, Till & Lolli, David [Vis alle 8 forfattere av denne artikkelen] (2023). Specific collagen peptides increase adaptions of patellar tendon morphology following 14-weeks of high-load resistance training: A randomized-controlled trial. European Journal of Sport Science (EJSS). ISSN 1746-1391. doi: 10.1080/17461391.2023.2232758. Fulltekst i vitenarkiv Vis sammendrag

  The purpose of this study was to investigate the effect of a supplementation with specific collagen peptides (SCP) combined with resistance training (RT) on changes in structural properties of the patellar tendon. Furthermore, tendon stiffness as well as maximal voluntary knee extension strength and cross-sectional area (CSA) of the rectus femoris muscle were assessed. In a randomized, placebo-controlled study, 50 healthy, moderately active male participants completed a 14-week resistance training program with three weekly sessions (70–85% of 1 repetition maximum [1RM]) for the knee extensors. While the SCP group received 5g of specific collagen peptides daily, the other group received the same amount of a placebo (PLA) supplement. The SCP supplementation led to a significant greater (p < 0.05) increase in patellar tendon CSA compared with the PLA group at 60% and 70% of the patellar tendon length starting from the proximal insertion. Both groups increased tendon stiffness (p < 0.01), muscle CSA (p < 0.05) and muscular strength (p < 0.001) throughout the intervention without significant differences between the groups. The current study shows that in healthy, moderately active men, supplementation of SCP in combination with RT leads to greater increase in patellar tendon CSA than RT alone. Since underlying mechanisms of tendon hypertrophy are currently unknown, further studies should investigate potential mechanisms causing the increased morphology adaptions following SCP supplementation.

• Rice, Hannah; Seynnes, Olivier R. & Werkhausen, Amelie (2023). Effect of increased running speed and weight carriage on peak and cumulative tibial loading. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. doi: 10.1111/sms.14476. Vis sammendrag

  Introduction: Tibial stress injuries are a burdensome injury among military recruits. Military activities include running and the carriage of additional weight, and this may be related to the high risk of bone stress injuries. The aim of this study was to quantify tibial loading when running at two different speeds, with and without additional weight, and to quantify their combined influence. Methods: Fourteen male distance runners who ran at least 40 km per week ran barefoot on a force-instrumented treadmill in four conditions representing preferred running speed (mean (SD) 3.1 (0.3) m/s) and 20% increased running speed (3.8 (0.4) m/s), with and without 20% of body weight carried in a weight vest. Kinematics and kinetics were synchronously collected. Bending moments were estimated about the medial-lateral axis of the tibial centroid located 1/3rd of the length from distal to proximal. Static equilibrium was ensured at each 1% of stance. Peak bending moments were obtained in addition to cumulative-weighted loading, where weighted loading accounted for the relative importance of the magnitude of the bending moment and the quantity of loading using a bone-dependent weighting factor. Results: There were no interaction effects for running speed and weight carriage on peak or cumulative tibial loading. Running at a 20% faster speed increased peak and cumulative loading per kilometer by 8.0% (p < 0.001) and 4.8% (p < 0.001), respectively. Carriage of an additional 20% of body weight increased peak and cumulative loading per kilometer by 6.6% (p < 0.001) and 8.5% (p < 0.001), respectively. Interpretation: Increasing the physical demand of running by increasing speed or weight carriage increased peak tibial loading and cumulative tibial loading per kilometer, and this may increase the risk of tibial stress injury. Running speed and weight carriage independently influenced tibial loading.

• Myrholt, Roger Behrman; Solberg, Paul Andre; Pettersen, Henrik; Seynnes, Olivier R. & Paulsen, Gøran (2023). Effects of Low- Versus High-Velocity-Loss Thresholds With Similar Training Volume on Maximal Strength and Hypertrophy in Highly Trained Individuals. International Journal of Sports Physiology and Performance (IJSPP). ISSN 1555-0265. 18(4), s. 368–377. doi: 10.1123/ijspp.2022-0161. Vis sammendrag

  Aims: In the present intervention study, low-velocity-loss (LVL) versus high-velocity-loss (HVL) thresholds in the squat and bench press were compared for changes in muscle strength, power, and hypertrophy. Methods: Strength-trained volunteers (7♀ and 9♂; age: 27.2 [3.4] y; height: 174.6 [8.0] cm; body mass: 75.3 [10.1] kg) were randomized into an LVL or HVL threshold group (LVL n = 3♀ + 5♂, and HVL n = 4♀ + 4♂). Training took place 3 times per week over 6 weeks (loads: ∼75%–90% of 1-repetition maximum [1RM]). The thresholds of LVLs and HVLs were set at 20% and 40% of maximal velocity, respectively, for the squat, and at 30% and 60%, respectively, for the bench press. Before and after the intervention, 1RM, leg press power, and squat jump were tested. The load (∼45% of 1RM) corresponding to 1-m/s velocity was assessed in all sessions for both exercises. In addition, the thickness of the vastus lateralis and triceps brachii and body composition (dual-energy X-ray absorptiometry [DEXA]) were measured. Results: Squat and bench-press 1RM increased similarly in both groups by 7% to 11% (SD: 4%–6%, P < .05). No group differences were observed for changes in jump height, leg press power, or DEXA lean mass. However, HVL showed a small increase in muscle thickness of the vastus lateralis compared with LVL (6 ± 6% [95% CI] group difference, P < .05). Conclusion: For strength-trained individuals, high-volume lower-velocity-loss thresholds were as effective as higher thresholds for improvements in 1RM strength; but local hypertrophy was seemingly elicited faster with higher velocity-loss thresholds.

• Werkhausen, Amelie; Gløersen, Øyvind; Nordez, Antoine; Paulsen, Gøran; Bojsen-Møller, Jens & Seynnes, Olivier R. (2023). Linking muscle architecture and function in vivo: conceptual or methodological limitations? PeerJ. ISSN 2167-8359. 11. doi: 10.7717/peerj.15194. Fulltekst i vitenarkiv Vis sammendrag

  Background Despite the clear theoretical link between sarcomere arrangement and force production, the relationship between muscle architecture and function remain ambiguous in vivo. Methods: We used two frequently used ultrasound-based approaches to assess the relationships between vastus lateralis architecture parameters obtained in three common conditions of muscle lengths and contractile states, and the mechanical output of the muscle in twenty-one healthy subjects. The relationship between outcomes obtained in different conditions were also examined. Muscle architecture was analysed in panoramic ultrasound scans at rest with the knee fully extended and in regular scans at an angle close to maximum force (60°), at rest and under maximum contraction. Isokinetic and isometric strength tests were used to estimate muscle force production at various fascicle velocities. Results: Measurements of fascicle length, pennation angle and thickness obtained under different experimental conditions correlated moderately with each other (r = 0.40−.74). Fascicle length measured at 60° at rest correlated with force during high-velocity knee extension (r = 0.46 at 400° s−1) and joint work during isokinetic knee extension (r = 0.44 at 200° s−1 and r = 0.57 at 100° s−1). Muscle thickness was related to maximum force for all measurement methods (r = 0.44–0.73). However, we found no significant correlations between fascicle length or pennation angle and any measures of muscle force or work. Most correlations between architecture and force were stronger when architecture was measured at rest close to optimal length. Conclusion: These findings reflect methodological limitations of current approaches to measure fascicle length and pennation angle in vivo. They also highlight the limited value of static architecture measurements when reported in isolation or without direct experimental context.

• Centner, Christoph; Jerger, Simon; Lauber, Benedikt; Seynnes, Olivier R.; Friedrich, Till & Lolli, David [Vis alle 8 forfattere av denne artikkelen] (2023). Similar patterns of tendon regional hypertrophy after low-load blood flow restriction and high-load resistance training. Scandinavian Journal of Medicine & Science in Sports. ISSN 0905-7188. doi: 10.1111/sms.14321. Fulltekst i vitenarkiv Vis sammendrag

  Purpose: Recent evidence indicates that low-load blood flow restriction (LL-BFR) training elicits an anabolic response in tendinous tissue. The purpose of the present study was to investigate the hypertrophic pattern induced in the Achilles tendon by LL-BFR, in comparison with the regional hypertrophy typically observed with conventional high-load (HL) resistance training. Methods: N = 40 male participants were randomly and concealed allocated to one of two groups: LL-BFR training (20–35% one-repetition maximum/1RM) or HL training (70–85% 1RM). The training was completed three times per week for a total of 14 weeks. Before and after the training period, Achilles tendon morphology was assessed using magnetic resonance imaging along the entire tendon length. Additionally, dynamic strength measures of the plantar flexors were evaluated. Results: In line with previous findings, dynamic plantar flexion strength was improved to a comparable extent in both groups (LL-BFR: 43.6%; HL: 43.5%). The results also confirmed significant increases in Achilles tendon cross-sectional area with LL-BFR (+5.2%). Moreover, they revealed that the hypertrophic pattern obtained with LL-BFR was similar to regional changes seen with conventional HL training. Conclusion: The present findings point towards the notion that despite the low loads being applied, LL-BFR training induces Achilles tendon hypertrophy by potentiating anabolic responses in the same regions as with conventional high-load training. Future studies are needed to (i) focus on the potential mechanisms underlying these tendon morphology changes and (ii) apply and evaluate LL-BFR training in clinical populations to validate these results in rehabilitative settings.

• Werkhausen, Amelie; Gløersen, Øyvind Nøstdahl; Nordez, Antoine; Paulsen, Gøran; Bojsen-Møller, Jens & Seynnes, Olivier R. (2022). Rate of force development relationships to muscle architecture and contractile behavior in the human vastus lateralis. Scientific Reports. ISSN 2045-2322. 12(1). doi: 10.1038/s41598-022-26379-5. Fulltekst i vitenarkiv Vis sammendrag

  In this study, we tested the hypotheses that (i) rate of force development (RFD) is correlated to muscle architecture and dynamics and that (ii) force–length–velocity properties limit knee extensor RFD. Twenty-one healthy participants were tested using ultrasonography and dynamometry. Vastus lateralis optimal fascicle length, fascicle velocity, change in pennation angle, change in muscle length, architectural gear ratio, and force were measured during rapid fixed-end contractions at 60° knee angle to determine RFD. Isokinetic and isometric tests were used to estimate individual force–length–velocity properties, to evaluate force production relative to maximal potential. Correlation analyses were performed between force and muscle parameters for the first three 50 ms intervals. RFD was not related to optimal fascicle length for any measured time interval, but RFD was positively correlated to fascicle shortening velocity during all intervals (r = 0.49–0.69). Except for the first interval, RFD was also related to trigonometry-based changes in muscle length and pennation angle (r = 0.45–0.63) but not to architectural gear ratio. Participants reached their individual vastus lateralis force–length–velocity potential (i.e. their theoretical maximal force at a given length and shortening velocity) after 62 ± 24 ms. Our results confirm the theoretical importance of fascicle shortening velocity and force–length–velocity properties for rapid force production and suggest a role of fascicle rotation.

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• Ritsche, Paul; Faude, Oliver; Franchi, Martino V.; Finni, Taija; Seynnes, Olivier R. & Cronin, Neil J. (2023). DL_Track - Automated analysis of muscle architecture from B-mode ultrasonography images using deep learning . Current Issues in Sport Science. ISSN 2414-6641. 8(2), s. 88–88. doi: 10.36950/2023.2ciss088.

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