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Background: Hamstring strain injuries are associated with significant time away from sport and high reinjury rates. Recent evidence suggests that hamstring injuries often occur during accelerative running, but investigations of hamstring mechanics have primarily examined constant speed running on a treadmill. To help fill this gap in knowledge, this study compares hamstring lengths and lengthening velocities between accelerative running and constant speed overground running.
Methods: We recorded 2 synchronized videos of 10 participants (5 female, 5 male) during 6 accelerative running trials and 6 constant speed running trials. We used OpenCap (a markerless motion capture system) to estimate body segment kinematics for each trial and a 3-dimensional musculoskeletal model to compute peak length and step-average lengthening velocity of the biceps femoris (long head) muscle-tendon unit. To compare running conditions, we used linear mixed regression models with running speed (normalized by the subject-specific maximum) as the independent variable.
Results: At running speeds below 75% of top speed accelerative running resulted in greater peak lengths than constant speed running. For example, the peak hamstring muscle-tendon length when a person accelerated from running at only 50% of top speed was equivalent to running at a constant 88% of top speed. Lengthening velocities were greater during accelerative running at all running speeds. Differences in hip flexion kinematics primarily drove the greater peak muscle-tendon lengths and lengthening velocities observed in accelerative running.
Conclusion: Hamstrings are subjected to longer muscle-tendon lengths and faster lengthening velocities in accelerative running compared to constant speed running. This provides a biomechanical explanation for the observation that hamstring strain injuries often occur during acceleration. Our results suggest coaches who monitor exposure to high-risk circumstances (long lengths, fast lengthening velocities) should consider the accelerative nature of running in addition to running speed.
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http://dx.doi.org/10.1101/2024.03.25.586659 | DOI Listing |
J Strength Cond Res
June 2025
Physical Activity, Sport and Recreation Research Focus Area (Phasrec), Faculty of Health Sciences, North-West University, South Africa.
Prevoo, M, Broodryk, A, and Kramer, M. Effects of a sleep hygiene intervention period on the internal and external, inter- and intra-match demands of male university-level soccer players during a tournament. J Strength Cond Res 39(6): e798-e805, 2025-Soccer is a physiologically and psychologically demanding sport, requiring players to optimize their sleep to enhance their recovery and ensure optimal performance during a match.
View Article and Find Full Text PDFMed Sci Sports Exerc
March 2025
Department of Bioengineering, Stanford University, Stanford, CA.
J Strength Cond Res
August 2024
Department of Biomolecular Sciences, Section of Exercise and Health Sciences, University of Urbino Carlo Bo, Urbino, Italy.
Amatori, S, Helsen, WF, Baldari, C, Serra, T, Belli, A, Guidetti, L, Rocchi, MBL, Sisti, D, and Perroni, F. High-speed efforts of elite association football referees in national and international matches. J Strength Cond Res 38(8): e417-e422, 2024-Field referees (FRs) need to move throughout the pitch to identify any infringements of the game's laws.
View Article and Find Full Text PDFMed Sci Sports Exerc
September 2024
La Trobe Sport and Exercise Medicine Research Centre (LASEM), La Trobe University, Melbourne, Victoria, AUSTRALIA.
Introduction: Maximal acceleration and deceleration tasks are frequently required in team sports, often occurring rapidly in response to external stimuli. Accelerating and decelerating can be associated with lower limb injuries; thus, knowledge of joint mechanics during these tasks can improve the understanding of both human high performance and injury mechanisms. The current study investigated the fundamental differences in lower limb joint mechanics when accelerating and decelerating by directly comparing the hip, knee, and ankle joint moments and work done between the two tasks.
View Article and Find Full Text PDFbioRxiv
March 2024
Department of Bioengineering, Stanford University, Stanford, CA 94305, USA.
Background: Hamstring strain injuries are associated with significant time away from sport and high reinjury rates. Recent evidence suggests that hamstring injuries often occur during accelerative running, but investigations of hamstring mechanics have primarily examined constant speed running on a treadmill. To help fill this gap in knowledge, this study compares hamstring lengths and lengthening velocities between accelerative running and constant speed overground running.
View Article and Find Full Text PDF