Abstract
Introduction & PurposeHamstring injuries are common in sprint-based sports, often occurring during eccentric contraction in the late swing phase of sprinting (Ahmad et al., 2014; Liu et al., 2012; Verrall et al., 2003). Neuromuscular fatigue is a key risk factor, as it compromises a muscle’s ability to absorb energy, increasing the likelihood of excessive fiber elongation (Danielsson et al., 2020; Mair et al., 1996; Thelen et al., 2005). The biceps femoris long head (BFLH), the most frequently injured hamstring (Thelen et al., 2005), is particularly vulnerable late in competition when fatigue is high (Ekstrand et al., 2011; Woods et al., 2004), a link also supported by post-exercise strength deficits (Bourne et al., 2021; Brocherie et al., 2015; Small et al., 2010). This study investigated how a repeated-sprint protocol affects force and work distribution across the hamstring muscles. We hypothesized that fatigue would induce a redistribution of mechanical loading among them.
MethodsThis analysis used data from 38 participants in a prior study who performed overground sprints before and after a fatiguing repeated-sprint protocol (12 x 30m) (Gonçalves et al., 2023). 3D motion capture, force plates, and surface EMG data were used to drive an EMG-informed neuromusculoskeletal analysis. A generic musculoskeletal model (Rajagopal et al., 2016) was scaled to each participant’s anthropometry (Kainz et al., 2017) and optimized (Modenese et al., 2016) to derive dynamics for the BFLH, semitendinosus (ST), and semimembranosus (SM). Pre-to-post changes in eccentric muscle force and mechanical work were analyzed using ANCOVA, with running speed included as a covariate.
ResultsThe protocol induced fatigue, confirmed by a significant running speed decline (−16.0%, p . The American Journal of Sports Medicine, 31(6), 969–973. https://doi.org/10.1177/03635465030310063701
Woods, C., Hawkins, R. D., Maltby, S., Hulse, M., Thomas, A., & Hodson, A. (2004). The Football Association Medical Research Programme: An audit of injuries in professional football—analysis of hamstring injuries. British Journal of Sports Medicine, 38(1), 36–41. https://doi.org/10.1136/bjsm.2002.002352