Medial gastrocnemius muscle fascicles shorten throughout stance during sprint acceleration

The compliant nature of distal limb muscle-tendon units is traditionally considered suboptimal in explosive movements when positive joint work required. However, during accelerative running, ankle net mechanical positive. Therefore, this study aims to investigate how plantar flexor behavior modulated fast accelerations. Eleven female sprinters performed maximum sprint accelerations from starting blocks, while gastrocnemius muscle fascicle lengths were estimated using ultrasonography. We combined motion analysis and ground reaction force measurements assess lower kinematics kinetics, estimate unit length the first two acceleration steps. Outcome variables resampled stance phase averaged across three five trials. Relevant scalars extracted analyzed one-sample two-sample t-tests, vector trajectories compared statistical parametric mapping. found that an uncoupling effectively used produce at acceleration. Muscle fascicles shortened throughout second steps, shortening occurred earlier step, where negative was with step. Elastic strain energy may be stored dorsiflexion after touchdown since did not lengthen same time dissipate energy. Thus, generation accommodated by reuse elastic along work. Our results show a mechanism muscles high in-series compliance can contribute