Abstract
The purpose of this study is to determine the muscle function considering the contraction mode during the support phase in running. Four male runners ran at 4m/s and marker's trajectories and ground reaction forces were measured by a motion capture system and a force plate, respectively. The musculoskeletal model was developed by the SIMM software, and muscle forces of the support leg were estimated from the joint torques of the leg calculated by the inverse dynamics approach. The contribution of the support leg muscles to the propulsion/braking and support (i.e. forward/backward and upward acceleration) of the body CG (center of gravity) was derived from a dynamics analysis based on the equation of whole-body motion. The results show that (1) the quadriceps muscle group contributes to braking and support by muscle forces of both eccentric and concentric contraction in braking phase, and contributes to those by the only concentric contraction in propulsion phase, (2) the soleus was the greatest contributor to propulsion and support during support phase, and (3) the muscle energy, in especially eccentric contraction phase, was effectively converted to CG acceleration as compared with other muscles.
