The purpose of this study is to investigate the muscle characteristics of the support leg based on muscle relative load and dynamics conversion ratio during the support phase in the constant pace running. Eleven male subjects, who are heel strikers, ran at the speed of 3.3m/sec. The musculoskeletal model of the individual subject was constructed by using the SIMM software, and the muscle forces of the support leg were estimated from the muscle force optimization approach that satisfies the net joint torques obtained from the inverse dynamics calculation. The muscle relative load is defined as the ratio of the actual muscle force to the muscle capacity which is the maximum value of muscle force obtained by using the Hill-type model governed by the force-length-velocity intrinsic muscle relationships. Muscle force contribution to the generation of the inertia force of the whole-body was calculated from multi-body dynamics analysis utilizing the equation of whole-body motion, and dynamics conversion ratios of individual muscle were defined as the muscle contribution per muscle force to the generation of the inertia force. The results obtained in this study indicate that (1) dorsal flexor showed small muscle relative load and large conversion ratio, while gluteal muscle showed large muscle relative load but small conversion ratio, (2) each muscle of quadriceps had similar characteristics in the generation of muscle force with the exception that vastus muscle group showed larger conversion ratio than that of rectus femoris during the eccentric contraction phase, and (3) soleus and gastrocnemius generating vertical and horizontal body motion effectively showed almost same relative load values.
The Proceedings of Joint Symposium: Symposium on Sports Engineering, Symposium on Human Dynamics
