Abstract
The purposes of this study are 1) to propose an evaluation index for the function of support leg joints during running under the conditions of wearing shoes with different sole properties and 2) to determine the influence of increasing sole bending stiffness on the function of support leg joints. We discussed about the methodology to select the optimal sole bending stiffness distribution for each runner. Four male runners participated and 4 types of shoes, which have different midsole bending stiffness, were used in this study. The contribution of joint axial torques to the acceleration of body CG (center of gravity) was derived from dynamics analysis. We defined a contribution index as the ratio of total torque contribution to the sum of leg joint torque contributions to the generation of the horizontal acceleration. Increasing midsole bending stiffness led to increasing the contribution of ankle planter/dorsal flexion torque to horizontal acceleration and MP joint planter/dorsal flexion torque to horizontal deceleration. Furthermore, the results indicate that the optimal bending stiffness of midsole, which improves the contribution index, may exist for each runner.
