216 Evaluation of dynamics functional roles of shoe sole in constant speed running motion : Influence of foot contact type and running speed on the roles

Abstract

The purpose of this study was to quantify the functional role of compressive characteristics of shoes sole parts by combining a finite-truss-element shoes model and the equation of whole-body motion. The equation of the shoes sole deformation was developed by modeling shoes sole as a construction of truss elements with nonlinear spring and damper properties. The shoe sole was divided into five regions; such as fore/mid and lateral/medial parts in addition to heel part of sole. The coefficients of eight points of the sole properties were identified from impact test by using an impact device consisting of accelerometer and arm with impactor. The equation of whole-body motion was derived by modeling the human body as a system of 15-rigid linked segments. Dynamic contributions of the support leg joint torques, which were caused mainly by the elastic property of the shoes sole, to the generation of whole-body CG's acceleration were calculated under two kinds of constant running speed conditions, such as Fast(5m/s) and Slow(4m/s), for heel strikers and fore/mid strikers. The results in this study indicate that 1) vertical ground reaction forces were mainly caused by elastic components of sole force regardless of the foot strike types, 2) the plantar flexion torque about the ankle caused by the force exerted at the forepart of shoes sole contributes to the horizontal acceleration of whole-body CG, and 2) the extensional torque about the knee showed negative contribution to the horizontal acceleration.