Optimal running occurs around natural bending stiffness of metatarsophalangeal joint

Abstract

Increase of bending stiffness of shoe has been known to improve the running performance and the running economy [1]. However, the underlying mechanism hasn’t been clearly known, partially due to separate studies of examining joint kinetics or metabolic cost, and possibly due to a limited range of insole stiffness tested. In this research we examined the joint mechanics and metabolic cost of running with various insole bending stiffness over the natural foot joint stiffness, with a hypothesis that the benefit of added insole stiffness would be maximized by compromising between the reutilization of elastic energy stored in insole and the loss propulsion force caused by resisted metatarsophalangeal (MTP) joint flexion by insole stiffness.