Simulating the effects of long distance running on shoe midsole foam

A repeat impact machine was developed to analyse changes in the mechanical response of ethylene vinyl acetate copolymer foams used in running shoes. Impacts of energy 0.6 J were repeated at 1.7 Hz frequency, with daily recovery periods, to simulate the typical shoe use of long distance runners. Piezoelectric force measurement and non-contact extensometry was used to generate the compressive stress strain curve of the foam. The peak stresses were approximately 500 kPa, comparable with stresses measured at the foot-shoe interface. Foam material parameters, Such as cell gas pressure and polymer yield stress, were generated. (C) 2003 Elsevier Ltd. All rights reserved.