Effect of insole material and wear condition on heel cushioning of running shoes

Abstract

This study investigated the effect of insole materials and wear condition on heel cushioning of running shoes. Three insole materials, namely, open-cell foam, close-cell foam and gel were selected for comparison. These insoles were compared amongst each other when new and after they had been worn for a fixed number of steps. The insoles were compared according to the peak force and displacement upon impact. Using the data from the impact trials, the energy dissipated relative to the energy absorbed by the shoe upon impact were calculated and compared amongst the insoles. A higher amount of energy dissipated leads to greater damping. Thus, a higher energy dissipated to energy absorbed ratio was desired. This energy ratio would be used to determine the cushioning properties of the insoles.

The gel insoles were found to have the best cushioning properties amongst the three insoles. In addition, the findings suggest that the reduction in thickness of the worn insoles did affect its cushioning properties, as there was a decrease in amount of energy dissipated relative to energy absorbed upon impact. The gel insoles were also able to retain a significant amount of its energy absorbing properties even after it has been worn.

The mechanical properties of these insoles were also measured, namely thickness, density and hardness of the insoles. It was observed that a thicker, denser and harder material was able to dissipate a higher amount of energy relative to its energy absorbed upon impact. However as only three insoles were selected in this study, further exploration was required for a conclusive deduction. Recommendations for future work proposed include areas regarding insole material composition, additional mechanical properties of insoles, such as viscoelastic properties and the geometry of insoles.