Impact analysis of shoes using the structural intensity technique

Abstract

Impacts of shoes with the ground during sports activities are unavoidable. This can induce excessive impact forces and shock waves to the lower extremity which may cause sports injuries. Wearing proper sport shoes is important for the appropriate execution of sport activities as well as to reduce the chance of sport fatigue and injury. Finite element analysis allows the study of complex biological structures under different boundary conditions. In the current study, a foot model and a sport shoe model with different designs were constructed using 3D finite element mesh. The foot model was based on MRI and built using PATRAN. It contains bones, ligaments, and soft tissues. The shoe model contains shoe cover, shoe sole and shoe inserts using different materials. Hyper elastic models are employed for the soft tissue and shoe sole. In order to reduce the impact forces and have a better understanding of shoe-foot interaction, the stress, plantar pressure are compared for different shoe designs. Focuses are given to characterize power flow using structural intensity (SI) during impact. SI is a vector quantity indicating the direction and magnitude of power flow inside a dynamically loaded structure. By analyzing the SI patterns of shoes and/or foot, we can identify how the power is transferred from ground to the shoes and lower extremity. It is also possible to guide the design of shoes based on the SI results. We also show the stress can be effectively reduced by properly selecting shoe materials and structures. © 2009 Springer Berlin Heidelberg.