Lower extremity stiffness when running in minimalist, traditional, and ultra-cushioning shoes

Abstract

Differences in running mechanics between minimalist (MIN) and traditional (TRAD) running shoes have been the subject of much research in the last decade. More recently, ultra-cushioning (ULTRA) shoes featuring oversized midsoles have emerged and are growing in popularity. However, relatively little is known regarding how ULTRA shoes effect running mechanics. Therefore, the purpose of this study was to compare foot strike, leg stiffness, joint stiffness, and negative joint work when running in MIN, TRAD, and ULTRA shoes. Fifteen recreational runners ran on an instrumented treadmill in each shoe while their whole body kinematics were recorded using a 12-camera motion capture system. Foot strike pattern was quantified using the strike index (SI) and foot strike angle (FSA). Leg stiffness was calculated using a spring-mass model. Joint stiffness was calculated as change in joint moment relative to change in joint angle during the absorption period. Negative joint work was calculated by integrating the negative portion of the joint power curve. Differences between shoes were evaluated using a one-way repeated measures ANOVA. Results showed there were no differences between MIN and TRAD shoes for any of the dependent variables. In the ULTRA shoe, participants used a more pronounced rearfoot strike pattern. There were no differences in leg stiffness between shoes. Compared to the MIN and TRAD shoes, in the ULTRA shoes the ankle was stiffer and performed less negative work while the knee and hip were less stiff and performed more negative work. These findings suggest a reorganization of the neuromuscular control of the limb when running in ULTRA compared to MIN or TRAD shoes. This reorganization may have implications for running performance or injury prevention.