The effects of carbon insoles on reactive strength and vertical leg stiffness as an indicator to sprint performance.

Abstract

Sprinting is the peak expression of performance. Different strength and physical characteristics play roles in the expression speed. Leg stiffness is a major factor on rate of force development, and performance. The pairing of eccentric and concentric contractions is termed the stretch shortening cycle and is assessed by the reactive strength index (RSI). The purpose of this study was: (1) to investigate the effects of the carbon insole on the expression of vertical leg stiffness (kvert) and RSI; (2) examine the effects of the carbon insoles on sprint kinematics. Fifteen participants were recruited and were asked to perform a drop jump and a 20-yard sprint in two conditions (carbon, traditional insoles). The only significant differences between conditions for the performance variables were in the drop jump (p > 0.05). Further research is needed looking at sprint kinetics and kinematics and varying insole stiffness at maximal velocity.