Vertical and leg stiffness and stretch-shortening cycle changes across maturation during maximal sprint running.

The purpose of this study was to investigate whether vertical and leg stiffness, and stretch-shortening cycle (SSC) ability differed in developing athletes of various maturity status during maximal sprint running. Seventy-four male participants between 8 and 16 years of age were categorized into pre-, mid- or post-peak height velocity (PHV) and sprinted for 30 meters on a non-motorized treadmill. Dimensionless vertical stiffness increased significantly (p<.05) from pre-, to mid- and post-PHV state, while dimensionless leg stiffness was significantly higher in post- compared to mid- (18.4%) and pre-PHV participants (44.5%). Eccentric power was significantly lower in pre- compared to the mid- and post-PHV participants. Concentric power increased from pre- to mid- and post-PHV state. An analysis of covariance revealed no significant differences between all groups in dimensionless vertical and leg stiffness, eccentric and concentric time and power when controlling for years from PHV (maturation). Eccentric or concentric power, were found to be the best predictors of maximum velocity across all maturation groups (r2=.37-.68). It seems that maturation affects the ability to absorb and produce power and furthermore these variables are important predictors of maximal running velocity.