Motor development and gender effects on stretch-shortening cycle performance.

A substantial part of human movement such as jumping, hopping, leaping and other bounding movements are improved by making a counter-movement. These activities are often described as stretch shortening cycle (SSC) movements. The aim of this study was to determine whether the SSC affects performance in vertical jump in children to the same extent as it does in adults. Comparisons were made between counter-movement jump (CMJ) and squat jump (SJ) performance in children and adults. The ratio of take-off velocity between jumps was used to measure performance of the SSC. Two groups of subjects comprising of 22 adults and 20 children performed three CMJ's and three SJ's from a force platform. Impulse, take-off velocity and power were obtained by numerical integration of the force n time traces. Performance was calculated from the velocity at take off. Both groups jumped significantly higher in the CMJ but there was a higher degree of variability in the performance of the children. The results indicated that children could utilise a SSC to enhance jumping performance. Variability in the take-off velocities in children, particularly in the SJ suggests the children performed this jump non-optimally.