Specificity of test selection for the appropriate assessment of different measures of stretch-shortening cycle function in children

Abstract

The purpose of this study was to determine from a range of vertical jump and rebound tests, which were the most suitable to measure different forms of stretch-shortening cycle function, and whether such tests could be used interchangeably.Two hundred and fifty male youths (age, 12.26 ± 2.94 years; body mass, 47.11 ± 16.91 kg; standing height, 152.98 ± 17.40 cm; and sitting height, 76.89 ± 9.32 cm) were tested for squat and countermovement jump height, reactive strength index (during a maximal hopping test), and leg stiffness (during a sub-maximal hopping test). Stepwise multiple regressions were used to examine the relationships between different measures of SSC function in youths.Absolute leg stiffness was best predicted by body mass (r2=62%), however the explained variance was significantly reduced when normalized to leg length and body mass (r2=15.3%). Squat jump height best explained the total variance for reactive strength index (r2=53.9%), whilst countermovement and squat jump height were the best predictors of each other (r2=86%).Results would suggest that the test protocols used in this study were representative of different forms of SSC performance. Coaches and athletes should take these findings into account when attempting to select the appropriate testing protocols to measure the correct SSC action.