The influence of maturity status on drop jump kinetics in male youth

The aim of this study was to examine the effects of maturity status on drop jump (DJ) kinetics in young male athletes (categorised as early-pre [< -2.51 years], late-pre [-1.99 to -1.00 years], circa [-0.50 to 0.50 years] and post-PHV [>1.00 years]). All athletes performed a DJ from a 30 cm box onto force plates with performance variables (jump height, ground contact time and reactive strength index), and absolute and relative kinetic variables during the braking and propulsive phases assessed. Participants were categorised into GOOD (no impact-peak and spring-like), MODERATE (impact-peak and spring-like), or POOR (impact-peak and not spring-like) stretch-shortening-cycle (SSC) function. The post-PHV group exhibited significantly greater values for most absolute kinetic variables compared to early-pre, late-pre- and circa-PHV (p < 0.05). The differences observed between consecutive maturity groups were similar in magnitude for most absolute variables (Cohen’s d = 0.53 - 1.70). Post-PHV male athletes out perform their less mature counterparts during a DJ and this may be attributed to the growth and maturity-related structural and motor control strategy changes that occur in children. SSC function in boys appears to improve with maturity status reflected by a greater number of post-PHV displaying GOOD SSC function (65.8%,) and a greater number of early-pre-PHV displaying POOR SSC function (54.4%). However, a number of mature boys displayed POOR SSC function (17.8%), suggesting the development of SSC function is not exclusively related to maturation