Effect of In-Season Plyometric Training and Biological Maturation on Development of Slow and Fast Stretch-Shortening...

The aim of this study was to determine slow (> 250 ms) and fast (< 250 ms) stretch-shortening cycle (SSC) function in youth female soccer players at different stages of maturity and observe the effect of supplementing 8-week soccer training with a low-frequency (once-per-week) plyometric training (PT) programme on SSC function in this population. The main findings were that soccer plus PT resulted in significant improvements in slow (countermovement jump height) and fast (reactive strength index, leg stiffness and linear sprinting) SSC function in youth female soccer players, regardless of maturity (p ≤ 0.001), with two exceptions in the pre-PHV group (p ≥ 0.281). In comparison, only two markers of fast SSC function improved following 8-week soccer training without PT: one in the mid-PHV group (p ≤ 0.05) and one marker in the post-PHV group (p ≤ 0.05). This study is the first to demonstrate that soccer training supplemented with low-frequency PT is more effective at improving slow and fast SSC function in youth female soccer players, regardless of maturity status, than soccer training alone. This information is useful for strength and conditioning practitioners working with youth female soccer players to inform future warm-up and/or training programmes with this population that might improve playing performance and mitigate the risk of anterior cruciate ligament (ACL) injury in a population more susceptible to such injuries than boys.