Effect of Plyometric Training on Vertical Jump Height in Pre‐Peak Height Velocity Boys and Girls Aged 9–11 Years

This study aimed to compare changes in countermovement jump (CMJ) height and take-off velocity, force and power in pre-peak height velocity (pre-PHV) boys and girls aged 9-11 years following 6 weeks of lower body plyometric training (PT). Forty pre-PHV children (20 boys and 20 girls) were allocated to a plyometric training group (PG; n = 20) or a control group (CG; n = 20). The PG completed a progressive plyometric training programme twice weekly for 6 weeks, whereas the CG maintained usual physical activity. CMJ height and kinetic variables were assessed pre- and post-intervention, and training effects were analysed using repeated-measures ANOVA. Results demonstrated a significant between-group difference in CMJ height (p = 0.018) driven by an increase in PG (5.8%; p = 0.013) and no change in CG (-0.5%; p = 0.083). No significant sex differences were observed within PG (p ≥ 0.359); however, CMJ height increased significantly in girls (7.0%; p = 0.030) but not boys (4.7%; p = 0.211). For kinetic variables, only take-off velocity increased in PG (3.2%; p = 0.002), with comparable responses in boys (3.0%; p = 0.038) and girls (3.4%; p = 0.029), whereas force and power showed no significant changes (p ≥ 0.202). No significant changes were observed in CG for CMJ or kinetic variables (p ≥ 0.083). In conclusion, plyometric training improved CMJ performance in pre-PHV children, with no significant sex differences observed. Training adaptations at this stage should be interpreted considering biological maturation status.