Is Warm-Up Preservation Modulated by Biological Maturation and Sex? Effects on Lower Limbs Performance

Children and adults may react differently to warm-up preservation due to different physical characteristics. This study aimed to: (i) assess the impact of different rewarm-up routines in swimmers during a transition phase (20-25 min), including passive rest (SWU) or dynamic activities (RWU), on countermovement jump and swimming start performances, and (ii) explore potential RWU adaptations considering maturity offset (peak height velocity-PHV) and sex. Performance was analyzed using mixed effect ANCOVA, considering protocol, maturity offset (pre-PHV, mid-PHV, post-PHV, and adv. post-PHV), and sex. Results favored RWU over SWU with substantial magnitudes for jump height: pre-PHV (min-20, ES = 1.21; min-25, ES = 1.65), mid-PHV (min-20, ES = 1.23; min-25, ES = 1.14), post-PHV (min-20, ES = 1.37; min-25, ES = 0.73), and adv. post-PHV (min-20, ES = 1.03; min-25, ES = 0.65). Significant interactions at 25 min (p = 0.033, 0.047) showed that RWU outperformed SWU, especially in younger groups (pre-PHV, mid-PHV). RWU was superior to SWU for the reactive strength index at 20 min (p = 0.042) and 25 min (p = 0.047), with females having lower RSI than males at 20 min (p = 0.008, p = 0.015) and 25 min (p = 0.049) in later developmental stages. The flight distance (p = 0.009) and horizontal hip velocity (p = 0.014) revealed significant three-way interactions, with the male adv. post-PHV group responding better to RWU. Knee angular velocity was also higher after RWU, with male adv. post-PHV group showing more pronounced improvements (p = 0.016). These results suggest that though RWU had higher influence in male adults, it is a valuable approach for varying ages athletes.