Inter-Limb Jump Asymmetries and Their Association with Sport-Specific Performance in Young Male and Female Swimmers

This study aimed to examine inter-limb jump asymmetries and their association with sport-specific performance in young swimmers. Thirty-eight (male, n = 19; female, n = 19) regional/national level young swimmers (age: 12.3 ± 1.2 years; height: 159.6 ± 8.2 cm; body mass: 52.5 ± 9.2 kg) participated in this study. Inter-limb asymmetries were assessed for single-leg countermovement jump (_SLCMJ) and single-leg standing long jump (_SLSLJ). Sport-specific performance was evaluated using front crawl (i.e., 50 m and 25 m) and front crawl kick (i.e., 50 m and 25 m). The kappa coefficient revealed a "slight" level of agreement (Κ = 0.156, 0.184, and 0.197 for female, male, and all, respectively) between the direction of asymmetry for _SLCMJ and _SLSLJ, indicating that asymmetries rarely favored the same limb during both tests. A paired sample t-test showed a significant difference (p = 0.025) between asymmetry scores obtained in _SLCMJ and _SLSLJ. No significant difference was found in asymmetry scores between males and females (p = 0.099 to 0.977). Additionally, no association between asymmetry scores and sport-specific performance was observed (p > 0.05). Our findings highlight the independent nature of inter-limb asymmetries derived from _SLCMJ and _SLSLJ among young male and female swimmers. Further, our results suggest no association between jumping asymmetries and sport-specific performance.