Limb asymmetry in swimmers and its correlation with sprint performance

Background: Inter-limb strength asymmetry is well-established as an injury risk factor, yet its relationship with athletic performance remains controversial and context-dependent. In swimming-a bilateral cyclical sport theoretically requiring symmetrical force production-the characteristics and performance implications of strength asymmetry remain insufficiently understood, particularly regarding contraction velocity and sex. Objective: This study aimed to: (1) characterize shoulder and hip isokinetic strength asymmetry in competitive swimmers at 60°/s and 180°/s; (2) explore sex differences in asymmetry profiles; and (3) examine associations of absolute strength and strength asymmetry with sprint performance. Methods: Thirty-two swimmers (20 males, 12 females) aged 18-22 years completed isokinetic assessments of shoulder flexion/extension, shoulder internal/external rotation, and hip flexion/extension at 60°/s and 180°/s. Asymmetry indices were calculated using the percentage difference method. Swimming performance was evaluated via 15-m start, turn, and 100-m freestyle times. Between-session reliability was established (ICC = 0.988-0.998; CV = 1.85%-6.25%). Mann-Whitney U tests, Wilcoxon signed-rank tests, and Spearman rank correlation were performed. Results: Males demonstrated significantly greater absolute strength and faster performance times than females (all p