The Relationship Between Trunk Strength and Turn Performance in 400-m Front Crawl for National-Level Swimmers.

PURPOSE: Turns are critical in 400-m front crawl (FC) swimming and may rely on trunk strength for efficient rotation and underwater propulsion. This study investigated the relationship between trunk strength and turn performance in 400-m FC. METHODS: Twenty national-level swimmers completed trunk strength assessments using an IsoMed 2000 dynamometer: isokinetic flexion/extension (60°/s and 180°/s), bilateral rotation (90°/s and 150°/s), and isometric strength in 4 directions. Turn performance, including 15-m turn time, 5 m before and 5 m/10 m after wall contact, and 5-m round-trip time, as well as overall turn time and 400-m FC performance were obtained from a 400-m FC test. Pearson or Kendall correlations examined relationships between peak torque (PT), weight-normalized PT (wPT), and performance metrics. Multiple linear regression examined sex moderation effects. RESULTS: 15-m turn time, 5-m round-trip time, 5 m/10 m after wall contact, and overall turn time showed moderate to strong negative correlations with trunk flexion-extension PT and wPT at 60°/s (r = -.466 to -.734, P < .05) and bilateral rotation PT and wPT at 150°/s (r = -.515 to -.799, P < .05). Isometric flexion and bilateral rotation PT were also significantly correlated with most turn parameters (r = -.480 to -.669, P < .05). Sex did not significantly influence the most correlated associations. CONCLUSIONS: Trunk strength, particularly in flexion-extension at lower angular velocities and bilateral rotation at higher velocities, is closely associated with turn performance in national-level 400-m FC swimmers.