Pace-dependent reorganisation of shoulder-hip coordination in front crawl swimming

Shoulder and hip roll are distinct but coordinated components of body roll during front crawl swimming, yet shoulder-hip coordination has largely been examined using discrete measures. This study applied continuous relative phase (CRP), Statistical Parametric Mapping (SPM), and complementary coupling analyses to a previously published kinematic dataset, to examine shoulder-hip coordination during sprint and 400 m pace front crawl. Three-dimensional kinematic data from 15 national-level male swimmers were analysed during non-breathing stroke cycles at sprint (25 m) and 400 m pace. SPM revealed pace-dependent differences in shoulder- and hip-roll waveforms, with roll angle more positive at sprint pace during mid-stroke and at 400 m pace during the stroke-transition region. Mean CRP shifted from slightly shoulder-leading at 400 m pace (3.08 ± 3.14°) to hip-leading at sprint pace (-3.44 ± 6.47°; p < 0.001). Sprint swimming also exhibited greater coordination variability (SD CRP: 18.02 ± 6.20° vs. 10.68 ± 2.51°) and weaker shoulder-hip coupling (0.92 ± 0.04 vs. 0.97 ± 0.01). Coordination differences were concentrated in the recovery phase, whereas the push phase was unaffected by pace. Non-breathing cycles performed under sprint and 400 m pace conditions were characterised by distinct shoulder-hip coordination patterns rather than uniform differences in rotation magnitude.