Muscle synergy characteristics of pumping in Chinese elite windsurfers

The functional roles of different muscle synergies can be defined through their correlation with biomechanical parameters, making this approach widely applicable in sports science. Muscle synergy analysis has demonstrated unique value in developing specialized skill training. This study aimed to investigate muscle synergy characteristics during pumping in elite windsurfers. Eight elite athletes were recruited to perform 30-s on-shore pumping trials on a windsurfing simulator. Muscle activity was recorded using a 16-channel wireless surface electromyography system (Myon, Cometa, Italy). Non-negative matrix factorization was applied to extract muscle synergy contributions and activation patterns across two pumping phases. Four muscle synergies (S1–S4) were consistently identified across both pumping phases. Phase-specific lateral asymmetries were observed in muscle contributions: the bent-knee phase showed significant left–right differences in triceps brachii (TB), biceps femoris (BF), trapezius (TRA), and rectus femoris (RF) (p < 0.05), while the extended phase exhibited asymmetries in TB, gluteus maximus (GM), RF, and BF (p < 0.05). Activation analysis revealed S2 maintained the highest activation level in both phases (S2 > S3 > S1 > S4, p < 0.05), with no significant differences in overall synergy patterns between phases (p > 0.05), indicating similar neuromuscular coordination strategies despite kinematic differences. This study reveals that elite windsurfers employ four consistent muscle synergies during pumping, with phase-specific lateral asymmetries in muscle contributions and a stable activation hierarchy (S2 > S3 > S1 > S4). These findings provide actionable insights for targeted training, emphasizing unilateral coordination drills and S2 synergy development to optimize pumping performance.