Temporal Refinement of Muscle Synergies in Skilled Golf Swings.

Muscle synergies, defined as coordinated activations of muscle groups, are thought to simplify motor control by reducing dimensionality and providing a repertoire of adaptable motor solutions. While prior research has investigated synergy adaptation in clinical populations and healthy individuals, most evidence stems from constrained or low-degree-of-freedom (DOF) tasks. A critical gap remains in understanding how synergies are refined in high-DOF, performance-driven contexts that demand full-body coordination. To address this, we examined neuromuscular strategies in professional and amateur golfers performing a 7-iron swing. Electromyographic recordings from 27 muscles, along with kinematic and kinetic data, were analyzed to identify kinematic predictors of clubhead speed and their associated muscle activation patterns. Muscle synergy and clustering analysis of these key muscles revealed two group-invariant synergies, pelvis rotation and plantarflexion, whose peak activation timings were significantly correlated with clubhead speed. A significant subject-specific synergy and a significant amateur-exclusive synergy further highlighted how adaptation involves both individualized tuning and filtering of suboptimal strategies. These findings suggest that expert performance in complex, high-DOF tasks relies on temporal refinement of existing synergies rather than structural reorganization, highlighting the importance of managing, rather than minimizing, motor complexity in the acquisition of advanced motor skills. Furthermore, our approach for identifying neuromuscular patterns linked to performance outcomes provides a foundation for targeted training interventions aimed at enhancing or restoring complex movement patterns.