Expertise Modulates Anticipatory Synergy Adjustments in a Rapid Motor Skill Under Temporal Constraints

Anticipatory synergy adjustments (ASA) represent a feedforward mechanism by which the central nervous system transiently weakens postural synergies to enable rapid changes in performance variable, embodying the stability-agility tradeoff. This study investigated how temporal constraints and expertise modulate ASA onset time and magnitude during table tennis forehand strokes. Twenty male participants (10 skilled, 10 novice) performed 20 forehand trials in response to fast (5 m/s) and slow (1 m/s) visual stimuli in a coincidence anticipation timing task. Electromyography from 14 muscles and the center of pressure (COP) displacement were recorded. Synergy indices were computed using the uncontrolled manifold hypothesis. Results revealed that stimulus speed did not significantly affect ASA onset time (p = 0.519) or amplitude (p = 0.305). In contrast, skilled players exhibited significantly earlier ASA onset (p < 0.001) and larger magnitude (p = 0.002) than novices. Among skilled players, ASA features positively correlated with postural agility metrics (peak COP velocity and displacement) but not with timing errors. These findings indicate that ASA is shaped primarily by expertise rather than temporal task demands, reflecting refined neuromuscular control strategies that optimize the stability-agility tradeoff for rapid motor performance.