Premovement silence in agonist muscles preceding maximum efforts.

Electromyographic silent periods (premovement silence) preceding the initial agonist burst were studied in 11 healthy subjects who performed rapid forearm flexions and extensions. Premovement silence occurred with higher frequency during self-paced movements when subjects produced maximum power efforts than during a reaction time paradigm. The occurrence and duration were significantly correlated with the peak acceleration of the movement. Premovement silence occurred specifically in those muscles involved in the intended movement, often in several synergists with different latencies and durations. The shortest latency of premovement silence was considerably briefer than that of the earliest voluntary increase in EMG. The findings suggest that premovement silence may increase peak muscular force by bringing motoneurons into a nonrefractory state prior to their activation. The fact that it occurred on some, but not all, trials within single subjects and had a variable duration from trial to trial suggests that it may be a learned, rather than automatic, motor response.