Ballistic movement: muscle activation and neuromuscular adaptation.

Movements that are performed with maximal velocity and acceleration can be considered ballistic actions. Ballistic actions are characterized by high firing rates, brief contraction times, and high rates of force development. A characteristic triphasic agonist/antagonist/agonist electromyographic (EMG) burst pattern occurs during ballistic movement, wherein the amount and intensity of antagonist coactivation is variable. In conditions of low-grade tonic muscular activity, a premovement EMG depression (PMD; or silent period, PMS) can occur in agonist muscles prior to ballistic contraction. The agonist PMD period may serve to potentiate the force and velocity of the following contraction. A selective activation of fast twitch motor units may occur in ballistic contractions under certain movement conditions. Finally, high-velocity ballistic training induces specific neuromuscular adaptations that occur as a function of the underlying neurophysiological mechanisms that subserve ballistic movement.