Ballistic Elbow Extension Actions in Karate-Trained and Control Subjects: Agonist Premovement Depression (PMD) and Movement Performance

Abstract

Ballistic movements have been shown to be controlled differently by the central nervous system than slow, ramp actions. It has been suggested that the cerebellum is involved primarily with ballistic actions, while the basal ganglia primarily control slower movements. These command and control differences have been shown to manifest in unique ways at the neuromuscular level. Ballistic actions evidence high firing rates, brief contraction times, and high rates of force development. A characteristic triphasic agonistantagonist-agonist burst pattern presents itself during ballistic movement, wherein the amount and intensity of antagonist co-activation is variable. In conditions of low-grade tonic muscular activity, a premovement depression (P:MD; or silent period, PMS) can occur in both agonist and antagonist muscles prior to ballistic contraction. The agonist P:MD 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 are representative of the underlying neurophysiological mechanisms that sub serve ballistic movement.