Antagonist muscle activity during rapid arm movements: central versus proprioceptive influences.

Seven normal subjects were instructed to adduct the arm as fast as possible. On some trials the movement was prevented mechanically. For each movement or attempted movement, the EMG response in the antagonist muscle was measured. On trials in which no movement occurred, the respones were significantly smaller than those obtained during free, ballistic movement. The results demonstrate the role of proprioceptive influences on the contraction of the antagonist muscle.