Electromyography during voluntary movement: the two-burst pattern.

Abstract During rapid movement of an extremity, the agonist muscle shows two distinct bursts of EMG activity. Tests were conducted to determine whether the two-burst pattern occurs in movements of different speed, elicited by varying the distance to target and the inertial load. A two-burst pattern was recognizable on practiced moves under all conditions. The first peak of EMG activity was associated with acceleration of the limb and the second with deceleration. The time of minimal EMG activity was correlated with the time of maximal velocity. The findings were analyzed in terms of known physiological mechanisms.