On-line control of a speeded motor response.

Evidence for a point of no return in a motor act has been reported to occur very late in its preparation and even to the point at which the response is executed. We report a qualitative example from electromyographic (EMG) data of an elbow-extension movement from 1 of 12 adults which suggests that the response can be stopped at any time up to its production, from which we conclude that the response is subject to on-line control at all times.