Electromyographic control of movement time in a rapid aiming movement.

One of the major issues to emerge from research on human-limb movement is the manner in which the central nervous system regulates electromyographic (EMG) activity to produce movements that differ in duration and distance. Different models of control predict different relations between EMG characteristics and movement kinematics, particularly with regard to the role of EMG burst duration and movement time. However, models have been evaluated with means averaged over individuals and across large numbers of practice trials. The goal of this study was to assess how well individual subjects' data conform to the predictions of the control models. Participants (n = 4) performed an elbow flexion and extension task over 45 degrees in movement times between 90 and 260 msec. EMG amplitude and EMG burst duration from the right elbow flexors were correlated with movement time for each individual. As expected, movement time was positively correlated with EMG burst duration and negatively correlated with EMG amplitude, with wider ranges in the EMG burst duration-movement time correlations across participants. Data from all participants supported predictions of the impulse-timing control model, but the slopes of the studied relations varied across participants.