EMG biofeedback in patients with motor disorders: an aid for co-ordinating activity in antagonistic muscle groups.

A computer program was developed to analyse the relative amount of EMG activity in an agonist-antagonist pair of muscles while subjects performed voluntary flexion-extension movements at the wrist to track a visual target. The data were presented to the subjects in the form of a vector display, the angle and length of which was determined from calculation of EMG power in the two muscles. This new approach to EMG biofeedback was evaluated in two hemiplegic patients and three patients with cerebellar incoordination. Over a training period of several weeks, all the subjects were able to modify the pattern of EMG activity in the muscles to reduce the amount of inappropriate coactivation of flexors and extensors and to produce more sustained and regular activation of individual muscle groups.