Electromyographic feedback: effect on voluntary muscle contractions in paretic subjects.

To evaluate the efficacy and function of emg feedback (emgFB) in muscle reeducation, skeletal muscle contractions with and without emgFB were compared under controlled experimental conditions in human subjects with paresis due to brain damage (n=6) or peripheral nervous system damage (n=6). Each subject was instructed to produce 12 sustained 30-second contractions of a muscle below functional strength, 6 contractions in each of 2 sessions. EmgFB was provided in half the trials, alternating with nonfeedback trials. Emg activity during each trial was quantitified and the data analyzed statistically. By the 2nd session, emg activity was significantly greater during voluntary muscle contractions attempted with emgFB for both subject categories. This differential developed over the 1st 10 seconds of the muscle contraction and remained relatively constant until the end of the 30-second trial period. Response to emgFB was not closely linked to type of injury, duration of injury, or age. These results indicated a substantial and positive response to such feedback.