The use of audiovisual displays of myoelectric potentials (myofeedback) has been suggested for retraining and strengthening of paretic muscles in patients with hemiplegia from stroke. This controlled study examines the specificity and efficiency of myofeedback in the strengthening of paretic muscles in hemiplegic patients. Eighteen patients with trace to fair-minus grade of deltoid muscle power resulting from strokes that had occurred at least six weeks earlier were randomly assigned to the six possible orders of accurate (true), positive noncontingent (placebo) and no feedback conditions. On three successive days, each patient received one session of each feedback condition, consisting of 20 isometric contractions of five seconds each with ten seconds of intervening rests. In addition, each patient's motivational level was rated. Averaged myoelectric potentials were quantified for each contraction for analysis. When the data were analyzed without grouping, no statistical differences among the three feedback conditions were noted. However, when the subjects were grouped according to age and motivational level, during true and no feedback sessions, the older and the poorly motivated groups were found to show progressive increment of myoelectric output, whereas the younger and the better motivated showed the opposite results. With placebo feedback, both groups showed progressive decrement of myoelectric output. It is concluded that the effect of myofeedback is nonspecific at least in its short-term application for the retraining of hemiplegically paretic muscles.

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