EMG-controlled functional electrical stimulation of the paretic hand.

A new apparatus is described which delivers a functional electric stimulation, controlled by the peak EMG output signal as recorded from the forearm muscles. Twelve paretic hands were stimulated with this apparatus. The EMG output, the stimulus strength, the stimulus frequency, and the corresponding improvement of the wrist extension force were measured. Different arrangements of electrodes and various relay adjustments were tested. The investigations showed that even severely paretic muscles were capable of delivering an efficient EMG output, and the resulting improvement of wrist extension force was statistically significant. The necessary stimulus intensity showed no relationship to the degree of paresis, but a certain relationship to the recovery tendency of the hand was evident. Acceptance of the apparatus among the patients was satisfactory; only a few complained of pain during stimulation.