Electrically induced flexion reflex in gait training of hemiplegic patients: induction of the reflex.

Since the introduction of the concept of functional electrical stimulation, the use of multiple stimulation sites to activate several paretic muscles in a coordinated fashion during ambulation has been suggested. Rather than stimulating multiple muscles, we have applied a train of electrical pulses to a single skin area to activate several muscles simultaneously through the induction of a flexion reflex, and evaluated the effectiveness of this reflex in producing or assisting the swing phase of the gait cycle in the hemiplegic patient. Two considerations in selecting the best stimulus site were (1) the magnitude of the reflex as measured by the length of time the foot was off the floor following a stimulus and (2) the patient's tolerance to the stimulus. The magnitude of the reflex was proportional to the strength of the stimulus current in all skin areas tested; namely the sole, dorsum of the foot, and lower posterior thigh. Of the six patients tested a flexion reflex was not elicitable by sole stimulation in one and by posterior thigh stimulation in another. In every case, compared to the two other areas, stimulation of the sole was best tolerated and produced responses of equal or greater magnitude with the same intensity of current, even though larger voltages were required owing to greater tissue impedances. With a fixed frequency of 30 Hz, a pulse duration of 3 msec, and a stimulus current sufficient to produce the reflex, the duration of the reflex could be adjusted for each patient by varying the train duration from 100 to 700 msec. This technique offers a means of providing or assisting the swing phase in the gait training of the hemiplegic patient.