[Neuromuscular effects of superimposed and combined transcutaneous electrical stimulation with voluntary activity: a...

With voluntary muscular contraction (VOL), small motor units (MUs) are recruited before large MUs are (a submaximal muscular contraction recruits only small MUs), whereas electrical stimulation (ES) tends to reverse the recruitment order. On the basis of this observation, some authors have tested the physiological effects of ES superimposed simultaneously with VOL (superimposed technique [ST]) or separately (combined technique [CT]). With healthy subjects, ST does not recruit more MUs than VOL, except with eccentric contractions. After health subjects undergo training programs, ST appears to be as efficient as VOL in enhancing subjects' neuromuscular qualities. Nevertheless, the use of CT seems more effective than VOL. In postsurgical rehabilitation, both ST and CT are more effective than VOL. Actually, following knee surgery, ST and CT compensate for volume and muscle strength deficits with more efficiency than does VOL.