
In 1855 Guillaume Duchenne, the father of electrotherapy, announced that alternating was superior to direct current for electrotherapeutic triggering of muscle contractions. What he called the 'warming affect' of direct currents irritated the skin, since, at voltage strengths needed for muscle contractions, they cause the skin to blister (at the anode) and pit (at the cathode). Furthermore, with DC each contraction requiring the current to be stopped and restarted. Moreover alternating current could produce strong muscle contractions regardless of the condition of the muscle, whereas DC-induced contractions were strong if the muscle was strong, and weak if the muscle was weak.
Since that time almost all rehabilitation involving muscle contraction has been done with a symmetrical rectangular biphasic waveform. In the 1940s, however, the US War Department, investigating the application of electrical stimulation not just to retard and prevent atrophy but to restore muscle mass and strength, employed what was termed galvanic exercise on the atrophied hands of patients who had an ulnar nerve lesion from surgery upon a wound. These Galvanic exercises employed a monophasic wave form, direct current - electrochemistry.
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