a method and apparatus are provided for electrically stimulating muscle of individuals having little or no nerve damage so the muscle can be power contracted with little pain to the individual . a therapeutic current is applied to the muscle which includes alternating desensitizing and stimulus currents . the desensitizing current is a high frequency , low amplitude current to desensitize the muscle and the stimulus current is a low frequency , high amplitude current to stimulate the muscle . the currents alternate at a point where the amplitude and slope of the two currents are substantially identical to avoid abruptions in the current . an onset failure monitor circuit is also provided to detect an increase in skim / electrode impedance indicative of possible subsequent failure of the skin - electrode connection or electrode failure .