The control of parameters within the therapeutic range in neuromuscular electrical stimulation

The purpose of this article was to investigate the pattern of differences among three parameters according to the increased level of the muscle force obtained in response to neuromuscular electrical stimulation (NMES). Ten healthy subjects were enrolled in this study, which involved applying NMES to the wrist extensor of the nondominant side. The threshold intensity that induced target motion was determined at first and NMES was then applied while changing three parameters. The muscle force was measured by means of a dynamometer for each parameter. Thus, the increased pattern of the muscle force was compared for each parameter. Compared with the duration or the frequency, the increase of the muscle force that accompanied the increase of intensity was more prominent. When the duration was doubled, the increase of muscle force was more evident at threshold intensity than at high intensity (p < .01). When the intensity was doubled, the increase of muscle force was more prominent at 0.2 than at 0.4 milliseconds duration (p < .01). However, there was no such interaction between the increase of the frequency and either the duration or the intensity. The data suggest that stimulus intensity may be the most effective parameter that can be used to enhance the strengthening of the muscle.