Effects of interphase interval and stimulation form on dorsiflexors contraction force

BACKGROUND: Neuromuscular electrical stimulation (NMES) is commonly used in rehabilitation to restore movement to patients following orthopedic and neurological injuries. When applying NMES the goal is to induce the strongest contractions with minimal discomfort. OBJECTIVE: This study aimed to determine whether introducing an interphase interval (IPI) to 400 mu sec biphasic pulses during stimulation of the dorsiflexor muscles would have the same effect on force production and stimulation discomfort when stimulation was controlled by constant current (CC) or constant voltage (CV). METHODS: Eighteen healthy volunteers participated in the study. Each subject participated in one session. Electrically induced contraction (EIC) forces and degree of discomfort were measured during stimulation of the ankle dorsiflexors with 0, 100 and 200 mu sec IPI settings with CC or CV. RESULTS: Compared to IPI = 0 mu sec, introduction of a 200 mu sec IPI increased force production with CC stimulation without increasing discomfort. No other enhancements in the EIC force compared to IPI = 0 mu sec were found between the IPIs with CC or CV. CONCLUSIONS: IPI may increase the effectiveness of biphasic pulse with CC, but not with CV stimulation.