Influence of muscle contraction and intensity of stimulation on the cutaneous silent period.

We evaluated the influence of stimulus intensity (SI) and the amount of voluntary muscle contraction (VMC) on parameters of the cutaneous silent period (CSP). The CSP was measured in 15 healthy subjects at 20%, 40%, and 60% of maximal VMC and after an electric stimulus of 10, 15, and 20 times the sensory threshold. Average EMG amplitudes prior to stimulus and during the CSP increased with the amount of VMC. The CSP duration increased, and suppression index decreased, with increasing SI. The CSP onset and end latencies seemed to shorten and prolong, respectively, with the increasing SI, although this was not statistically significant. Considering the more meaningful temporal parameters of the CSP and the suppression index, it is not necessary to control the VMC, but it is advisable to control the SI.