Facilitation of Nerve Action Potential by Distant Muscle Contraction

ABSTRACT

OBJECTIVE: To investigate the effect of distant muscle contraction on the sensory and motor nerve conduction and F-wave studies. METHOD: During isometric contraction (10%, 25% and 50% of maximal voluntary contraction) of dominant hand using hand held dynamometer, sensory nerve action potentials (SNAPs), compound muscle action potentials (CMAPs) and F-waves were examined on contralateral upper and ipsilateral lower extremities in 20 healthy adult subjects. SNAPs of median and sural nerves, CMAPs and F-waves of median and tibial nerves were recorded with submaximal and supramaximal intensity stimulation. RESULTS: At submaximal stimulation the amplitudes and areas of median and sural SNAPs and median nerve CMAPs were significantly increased during distant muscle contraction (p<0.05). Distant muscle contraction did not effect on the parameters of SNAPs and CMAPs at supramaximal stimulation. The latencies of F-waves were significantly shortened and amplitudes of F-waves were increased during distant muscle contraction (p<0.05). Especially the amplitudes of F-waves were significantly positive correlated with the level of muscle contraction (p<0.05). CONCLUSION: SNAPs and CMAP were augmented by the distant muscle contraction only submaximal stimulation. Due to facilitation, the distant muscle contraction should be considered during routine F-wave studies.