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Voluntary contraction and responses to submaximal cervical nerve root stimulation
Author(s) -
Shafiq Ruxsana,
Macdonell Richard
Publication year - 1994
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.880170615
Subject(s) - stimulation , contraction (grammar) , stimulus (psychology) , medicine , peripheral , compound muscle action potential , muscle contraction , transcranial magnetic stimulation , h reflex , wrist , anatomy , cardiology , neuroscience , electrophysiology , psychology , psychotherapist
Voluntary contraction of hand muscles increases compound muscle action potential (CMAP) amplitudes evoked by submaximal electrical percutaneous cervical stimulation (EPCS). This has been reported to be due to an intraspinal, presynaptic mechanism. We studied the effects of voluntary contraction on hypothenar CMAP amplitudes in 5 volunteers following electrical peripheral nerve stimulation at the wrist, EPCS, magnetic stimulation at the neck and the effects of a conditioning subthreshold cortical magnetic stimulus on CMAPs evoked by EPCS at rest. CMAP amplitudes increased with voluntary contraction of the target muscle, regardless of type or location of stimulus ( P < 0.001). No increase in CMAP amplitude occurred when a conditioning transcranial stimulus was employed with EPCS ( P = 0.35). Our findings indicate a peripheral rather than central mechanism underlies this effect of voluntary contraction. It is probably related to the recruitment order of motor axons, comparing voluntary activation with electrical or magnetic stimulation. © 1994 John Wiley & Sons, Inc.