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Power spectral changes of the superimposed M wave during isometric voluntary contractions of increasing strength
Author(s) -
RodriguezFalces Javier,
Place Nicolas
Publication year - 2015
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.24418
Subject(s) - isometric exercise , electromyography , vastus medialis , stimulus (psychology) , anatomy , contraction (grammar) , medicine , physical medicine and rehabilitation , physical therapy , psychology , psychotherapist
ABSTRACT Introduction : We examined the power spectral changes of the compound muscle action potential (M wave) evoked during isometric contractions of increasing strength. Methods : Surface electromyography (sEMG) of the vastus lateralis and medialis was recorded from 20 volunteers who performed 4‐s step‐wise isometric contractions of different intensities. A maximal M wave was elicited by a single stimulus to the femoral nerve and superimposed on the voluntary contractions. The spectral characteristics (Fmean and Fmedian) of sEMG and M‐wave signals were calculated. Results : M‐wave spectral indicators increased systematically with contraction intensity up to 60% MVC and then leveled off at higher forces. Over the 10–60% MVC range, the increase in spectral indicators was 3 times higher for M waves (36%) than for sEMG (12%). Conclusions : The consistent increase in M‐wave spectral characteristics with force is due to the fact that the number of motor units recruited by the superimposed supramaximal stimulus is approximately stable. Muscle Nerve 51: 580–591, 2015