Premium
Amplitude of the surface electromyogram during fatiguing isometric contractions
Author(s) -
Lind Alexander R.,
Petrofsky Jerrold S.
Publication year - 1979
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.880020404
Subject(s) - isometric exercise , amplitude , electromyography , physical medicine and rehabilitation , contraction (grammar) , muscle contraction , medicine , cardiology , physical therapy , mathematics , physics , anatomy , quantum mechanics
Five volunteer subjects held isometric handgrip contractions at specific submaximal tensions until the required tension could no longer be maintained. At the start of those contractions, the amplitude of the surface electromyogram (EMG) was linearly related to the tension exerted; the amplitude of the EMG increased linearly throughout these sustained contractions by a constant amount—about 30% of the maximum. During sustained contractions, brief, intermittent maximal efforts showed that strength declined linearly at all tensions. At 25% maximal voluntary contraction (MVC), there was a linear fall in the EMG amplitude associated with the brief maximal efforts, but the fall in strength was more rapid than the fall in EMG amplitude. At 70% MVC, there was no fall in the EMG amplitude in response to the brief maximal efforts, while the muscle strength fell linearly.