Why the study?
What are the metabolic and electromyographic changes during sustained isometric contraction of forearm flexor muscles until exhaustion?
What are the metabolic and electromyographic changes during sustained isometric contraction of forearm flexor muscles until exhaustion?
The study demonstrates linear relationships between low-frequency EMG energy, intracellular pH, and PCr content during sustained isometric contraction, but no overall correlation between the H/L EMG ratio and muscle metabolism changes.
Low-frequency EMG energy may track metabolic fatigue in isometric exercise; hypothesis-generating and leaves open H/L ratio clinical utility.
Metabolic changes measured by 31P-magnetic resonance spectroscopy and surface electromyograms were simultaneously recorded during isometric contraction of forearm flexor muscles sustained at 60% of maximal force until exhaustion. Throughout the fatigue trial, energy in the low-frequency (L) band continuously increased whereas energy in the high-frequency (H) band first increased and fell only prior to exhaustion. PCr content decreased linearly. Intracellular pH (pHi) transiently increased during the first 22 s of trial. The triggering of acidosis was associated with critical PCr values (35-70% of initial content) and decreased electromyogram (EMG) energy in the H band. Linear relationships were only found between energy in the L band, pHi, and PCr content. The interindividual variability of metabolic and EMG changes was high despite standardized conditions of contraction. Maximal PCr consumption was correlated with the maximal pHi decrease measured at the end of the trial. Overall, there was no correlation between H/L EMG ratio and changes in muscle metabolism.
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Bendahan et al. (1996) studied this question.
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