Changes in electromechanical delay during fatiguing dynamic muscle actions
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Updated: Mar 10, 2026
Ex Vivo Assessment of Contractility, Fatigability and Alternans in Isolated Skeletal Muscles
Published on: November 1, 2012
Cory M Smith1, Terry J Housh1, Ethan C Hill1
1Department of Nutrition and Health Sciences, 110 Ruth Leverton Hall, University of Nebraska-Lincoln, Lincoln, Nebraska, 68583-0806, USA.
Introduction:
The onsets of the electromyographic (EMG) signal, mechanomyographic (MMG) signal, and force production were used to identify voluntary electromechanical delay (EMD) during maximal and submaximal leg extensions.
Methods:
Twelve men performed 30% 1-repetition-maximum concentric, dynamic constant external resistance leg extensions to failure. The time periods for the onsets of EMG to MMG (EMDE-M ), MMG to force (EMDM-F ), and EMG to force (EMDE-F ) were assessed before, during, and after testing.
Results:
Pretest vs. posttest assessments indicated approximately equal contributions from excitation-contraction coupling (EMDE-M ) and series elastic component (EMDM-F ) to the overall EMDE-F . During the workbout, excitation-contraction coupling failure and increases in the compliance of the series elastic component began at 40% and 30% of the repetitions to failure, respectively, and continued to failure.
Conclusions:
Increases in the series elastic component (EMDM-F ) began to affect EMDE-F before excitation-contraction coupling failure (EMDE-M ), and both contributed to EMDE-F throughout the remainder of the fatiguing workbout. Muscle Nerve 56: 315-320, 2017.
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