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Updated: Jul 1, 2026
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Ex Vivo Assessment of Contractility, Fatigability and Alternans in Isolated Skeletal Muscles
Published on: November 1, 2012
EMG differences between concentric and eccentric maximum voluntary contractions are evident prior to movement onset
1Department of Biomedical Engineering, The Lerner Research Institute, The Cleveland Clinic Foundation, USA. grabiner@uic.edu
Experimental Brain Research
|August 13, 2002
Summary
Muscle activation signals measured by surface electromyography (EMG) differ before voluntary maximum concentric and eccentric knee contractions. These differences suggest the central nervous system distinguishes between contraction types before movement begins.
Area of Science:
- Neuromuscular Physiology
- Biomechanics
- Motor Control
Background:
- Surface electromyography (EMG) measures muscle electrical activity.
- Muscle contractions can be concentric (shortening) or eccentric (lengthening).
- Understanding pre-movement activation differences is crucial for motor control research.
Purpose of the Study:
- To investigate if pre-movement muscle activation signals differ between voluntary maximum concentric and eccentric knee extensor contractions.
- To determine if these differences occur before muscle length changes influence EMG.
- To explore central nervous system (CNS) distinctions between contraction types.
Main Methods:
- Utilized isokinetic knee extensions with surface EMG measurement.
- Recorded EMG from vastus lateralis, vastus medialis, rectus femoris, and hamstrings.
- Measured knee extension moment during the isometric phase preceding motion onset.
Main Results:
- EMG signals for eccentric contractions were significantly smaller than for concentric contractions.
- The rate of change in knee extension moment did not significantly differ between contraction types.
- Differences in EMG were observed prior to any muscle length changes.
Conclusions:
- Initial differences in EMG between maximal concentric and eccentric contractions are pre-programmed (a priori).
- The CNS appears to differentiate between maximal eccentric and concentric contractions.
- Pre-movement EMG differences suggest supraspinal influences on motor command generation.
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