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Mechanomyography and electromyography force relationships during concentric, isometric and eccentric contractions
P Madeleine1, P Bajaj, K Søgaard
1Center for Sensory-Motor Interaction (SMI), Aalborg University, Fredrik Bajers Vej 7, Bldg. D-3, DK-9220, Aalborg East, Denmark. pm@smi.auc.dk
Summary
Electromyography (EMG) and mechanomyography (MMG) signals offer complementary insights into muscle activity. Combining EMG and MMG reveals non-linear relationships with force, influenced by contraction type and intensity.
Area of Science:
- Biomechanics
- Motor Control
- Muscle Physiology
Background:
- Electromyography (EMG) measures electrical activity, while mechanomyography (MMG) captures mechanical responses.
- Understanding the relationship between electrical and mechanical muscle activity is crucial for motor control research.
- Previous studies have explored EMG and MMG independently, but their combined complementary information requires further systematic investigation.
Purpose of the Study:
- To systematically investigate the complementary knowledge obtainable from electromyography (EMG) and mechanomyography (MMG) signals.
- To analyze the non-linear relationships between EMG/force and MMG/force during various contraction types and intensities.
- To determine the influence of contraction type, level, and angular velocity on electromechanical efficiency.
Main Methods:
- EMG and MMG activities were recorded from the first dorsal interosseous muscle.
- Recordings were performed during slow concentric, isometric, and eccentric contractions at varying percentages of maximal voluntary contraction (MVC).
- Statistical analysis was used to assess the significance of EMG/force and MMG/force relationships and the MMG to EMG ratio.
Main Results:
- Significant non-linear EMG/force and MMG/force relationships were observed (P<0.001).
- EMG root mean square (rms) values increased with contraction intensity, with variations between concentric, isometric, and eccentric contractions.
- MMG rms values showed significant increases during concentric contractions up to 50% MVC.
- Contraction type, level, and angular velocity significantly influenced electromechanical efficiency (MMG/EMG ratio, P<0.05).
Conclusions:
- EMG and MMG provide complementary information regarding the electrical and mechanical activity of muscles.
- The observed non-linear relationships are dependent on contraction type, intensity, and angular velocity.
- Different muscle activation strategies are employed during graded isometric and anisometric contractions, highlighting the utility of combined EMG and MMG analysis.