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Electromechanical delay in human skeletal muscle under concentric and eccentric contractions
European Journal of Applied Physiology and Occupational Physiology
|November 1, 1979
Summary
The electromechanical delay in skeletal muscle contraction varies with movement type. Eccentric contractions showed a shorter delay, suggesting faster force development due to optimal series elastic component stretch.
Area of Science:
- Biomechanics
- Human Physiology
- Motor Control
Background:
- A delay, known as electromechanical delay (EMD), exists between electrical muscle activation and force generation.
- This delay, typically 30-100 ms, can impact performance in rapid movements.
- Understanding factors influencing EMD is crucial for optimizing muscle function.
Purpose of the Study:
- To investigate how initial muscle conditions affect the electromechanical delay.
- To compare EMD during eccentric, concentric, and isometric contractions.
Main Methods:
- Surface electromyography (EMG) and force were recorded from elbow flexors in 14 subjects.
- Subjects performed maximal contractions under visual stimulus during passive forearm oscillation.
- EMD was calculated during eccentric, concentric, and isometric conditions at a consistent muscle length.
Main Results:
- The mean EMD was significantly shorter during eccentric (49.5 ms) compared to isometric (53.9 ms) and concentric (55.5 ms) contractions (p < 0.05).
- These findings suggest that the series elastic component (SEC) plays a major role in EMD.
- Eccentric contractions appear to place the SEC in a more advantageous state for rapid force production.
Conclusions:
- The series elastic component's stretch is a primary determinant of electromechanical delay.
- Eccentric muscle actions facilitate quicker force development compared to isometric and concentric actions.
- These insights are relevant for understanding muscle performance and designing training protocols.