Related Experiment Video
Updated: Jul 10, 2026
14:02
Ex Vivo Assessment of Contractility, Fatigability and Alternans in Isolated Skeletal Muscles
Published on: November 1, 2012
Muscle synergy adaptation with fatigue development in constant-power cycling
Shahram Rasoulian1, Reza Ahmadi2, Samira Fazeli Veisari3
1Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Canada.
Computers in Biology and Medicine
|July 8, 2026
Summary
Neuromuscular fatigue alters muscle coordination during cycling. As fatigue progresses, the central nervous system constrains muscle synergies, increasing overlap and reducing adaptability near task failure.
Area of Science:
- Biomechanics
- Motor Control
- Exercise Physiology
Background:
- Neuromuscular fatigue impacts muscle activation patterns.
- The effect of fatigue on the modular control of cycling, specifically muscle synergies, remains unclear.
Purpose of the Study:
- To investigate how neuromuscular fatigue affects the structure and coordination of lower-limb muscle synergies during constant-power cycling.
Main Methods:
- Twenty recreational cyclists performed a constant-power cycling test at 70% of peak power until task failure.
- Electromyography (EMG) data from seven lower-limb muscles were collected and decomposed into muscle synergies using non-negative matrix factorization.
- Synergy Index (SI) and Synergy Coordination Index (SCI) were calculated at initial, midpoint, and final stages of the task.
Main Results:
- Four muscle synergies accurately reconstructed EMG signals across all time points (VAF >0.95).
- Synergy Index (SI) remained consistent, indicating stable joint-level flexor-extensor balance.
- Synergy Coordination Index (SCI) significantly increased from initial to midpoint and final stages, indicating greater synergy overlap and constrained coordination as fatigue developed.
Conclusions:
- The central nervous system maintains a consistent set of motor modules and joint-level balance during fatiguing cycling.
- Muscle coordination becomes more constrained, with increased synergy overlap, early in fatigue development and remains elevated near task failure.
- This suggests a shift from flexible adaptation to constrained control strategies as neuromuscular fatigue progresses.
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