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EMG hysteresis patterns in human elbow muscles under simultaneous force and length changes
Andriy Gorkovenko1, Oleksii Lehedza1, Andriy Maznychenko2,3
1Department of Movement Physiology, Bogomoletz Institute of Physiology, Bogomoletz Str. 4, Kyiv, 01024, Ukraine.
Scientific Reports
|October 22, 2025
Summary
Human motor control is complex. This study shows that muscle activation (EMG) varies with coinciding versus opposing changes in muscle length and force, impacting motor control models.
Area of Science:
- Biomechanics
- Neuroscience
- Human Motor Control
Background:
- Understanding muscle activation during movement is key for motor control models.
- Mechanical parameters like muscle length and force influence electromyograms (EMGs).
Purpose of the Study:
- To investigate how coinciding and opposing changes in muscle length and force affect EMG signals.
- To refine models of motor control by analyzing muscle activation patterns.
Main Methods:
- Eight participants performed elbow flexor contractions using a robotic device with biofeedback.
- Muscle length and force changes were programmed using a double trapezoid waveform.
- EMG signals were recorded and compared for opposing (OP) and coinciding (CP) patterns.
Main Results:
- CP movements showed reduced EMG variation, indicating compensation for length and force changes.
- Directional force factors and their interactions significantly affected EMG, unlike force amplitude.
- Muscle hysteresis effects were inconsistently observed across different muscles.
Conclusions:
- Muscle activation is modulated by the interplay of muscle length and force direction.
- Findings offer insights into force redistribution among synergistic muscles.
- Results may help refine thermodynamic models of muscle activation in motor tasks.
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