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Electromyogram mean power frequency in non-fatigued trapezius muscle
T Oberg1, L Sandsjö, R Kadefors
1Department of Biomechanics, University College of Health and Care, Jönköping, Sweden.
Summary
This study found that mean power frequency (MPF) in electromyography (EMG) from the trapezius muscle shows minimal variation with different loads and positions. This stability allows MPF to reliably track muscle fatigue.
Area of Science:
- Biomechanics
- Neuroscience
- Human Physiology
Background:
- Electromyography (EMG) is crucial for assessing muscle activity.
- Mean Power Frequency (MPF) is a common EMG spectral analysis parameter sensitive to muscle fatigue.
- Understanding MPF variations in non-fatigued muscles is essential for accurate fatigue detection.
Purpose of the Study:
- To investigate the variability of MPF in the non-fatigued trapezius muscle.
- To determine the influence of external loads, joint positions, torques, and movement planes on MPF.
- To establish a reliable baseline for MPF to quantify muscle fatigue.
Main Methods:
- Surface EMG was recorded from 19 healthy subjects.
- MPF was analyzed across various shoulder joint positions, torques, and movement planes within the functional range.
- Normalized MPF values were calculated and analyzed using regression analysis.
Main Results:
- Normalized MPF showed no significant variations across different loads and movement conditions.
- The largest systematic variation in normalized MPF was approximately +/- 8%, primarily linked to joint angle.
- These findings suggest MPF is relatively stable in non-fatigued states within the functional range of motion.
Conclusions:
- The initial MPF value can serve as a reliable baseline for calculating relative decreases due to muscle fatigue.
- A decrease exceeding 8% of the initial MPF value is considered a significant indicator of muscle fatigue.
- This research supports the use of MPF for objective muscle fatigue assessment in the trapezius muscle.