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Variability and interrelationships of surface EMG parameters during local muscle fatigue
W H Linssen1, D F Stegeman, E M Joosten
1Institute of Neurology, University of Nijmegen, The Netherlands.
Muscle & Nerve
|August 1, 1993
Summary
This study on biceps brachii fatigue found muscle fiber conduction velocity (MFCV) is reproducible. While MFCV influences the surface EMG power density spectrum (PDS), fatigue-induced shifts in PDS are not solely explained by MFCV changes.
Area of Science:
- Exercise Physiology
- Neuromuscular Physiology
- Biomedical Engineering
Background:
- Understanding neuromuscular fatigue is crucial for optimizing training and rehabilitation.
- Surface electromyography (sEMG) and muscle fiber conduction velocity (MFCV) are key metrics for assessing muscle function.
- Inter- and intraindividual variability in these parameters can affect study outcomes.
Purpose of the Study:
- To investigate the variability of sEMG parameters and MFCV during fatiguing isometric exercise.
- To determine the influence of sex and age on these neuromuscular responses.
- To explore the relationship between MFCV, sEMG, and power density spectrum (PDS) shifts during fatigue.
Main Methods:
- 26 healthy volunteers performed fatiguing isometric intermittent exercise of the biceps brachii at 80% maximal voluntary contraction.
- Surface EMG amplitude, frequency power density spectrum (PDS), and MFCV were measured.
- Data were analyzed for inter- and intraindividual variability, age, and sex effects.
Main Results:
- No significant age-related effects were observed.
- Males exhibited greater strength and higher initial sEMG amplitude compared to females.
- Fatigue caused a proportional compression of sEMG frequency content, with a significant shift of the PDS to lower frequencies, correlated with males.
- MFCV demonstrated high intraindividual reproducibility (r=0.81).
- Despite MFCV's influence on PDS, fatigue-induced PDS shifts were not solely attributable to MFCV changes.
Conclusions:
- Sex influences neuromuscular fatigue responses, with males showing distinct sEMG characteristics.
- MFCV is a reliable measure with high intraindividual reproducibility during fatiguing exercise.
- The shift in the sEMG power density spectrum during fatigue is complex and not fully explained by MFCV alterations alone, suggesting other factors contribute to neuromuscular changes.