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Updated: May 7, 2026
Ex Vivo Assessment of Contractility, Fatigability and Alternans in Isolated Skeletal Muscles
Published on: November 1, 2012
Shifts in EMG spectral power during fatiguing dynamic contractions
Travis W Beck1, Matt S Stock, Jason M Defreitas
1University of Oklahoma, Department of Health and Exercise Science, 110 Huston Huffman Center, Norman, OK, 73019-6081, USA.
Introduction:
We examined the etiology of the electromyographic (EMG) spectral shift during dynamic fatigue.
Methods:
Nineteen subjects (mean ± SD age = 22.4 ± 1.6 years) performed 50 consecutive maximal concentric isokinetic contractions of dominant leg extensors. Surface EMG signals were detected from the vastus lateralis, rectus femoris, and vastus medialis during each contraction, processed with a wavelet analysis, and the resulting spectra were decomposed with a nonparametric spectral decomposition procedure.
Results:
The results indicated that the decreases in EMG frequency during the 50 contractions were generally due to reductions in high-frequency power and increases in low-frequency power. In addition, the spectral shifts were most pronounced for the rectus femoris, followed by the vastus lateralis, and then the vastus medialis.
Conclusions:
The spectral decomposition procedure is much more sensitive for tracking dynamic fatigue than is EMG mean frequency or median frequency.
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