Advantages of the Area/Amplitude Ratio over Wavelet-derived Parameters, in Monitoring Neuromuscular Fatigue

The work compares the Raa (Area/Amplitude Ratio) with Instantaneous Mean Scale (IMS) and Instantaneous Median Scale (IMedS) both computed via Wavelet Transform (WT) in a fatiguing contraction (Biceps Brachii, 50% MVC, (six females, six males), computed on different epochs (100, 200, 500 ms) from the surface electromyogram (SEMG) and mechanomyogram (MMG) from same motor territory. All three parameters increase from the beginning of the contraction, demonstrating the central component of neuromuscular fatigue. The ANOVA test shows no significant differences (P=0.05) among epochs or between sexes and no interaction between epochs and sexes, which proves Raa as a practical alternative to WT. Raa is 5.52±.97 (MEAN±STDEV) times quicker and requires 285±57 (MEAN±STDEV) times less buffer memory space than the WT. The simple definition and computational efficiency of Raa are major advantages over the WT approach, thus allowing the efficient monitoring of fatigue on very short epochs, also in a dynamic contraction.