Analysis of sustained maximal grip contractions using Empirical Mode Decomposition

Muscle fatigue and physiological tremor during a Sustained Maximal Grip Contraction (SMGC) were analyzed using Empirical Mode Decomposition (EMD) in this study. Thirty-nine healthy subjects volunteered for the experiment and performed a 25-s SMGC. Fatigue parameters such as the relative power output (RPO) were calculated from the residual of SMGC after applying EMD. Using the energy spectrum of the intrinsic mode functions (IMF) obtained using Hilbert-Huang Transform (HHT), physiological tremor was identified from the 4-12 Hz region in IMF3 and IMF4. Data were analyzed for five consecutive 5-s epochs to identify changes in fatigue and tremor over time. The EMD method was able to identify a greater resistance to fatigue in women compared to men (p<;;0.05) and in non-dominant hands compared to dominant hands (p<;;0.05). Consistent with the results for fatigue, women had less tremor than men (p<;;0.05), while non-dominant hands trembled less than did dominant hands (p<;;0.05). Higher levels of tremor were observed for non-fatigue-resistant subjects for both 10-15 s and 15-20 s epochs (p<;;0.05). The EMD is an appropriate method to indentify both fatigue and tremor during SMGC