Bandwidth optimization for filter-based fatigue index in different inter-electrode distances

In this study, the bandwidth of the filter-based fatigue index was determined by the comparison of optimized cutoff frequencies in different inter-electrode distances. Sixty-one subjects participated in isometric knee extension, isotonic ankle dorsiflexion, and isotonic elbow extension exercises. Electromyography (EMG) signals were obtained from right rectus femoris, triceps brachii, and tibialis anterior muscles during exercises. The filter-based fatigue index was compared with mean root-mean-square values, median frequency, Dimitrov spectral index, and Gonzalez-Izal wavelet index. Optimized cutoff frequencies of the high-pass filter for three different exercises and three different inter-electrode distances were about 350 Hz. Results from this study support that around 350 Hz high-pass filter could be useful to determine cut-off frequency for fatigue prediction in general purposes.