Multifractal characterization of the electromyogram signals in presence of fatigue

This paper presents an investigation of the chaotic behaviour of the EMG signals originating from the trapezius and middle deltoid muscles during an isotonic and isometric contraction, using the variance, correlation, and Renyi fractal dimensions of these signals as promising alternatives to the currently used features for detecting fatigue. Experiments were performed on eight healthy subjects, using surface electrodes with two different test positions which were held to the limit of fatigue. The results of this study show an increase of the correlation dimension of the signal in fatigue and also specific and realizable pattern of variations in the spread of the Renyi dimensions. A single valued variance dimension trajectory of the signal has also been calculated which reveals a clear decrease of this variable in the presence of fatigue.