Design and development of a practical muscle fatigue monitor

The purpose of the study is to develop a method to monitor the patient during the exercise and advice him to stop as he is approaching the fatigue condition. The median frequency of the EMG signal has been recognized as the best indicator of the muscular fatigue during the voluntary contraction of skeletal muscles. The EMG signal is picked up from the body using a pair of biopotential electrodes. A special preamplifier and a band-pass filer are designed to process the raw signal. The signal is applied into a personal computer (PC) via the sound card. The power spectrum of the signal is calculated using the Fast Fourier Transform (FFT) algorithm in MATLAB. The median frequency is calculated and plotted against time during the exercise. Experiments are designed to test the procedure in the lab. The fluctuations in the median frequency are eliminated using averaging over time. The tests indicate a drop in the mean value of the median frequency before the test subject feels the fatigue.