Assessment of Muscle Fatigue During The Walk on a Treadmill in Healthy Subjects Based on Median Frequency of Surface Electromyogram

The physical performance of an athlete is based on monitoring several parameters in response to a known stimulus in a controlled environment. In our study, we applied a stress test on a treadmill with the regulated speed and incline. Because traditional parameters describing physical performance (heart rate, blood lactate concentration, VO2max) do not provide specific information about muscle activity, an alternative approach is needed. Such information may be derived from the analysis of electromyograms (EMG signals) in the frequency domain-in the form of median frequency (MDF). The changes of MDF were analyzed for four phases of the experiment: the initial state, walking with the velocity of 4 mph (6.44km/h), walking with the highest walking velocity (4.5-6 mph; 7. 24-9.66km/h), and the rest. The coefficients of linear regression (slope and intercept) indicate the decrease of median frequency of the EMG signal during phases 2 and 3 and the increase of MDF during the rest. Observed values of linear regression of the median frequency of surface EMG during the analyzed phases indicate the usefulness of such analyses in evaluating muscle fatigue, which may find its use in monitoring the interval training.