The EMG Frequency Fatigue Report is designed for the purpose of tracking and analyzing fatigue-related changes in neuromuscular recruitment. Changes in the frequency (Mean & Median) and amplitude parameters (Zero Crossings & Mean Amplitude) can be used to determine the local muscle fatigue.
For instance, EMG frequency power spectrum is expected to shift to lower frequencies during fatiguing contractions, so the Mean and Median frequency plots can be used to estimate the magnitude of that shift. This phenomenon is well established for static contractions at constant load levels and strongly reflects local fatigue. Zero crossings of the raw EMG signal are highly correlated to the Mean and Median frequency parameters and can also serve as an alternative calculation of frequency characteristics.
The trend in amplitude reflects the recruitment characteristics within the pool of motor units measured. In typical submaximal fatigue experiments, there is an increase in recruitment, which can be observed as an increase of the mean amplitude value and/or the total power. However, the mean amplitude may decrease in contractions near the level of maximal effort.