The aim of this study is to introduce a new parameter for fatigue investigations, which relies on a bi-dimensional analysis of sEMG signals in temporal and spectral domains. The new parameter, the
, is defined in a space domain whose coordinates are the amplitude and the mean spectral frequency of the sEMG signal. The performance of the
has been compared to those of classical parameters. The analysis has been carried on signals recorded from Rectus Femoris, Vastus Lateralis and Vastus Medialis during knee extension repetitions performed until exhaustion. The task was repeated twice with different biomechanical loads in order to test the muscular activity variations with respect to the different force demands.
The performance of the
in assessing the occurrence of muscular fatigue are promising, and the obtained preliminary results open an interesting scenario for the application of this parameter to several fields.