“…In this respect, it has been observed that, at low contraction forces, the sEMG PDF approximates to a Laplacian due to the little overlapping between MUPs of different motor units, whereas, as force increases, overlapping also increases and the PDF converges to a Gaussian (Nazarpour et al, 2007(Nazarpour et al, , 2013Ayachi et al, 2014). In a recent study of our group we presented a new index, the EMG filling factor to quantify the degree to which an EMG signal has been filled (Navallas et al, 2023). The filling factor is grounded on an analytical derivation of the EMG PDF based on the MUP waveforms and firing rates, and thus this index informs about the shape of the sEMG PDF distribution, and also serves as a measure of the overlapping between MUPs (Fig.…”