A mathematical model of myoelectric signals obtained during locomotion

An analytical expression for the myoelectric signal was derived using the integral pulse frequency and amplitude modulation (IPFAM) approach. The results indicate that, in the frequency domain, the general envelope of the EMG spectrum is affected primarily by the motor unit action potential (MUAP) and its interaction with the pulse amplitude modulation (PAM) and pulse frequency modulation (PFM) processes. Furthermore, the component associated with force modulation co-exists at its modulating frequency with factors related to the MUAP. Therefore, the conventional low-pass filtering is not adequate for reconstructing dynamic muscular force signals from nonstationary myoelectric signals obtained during locomotion