System identification of mechanomyograms detected with an acceleration sensor and a laser displacement meter

The purpose of this study is to investigate the transfer functions of mechanomyograms (MMGs) detected with an acceleration sensor and a laser displacement meter. The MMGs evoked by electrical stimulation to the peroneal nerve were recorded on the skin of the tibial anterior muscle. The displacement MMG (DMMG) and the acceleration MMG (AMMG) systems were identified using a singular value decomposition method. The appropriate order of the AMMG system was six and that of the DMMG system was four. The undamped natural frequencies of the systems were compared to resonance frequencies of human soft tissue. Some of the undamped natural frequencies estimated from the AMMG systems agreed with the resonance frequencies in the literature but others were lower than the resonance frequencies. The undamped natural frequencies estimated from the DMMG systems were lower than the resonance frequencies.