Detection and Filtering of EMG for Assessing Voluntary Muscle Activity during FES

Abstract

The aim of this work was to develop a laboratory set-up to assess voluntary activity of up to 4 different muscles which undergo simultaneously an artificial electrical stimulation. Voluntary muscle activity is detected from surface EMG. To eliminate stimulation artefacts, the EMG amplifier is automatically muted during stimulation pulses. The measured EMG between stimulation pulses is then considered as superposition of a lower frequency component (m-wave, muscle artefact) caused by electrical stimulation and a higher frequency component caused by voluntary muscle contractions. The latter part is extracted using a digital high pass filter. The entire set-up was realised by using commercially available hardware, which is controlled in soft real-time from a PC running Matlab/SimulinkTM under standard Linux.