EMG as a feedback signal in surfaces FES applications: issues and preliminary results

The authors have measured RMS EMB (electromyogram) and mean EMG frequency as a function of simulated muscle force in isometric quadriceps muscle of able-bodied human subjects using an artifact-suppressing surface stimulator and blanking EMG amplifier. Preliminary a results demonstrate that the EMG signal contains useful information about the state of electrically stimulated muscle that may be useful in functional electrical stimulation (FES) applications, but that significant measurement problems must be solved before accurate, selective EMG recordings in the presence of surface stimulation are possible. Also, the nature of the EMG signal for stimulated muscle in nonisometric conditions needs to be explored