Development of an EMG recording device from stimulation electrodes for functional electrical stimulation

Area of Science:

• Biomedical Engineering
• Neurorehabilitation
• Signal Processing

Background:

• Functional Electrical Stimulation (FES) systems require reliable electromyography (EMG) signal acquisition for closed-loop control.
• Acquiring EMG signals from small muscles is challenging due to difficulties in electrode placement and potential interference from stimulation artifacts.
• Existing methods often struggle to isolate voluntary EMG from stimulation pulses, limiting FES system performance.

Purpose of the Study:

• To develop and validate a novel device for recording voluntary EMG signals using the same surface electrodes employed for FES.
• To overcome the challenges of EMG acquisition in small muscles within an FES context.
• To enable robust EMG-controlled FES systems applicable to a wider range of clinical scenarios.

Main Methods:

• The developed device integrates photo-MOS relays to effectively disconnect the stimulator during recording phases.
• It incorporates circuitry to ground the stimulation electrodes immediately after pulse delivery, minimizing after-effects.
• The system dynamically adjusts the EMG amplifier gain, reducing it during stimulation periods to prevent signal saturation.

Main Results:

• The device successfully recorded voluntary EMG signals from small muscles using only the FES surface electrodes.
• Effective artifact suppression was achieved, allowing clear detection of EMG activity.
• The system demonstrated reliable performance in an EMG-controlled FES setup.

Conclusions:

• The developed device provides a practical solution for simultaneous EMG recording and FES delivery using a single pair of surface electrodes.
• This technology enhances the feasibility of EMG-controlled FES, particularly for targeting small or difficult-to-access muscles.
• The findings pave the way for more sophisticated and user-friendly neuroprosthetic and rehabilitation devices.