Surface EMG as a fatigue indicator during FES-induced isometric muscle contractions

Area of Science:

• Biomedical Engineering
• Neurorehabilitation
• Signal Processing

Background:

• Electromyogram (EMG) signals indicate muscle fatigue, crucial for functional electrical stimulation (FES) applications.
• Detecting muscle fatigue can prevent lower limb collapse in FES-assisted standing, reducing fall risk.
• Surface EMG measurements are compromised by stimulation artifacts during FES.

Purpose of the Study:

• To develop and evaluate modified equipment and techniques for minimizing stimulation artifacts in surface EMG during FES.
• To assess the feasibility of using EMG-derived fatigue indicators in FES-aided standing systems.
• To investigate fatigue tracking performance in able-bodied and spinal cord injured (SCI) individuals.

Main Methods:

• Designed and constructed modified surface stimulation and EMG detection equipment.
• Implemented artifact reduction techniques: shorting stimulator leads and slew rate limiting/blanking.
• Conducted isometric fatigue experiments stimulating the quadriceps muscle in able-bodied and SCI subjects.

Main Results:

• Fatigue tracking indicators were derived from EMG amplitude (RMS) and median frequency (MF).
• Reliable fatigue tracking for practical FES applications proved difficult to obtain.
• Amplitude-based EMG measures demonstrated potential in spinal cord injured subjects.

Conclusions:

• Minimizing stimulation artifacts is critical for utilizing EMG in FES.
• While challenging, EMG-based fatigue detection holds promise, particularly amplitude measures in SCI individuals.
• Further research is needed to optimize EMG-based fatigue monitoring for FES applications.