Joint angle based motor point tracking stimulation for surface FES: A Study on biceps brachii

Area of Science:

• Rehabilitation Engineering
• Biomedical Engineering
• Neuroscience

Background:

• Functional electrical stimulation (FES) aids motor function recovery but faces limitations in stimulation efficiency and muscle fatigue due to suboptimal motor unit recruitment.
• Optimizing electrode placement to target the motor point (MP) can enhance FES efficiency.
• Muscle geometry changes during dynamic exercise cause MP location shifts, challenging consistent FES efficacy.

Purpose of the Study:

• To maintain FES stimulation efficiency during dynamic exercise by developing and evaluating MP tracking strategies.
• To investigate the impact of MP position shifts on FES efficacy during dynamic movements.

Main Methods:

• Measured the shift of the biceps brachii MP relative to elbow joint angle.
• Compared four FES methods: 2-channel simultaneous stimulation (SS), 2-channel time-based shifting stimulation (TSS), 2-channel joint angle-based shifting stimulation (JASS), and 3-channel JASS.
• Assessed performance based on changes in maximal elbow angle and angular velocity.

Main Results:

• 3-channel JASS demonstrated the least reduction in maximal elbow angle and angular velocity.
• MP tracking stimulation, particularly joint angle-based, proved effective for sustained muscle contraction induction.
• Both tracking selectivity and density were identified as crucial factors for improving FES efficiency.

Conclusions:

• Joint angle-based MP tracking is a viable strategy to enhance FES efficacy during dynamic activities.
• Optimized electrode positioning that adapts to MP shifts is essential for improving FES performance in dynamic exercise.
• Further research into tracking selectivity and density can lead to more efficient FES applications in rehabilitation.