Delayed fatigue in finger flexion forces through transcutaneous nerve stimulation

Area of Science:

• Biomedical Engineering
• Neurorehabilitation
• Muscle Physiology

Background:

• Hand weakness significantly impacts daily living and independence.
• Neuromuscular electrical stimulation (NMES) aids muscle strength restoration but traditional methods cause rapid fatigue.
• Investigating alternative NMES strategies is crucial for improving functional recovery.

Purpose of the Study:

• To compare the force sustainability of finger flexor muscles using transcutaneous nerve stimulation versus traditional motor point stimulation.
• To evaluate the impact of stimulation location on muscle fatigue onset and muscle activation patterns.

Main Methods:

• Electrical stimulation was applied to ulnar and median nerves proximally and to the finger flexor motor point.
• Finger flexion forces and high-density electromyogram (HD EMG) signals were recorded.
• Muscle fatigue was induced over 5 minutes, with force decay and EMG amplitude analyzed.

Main Results:

• Proximal nerve stimulation resulted in significantly slower force and EMG decay compared to motor point stimulation.
• Proximal nerve stimulation promoted a more distributed muscle activation across intrinsic and extrinsic finger flexors.
• A wider activation area within extrinsic muscles was observed with proximal nerve stimulation.

Conclusions:

• Stimulating proximal nerve bundles enhances sustained force output and delays fatigue.
• This effect is attributed to more spatially distributed muscle fiber activation.
• This nerve stimulation approach holds promise for improved functional outcomes in rehabilitation and assistance applications.