Myoelectric Analysis of Dynamic Spring-Loaded Orthosis Training for Individuals With Stroke

Area of Science:

• Rehabilitation Medicine
• Neuroscience
• Biomedical Engineering

Background:

• Post-stroke patients often experience impaired voluntary movement, characterized by spasticity, weakness, and abnormal muscle coactivation.
• A dynamic spring-loaded orthosis has been developed to aid finger movement, but its effect on muscle activity (electromyographic (EMG) activity) needs investigation.

Purpose of the Study:

• To investigate muscular activity and coactivation patterns in stroke patients while using a dynamic spring-loaded orthosis.

Main Methods:

• A repeated-measures experimental design compared orthosis-wearing and free conditions across affected and unaffected hands.
• Surface electromyography (EMG) of the flexor digitorum superficialis (FDS) and extensor digitorum common (EDC) was recorded during isometric and dynamic tasks.
• Normalized electromyography (nEMG) and cocontraction index (CCI) were calculated to quantify muscle activity and coactivation.

Main Results:

• Significantly higher nEMG was observed for both EDC and FDS in the affected hand when wearing the orthosis compared to the free condition.
• The affected hand's EDC showed higher nEMG during dynamic tasks than the unaffected hand, but not during isometric tasks.
• The cocontraction index (CCI) was significantly lower on the affected side when wearing the orthosis.

Conclusions:

• Dynamic orthosis use significantly enhances muscular contraction during movement in stroke survivors.
• The findings support the dynamic orthosis' efficacy for muscle strength training, including concentric resistance for finger flexors and eccentric resistance for finger extensors.
• Improved dexterous movement through orthosis use can contribute to enhanced functional independence in post-stroke patients.