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

Poststroke patients have insufficient voluntary movement that is usually accompanied with spasticity, weakness, and abnormal muscle coactivation. A dynamic spring-loaded orthosis was designed to assist patients' finger movements via a steel wire spring, but relevant evidence for muscle contractions by electromyographic (EMG) activity while the orthosis is worn is lacking.

To explore muscular activity and muscular coactivation during orthosis use.

A 2 (orthosis condition: wearing vs. free) × 2 (hand condition: affected side vs. unaffected side) mixed repeated-measures experimental design.

Rehabilitation clinic.

Thirty participants with a diagnosis of stroke were enrolled.

The surface EMG of the flexor digitorum superficialis (FDS) and extensor digitorum common (EDC) was recorded in isometric and dynamic tasks. Two dependent variables, normalized electromyography (nEMG) and cocontraction index (CCI), were calculated.

The nEMG of the EDC and FDS of the affected side were significantly higher in the wearing condition than in the free condition. The nEMG of the EDC of the affected hand was significantly higher than that of the unaffected hand during dynamic activities but not during isometric activities. CCI was significantly lower on the affected side than on the unaffected side in the wearing condition.

Muscular contraction significantly increased during dynamic orthosis use. The efficacy of the dynamic orthosis in muscle strength training (concentric resistance training of finger flexors and eccentric resistance training of finger extensors) for stroke patients was supported. Plain-Language Summary: People who have experienced a stroke have insufficient voluntary movement that is usually accompanied by spasticity, weakness, and abnormal muscle coactivation. This study explored muscular activity and muscular coactivation for stroke patients using a dynamic spring-loaded hand orthosis that was designed to assist patients' finger movements via a steel wire spring. The study found that muscular contraction significantly increased when the dynamic orthosis was worn than when it was not worn during grasp-and-release tasks. The study results support the efficacy of the dynamic orthosis in muscle strength training for stroke patients. Dexterous movement improvements will contribute to achieving functional independence for poststroke patients.