Effects of electromyography-driven robot-aided hand training with neuromuscular electrical stimulation on hand control performance after chronic stroke

Purpose: An electromyography-driven robot system integrated with neuromuscular electrical stimulation (NMES) was developed to investigate its effectiveness on post-stroke rehabilitation. Methods: The performance of this system in assisting finger flexion/extension with different assistance combinations was evaluated in five stroke subjects. Then, a pilot study with 20-sessions training was conducted to evaluate the training’s effectiveness. Results: The results showed that combined assistance from the NMES–robot could improve finger movement accuracy, encourage muscle activation of the finger muscles and suppress excessive muscular activities in the elbow joint. When assistances from both NMES and the robot were 50% of their maximum assistances, finger-tracking performance had the best results, with the lowest root mean square error, greater range of motion, higher voluntary muscle activations of the finger joints and lower muscle co-contraction in the finger and elbow joints. Upper limb function improved after the 20-session training, indicated by the increased clinical scores of Fugl-Meyer Assessment, Action Research Arm Test and Wolf Motor Function Test. Muscle co-contraction was reduced in the finger and elbow joints reflected by the Modified Ashworth Scale. Conclusions: The findings demonstrated that an electromyography-driven NMES–robot used for chronic stroke improved hand function and tracking performance. Further research is warranted to validate the method on a larger scale.

• Implications for Rehabilitation

• The hand robotics and neuromuscular electrical stimulation (NMES) techniques are still separate systems in current post-stroke hand rehabilitation. This is the first study to investigate the combined effects of the NMES and robot on hand rehabilitation.

• The finger tracking performance was improved with the combined assistance from the EMG-driven NMES–robot hand system. The assistance from the robot could improve the finger movement accuracy and the assistance from the NMES could reduce the muscle co-contraction on finger and elbow joints.

• The upper limb functions were improved on chronic stroke patients after the pilot study of 20-session hand training with the combined assistance from the EMG-driven NMES–robot. The muscle spasticity on finger and elbow joints was reduced after the training.