Post-stroke wrist rehabilitation assisted with an intention-driven functional electrical stimulation (FES)-robot system

In this work, a novel FES-robot system was developed for wrist rehabilitation training after stroke. The FES-robot system could be continuously controlled by electromyography (EMG) from the residual wrist muscles to facilitate wrist flexion and extension tracking tasks on a horizontal plane by providing assistance from both FES and robot parts. The system performance with five different assistive combinations from the FES and robot parts was evaluated by subjects with chronic stroke (n=5). The results suggested that the assistance from the robot part mainly improved the movement accuracy in the tracking tasks; and the assistance from the FES part mainly suppressed the excessive muscular activities from the elbow joint. The best combination was when the assistances from FES and robot was 1:1, and the results showed better wrist tracking performance with less muscle co-contraction from the elbow joint.

I. Introduction

Intensive and repetitive physical practice of the paralyzed limbs with motor efforts from the paretic neuromuscular system is a key for effective motor recovery after stroke [1]. Functional electrical stimulation (FES) can stimulate the muscles through electrical current, which generates limb movement by activating a person's own muscles to restore motor functions and also evoke sensory feedback to the brain during muscle contraction to promote motor relearning [2], [3]. Although the muscular activities evoked by FES are different from the natural motor unit recruitment during voluntary muscle contractions, FES induced muscle practices also could effectively improve muscle strength in rehabilitation training [3]. By accurately stimulating target muscles, FES may also limit the problem of “learned disuse” that stroke survivors are gradually accustomed to managing their daily activities without using certain muscles, which has been considered as a significant barrier to maximizing the recovery of post-stroke motor function [4]. On the other hand, rehabilitation robotic system can provide external assistive support to body parts (e.g. limbs), which help persons to experience pre-programmed limb movements at the paretic side to improve related sensory- motor functions through repetitive practices [5], [6]. Both FES systems and rehabilitation robots have been used for rehabilitation applications on disabled persons after stroke.