Early Stroke Rehabilitation of the Upper Limb Assisted with an Electromyography-Driven Neuromuscular Electrical Stimulation-Robotic Arm

Abstract

Background: Effective poststroke motor rehabilitation depends on repeated limb practice with voluntary efforts. An electromyography (EMG)-driven neuromuscular electrical stimulation (NMES)-robot arm was designed for the multi-joint physical training on the elbow, the wrist, and the fingers.

Objectives: To investigate the training effects of the device-assisted approach on subacute stroke patients and to compare the effects with those achieved by the traditional physical treatments.

Method: This study was a pilot randomized controlled trial with a 3-month follow-up. Subacute stroke participants were randomly assigned into two groups, and then received 20-session upper limb training with the EMG-driven NMES-robotic arm (NMES-robot group, n = 14) or the time-matched traditional therapy (the control, n = 10). For the evaluation of the training effects, clinical assessments including Fugl-Meyer Assessment (FMA), Modified Ashworth Score (MAS), Action Research Arm Test (ARAT), and Function Independence Measurement (FIM) were conducted before, after the rehabilitation training, and 3 months later. Session-by-session EMG parameters in the NMES-robot group, including normalized co-contraction Indexes (CI) and EMG activation level of target muscles, were used to monitor the progress in muscular coordination patterns.

Results: Significant improvements were obtained in FMA (full score and shoulder/elbow), ARAT, and FIM [P < 0.001, effect sizes (EFs) > 0.279] for both groups. Significant improvement in FMA wrist/hand was only observed in the NMES-robot group (P < 0.001, EFs = 0.435) after the treatments. Significant reduction in MAS wrist was observed in the NMES-robot group after the training (P < 0.05, EFs = 0.145) and the effects were maintained for 3 months. MAS scores in the control group were elevated following training (P < 0.05, EFs > 0.24), and remained at an elevated level when assessed 3 months later. The EMG parameters indicated a release of muscle co-contraction in the muscle pairs of biceps brachii and flexor carpi radialis and biceps brachii and triceps brachii, as well as a reduction of muscle activation level in the wrist flexor in the NMES-robot group.

Conclusion: The NMES-robot-assisted training was effective for early stroke upper limb rehabilitation and promoted independence in the daily living comparable to the traditional physical therapy. It could achieve higher motor outcomes at the distal joints and more effective release in muscle tones than the traditional therapy.

Clinical trial registration: ClinicalTrials.gov, identifier NCT02117089; date of registration: April 10, 2014.

Keywords: electromyography; neuromuscular electrical stimulation; robot; stroke; upper limb.

Figures

Figure 1

The experimental and training setup of the electromyography-driven neuromuscular electrical stimulation (NMES)-robot system: (A) the mechanical exoskeleton module of the system consisted of the wrist part and the elbow part; (B) the training setup in a session assisted with the NMES-robot training system, the visual feedback interface, and the hanging system.

Figure 2

(A) The electrode configuration on the target muscles, i.e., the biceps brachii (BIC), the triceps brachii (TRI), flexor carpi radialis (FCR), and the muscle union of the extensor carpi ulnaris and extensor digitorum (ECU-ED). The reference electrode was attached on the olecranon; (B) the illustration of the configuration of the electromyography electrodes and neuromuscular electrical stimulation (NMES) electrodes on a target muscle.

Figure 3

The Consolidated Standards of Reporting Trials flowchart of the experimental design.

Figure 4

The clinical scores [evaluated before the first and after the 20th training session, as well as the 3-month follow-up (3MFU)] of the participants in both neuromuscular electrical stimulation (NMES)-robot and control groups: (A) Fugl-Meyer Assessment (FMA) full scores, (B) FMA shoulder/elbow scores, (C) FMA wrist/hand scores, (D) Action Research Arm Test (ARAT) scores, (E) Function Independence Measurement (FIM), and (F) Modified Ashworth Score (MAS) scores at the elbow, the wrist, and the fingers, presented as mean value with 2-time SE (error bar) in each evaluation session. The solid lines are for the NMES-robot group, and the dashed lines are for the control group. The significant inter-group difference is indicated by “*” (P < 0.05, one-way analysis of covariance), and “#” is used to indicate the significant intragroup difference (P < 0.05, one-way analysis of variance with Bonferroni post hoc tests).

Figure 5

The variation of electromyography (EMG) parameters recorded across the 20 training sessions: (A) the changes of the normalized EMG activation levels with significant decline observed in the flexor carpi radialis (FCR) muscle (P < 0.05, 1-way analysis of variance (ANOVA) with Bonferroni post hoc tests); (B) the significant decline of the normalized co-contraction Indexes (CI) values observed in the BIC&TRI and FCR&BIC muscle pairs (P < 0.05, 1-way ANOVA with Bonferroni post hoc tests). The values are presented as mean value with 2-time SE (error bar) in each session.