A randomized controlled trial on the effects induced by robot-assisted and usual-care rehabilitation on upper limb muscle synergies in post-stroke subjects

Abstract

Muscle synergies are hypothesized to reflect connections among motoneurons in the spinal cord activated by central commands and sensory feedback. Robotic rehabilitation of upper limb in post-stroke subjects has shown promising results in terms of improvement of arm function and motor control achieved by reassembling muscle synergies into a set more similar to that of healthy people. However, in stroke survivors the potentially neurophysiological changes induced by robot-mediated learning versus usual care have not yet been investigated. We quantified upper limb motor deficits and the changes induced by rehabilitation in 32 post-stroke subjects through the movement analysis of two virtual untrained tasks of object placing and pronation. The sample analyzed in this study is part of a larger bi-center study and included all subjects who underwent kinematic analysis and were randomized into robot and usual care groups. Post-stroke subjects who followed robotic rehabilitation showed larger improvements in axial-to-proximal muscle synergies with respect to those who underwent usual care. This was associated to a significant improvement of the proximal kinematics. Both treatments had negative effects in muscle synergies controlling the distal district. This study supports the definition of new rehabilitative treatments for improving the neurophysiological recovery after stroke.

Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1

Flow chart of the study.

Figure 2

(A) In the left panel a subject using the robot device is reported. The central panel reports the virtual scenario shown to the subject during the object placing (B) and forearm pronation (D) tasks. The blue ball/donuts represents hand’s movement, the green box is the starting position, the yellow box is the target position. The red line shows the trajectory of one representative subject (not shown during the test). The right panel reports the muscle synergies extracted on healthy subjects for object placing (C) and forearm pronation (E) tasks. The bars indicate the group mean and ± 1 SD of motor weightings, while the solid line shows the group average activation profile with the grey area representing ± 1 SD of profiles inter-subject variability.

Figure 3

Pre to post change scores from baseline attained by post-stroke participants after robot therapy (RG, white circles) and usual care intervention (UCG, gray circles) during the object placing task for muscle weightings (top panels) and activation profiles (bottom panels) of synergy 1 (B–D) and 2 (C–E). Circles and whiskers represent, respectively, mean change score and 95% confidence interval adjusted for baseline score through ANCOVA procedure. *P < 0.05 (RG vs. UCG, ANCOVA test). + 0.05 ≤ P < 0.1 (RG vs UCG, ANCOVA test).

Figure 4

Pre to post change scores from baseline attained by post-stroke participants after robot therapy (RG, white circles) and usual care intervention (UCG, gray circles) during the forearm pronation task for muscle weightings (top panels) and activation profiles (bottom panels) of synergy 1 (B–D) and 2 (C–E). Circles and whiskers represent, respectively, mean change score and 95% confidence interval adjusted for baseline score through analysis of covariance ANCOVA test. *P < 0.05 (RG vs. UCG, ANCOVA test). + 0.05 ≤ P < 0.1 (RG vs UCG, ANCOVA test).