A Longitudinal Electromyography Study of Complex Movements in Poststroke Therapy. 2: Changes in Coordinated Muscle Activation

Abstract

Fine motor control is achieved through the coordinated activation of groups of muscles, or “muscle synergies.” Muscle synergies change after stroke as a consequence of the motor deficit. We investigated the pattern and longitudinal changes in upper limb muscle synergies during therapy in a largely unconstrained movement in patients with a broad spectrum of poststroke residual voluntary motor capacity. Electromyography (EMG) was recorded using wireless telemetry from 6 muscles acting on the more-affected upper body in 24 stroke patients at early and late therapy during formal Wii-based Movement Therapy (WMT) sessions, and in a subset of 13 patients at 6-month follow-up. Patients were classified with low, moderate, or high motor-function. The Wii-baseball swing was analyzed using a non-negative matrix factorization (NMF) algorithm to extract muscle synergies from EMG recordings based on the temporal activation of each synergy and the contribution of each muscle to a synergy. Motor-function was clinically assessed immediately pre- and post-therapy and at 6-month follow-up using the Wolf Motor Function Test, upper limb motor Fugl-Meyer Assessment, and Motor Activity Log Quality of Movement scale. Clinical assessments and game performance demonstrated improved motor-function for all patients at post-therapy (p < 0.01), and these improvements were sustained at 6-month follow-up (p > 0.05). NMF analysis revealed fewer muscle synergies (mean ± SE) for patients with low motor-function (3.38 ± 0.2) than those with high motor-function (4.00 ± 0.3) at early therapy (p = 0.036) with an association trend between the number of synergies and the level of motor-function. By late therapy, there was no significant change between groups, although there was a pattern of increase for those with low motor-function over time. The variability accounted for demonstrated differences with motor-function level (p < 0.05) but not time. Cluster analysis of the pooled synergies highlighted the therapy-induced change in muscle activation. Muscle synergies could be identified for all patients during therapy activities. These results show less complexity and more co-activation in the muscle activation for patients with low motor-function as a higher number of muscle synergies reflects greater movement complexity and task-related phasic muscle activation. The increased number of synergies and changes within synergies by late-therapy suggests improved motor control and movement quality with more distinct phases of movement.

Feasibility of Muscle Synergy Outcomes in Clinics, Robotics, and Sports: A Systematic Review

“…Among them, we reviewed the two following articles, Cheung et al [ 36 ] and Roh et al [ 38 ], considering that both works rigorously characterized abnormal muscle coordination in stroke using different behavioural paradigms. In addition, we reviewed Hesam-Sariati et al [ 42 ] which examined the effects of therapeutic activities on the organization of muscle synergy as well as Godlove et al [ 43 ] which addressed the neural correlates of normal and abnormal muscle synergies identified from a unique stroke case.…”

A Longitudinal Electromyography Study of Complex Movements in Poststroke Therapy. 1: Heterogeneous Changes Despite Consistent Improvements in Clinical Assessments

“…Single muscle analysis provides some information about corticomotor changes in motor control but little about the coordination of muscles in the production of a complex movement. For this reason, these data were further analyzed to investigate the neuromuscular coordination of these complex movements [see ( 64 )].…”

Does Cycling Training Augmented by Functional Electrical Stimulation Impact on Muscle Synergies in Post-acute Stroke Patients?

“…Then, the NNMF algorithm was applied fixing the number of synergies to 4 in order to allow a comparison with previous results achieved on a group of age matched healthy subjects (Wheatlhy and Hhealthy) [1]. The similarity (SIM) was quantified by using the cosine of the angle between the synergy vectors W obtained by the affected side of the patients and Whealthy [5]. The synergy activation coefficient H were finally compared with Hhealthy by means of the Shape Symmetry Index (SSI) [1] computed as follows:…”

“…A promising approach to assess motor recovery is the study of muscular coordination through muscle synergies, analyzing their timing and spatial components [4], [5]. However, up to now muscle synergies have been studied mainly during walking [4], [5], while only one work evaluated the modular control during cycling in post-stroke patients [1]. The results of this study supported the study of muscle synergies during pedaling as an assessment method in the early phase after stroke, when patients can be still unable to walk independently.…”