Motor Module-Guided Human-Machine Interaction Promotes Improvement of Neuromuscular Coordination and Reduction in Motor Impairment in Chronic Stroke: A Pilot Study

ABSTRACT Background Stroke often leads to upper-extremity motor impairments, including abnormal neuromuscular coordination (i.e., motor modules), which reduce independent joint control and impair activities of daily living. Conventional rehabilitation mainly targets the resultant motor deficits (e.g., impaired movement) rather than the underlying neuromuscular dysfunction, potentially limiting transferability of gains beyond trained tasks. Therefore, we propose a customized, motor module-guided exercise facilitated by human-machine interaction to improve neuromuscular coordination and reduce motor impairment. Methods Five chronic stroke survivors with severe-to-mild upper extremity impairment participated in a six-week motor module-guided intervention in which they learned to selectively activate muscle groups identified in healthy individuals. In addition, three stroke survivors completed a force-guided intervention as an active control group. Standardized clinical assessments, including the Upper Extremity Fugl-Meyer Assessment and Action Research Arm Test, were performed before and after training and repeated one and three months later to assess retention. Neuromuscular coordination was quantified using non-negative matrix factorization of surface electromyography, and inter-joint coordination was evaluated during dynamic tasks using a motion capture system before and after training. Results Four of the five participants in the motor module-guided intervention improved neuromuscular coordination. These participants also showed clinically meaningful improvements in motor impairment, which were generally maintained at one and three months after training. In contrast, although the force-guided group showed improvements in task-specific performance and force control, no significant changes in neuromuscular coordination or motor impairment were observed. Notably, improvements in motor impairment correlated with enhanced stroke-induced motor module composition. Finally, findings suggest potential transferability of enhanced neuromuscular control from the trained isometric condition to untrained dynamic behaviors. Conclusion This pilot study showed that motor module-guided rehabilitation could induce improvement of stroke-affected neuromuscular coordination, even in severely impaired chronic stroke survivors, reducing motor impairment and improving motor control beyond the trained task. These findings support neuromuscular coordination-guided rehabilitation as a promising framework for post-stroke recovery.