Effects of an innovative exoskeleton-assisted gait training intervention on muscle synergies in healthy adults and chronic stroke survivors

Ph.D. ; In stroke survivors, disrupted muscle activation patterns often result in gait impairment. The clinical effectiveness of robot-assisted gait therapies is still under investigation. To prove their ability to enhance motor recovery, it would be fundamental to understand if, and how, they promote the re-emergence of normal, functional muscle patterns in stroke survivors. ; The present work aims to investigate the effects induced by an exoskeleton-based gait training session on the leg muscle activation patterns in healthy adults and chronic stroke survivors with motor impairment. The exoskeleton under investigation, developed by teams at The Chinese University of Hong Kong and the Hong Kong Polytechnic University, consisted in a light, powered ankle foot-orthosis (AFO) designed to support foot plantar/dorsi-flexion during walking. ; Healthy adults (N=10) and chronic stroke survivors (N=11) performed overground walking trials in 3 conditions: I) unassisted walking without wearing the exoskeleton; II) walking while wearing the inactive exoskeleton; III) walking while wearing the powered exoskeleton. ; To investigate the changes induced by the perturbative forces of the exoskeleton on muscle activations, we asked whether walking with the AFO was associated with alterations of muscle-synergy patterns. Muscle synergies model the highly-variable muscle activation profiles through a low-dimensional spatio-temporal structure, thus representing the underlying statistic regularities of muscle patterns. ; For all 3 walking conditions, muscle synergies were extracted from multi-channel electromyographic signals (EMGs) recorded from lower-limb and trunk muscles, by means of the Non-Negative Matrix Factorization (NNMF) algorithm. For the stroke survivors, the ankle range of motion (ROM), Fugl-Meyer Lower-Extremity Score (FMA-LE) and Berg Balance Scale (BBS) were evaluated, to see any potential correlation between the kinematic or clinical parameters and AFO-induced changes of the muscle synergies. ; Our results showed ...