Personalized Synergy-based Functional Electrical Stimulation Improves Lower Limb Motor Functions of Chronic Stroke Survivors by Restoring Gait Control Modules

AbstractConventional motor rehabilitation for stroke remains labor intensive and shows limited efficacy for chronic survivors. Non-invasive functional electrical stimulation (FES) of the neuromuscular system is promising for restoring mobility. However, traditional FES interventions for stroke are limited by single-channel protocols that target isolated muscles and lack integration with neuromotor control strategies, thus failing to address the heterogeneity of post-stroke motor deficits. To overcome these challenges, we employed a personalized FES paradigm grounded in muscle synergies -- neuromotor modules that coordinate multimuscle activation during movement. By leveraging muscle synergies as biomarkers of motor impairment, our intervention delivers coordinated multi-muscle stimulation that mimics the healthy muscle patterns absent in each stroke survivor. Compared with sham group (N = 10), chronic stroke survivors in the treatment group (N = 23) demonstrated higher synergy similarity to the normative synergies after treatment (p = 0.01). Notably, this improvement correlated with the gain in lower-limb Fugl-Meyer (FM) score ({bigtriangleup}FM = 2.6 vs. 0.7, p = 0.04) and enhancement in gait symmetry. Our study shows, for the first time, that muscle synergy-based FES can address the one-size-fits-all limitation of conventional FES by offering a personalized, efficacious, and neuroscience-based intervention that may improve gait kinematics and motor control even in chronic stroke survivors through restoration of muscle synergies.