Advancing lower-limb post-stroke rehabilitation: leveraging muscle synergies and multichannel functional electrical stimulations

Functional electrical stimulation of muscles (FES) during task performance

is a promising intervention that may effectively restore post-stroke motor

impairment. Here, we characterize the efficacy of multi-muscle FES for gait rehabilitation

when the FES stimulus is personalized based on the altered muscle synergies

of the stroke survivor. Chronic hemiparetic stroke survivors were assigned

to the FES (N = 23) or sham (N = 10) group. Customized FES (5 sessions) was

applied to 6–7 muscles of the affected leg during overground walking (>600 steps

per session). Individualized FES stimuli were constructed as muscle activities

re-composed from selected muscle synergies of age-matched healthy subjects.

Synergy-based FES induced higher increases in the lower-limb Fugl-Meyer score

than sham FES. Significant improvements in knee flexion and ankle dorsiflexion

were also observed in the FES group. More importantly, the subjects’ synergies

selected for design of the FES stimuli had higher similarity to healthy synergies

after FES in the FES group. Our results indicate that synergy-based FES may

lead to motor functional improvement by promoting the recruitment of closer-tonormal

muscle synergies for gait, thereby resulting in more naturalistic gait after

FES.