Functional electrical stimulation (FES) facilitates ambulatory function after paralysis by activating the muscles of the lower extremities. Individuals with incomplete spinal cord injury (iSCI) retain partial volitional control of muscles below the level of injury, necessitating careful integration of FES with intact voluntary motor function for efficient walking. The FES-assisted stepping can be triggered automatically at a fixed rate (autotrigger), by a manual switch (switch-trigger), or by an electromyogram-based gait-event-detector (EMG-trigger). It has been postulated that EMG may be a more natural command source than manual switches, and therefore will enable better coordination of stimulated and volitional motor functions necessary during gait. In this study, the above stated hypothesis was investigated in two volunteers with iSCI during the over-ground FES-assisted gait initiation. Four able-bodied volunteers provided the normative data for comparison. The EMG-triggered FES-assisted gait initiation was found to be more coordinated and dynamically more stable than autotriggered and switch-triggered cases.
This study highlighted the potential of surface EMG as a natural command interface to better coordinate stimulated and volitional muscle activities during gait.