Functional Electrical Stimulation to Augment Poststroke Reach and Hand Opening in the Presence of Voluntary Effort

BACKGROUND: Hemiparesis after stroke can severely limit an individual's ability to perform activities of daily living. Functional electrical stimulation (FES) has the potential to generate functional arm and hand movements. We have observed that FES can produce functional hand opening when a stroke patient is relaxed, but the FES-produced hand opening is often overpowered by finger flexor coactivation in response to patient attempts to reach and open the hand. OBJECTIVE: To determine if stimulating both reaching muscles and hand opening muscles makes it possible to achieve useful amounts of simultaneous reach and hand opening even in the presence of submaximal reaching effort. METHODS: We measured reach and hand opening during a reach-then-open the hand task under different combinations of voluntary effort and FES for both reach and hand opening. RESULTS: As effort was reduced and stimulation generated more movement, a greater amount of reach and hand opening was achieved. For the first time, this study quantified the effect of voluntary effort for reach and hand opening on stimulated hand opening. It also showed variability in the interaction of voluntary effort and stimulation between participants. Additionally, when participants were instructed to reach with partial effort during simultaneous FES, they achieved greater reach and hand opening. CONCLUSIONS: Simultaneous reaching and FES hand opening is improved by including FES for reach and reducing voluntary effort. In the future, an upper extremity neuroprosthesis that uses a combination of voluntary effort and FES assistance may enable users to perform activities of daily living.