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Hemiparesis after stroke makes bimanual tasks difficult. Functional Electrical Stimulation (FES) for reach and hand opening, coupled with residual voluntary movement, may be able to provide functional arm and hand movement. This type of approach has been attempted in the past, focused on the hand, but effort to reach and open the hand produces involuntary flexor co-activation that hand opening stimulation cannot overpower. Limiting effort and augmenting it with stimulation may limit the expression of co-activation patterns and produce useful movements. Low levels of effort that limit the expression of co-activation patterns may provide an effective command signal as well. The end goal is an FES system that uses limited effort as a command signal and produces movement through a combination of residual movement and FES.We tested key aspects of the system by evaluating 1) the feasibility of using stimulation to produce functional movement in the presence of voluntary effort and 2) how well stroke patients can control assistive forces analogous to those produced by FES. To assess these aspects of this approach we evaluated the following aims: 1) Determine if FES in the presence of limited effort produces useful reach and hand opening. 2) Evaluate the interaction of FES with voluntary effort in stroke to understand if stimulation of a volitionally activated muscle produces additional force/movement and how those forces combine. 3) Evaluate poststroke control of assistive forces to assist in reach.Results indicate that FES coupled with limited effort can produce useful reach and hand opening in some stroke patients. The force increment provided by this stimulation decreases as the voluntary effort exerted increases, but it still adds to the assistive force. Additionally, stroke patients can control assistive forces from a robot using residual arm movements on their affected side, indicating that EMG from the affected upper extremity could be used as an effective command signal to control FES and might be used in concert with FES to produce useful arm and hand movements. The positive results from these studies are a step towards an assistive technology to help people move their arm and hand after stroke. |
