Upper limb stroke rehabilitation using functional electrical stimulation mediated by iterative learning control

Introduction Following stroke, over 50% of patients have an impairment of one arm, affecting their ability to perform everyday reach and grasp tasks. Functional electrical stimulation (FES) has been shown to restore movement, with effectiveness increased when combined with voluntary intention. Recent clinical trials that incorporated an advanced control framework to adjust FES applied to two muscle groups in a virtual reality scenario showed reductions in impairment. Aim The current study examines the feasibility of providing precisely controlled FES to three muscle groups in the upper limb, assisting performance of real-world, functional reach and grasp tasks. Method Data were recorded from 5 hemiparetic, chronic stroke participants who undertook 18, 1 hour training sessions comprising functional tasks, such as button pressing and closing a drawer. Assistive FES, controlled by advanced iterative learning (ILC) algorithms, was applied to the anterior deltoid, triceps and wrist extensors of the impaired limb. ILC uses data from previous task attempts to update the FES applied to each muscle group on the next trial, increasing performance and encouraging voluntary effort. For assessment, participants completed unassisted and assisted functional tasks, and the error between participants’ movement and idealised trajectories were recorded. The Fugl-Meyer and Action Research Arm Test were also completed pre and post-training. Results Preliminary results show that performance error reduced over a range of functional tasks. Overall improvements ranged from 22-32%, though individual joint improvement reached 63%. Data collection is on-going. Discussion The feasibility of applying precisely controlled FES to three muscle groups in the upper limb was demonstrated. The application of this technology is expected to significantly reduce upper limb impairment following chronic stroke. Work is underway to include an electrode array to precisely stimulate individual finger and hand extensors, and to adapt the system for home use.