Advances in neuromuscular electrical stimulation for the upper limb post-stroke

Objectives: To review current and explore future applications of neuromuscular electrical stimulation (NMES) to restore or retrain upper limb (UL) recovery after stroke. Methods: Short summaries of NMES applications that have been investigated and a discussion of future research directions are presented. Results: Neuromuscular electrical stimulation applications that have been developed and investigated to restore or retrain UL recovery after stroke include: cyclic NMES; triggered NMES which includes electromyogram-triggered NMES (EMG-NMES), positional feedback NMES, contralateral-triggered NMES, outcome-triggered NMES and accelerometer-triggered NMES; iterative learning control mediated NMES; and neuroprostheses such as the Bioness H200. Overall, published studies of these applications indicate that NMES can improve UL function after stroke, with improvements at the impairment level more common than improvements at the activity level. While EMG-NMES has been researched most widely and has the highest level of evidence to support its use, newer applications (e.g. outcome-triggered NMES, accelerometer-triggered NMES) appear promising, on the basis that key requirements for motor learning are employed. Discussion: There are several areas for further research of NMES to achieve greater functional gains at the activity level than are currently achieved post-stroke. These include the use of NMES to retrain multijoint movements; and exploration of single-versus multichannel stimulation, cortical changes that occur after NMES, and NMES with other technologies. Use of NMES to restore or retrain UL function after stroke has come a long way and presents exciting challenges for research and clinicians in the future.