Functional electrical stimulation (FES) is a form of neuromuscular electrical stimulation (NMES) (see NMES section). Similar to NMES, FES involves the application of peripheral electrical stimulation to the nerves to activate muscles and induce movement of an impaired limb (Hodkin et al., 2018). However, FES simultaneously stimulates a number of muscle groups to coordinate movement of a functional activity such as cycling, standing or walking, unlike NMES (Bekhet et al., 2019). In a recent meta analysis, FES interventions improved activity in stroke patients when compared to no intervention and training alone (Howlett et al., 2015). The beneficial effects of FES are thought to arise from neuroplastic changes in motor circuits (Hodkin et al., 2018). These changes may be induced through the pairing of cortical and peripheral activity, whereby “cells that fire together, wire together” (Hebb’s principle) (Hodkin et al., 2018).
A total of seven studies investigating FES to enhance upper extremity rehabilitation were found. The methodological details and results of these studies are presented in Table 14.
Upon review of the literature, there is conflicting evidence on the efficacy of FES. Four randomized controlled trials found that FES has no added benefit over conventional therapy on upper extremity motor function. On the other hand, two randomized controlled trials, one prospective controlled trial and a systematic review found that FES improves motor control and function of the upper extremity. These discrepancies are likely due to differences in methodologies. An ongoing challenge in the FES field is determining what electrical stimulation patterns and duration of treatment are necessary. Future research should focus on determing effective electrical stimulation patterns. In addition, subject variability may also be a contributing factor to differences in outcomes and should be examined in further research. In summary, there is conflicting evidence to support the use of FES therapy.
There is level 1b evidence (from two randomized controlled trials; Harvey et al., 2017; Popovic et al., 2006) that FES has no added benefit over conventional therapy.
There is level 2 evidence (from one randomized controlled trial; Iwahashi et al., 2017) that therapeutic electrical stimulation has no effect on upper extremity motor function.
There is level 2 evidence (from two randomized controlled trials; Zoghi and Galea, 2017; Hoffman & Field-Fote 2013) that FES in combination with intensive hand task training improves upper extremity motor function.
There is level 2 evidence (from one prospective controlled trial; Hodkin et al., 2018) that multiple FES sessions improves upper extremity motor function.
The evidence is conflicting as to whether FES is effective alone or in combination with massed practice training.