There is considerable evidence that adding TENS to functional task practice significantly improves hand motor function and performance. All of the studies reported improvements in functional measurements such as the nine-hole peg test and pinch grip. However, it is important to note that outcome measures related to quality of life or activities of daily living were not reported. When evaluating TENS as a therapy by itself, the evidence is much more conflicting, with the majority of studies suggesting that TENS is not effective alone. Given the availability and low cost of TENS therapy, it may be a good adjunct to functional task practice for the improvement of arm and hand function; however, more clinical research is necessary to determine the long-term rehabilitative effects and impact on quality of life. Future research is also necessary to determine the efficacy of TENS therapy alone.
There is level 1a evidence (from one crossover RCT; Gomes-Osman & Field-Fote 2015 that TENS and tDCS, when combined with functional task practice improves aspects of hand-related function.
There is level 1a evidence (from three randomized controlled trials; Bekkhuizen & Field-Fote 2005, 2008; Hoffman & Field-Fote 2013) that showed that massed practice (repetitive activity) and somatosensory stimulation (median nerve stimulation) demonstrated significant improvement in upper extremity function, grip and pinch strength required for functional activity use.
There is level 1b evidence (from one randomized controlled trial; Gomes-Osman et al., 2017) that peripheral sensory stimulation combined with functional task practice improves grip force in individuals with SCI.
There is level 4 evidence (from one pre-post test; Gad et al., 2018) that transcutaneous spinal cord stimulation combined with hand grip training significantly improves hand function.
There is level 4 evidence (from one pre-post study; Nasser et al., 2014) that showed massed practice and somatosensory stimulation significantly improved motor function and pinch grip strength compared to traditional rehabilitation programs over time.
When combined with TENS, functional task practice may improve aspects of hand-related function, however, more clinical trials to determine the long-term rehabilitative effects of TENS therapy are necessary.