Effect of Transcutaneous High-Frequency Alternating Current Over Handgrip Muscle Strength

High frequency alternating current (HFAC) stimulation has been shown to produce a peripheral nerve conduction block. Currently, all the studies applying HFAC stimulation in clinical studies have employed frequencies below 20 kHz. The main aim of this study was to investigate the neuromodulatory effect of transcutaneous HFAC applied at higher than 20 kHz on maximal handgrip strength (MHS). A randomized, crossover, double-blinded, placebo-controlled trial was conducted in eight healthy volunteers. Transcutaneous stimulation at 30–40–50 kHz and sham stimulation were applied over the ulnar and median nerves for 20 min. MHS was registered prior to, during, immediately after, and 10 min following stimulation. The 30 and 40 kHz HFAC stimulation reduced MHS during the stimulation when compared to baseline, suggesting a partial block of nerve activity. These results open potential development of this non-invasive stimulation technique as a therapy in subjects with motor nerve hyperactivity.