Effect of high-frequency alternating current transcutaneous stimulation over muscle strength: a controlled pilot study

BackgroundHigh-frequency alternating currents of greater than 1kHz applied on peripheral nerves has been used in animal studies to produce a motor nerve block. It has been evidenced that frequencies higher than 5kHz are necessary to produce a complete peripheral nerve block in primates, whose nerve thickness is more similar to humans. The aim of the study was to determine the effect on muscle strength after the application of a high-frequency stimulation at 5 and 10kHz compared to sham stimulation in healthy volunteers.FindingsTranscutaneous stimulation at 5kHz, 10kHz and sham stimulation were applied to eleven healthy volunteers over the ulnar and median nerves for 20min. Maximal handgrip strength was measured before, during, immediately after the intervention, and 10min after the end of intervention. The 10kHz stimulation showed a lower handgrip strength during the intervention (28.1N, SEM 3.9) when compared to 5kHz (31.1N, SEM 3.6; p<0.001) and to sham stimulation (33.7N, SEM 3.9; p<0.001). Furthermore, only stimulation at 10kHz decreased handgrip strength when compared to baseline.ConclusionsThese findings suggest high-frequency stimulation has an inhibitory effect over muscle strength. Future studies are required in patients that are characterized by motor hyperactive such as spasticity or tremors.Clinical trial registrationNCT, NCT03169049. Registered on 30 May 2017