Abstract
BackgroundHigh frequency alternating current (HFAC) stimulation have been shown to produce a peripheral nerve conduction block. Currently, all the studies applying HFAC stimulation in clinical studies, have employed frequencies below 10 kHz. The main aim of this work was to investigate the neuromodulatory effect of transcutaneous 20 kHz stimulation on somatosensory and pain thresholds, and maximal handgrip strength.MethodsA randomized, crossover, single-blinded, placebo-controlled trial was conducted following recruitment of fourteen healthy volunteers. Transcutaneous stimulation at 20 kHz and sham stimulation were applied over the ulnar and median nerves of fourteen healthy volunteers for 20 min. Maximal handgrip strength (MHS), mechanical detection threshold (MDT) and pressure pain threshold (PPT) were registered prior to, during (15 min), immediately after the end (20 min), and 10 min following stimulation.ResultsThe 20 kHz stimulation showed a lower MHS during the stimulation at the 15 min (30.1 kgs SE 2.8) and at 20 min (31.8 kgs, SE 2.8) when compared to sham stimulation (35.1 kgs, SE 3.4; p < 0.001 and 34.2 kgs, SE 3.4; p = 0.03, respectively). The 20 kHz stimulation resulted in a slight increase in MDT at 15 min (0.25 mN; 0.25–2.00) when compared to the sham stimulation (0.25 mN; 0.25–0.25; p = 0.02), and no effects were showed for PPT.ConclusionsHigh-frequency stimulation at 20 kHz suggests a partial block of nerve activity. Studies in subjects with neurological disorders characterized by nerve hyperactivity are needed to confirm the clinical impact of this non-invasive electrical stimulation technique.Trial registrationNCT, NCT02837458. Registered on 12 April 2017.
Highlights
High frequency alternating current (HFAC) stimulation have been shown to produce a peripheral nerve conduction block
In a previous study conducted by our group, 5 kHz HFAC stimulation applied over the radial nerve for 20 min produced similar modulatory effects on somatosensory thresholds when compared to transcutaneous electrical nerve stimulation (TENS) [7]
Similar results have been shown by Kim et al [10], reported an increase in mechanical detection threshold (MDT) and pressure pain threshold (PPT) after 10 kHz HFAC stimulation of the median nerve, and an additional decrease in finger muscle contraction during the stimulation
Summary
High frequency alternating current (HFAC) stimulation have been shown to produce a peripheral nerve conduction block. In a previous study conducted by our group, 5 kHz HFAC stimulation applied over the radial nerve for 20 min produced similar modulatory effects on somatosensory thresholds when compared to transcutaneous electrical nerve stimulation (TENS) [7]. Another pilot study demonstrated a larger decrease in maximal handgrip strength during 10 kHz HFAC of the median and ulnar nerve, when compared to either a 5 kHz or sham stimulation [14]. Springer et al [11], who showed that the application of 7 kHz HFAC to the ulnar nerve resulted in a reduction in muscle activity of the abductor digiti minimi, as measured with electromyography, immediately after HFAC stimulation
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