20-kHz alternating current stimulation: effects on motor and somatosensory thresholds

Abstract

Background: High 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. Methods: A 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. Results: The 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. Conclusions: High-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.

Effect of Percutaneous Electric Stimulation with High Frequency Alternating Currents on the Sensory-Motor System of Healthy Volunteers

“…These ndings are in agreement with those by Springer et al [11] which delivered transcutaneous HFCA to the cubital nerve and evidenced an effect that persisted up to 10 minutes after stimulation. Similar to the outcomes of the present study, Kim et al [9] and Serrano et al [10,12] reported a reduction in strength with the transcutaneous application of currents, although this decrease was greater during the application of HFCA. The current study could not assess the effect on strength during the percutaneous application of currents due to the above-mentioned methodological reasons.…”

“…This is in contrast to the ndings of Avendaño et al [8], which applied 5KHz transcutaneous HFAC and reported changes in both the PPT and MDT, although these could stem from mechanisms that are unrelated to those involved in nerve blocking [51]. The results in the 20 kHz intervention in the present study were similar to those obtained by Serrano et al [12] applying transcutaneous HFAC. Unlike the results of the current trial, which did not nd an effect on the PPT or MDT, Kim et al [9] delivered 10 kHz currents and determined that the PPT increased as a function of current frequency.…”

“…Although the intensities applied in this work were lower than in transcutaneous application, the values of current density were much higher than in the trials by Serrano et al [10,12] and Avendaño et al [8]. As the current frequency increases, higher intensity is required to reach the nerve block threshold [2,43].…”

“…perception [9] that can persist up to 10 minutes after the stimulation [10][11]. A decrease in voluntary strength has also been observed during the transcutaneous application of 20 kHz HFAC [12].…”

Effect of Percutaneous Electric Stimulation with High-Frequency Alternating Currents on the Sensory-Motor System of Healthy Volunteers: A Double-Blind Randomized Controlled Study

“…The application of 10 kHz HFAC also showed the immediate inhibition of motor response and sensory perception [ 9 ] that could persist up to 10 min after the stimulation [ 10 , 11 ]. A decrease in voluntary strength has also been observed during the transcutaneous application of 20 kHz HFAC [ 12 ].…”