HFAC Stimulation (30-50 Kilohertz) in Healthy Volunteers (High Frequency Alternating Current Stimulation)

Effectiveness and Safety of Electrical Stimulation With Alternating High-frequency Currents (30-50 Kilohertz) on the Sensorimotor System in Healthy Volunteer Subjects

High-frequency alternating current (HFAC) stimulation (between 1 kilohertz (kHz) and 100 kHz) on the peripheral nerve has been shown in basic animal research to produce a rapidly reversible nerve block without nerve damage. In human studies, frequencies between 1 kHz and 30 kHz had been applied (both transcutaneously and percutaneously), showing rapidly reversible sensorimotor changes after stimulation without adverse effects. However, the effect of currents with a frequency higher than 30 kHz, which has been shown to be more effective in eliciting nerve block in primates, has not been investigated in humans.

The main objective of this study is to investigate the safety of the intervention and the effect in healthy volunteers of transcutaneous application of alternating currents with frequencies between 30 kHz and 50 kHz on neurophysiological changes in the nerve (nerve conduction velocity and antidromic sensory action potentials (SNAPs), sensory (pain to pressure, epicritic sensitivity and thermal pain to heat) and motor (maximal isometric force) components of the median nerve.

Electrical stimulation with high-frequency alternating currents (between 1 kHz and 100 kHz) on the peripheral nerve has shown, in basic research with animals, that it produces a rapidly reversible nerve block without causing damage to the nerve. In humans, studies have been carried out with frequencies between 1 kHz and 30 kHz applied both transcutaneously and percutaneously, showing rapidly reversible sensorimotor changes after stimulation and without causing adverse effects. However, the effect of currents with a frequency greater than 30 kHz has not been investigated in humans, which has been shown to be more effective in causing nerve block in primates.

The main objective of this study is to investigate the safety of the intervention and the effect in healthy volunteers of the transcutaneous application of alternating currents with frequencies between 30 kHz and 50 kHz on neurophysiological changes in the nerve (nerve conduction velocity and antidromic sensory compound action potentials (PACSA), the sensitive component (pressure pain, epicritic sensitivity and thermal pain to heat) and motor (maximum force) of the median nerve.

A randomized, double-blind, placebo-controlled crossover clinical trial has been designed. The participants will be healthy volunteers between 18 and 40 years old recruited from the students and staff of the Faculty of Physiotherapy and Nursing of the University of Castilla-La Mancha. Four interventions will be performed randomizing the order: Group A: 30 kHz, group B: 40 kHz, group C: 50 kHz and group D: sham electrical stimulation.

Inclusion Criteria:

• Healthy volunteer participants.
• Ability to perform all clinical tests and understand the study protocol, as well as obtain informed consent.
• Tolerance to the application of electrotherapy.

Exclusion Criteria:

• Having been treated with an electric current similar to the one applied prior to the intervention.
• Neurological pathology of peripheral or central origin.
• Altered sensitivity in the area of application of the intervention.
• No compromise of continuity.
• History of neuromuscular disease.
• Epilepsy.
• Trauma, surgery or pain affecting the upper limb.
• Diabetes.
• History of cancer.
• Cardiovascular, metabolic or immunological diseases.
• Presence of pacemaker or any other implanted electrical device.
• Taking medication during the study and in the 7 days prior to the study.
• Consumption of narcotic substances during the study and in the 7 days prior to the study.
• Presence of tattoos or any other external agent introduced in the area of treatment and treatment and assessment area (hand).
• Pregnancy.