Effects of Frequency Adjustment in Functional Electrical Stimulation on Genioglossus Muscle Activity

Reduced tone and weakness of the genioglossus muscle are critical factors in the pathophysiology of obstructive sleep apnea (OSA). In addition to the genioglossus, other upper airway-related muscles, including the thyrohyoid and additional infrahyoid muscles, contribute to airway stability. These muscles differ in anatomical depth from the skin surface and in muscle thickness, which necessitates differentiated electrical stimulation approaches to ensure selective activation and safety.This clinical trial is designed to evaluate the safety and efficacy of functional electrical stimulation (FES) applied to the genioglossus muscle with modulation of stimulation frequency. The study aims to determine whether frequency adjustment influences muscle morphology and functional outcomes.The primary objective is to assess frequency-dependent changes in muscle length and thickness using ultrasonography, as well as differences in tongue strength measured by the Iowa Oral Performance Instrument (IOPI) before and after electrical stimulation.The secondary objective is to evaluate discomfort, safety, and subjective treatment effects through questionnaires administered before and after the electrical stimulation intervention.