Measurement of Hyolaryngeal Muscle Activation Using Surface Electromyography for Comparison of Two Rehabilitative Dysphagia Exercises

Objective: To investigate the effects of a resistance-based chin-to-chest (CtC) exercise on measures of hyolaryngeal muscle activation compared with a head-lift exercise. Design: Within-subject, repeated-measures design. Setting: Academic research laboratory. Participants: Healthy young women (N=20) without a history of dysphagia, cervical spine conditions, neurologic disease, or head/neck cancer (mean age, 22.5y). Interventions: All participants performed an isometric jaw-opening exercise against resistance (CtC) and an isometric head-lift exercise, both targeting activation in the hyolaryngeal (suprahyoid) muscles. The CtC exercise required jaw opening into a chin brace secured against the upper torso for a duration of 10 seconds. The isometric head-lift exercise required lifting and holding the head from a supine position for 10 seconds. The degree to which each exercise activated the suprahyoid muscles was measured using surface electromyography (sEMG). Main Outcome Measures: Microvolts as measured from sEMG sensors placed on the skin surface above the hyolaryngeal muscles (surface of skin above geniohyoid, mylohyoid, and anterior digastric). Dependent variables included the peak microvolts during 10 seconds of sustained contraction and the difference in microvolts from rest to peak contraction for each exercise. Results: Activation in the hyolaryngeal musculature as measured via sEMG was significantly greater when participants performed the CtC exercise compared with the head-lift exercise. Measures of peak microvolts during contraction were significantly greater for CtC (t=10.72, P<.001) compared with the head-lift exercise, and difference measures in microvolts calculated between rest and contraction for each exercise revealed a 2-fold increase in hyolaryngeal muscular activation for CtC (t=8.27, P<.001). Conclusions: The isometric CtC exercise resulted in greater activation of the hyolaryngeal muscles compared with an isometric head-lift exercise. Results support the need for further investigations to determine whether the CtC exercise has a positive effect as a rehabilitative exercise for clinical populations with dysphagia secondary to upper esophageal sphincter dysfunction where hyolaryngeal excursion is a physiological impairment.