Effects of 2 Resistive Exercises on Electrophysiological Measures of Submandibular Muscle Activity.

OBJECTIVE

To compare the electrophysiological activity in submandibular hyolaryngeal muscles during performance of 2 exercises that incorporate resistance against muscular contraction.

DESIGN

Within-subject repeated-measures design.

SETTING

Academic research laboratory.

PARTICIPANTS

Healthy, young adult women (N=26; mean age, 24.1y) without a history of dysphagia, cervical spine conditions, neurologic disease, or head/neck cancer.

INTERVENTIONS: Participants performed 2 isometric exercises requiring contraction against resistance to the submandibular hyolaryngeal muscles: one requiring jaw opening against a semirigid brace (chin-to-chest [CtC] exercise) and one requiring a chin tuck against an air-inflated rubber ball (chin tuck against resistance [CTAR] exercise). Measures of electrophysiology using surface electromyography (sEMG) were obtained during exercise performance.

MAIN OUTCOME MEASURES: Microvolts as measured from sEMG electrode sensors placed on the skin surface above the hyolaryngeal muscles (surface of skin above geniohyoid, mylohyoid, and anterior digastric). Dependent variables included peak contraction amplitude (in μV) and mean contraction amplitude (in μV) across 10 seconds of sustained contraction.

RESULTS

Significant effects of exercise on peak and mean contraction amplitudes were present when both exercises were compared with baseline sEMG activity. (P<.001 for both). Normalized values of peak contraction amplitude and mean contraction amplitude during performance of CtC were not significantly different compared with CTAR.

CONCLUSIONS

This study provides supporting evidence for the influence of 2 published exercises on motor unit recruitment in the submandibular hyolaryngeal muscles, both of which have been previously proposed as rehabilitative modalities. Theoretical and clinical implications are discussed.