Date of Degree

5-2015

Document Type

Capstone Project

Degree Name

D.P.T.

Program

Physical Therapy

Advisor

Tom Holland

Subject Categories

Physical Therapy

Abstract

STUDY DESIGN: Within subjects repeated measures design.

OBJECTIVE: The aim of this research is to explore the effect that Forward Head Posture has on the mylohyoid muscle during swallowing in a healthy population.

BACKGROUND: Forward Head Posture (FHP) is the most common deviation from ideal head posture, and has become more prominent due to the rise of smart phones and the prevalence of computers in the household and workplace. FHP is associated with a variety of detrimental effects on the musculoskeletal system that arise from the abnormal positioning of the cranial and cervical bones and joints. In particular, the muscles involved in swallowing are placed in an abnormal biomechanical position that may affect the ease of swallowing. The resultant lengthening of the suprahyoid muscles has been reported in the research literature due to this postural deviation, but few have sought to evaluate the possible consequences imposed on swallowing due to this factor.

METHODS: Fourteen healthy adults, ages 20 to 50, were assessed for the purpose of this study. Surface Electromyography (sEMG) was recorded with bipolar synthetic gel surface electrodes placed over the right and left mylohyoid muscles of each subject. Subjects were given a cup filled with 25mL of water to be used as the stimuli bolus. Craniovertebral angles were measured for each subject in their habitual sitting posture (HP) and FHP prior to data collection. Three swallowing trials were recorded in the three different postures: the subject's HP, upright sitting while assuming an exaggerated FHP, and optimal sitting posture (OP) after postural education.

RESULTS: The average sEMG duration and amplitude were obtained for each subject during the three trials for each condition. Paired t-tests were used to compare the duration and amplitude of sEMG mylohyoid activity between the three treatment conditions (HP vs. FHP, HP vs. OP, and FHP vs. OP). The mean sEMG duration in the FHP and HP conditions were similar and longer than the OP treatment condition. A higher sEMG amplitude was also observed in the FHP condition. An analysis of correlation revealed that smaller craniovertebral angles in the HP and FHP resulted in a statistically significant (p =.008) inverse linear relationship with the amplitude of mylohyoid activity.

CONCLUSION: The preliminary results of this study appear to indicate that FHP leads to progressively larger amplitude and longer duration sEMG activity in the mylohyoid during swallowing. These results suggest that FHP may require a more effortful recruitment of the suprahyoid muscle that can predispose or exacerbate pre-existing dysphagia caused by suprahyoid impairment. Future studies are indicated with a larger sample size to further explore this apparent relationship.

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