Unstable sitting postures affect head and neck muscle activity during mastication.

Abstract

Purpose: This study aimed to assess whether masseter, suprahyoid, and trapezius muscle activities during mastication differed with changes in sitting posture.

Methods: Thirteen healthy young adults chewed gummy candies under three conditions: sitting with sole-ground contact, sitting without sole-ground contact, and sitting on an unstable balance board. Electromyographic electrodes were attached to the masseter, suprahyoid, and trapezius muscles to evaluate muscle activity. The examiner also evaluated the mastication time, total integral values for each muscle, and number of chewing cycles from start of mastication to swallowing.

Results: The total integral values for masseter and suprahyoid muscles were significantly higher for the no sole-ground contact and balance-board conditions than those under the sole contact condition. The total integral value for the right trapezius muscle was also significantly greater for the no sole-ground contact and balance-board conditions than that under the sole contact condition.

Conclusion: Increased masseter and suprahyoid muscle activity under unstable sitting conditions suggests that a stable sitting posture is necessary for efficient mastication. The right trapezius muscle also exhibited greater activity under unstable sitting conditions, which may have been a compensatory response to enhance postural stability alongside the masticatory muscles.