Objective: In this cross-sectional descriptive-analytical study, we sought to compare the ultrasonic thickness of the masseter muscle in people with severe forward head posture vs people without forward head posture, and to determine sex differences in muscle thickness.

Methods: Thirty-eight volunteers (19 with normal head postures and 19 with severe forward head postures), aged 18 to 35 years, entered the study. The severity of the forward head posture was measured by a plumb line and the craniovertebral angle drawn on the recorded images. Based on the recorded images, the masseter muscle thickness was also measured by a 7.5-MHz linear transducer using an ultrasound device in the seated position with 3 mouth positions (closed, half open, and fully open).

Results: The results showed that the head posture affects masseter thickness significantly (P = .01), with masseter thickness significantly lower in the participants without severe forward head postures compared to those with severe forward head postures in the closed, half-open, and fully open mouth positions (P < .05). Comparing the mean masseter thickness across sexes showed that the masseter muscle is significantly thicker in men compared to women (P = .01).

Conclusion: Head posture and thickness of the masseter muscle are linked, as the masseter muscle was thicker in all 3 positions in the participants with severe forward head postures.

Author keywords: Posture; Ultrasonography; Masseter Muscle

Author affiliations: ST, CTD, RB: Neuromuscular Rehabilitation Research Center, Semnan University of Medical Sciences, Semnan, Iran; MM: Social Determinants of Health Research Center, Semnan University of Medical Sciences, Semnan, Iran

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