Abstract
[Purpose] The purpose of this study was to identify changes in the thickness of the deep cervical flexors (DCFs) according to the degree of mouth opening (MO) in normal adults. [Subjects] The study's subjects were 50 normal adults (30 men, 20 women). [Methods] Ultrasound was used to obtain images of muscles, and the NIH ImageJ software was used to measure the thickness of each muscle. [Results] An increase in MO resulted in a corresponding increase in the thickness of the DCFs, and in isometric exercises (IEs), the thickness of the DCFs further increased during MO. [Conclusion] During MO, the thickness of the DCFs increased. This may be due to correlations between mandibular movements and DCFs. Therefore, the results are likely to be utilized as new clinical research data.