Examination of Relationship between Sitting Posture and Masticatory Function

Objectives: The purpose of this study was to evaluate the effect of changes in sitting posture on the stability of sitting posture and masticatory function.
Methods: Fifteen asymptomatic subjects (10 males and 5 females, ages 23-30 years, average age 25.9 years) were included in this study. The CONFORMat (Nitta Corp., Osaka, Japan) system was used to measure the result of changes in sitting posture (center of seat pressure: COSP) and the amount of glucose extraction from chewing gummy jelly was measured to evaluate masticatory performance while subjects maintained the following 2 postural positions: 1) sitting posture with feet flat on the ground (SP-FFG), and 2) sitting posture with feet off the ground (SP-FOG). The Wilcoxon signed rank test was used for statistical analysis. This study was approved by the Ethics Committee of Hokkaido University Graduate School of Dental Medicine.
Results: The total trajectory length of COSP in SP-FFG was longer than in SP-FOG (p<0.05). The COSP area in SP-FFG was smaller than in SP-FOG (p<0.05). The root mean square value of COSP in SP-FFG was smaller than in SP-FOG (p<0.05). There were no significant differences in the mean displacement of COSP in left-right direction between SP-FFG and SP-FOG. The mean displacement of COSP in anterior-posterior direction in SP-FFG was smaller than in SP-FOG (p<0.05). The amount of glucose extraction in SP-FFG was larger than in SP-FOG (p<0.05).
Conclusions: Based on these findings, it was found that body sway was more convergent and masticatory performance was superior when subjects maintained the sitting posture with feet flat on the ground than when they maintained the sitting posture with feet off the ground. In conclusion, changes in sitting posture affected the stability of sitting posture and masticatory function.