Effects of Two Sitting Positions on Chest Volume

Abstract

[Purpose] Measurement of chest expansion is a simple and practical method of assessing patients’ respiratory function. The purpose of this study was to investigate the relationship between chest expansion and changes in the chest volumes at specific locales of the thorax in two different sitting positions. [Subjects] The participants were 12 sedentary healthy men with a mean age of 21.9 years, a mean body mass of 61.7 kg, a mean height of 169.7 cm, and a body mass index of 21.3 kg/m². [Methods] A spherical reflective marker was placed at a selected point on the sternal notch, 3rd rib, xiphoid process, 8th rib, 10th rib and umbilicus. In the positions of stoop sitting with 20° pelvic tilt and upright sitting the differences in chest volumes during deep breathing were measured using a 3-dimensional motion analyzer. [Results] In upright sitting the upper thorax yielded a significantly larger decrease in chest volume compared to the lower thorax. In stooped sitting the lower thorax yielded a significantly larger decrease in chest volume compared to the upper thorax. [Conclusion] The position of stooped sitting may be a factor contributing to the overall decrease in vital capacity and maximum inspiratory capacity.