A kinesiological analysis of the stand-to-sit during the third trimester

Abstract

[Purpose] The purpose of this study was to kinesiologically analyze of the stand-to-sit motion in the third trimester. [Subjects] Eight pregnant women in their third trimester and 8 non-pregnant women participated in this study. [Methods] Subjects were asked to sit-down on a 400-mm-high seat from the standing position. A 3D motion analysis system and a force plate were used to collect data. Measurements analyzed were (1) the time taken to sit down; (2) the leg joint moment; (3) the antero-posterior and vertical floor reaction forces; and (4) the range of motion of the lower limbs and trunk. Statistical analyses were conducted to compare the pregnant with non-pregnant women using the Mann-Whitney U test. [Results] For pregnant women, the time taken to sit down, the knee extension moment, as well as the posterior and vertical components of the motion were significantly higher. The ranges of motion of the other joints were not significantly different between the pregnant and non-pregnant women. [Conclusion] Pregnant woman have unstable posterior balance when sitting down due to the increase of the posterior floor reaction force. In the third trimester, the sit-down motion requires attention because of the impact of weight gain and the shift in the center of gravity.