BIOMECHANICAL ANALYSIS OF CHAIR RISING IN THE PREGNANT WOMEN

Abstract

There were so many changes in physiological and psychological aspects during pregnancy. Rising from a chair was an important functional activity of daily life. These changes impose postural demands and limit the performance of activities of daily living. The overall goals of this study were to quantify the effects of physiological change due to pregnancy on the performance of chair-rise and to analyze why some pregnant female have more difficulty with these tasks. Twenty-four pregnant women were included in this study to investigate the performance and possible related biomechanical factors of chair-rise. Body movements of these subjects were recorded using video-based motion analysis system. Three force plates were applied to obtain the ground reaction forces of foot, seat and armrest. Kinematics and kinetics data were analyzed to evaluate the angles and moments of the hip, knee and ankle joints. The result indicated that the maximum moment of the three joints occurred nearly in the beginning of extension phase. As the chair height increased, the maximum flexion angles decreased significantly at the hip, knee, and ankle joints. The chair height had great influence on knee joint and hip joint moments, but less on ankle joint. In the third stage (chair height: 65% KH), the maximum hip moment significantly decreased because of a remarkable increase in abdominal depth. In contrast to the hip moment, the maximum knee moment greatly increased. This result revealed the reason why pregnant female have more difficulty on the performance of chair-rise. Additionally, rising with the armrest for pregnant female would significantly decreased the maximum knee moment. This study suggested that pregnant female should select armrest or higher chair to decrease the joint loading during chair-rise.