비만과 최대작업지속시간의 상관관계에 관한 연구

Abstract

Whether or not obesity is a causal factor of lower back pain(LBP) is a controversial issue. Previous studies have showed how extra body fat in obese people can have a negative influence on LBP through biomechanical evaluation including lifting kinematics and kinetics. However, our knowledge about the relationship is not well understood and still far from complete. At the most basic level, the effects of obesity on various lifting or task postures should be investigated. On this basis, the goal of this study is to reveal the effects of various lifting postures on maximum holding time(MHT) in both normal and obese populations. A total of twenty subjects were recruited from a university population and equally divided into two groups: a normal and an obese group(ten for each). Obesity was defined by considering both the body mass index(BMI: less than 25kg/m2(normal); over 25kg/m2(obese)) and the percentage body fat(PBF: less than 20%(normal); over 20%(obese)), evaluated by the body composition analyzer. The experiment was designed by a combination of three trunk angles (0°, 20°, 60°) and three lower extremity postures(straight, bent, kneeling) to reveal the effects of obesity. Before experimental trials, subjects performed MVC(maximum voluntary contraction) exertions in three trunk angles (0°, 20°, 60°) to calculate 30%MVC at the posture. In each trial, they were required to hold a designated posture with the handheld load (30%MVC) as long as they could. The results revealed a significant decrease of MHT in the obese group, suggesting that obesity has a negative influence of on lifting and tasks. This could be attributed to the extra body fat of obese subjects, which cannot generate any extension moment during weight holding tasks. The extra fat even increases the external momentum generated by the torso. Based on this, we can conclude that obesity can have a negative influence on MHT, and hence reduces work ability.