Affiliations: [a] Department of Physical Therapy, Faculty of Medical and Health Sciences, Tsukuba International University, Ibaraki, Japan | [b] Faculty of Sport Sciences, Waseda University, Saitama, Japan | [c] Department of Sports Medicine, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, Japan | [d] Department of Health, Faculty of Health Sciences, Physical Therapy Course, Tsukuba University of Technology, Ibaraki, Japan
Abstract: Background and Objective:Sitting posture may often place large burden on trunk muscles, while trunk muscle activities in the sitting posture have not been well clarified. In this study, a difference in trunk muscle activity between two kinds of sitting postures was evaluated, focusing on low back pain induced by posture holding. Material and Methods:An experiment was conducted on the subjects sitting on a stable-seat and on an unstable-seat, with the pelvis inclined forward, backward, rightward, and leftward. Results:With the pelvis inclined forward, rightward and leftward, muscle activities were significantly increased in a stable-seat sitting posture. In contrast, no significant increase in muscle activity was observed with the pelvis inclined in every direction in an unstable-seat sitting posture. Conclusions:With the pelvis inclined in the stable-seat sitting posture, muscle activities were imbalanced, while with the pelvis inclined in the unstable-seat sitting posture, muscle activities were not imbalanced. Thus, it is suggested that with the pelvis inclined to the maximum extent in the stable-seat sitting posture, low back pain may be induced by imbalanced muscle activities.
