title: Trunk muscle activity with different sitting postures and pelvic inclination.
abstract: 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.
  
  
  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.
authors.affiliation: Department of Physical Therapy, Faculty of Medical and Health Sciences, Tsukuba International University, Ibaraki, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Watanabe
authors.affiliation: Faculty of Sport Sciences, Waseda University, Saitama, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Kaneoka
authors.affiliation: Department of Sports Medicine, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Wada
authors.affiliation: Department of Sports Medicine, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, Japan Department of Health, Faculty of Health Sciences, Physical Therapy Course, Tsukuba University of Technology, Ibaraki, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Matsui
authors.affiliation: Department of Sports Medicine, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Ibaraki, Japan.
authors.forename: Shumpei
authors.initials: S
authors.lastname: Miyakawa
mesh_terms: D001696:Biomechanical Phenomena / Q000502:physiology; D004576:Electromyography; D006801:Humans; D008159:Lumbar Vertebrae / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010384:Pelvic Bones / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology; D011187:Posture / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology; D060726:Torso / Q000502:physiology*; D055815:Young Adult
keywords: Low back pain; electromyography; pelvis incline; posture; stable seat; trunk muscle; unstable seat