title: Trunk postural control in unstable sitting: Effect of sex and low back pain status.
abstract: BACKGROUND
  Adequate neuromuscular control of the lumbar spine is required to prevent lumbar injuries. A trunk postural control test protocol, controlling for the influence of body size on performance, was implemented to carry out between-subject comparisons. The aim of this study was to assess the effect of sex and low back pain status with the use of two measures of trunk postural control, the first based on chair motion, and the second based on trunk motion.
  
  
  METHODS
  Thirty-six subjects (with and without low back pain) performed three 60-s trunk postural control trials with their eyes closed while seated on an instrumented wobble chair, following a calibration procedure. Chair and trunk angular kinematics were measured with an optoelectronic system. A chair-based stabilogram and a trunk-based (lumbar spine) stabilogram were created using the angular motions produced in the sagittal and frontal planes. Twenty body-sway measures were computed for each stabilogram.
  
  
  RESULTS
  The calibration task efficiently controlled for the influence of body size. Several sex effects were detected, with most of them originating from the trunk-based measures. Subjects with low back pain and healthy controls showed comparable trunk postural control.
  
  
  CONCLUSIONS
  Sex differences were substantiated for the first time, but almost only with the trunk-based stabilogram, showing that the kinematic information captured on the trunk segments is quite different from what is captured on the wobble chair. Contrary to previous studies, pain status was not related to lowered trunk postural control, which can be attributed to the patients recruited or measurement reliability issues.
authors.affiliation: Occupational Health and Safety Research Institute Robert-Sauvé, Montreal, Quebec, Canada; Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal (CRIR), Montreal Rehabilitation Institute, Montreal, Canada. Electronic address: larchr@irsst.qc.ca.
authors.forename: Christian
authors.initials: C
authors.lastname: Larivière
authors.affiliation: University of Montreal, Montreal, Canada; Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal (CRIR), Montreal Rehabilitation Institute, Montreal, Canada.
authors.forename: Dany H
authors.initials: DH
authors.lastname: Gagnon
authors.affiliation: Occupational Health and Safety Research Institute Robert-Sauvé, Montreal, Quebec, Canada; Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal (CRIR), Montreal Rehabilitation Institute, Montreal, Canada.
authors.forename: Hakim
authors.initials: H
authors.lastname: Mecheri
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000503:physiopathology*; D008159:Lumbar Vertebrae / Q000502:physiology; D008297:Male; D009068:Movement; D004856:Postural Balance / Q000502:physiology*; D015203:Reproducibility of Results; D012737:Sex Factors; D060726:Torso / Q000502:physiology*
keywords: Kinematics; Low back pain; Lumbar spine; Postural control; Sitting balance; Wobble chair