title: Criterion validity and between-day reliability of an inertial-sensor-based trunk postural stability test during unstable sitting.
abstract: BACKGROUND
  Adequate neuromuscular control of the lumbar spine is required to prevent lumbar injuries. A trunk postural stability test has been proposed earlier, using a chair wobbling on a central pivot and four springs with adjustable positions to modulate task difficulty. An inertial sensor is fixed on the chair to measure postural sway. The aim of this study is to assess the criterion validity and between-day reliability of the calibration and testing components.
  
  
  METHODS
  Thirty six subjects (with and without low back pain) followed a calibration procedure, four practice trials and three 60-s trials on 2days. The criterion validity of the inertial sensor was tested against an optoelectronic system and a force platform. The reliability of 38 body sway measures obtained from the inertial sensor angular measures was estimated.
  
  
  RESULTS
  The inertial sensor led to valid estimates of postural sway. The reliability of the calibration procedure was moderate. Practically no learning effect was detected except for a few body sway measures in patients with CLBP. Three 60-s trials provided acceptable reliability for approximately half of the body sway measures, although this is more difficult to achieve in patients with CLBP.
  
  
  CONCLUSIONS
  The use of an easy to use inertial sensor led to valid measures of postural sway. A number of body sway measures were identified as reliable tools for individual follow-ups but inter-subject comparisons were anticipated as more difficult when patients with CLBP are involved.
authors.affiliation: Occupational Health and Safety Research Institute Robert-Sauvé, Montreal, Quebec, Canada. larchr@irsst.qc.ca
authors.forename: Christian
authors.initials: C
authors.lastname: Larivière
authors.forename: Hakim
authors.initials: H
authors.lastname: Mecheri
authors.forename: Ali
authors.initials: A
authors.lastname: Shahvarpour
authors.forename: Denis
authors.initials: D
authors.lastname: Gagnon
authors.forename: Aboulfazl
authors.initials: A
authors.lastname: Shirazi-Adl
mesh_terms: D000054:Acceleration; D056044:Actigraphy / Q000295:instrumentation*; D000293:Adolescent; D000328:Adult; D000368:Aged; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000503:physiopathology*; D008159:Lumbar Vertebrae / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D004856:Postural Balance; D011187:Posture; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014159:Transducers; D055815:Young Adult