title: Hip strategy for balance control in quiet standing is reduced in people with low back pain.
abstract: METHODS
  Quiet stance on supporting bases with different lengths and with different visual inputs were tested in 24 study participants with chronic low back pain (LBP) and 24 matched control subjects.
  
  
  OBJECTIVE
  To evaluate postural adjustment strategies and visual dependence associated with LBP.
  
  
  BACKGROUND
  Various studies have identified balance impairments in patients with chronic LBP, with many possible causes suggested. Recent evidence indicates that study participants with LBP have impaired trunk muscle control, which may compromise the control of trunk and hip movement during postural adjustments (e.g., hip strategy). As balance on a short base emphasizes the utilization of the hip strategy for balance control, we hypothesized that patients with LBP might have difficulties standing on short bases.
  
  
  METHODS
  Subjects stood on either flat surface or short base with different visual inputs. A task was counted as successful if balance was maintained for 70 seconds during bilateral stance and 30 seconds during unilateral stance. The number of successful tasks, horizontal shear force, and center-of-pressure motion were evaluated.
  
  
  RESULTS
  The hip strategy was reduced with increased visual dependence in study participants with LBP. The failure rate was more than 4 times that of the controls in the bilateral standing task on short base with eyes closed. Analysis of center-of-pressure motion also showed that they have inability to initiate and control a hip strategy.
  
  
  CONCLUSIONS
  The inability to control a hip strategy indicates a deficit of postural control and is hypothesized to result from altered muscle control and proprioceptive impairment.
authors.affiliation: Department of Physiotherapy, University of Queensland, Australia.
authors.forename: Nicola W
authors.initials: NW
authors.lastname: Mok
authors.forename: Sandra G
authors.initials: SG
authors.lastname: Brauer
authors.forename: Paul W
authors.initials: PW
authors.lastname: Hodges
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D002908:Chronic Disease; D005260:Female; D006621:Hip Joint / Q000503:physiopathology*; D006801:Humans; D017116:Low Back Pain / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D004856:Postural Balance / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D011434:Proprioception; D014785:Vision, Ocular