title: Competing effects of pain and fear of pain on postural control in low back pain?
abstract: METHODS
  A cross-sectional, observational study.
  
  
  OBJECTIVE
  To determine whether pain and fear of pain have competing effects on postural sway in patients with low back pain (LBP).
  
  
  BACKGROUND
  Competing effects of pain and pain-related fear on postural control can be proposed as the likely explanation for inconsistent results regarding postural sway in the LBP literature. We hypothesized that although pain might increase postural sway, fear of pain might reduce sway through an increased cognitive effort or increased cocontraction to restrict body movement. The cognitive strategy would be less effective under dual-task conditions and the cocontraction strategy was expected to be less effective when standing on a narrow base of support surface.
  
  
  METHODS
  Postural sway was measured in combined conditions of base of support (full and narrow) and cognitive loading (single and dual tasks) in 3 experimental groups with current LBP, recent LBP, and no LBP. Sway amplitude, path length, mean power frequency, and sample entropy were extracted from center-of-pressure data.
  
  
  RESULTS
  The current-LBP group and recent-LBP group reported significantly different levels of pain, but similar levels of pain catastrophizing and kinesiophobia. The current-LBP group tended to display larger sway amplitudes in the anteroposterior direction compared with the other 2 groups. Mean power frequency values in mediolateral direction were lower in patients with the current LBP compared with recent LBP. Smaller sample entropy was found in the current-LBP group than the other groups in most experimental conditions, particularly when standing on a narrow base of support.
  
  
  CONCLUSIONS
  Alterations of postural sway are mostly mediated by pain but not pain-related fear. LBP tends to increase sway amplitude, which seems to be counteracted by increased effort invested in postural control leading to decreased frequency and increased regularity of sway particularly under increased task demands.
  
  
  METHODS
  Cross-sectional study.
authors.affiliation: *MOVE Research Institute Amsterdam, Faculty of Human Move-ment Sciences, VU University Amsterdam, Amsterdam, the Netherlands †Musculoskeletal Research Center, Isfahan University of Medical Sciences, Isfahan, Iran; and ‡Musculoskeletal Rehabilitation Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
authors.forename: Masood
authors.initials: M
authors.lastname: Mazaheri
authors.forename: Elham
authors.initials: E
authors.lastname: Heidari
authors.forename: Javid
authors.initials: J
authors.lastname: Mostamand
authors.forename: Hossein
authors.initials: H
authors.lastname: Negahban
authors.forename: Jaap H
authors.initials: JH
authors.lastname: van Dieen
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D003430:Cross-Sectional Studies; D005239:Fear / Q000523:psychology*; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000503:physiopathology* / Q000523:psychology*; D008297:Male; D008875:Middle Aged; D009068:Movement; D004856:Postural Balance / Q000502:physiology; D011187:Posture / Q000502:physiology*; D013647:Task Performance and Analysis; D055815:Young Adult