title: Diurnal variation in stature: do those with chronic low-back pain differ from asymptomatic controls?
abstract: BACKGROUND
  Stature loss is a commonly used measure of spinal load. The aim of this study was to investigate the pattern of diurnal stature change in those with and without chronic low-back pain, over a 24-h period.
  
  
  METHODS
  Eight participants with chronic low-back pain (age 24.6 (SD 4.3) years, height 1.76 (SD 0.08) m, body mass 72.8 (SD 11.1) kg) and eight controls (age 21.8 (SD 2.0) years, height 1.75 (SD 0.10) m, body mass 71.8 (SD 11.6) kg) participated in this investigation. Twenty-four stature measurements were performed over a 24-h period.
  
  
  RESULTS
  The trough to peak variation in stature of 17.9 mm (low-back pain group) and 17.6mm (control group) did not differ between groups (P>0.05). Both groups experienced greatest stature change in the 1st hour after rising (31.3% [low-back pain] and 44.6% [control] of total stature change). At approximately 18:00h the LBP group reached a plateau whilst the control group continued to lose stature. Between 14:00 and 18:00h both groups demonstrated a previously unreported recovery of stature. A significant correlation was found between low-back discomfort and stature change in the low-back pain group only.
  
  
  CONCLUSIONS
  No significant difference existed between groups in relation to total stature loss; however the low-back pain group appeared to reach their nadir earlier, possibly exposing other spinal structures to loading for a greater duration. This is supported by the relationship found between stature loss and discomfort. The reversal in stature loss in the afternoon may be of clinical significance and warrants further investigation.
authors.affiliation: Arthritis Research UK Primary Care Centre, Primary Care Sciences, Keele University, Staffordshire, UK. e.healey@cphc.keele.ac.uk
authors.forename: Emma L
authors.initials: EL
authors.lastname: Healey
authors.forename: Adrian M
authors.initials: AM
authors.lastname: Burden
authors.forename: Islay M
authors.initials: IM
authors.lastname: McEwan
authors.forename: Neil E
authors.initials: NE
authors.lastname: Fowler
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D001827:Body Height; D002908:Chronic Disease; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D017116:Low Back Pain / Q000503:physiopathology*; D008297:Male; D008953:Models, Anatomic; D009068:Movement; D011187:Posture; D013131:Spine / Q000502:physiology*; D013997:Time Factors; D016474:Weight-Bearing