title: Changes in lumbar disk morphology associated with prolonged sitting assessed by magnetic resonance imaging.
abstract: OBJECTIVE
  To determine what if any changes occur to the lumbar disks in the spine after prolonged sitting with and without intermittent breaks during a 4-hour period.
  
  
  METHODS
  A prospective observational study.
  
  
  METHODS
  An academic outpatient clinic.
  
  
  METHODS
  The measurement of lumbar disk changes was performed with 12 subjects after an analysis of a mid sagittal lumbar magnetic resonance image, which measured lumbar disk height and disk diameter. Scanning and analysis were done over a 2-day period: day 1 at the start of the work day and 4 hours later after continuous sitting; at the start of work day 2 and after four hours after a change in position and stretching protocol every 15 minutes.
  
  
  RESULTS
  For this study, we first evaluated each level of the lumbar spine for any changes after prolonged sitting for 4 hours over the 2 days. Multiple comparisons bias was eliminated by a Bonferroni correction to limit the overall experiment-wise error rate to .05. The comparison was conducted by using a paired t-test when the normality condition was satisfied and by using a Wilcoxon signed rank test when normality was not satisfied. To test for normality, a Shapiro-Wilk test was used. We found that, for disk height, L4-5 was significantly decreased at the end of the sitting for day 1 but not for day 2. There were no significant height changes for the other lumbar disks. In addition, for disk diameter, there were no significant differences present for any of the disks.
  
  
  CONCLUSIONS
  Analysis of the data shows that the greatest change in disk height is at the L4-5 level after prolonged sitting without intermittent breaks. The other levels did not show a significant change in their height. The findings also showed that the L4-5 height changes were not significant with brief positional changes every 15 minutes. Fewer changes in disk height may correlate with an improvement in low back pain and disability.
authors.affiliation: Department of Orthopaedics, Penn State Orthopaedics, Penn State Hershey Bone and Joint Institute-State College, University Park, PA(∗). Electronic address: gbilly@hmc.psu.edu.
authors.forename: Gregory G
authors.initials: GG
authors.lastname: Billy
authors.affiliation: Department of Radiology, Penn State Hershey Medical Center, Hershey, PA†
authors.forename: Susan K
authors.initials: SK
authors.lastname: Lemieux
authors.affiliation: Department of Statistics, Eberly College of Science, Pennsylvania State University, University Park, PA‡
authors.forename: Mosuk X
authors.initials: MX
authors.lastname: Chow
mesh_terms: D006801:Humans; D008159:Lumbar Vertebrae / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D009068:Movement / Q000502:physiology*; D011187:Posture / Q000502:physiology; D011446:Prospective Studies; D057185:Sedentary Behavior; D013997:Time Factors