title: Changes in water content of intervertebral discs and paravertebral muscles before and after bed rest.
abstract: BACKGROUND
  Although low back pain can be principally produced or increased during action, it may also be induced or enhanced in the morning after bed rest. During bed rest, tissue edema (increased water content) may occur. In this study, we measured the changes in water content in the intervertebral disc and the paravertebral muscle before and after bed rest using a magnetization transfer magnetic resonance imaging (MT-MRI) technique that permits measuring water content in tissues.
  
  
  METHODS
  A total of 20 student volunteers were enrolled in this study. MT-MRI evaluation was performed before and after bed rest. To measure water content in the intervertebral disc and paravertebral muscle, two MRI sequences were performed using MT pulse-off and MT pulse-on. Based on the two images obtained, the equivalent cross-relaxation rate (ECR) was calculated.
  
  
  RESULTS
  The ECR for intervertebral discs was significantly lower after bed rest than before bed rest (P < 0.01). The ECR for paravertebral equivalent cross-relaxation rate muscles was significantly higher after bed rest than before bed rest (P < 0.05).
  
  
  CONCLUSIONS
  We obtained results indicating that after bed rest the water content in the intervertebral disc and the paravertebral muscle was increased and decreased, respectively.
authors.affiliation: Department of Orthopaedic Surgery, Mie University Graduate School of Medicine, 2-174 Edobashi Tsu, Mie, 514-8507, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Matsumura
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Kasai
authors.forename: Hideaki
authors.initials: H
authors.lastname: Obata
authors.forename: Shigeru
authors.initials: S
authors.lastname: Matsushima
authors.forename: Tadashi
authors.initials: T
authors.lastname: Inaba
authors.forename: Atsumasa
authors.initials: A
authors.lastname: Uchida
mesh_terms: D000328:Adult; D001416:Back Pain; D001510:Bed Rest; D001825:Body Fluid Compartments; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000502:physiology*; D008161:Lumbosacral Region / Q000502:physiology; D008279:Magnetic Resonance Imaging; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D055815:Young Adult