title: Delay of intracortical bone remodelling following a stress change: a theoretical and experimental study.
abstract: BACKGROUND
  A theoretical model and an experimental setup were specifically designed to identify and determine the delay of the cortical bone response (restricted to mineralization and demineralization) to a stress change.
  
  
  METHODS
  The in vivo experiment considered two groups of rats: a running group and a control sedentary group. The running group rats were compelled to a running activity for 15 weeks, followed by a sedentary activity for 15 weeks. Bone density was derived from hardness measurements. The parameters of the remodelling theory, including the response delay and the remodelling rates, were determined from these experimental measurements.
  
  
  RESULTS
  Bone density increased significantly during the activity period, and decreased rapidly when rats returned to sedentary state. The identification of the model's parameters produced evolution curves that were within the limits of the standard deviation of the experimental data. The densification rate was lower than the resorption rate, and the densification delay was greater than bone resorption delay.
  
  
  CONCLUSIONS
  The delays determined with this macroscopic model are related to response delays due to biological internal processes in bone.
authors.affiliation: Laboratoire de Recherche en Orthopédie, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland. alexandre.terrier@epfl.ch
authors.forename: Alexandre
authors.initials: A
authors.lastname: Terrier
authors.forename: Junpei
authors.initials: J
authors.lastname: Miyagaki
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Fujie
authors.forename: Kozaburo
authors.initials: K
authors.lastname: Hayashi
authors.forename: Lalao
authors.initials: L
authors.lastname: Rakotomanana
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D001696:Biomechanical Phenomena; D016723:Bone Remodeling / Q000502:physiology*; D005260:Female; D016018:Least-Squares Analysis; D008962:Models, Theoretical; D051381:Rats; D017208:Rats, Wistar; D012420:Running / Q000502:physiology*; D013314:Stress, Mechanical; D013977:Tibia / Q000502:physiology*