Sports Medicine

, Volume 32, Issue 7, pp 459–476 | Cite as

Skeletal Adaptations to Alterations in Weight-Bearing Activity

A Comparison of Models of Disuse Osteoporosis
  • Lora Giangregorio
  • Cameron J. R. Blimkie
Review Article


The removal of regular weight-bearing activity generates a skeletal adaptive response in both humans and animals, resulting in a loss of bone mineral. Human models of disuse osteoporosis, namely bed rest, spinal cord injury and exposure to micro-gravity demonstrate the negative calcium balance, alterations in biochemical markers of bone turnover and resultant loss of bone mineral in the lower limbs that occurs with reduced weight-bearing loading. The site-specific nature of the bone response is consistent in all models of disuse; however, the magnitude of the skeletal adaptive response may differ across models. It is important to understand the various manifestations of disuse osteoporosis, particularly when extrapolating knowledge gained from research using one model and applying it to another. In rats, hindlimb unloading and exposure to micro-gravity also result in a significant bone response. Bone mineral is lost, and changes in calcium metabolism and biochemical markers of bone turnover similar to humans are noted. Restoration of bone mineral that has been lost because of a period of reduced weight bearing may be restored upon return to normal activity; however, the recovery may not be complete and/or may take longer than the time course of the original bone loss. Fluid shear stress and altered cytokine activity may be mechanistic features of disuse osteoporosis. Current literature for the most common human and animal models of disuse osteoporosis has been reviewed, and the bone responses across models compared.


Bone Mineral Density Bone Loss Spinal Cord Injury Bone Mass Human Model 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



Funding was provided by the Ontario Neurotrauma Foundation. The results and conclusions are those of the authors. The authors have no conflicts of interest relevant to the contents of this manuscript.


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Copyright information

© Adis International Limited 2002

Authors and Affiliations

  • Lora Giangregorio
    • 1
  • Cameron J. R. Blimkie
    • 1
  1. 1.Department of KinesiologyMcMaster UniversityHamiltonCanada

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