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Journal of Osteoporosis
Volume 2011, Article ID 786752, 15 pages
http://dx.doi.org/10.4061/2011/786752
Review Article

Loading and Skeletal Development and Maintenance

1Department of Nuclear Medicine, Laboratory of Clinical Chemistry and Experimental Medicine, CHU Brugmann, Université Libre de Bruxelles, 4 Pl. Van Gehuchten, 1020 Brussels, Belgium
2Department of Medicine, CHU Brugmann, Université Libre de Bruxelles, 1020 Brussels, Belgium
3Division of Gerontology and Geriatrics, Center for Musculoskeletal Research, Department of Experimental Medicine, Catholic Leuven University, 3000 Leuven, Belgium
4Department of Rheumatology, Mont-Godinne University Hospital, Université Catholique de Louvain, 1200 Brussels, Belgium
5Rheumatology Unit, Saint-Luc University Hospital, Université Catholique de Louvain, 1200 Brussels, Belgium
6Unit for Osteoporosis and Metabolic Bone Diseases, Ghent University Hospital, 9000 Ghent, Belgium
7Department of Public Health Sciences, University of Liège, 4000 Liège, Belgium
8Department of Gynaecology-Obstetrics, Free University of Brussels, 1090 Brussels, Belgium

Received 8 September 2010; Accepted 6 November 2010

Academic Editor: Jian Sheng (Charles) Chen

Copyright © 2011 P. Bergmann et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Mechanical loading is a major regulator of bone mass and geometry. The osteocytes network is considered the main sensor of loads, through the shear stress generated by strain induced fluid flow in the lacuno-canalicular system. Intracellular transduction implies several kinases and phosphorylation of the estrogen receptor. Several extra-cellular mediators, among which NO and prostaglandins are transducing the signal to the effector cells. Disuse results in osteocytes apoptosis and rapid imbalanced bone resorption, leading to severe osteoporosis. Exercising during growth increases peak bone mass, and could be beneficial with regards to osteoporosis later in life, but the gain could be lost if training is abandoned. Exercise programs in adults and seniors have barely significant effects on bone mass and geometry at least at short term. There are few data on a possible additive effect of exercise and drugs in osteoporosis treatment, but disuse could decrease drugs action. Exercise programs proposed for bone health are tedious and compliance is usually low. The most practical advice for patients is to walk a minimum of 30 to 60 minutes per day. Other exercises like swimming or cycling have less effect on bone, but could reduce fracture risk indirectly by maintaining muscle mass and force.