The effects of repetitive physiologic loading on bone turnover and mechanical properties in adult female and male rats

Citation
Vr. Yingling et al., The effects of repetitive physiologic loading on bone turnover and mechanical properties in adult female and male rats, CALCIF TIS, 68(4), 2001, pp. 235-239
Citations number
30
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Endocrinology, Nutrition & Metabolism
Journal title
CALCIFIED TISSUE INTERNATIONAL
ISSN journal
0171-967X → ACNP
Volume
68
Issue
4
Year of publication
2001
Pages
235 - 239
Database
ISI
SICI code
0171-967X(200104)68:4<235:TEORPL>2.0.ZU;2-8
Abstract
Repetitive physiologic loading is widely believed to be beneficial in maint aining skeletal integrity. However, repetitive loading is also associated w ith bone injuries, including stress fractures and osteoporotic fractures, i ndicating that under certain conditions repetitive physiologic loading decr eases the functional capacity of bone. Our objective was to identify the re sponse of bone to excessive repetitive loading in adult rats. Male and fema le rats (8-9 months old) were exposed to 2 hours of treadmill running each day for 10 or 30 consecutive days. We examined bone response using biochemi cal, densitometric, and monotonic, relaxation, and cyclic mechanical outcom es. Urinary deoxypyridinoline, a marker of bone resorption, was not signifi cantly affected by running nor were tibial or femoral bone mineral density (BMD) (P > 0.05). Tibial mechanical properties following running were not d ecreased (P > 0.05). We did observe a slight decrease in displacement to fa ilure (P > 0.05) and energy to failure (P = 0.10) of the proximal femur. Th ese findings indicate that 14,000 physiologic loading cycles per day did no t increase systemic bone resorption levels or substantially degrade the mec hanical properties of long bones in adult rats. The lack of response to low magnitude, high cycle number physiologic loading is consistent with the vi ew that a metabolic bone disturbance, in addition to repetitive loading, ma y be necessary for the development of a stress injury in the adult skeleton .