Abstract:
Eight male volunteers were submitted to a 6-week anti-orthostatic bedrest trial followed by a 1-month reambulation period. We prospectively monitored whole-body composition by dual-energy X-ray absorptiometry, bone and connective tissue metabolism by biochemical markers and calcium regulating hormones by 1–84 parathyroid hormone and 1,25-dihydroxyvitamin D3. Bone mineral density (BMD) did not vary significantly; however, a trend toward an increase in head BMD and a decrease in trunk, lumbar vertebrae and lower limb BMD was observed. A decrease in the lower limb lean content occurred by day 27 and was maximum by day 42 after the beginning of bedrest; it normalized by day 30 after bedrest. The serum levels of both osteocalcin and C-terminal crosslinked telopeptide of type I collagen increased as a consequence of bedrest. A slight increase in the serum levels of the N-terminal propeptide of type III collagen, a marker of connective tissue metabolism, was observed during the bedrest period. Except for the C-terminal extension propeptide of type I collagen, all markers decreased to baseline pre-immobilization levels during the 1-month recovery phase. Serum PTH and 1,25-dihydroxyvitamin D3 levels were low during the bedrest period and rose during the reambulation phase. These results seem to reflect early changes in bone and connective tissue metabolism as a result of bedrest unloading, but their order of magnitude remains moderate, thus emphasizing the necessity to perform longer-duration trials.
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Received: 10 December 1998 / Accepted: 14 June 1999
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Uebelhart, D., Bernard, J., Hartmann, D. et al. Modifications of Bone and Connective Tissue after Orthostatic Bedrest. Osteoporos Int 11, 59–67 (2000). https://doi.org/10.1007/s001980050007
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DOI: https://doi.org/10.1007/s001980050007