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Evaluation of Treadmill Exercise in a Lower Body Negative Pressure Chamber as a Countermeasure for Weightlessness-Induced Bone Loss: a Bed Rest Study with Identical TwinsCounteracting bone loss is required for future space exploration. We evaluated the ability of treadmill exercise in a LBNP chamber to counteract bone loss in a 30-day bed rest study. Eight pairs of identical twins were randomly assigned to sedentary control or exercise groups. Exercise within LBNP decreased the bone resorption caused by bed rest and may provide a countermeasure for spaceflight. INTRODUCTION: Bone loss is one of the greatest physiological challenges for extended-duration space missions. The ability of exercise to counteract weightlessness-induced bone loss has been studied extensively, but to date, it has proven ineffective. We evaluated the effectiveness of a combination of two countermeasures-treadmill exercise while inside a lower body negative pressure (LBNP) chamber-on bone loss during a 30-day bed rest study. MATERIALS AND METHODS: Eight pairs of identical twins were randomized into sedentary (SED) or exercise/LBNP (EX/LBNP) groups. Blood and urine samples were collected before, several times during, and after the 30-day bed rest period. These samples were analyzed for markers of bone and calcium metabolism. Repeated measures ANOVA was used to determine statistical significance. Because identical twins were used, both time and group were treated as repeated variables. RESULTS: Markers of bone resorption were increased during bed rest in samples from sedentary subjects, including the collagen cross-links and serum and urinary calcium concentrations. For N-telopeptide and deoxypyridinoline, there were significant (p < 0.05) interactions between group (SED versus EX/LBNP) and phase of the study (sample collection point). Pyridinium cross-links were increased above pre-bed rest levels in both groups, but the EX/LBNP group had a smaller increase than the SED group. Markers of bone formation were unchanged by bed rest in both groups. CONCLUSIONS: These data show that this weight-bearing exercise combined with LBNP ameliorates some of the negative effects of simulated weightlessness on bone metabolism. This protocol may pave the way to counteracting bone loss during spaceflight and may provide valuable information about normal and abnormal bone physiology here on Earth.
Document ID
20050155279
Acquisition Source
Johnson Space Center
Document Type
Reprint (Version printed in journal)
Authors
Smith, Scott M.
(NASA Johnson Space Center Houston, TX United States)
Davis-Street, Janis E.
Fesperman, J. Vernell
Calkins, D. S.
Bawa, Maneesh
Macias, Brandon R.
Meyer, R. Scott
Hargens, Alan R.
Date Acquired
August 23, 2013
Publication Date
December 1, 2003
Publication Information
Publication: Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research
Volume: 18
Issue: 12
ISSN: 0884-0431
Subject Category
Aerospace Medicine
Report/Patent Number
JSC-CN-7846
Funding Number(s)
CONTRACT_GRANT: M01-RR00827
Distribution Limits
Public
Copyright
Other
Keywords
Twin Study
Clinical Trial
Randomized Controlled Trial

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