Dual-energy x-ray absorptiometry (DXA), magnetic resonance imaging (MRI), and quantitative computed tomography (QCT) scans were conducted at the start and end of bed rest to assess variations in bone mineral density, changes in muscle volume, and regional changes in both cortical trabecular bones. Strength measurements were collected pre- and post-bed rest, and urinary and serum markers of bone resorption and formation were assessed.
The information obtained as a result of this study would provide further insight into the role of skeletal loading in bone loss during long-duration spaceflight, and knowledge gained from this research will thereby contribute to a better understanding of the importance of exercise for the development and maintenance of bone strength among humans living in Earth gravitational fields. Knowledge in this area will be crucial to the treatment of bone disease for which exercise may or may not be an effective intervention.
This experiment was discontinued from the ground-based studies sponsored by NASA's Human Adaptation and Countermeasures Division (HACD). This study was discontinued due to cost and schedule limitations for use of the Flight Analogs Research Unit facility to complete DBLS as a standalone bed rest campaign.
Before this experiment was moved to NASA HACD, additional data was collected at the Cleveland Clinic on 11 subjects (5 exercisers, 6 controls) which were managed by the National Space Biomedical Research Institute (NSBRI). Mid-term review findings were assessed for some variables and were presented in detail at the 18th Annual International Academy of Astronautics Humans in Space Symposium, Houston, TX, April 11-15, 2011 (N=8, 3 additional subsequently completed). Results included statistically significant differences between exercisers and controls in the total hip and inter-trochanter bone mineral density. There were no exercise effect for knee extensor/ankle dorsiflexion strength and postural stability. Other guardedly positive exercise effect trends were found for: Ca, BSAP, NTx, most Hip vBMD measures, ankle plantar flexion strength, knee flexor and extensor fatigue-ability and VO2 max.
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