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Ground Based Study:    DBLS
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The Daily Bone Load Stimulus (DBLS) bed rest study was discontinued. The approach involved quantifying typical daily loads to the lower extremities in selected volunteer subjects who were not habitual exercisers and planning individual exercise prescriptions based on daily load stimulus theory. Subjects were assigned to control or exercise groups and confined to 6-degree head-down bed rest in the Flight Analogs Research Unit (FARU) at the University of Texas Medical Branch (UTMB) in Galveston, TX for 12 weeks.

The first six subjects to enroll in this study at UTMB were targeted for the exercise group. During this time, the exercise group would undergo individualized daily exercise programs in the unique standalone Zero Gravity Locomotion Simulator (sZLS) designed to replace the daily mechanical load stimulus experienced during free living. A treadmill, similar to that available on the International Space Station (ISS), was targeted for exercise use. Dual-energy x-ray absorptiometry (DXA), magnetic resonance imaging (MRI), and quantitative computed tomography (QCT) scans were to be conducted at the start and end of bed rest to assess variations in bone mineral density, changes in muscle volume, and regional changes (cortical versus trabecular) in bone. Strength measurements were to be collected pre- and post-bed rest, and urinary and serum markers of bone resorption and formation were also to be assessed. Dietary intake, sufficient to maintain constant body weight with a balanced intake of macro- and micronutrients were planned. Intake was to be supervised by a registered dietician and a physician was to be available 24 hr/day to attend to any medical needs. A rehabilitation program was to be offered to subjects in the 8 weeks following bed rest.

The purpose of this research was to determine if individualized mechanical load replacement and supplementation during bed rest would serve as a countermeasure to losses in bone mineral density, bone quality, and muscle atrophy during 12 weeks of bed rest. The experiments would provide a categorical answer to the question of whether or not intermittent load replacement can adequately protect the musculoskeletal system against hypokinetic osteopenia and muscle atrophy and may demonstrate the efficacy of individualized exercise countermeasure planning.

In addition to the Standard Measures testing, two external principal investigations were included with the DBLS study science requirements:

  • A Quantitative Test of On-Orbit Exercise Countermeasures for Bone Demineralization Using a Bed Rest Analog (UWSCI)
    (PI: Peter R. Cavanagh, Ph.D., D.Sc. Department of Orthopedics and Sports Medicine School of Medicine University of Washington, Seattle, WA
  • Non-Invasive Near Infrared Spectroscopy (NIRS)
    (PI: Babs R. Soller, Ph.D.Professor of Anesthesiology University of Massachusetts Medical School Department of Anesthesiology, Worcester, MA
  • This study has been discontinued; therefore, there are no results available from this study.

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