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Translational Medicine: From Ground-Based Studies of Cardiovascular and Musculoskeletal Countermeasures to Astronaut Health and Earth Benefits.    Alan R Hargens, Department of Orthopaedic Surgery, University of California, San Diego, CA  92103-8894

   Current exercise systems for space, which attempt to maintain preflight fitness, are unable to achieve loads similar to those on Earth.  Our NASA research is directed towards several risk factors and critical questions in the Bioastronautics Critical Path Road Map (http://bioastroroadmap.nasa.gov/index.jsp) related to countermeasures against cardiovascular and musculoskeletal loss.  We have evaluated lower body negative pressure (LBNP) treadmill exercise to prevent deconditioning during simulated microgravity.  Fifteen sets of identical twins (16 males and 14 females, 21-36 years) remained in 6º head-down tilt bed rest for 30 days to simulate microgravity. One twin from each pair (EX) was randomly selected to exercise supine in an LBNP chamber at 1.0-1.2 body weights for six days per week.  Their siblings served as non-exercise controls (CON). Orthostatic tolerance (time to pre-syncope) and sprint speed/emergency egress decreased significantly (p< 0.05) after 30 days bed rest in the CON group, but was relatively maintained in the EX group.  Upright VO2pk, muscle strength, and endurance decreased significantly in CON group, but were preserved in the EX group.  Also, the EX group had significantly higher back muscle strength and lower lumbar spine compressibility after bed rest than the CON group. The efficacy of our exercise countermeasure has been documented during simulated microgravity and translated to Earth benefit with respect to NIH and DOD priorities.  This research is applicable to rehabilitation of astronauts after flight and orthopaedic patients after surgery.  Finally, our studies of identical twins allow quantification of heritability of physiologic traits and evaluation of genetic versus environment factors in health and disease.

Supported by grants from NASA NAG9-1425, US Army ARM 25-10381552,  and NIH M01 RR00827.