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WISE-2005: Lower Body Negative Pressure Treadmill Exercise and Resistive Exercise Countermeasures Maintain Physiologic Function in Women during 60-days of Bed Rest.    B.R. Macias¹, S.M. Schneider, S.M.C. Lee, P. Guinet, S. Meuche, R.L. Hughson, S.M. Smith, S.R. Zwart, D.E. Watenpaugh, and A.R. Hargens¹.  Dept. of Orthopaedic Surgery, Univ. of California, San Diego, 92103-8894.

   INTRODUCTION: Current exercise systems for space flight do not provide loads equal to those on Earth.  We hypothesized that supine LBNP treadmill exercise combined with Flywheel resistive exercise maintains upright physiologic responses following 60-days of head-down tilt (HDT) bed rest (BR). METHODS: Sixteen healthy women (age 25-40 years) underwent a 20-day baseline period, followed by 60-days HDT (-6 degrees) BR and then 20-days recovery.  Women were assigned to either a non-exercise control group (CON, n=8) or to an exercise group (EX, n=8). EX subjects performed a 40-min, variable intensity (40-80% pre-BR VO₂pk) LBNP exercise protocol at foot-ward forces between 1.0-1.1 Helvetica,Arial,sans-serif body weight, followed by 10-min of resting LBNP 3-4 days/week. Resistive exercise of maximal concentric and eccentric supine leg press and heel raise exercises were performed using a gravity-independent flywheel ergometer 2-3 days/week. French/ NASA/UCSD IRBs approved this study with informed/written consent. RESULTS: Post-BR VO₂pk was not different in EX (-3.3±1.2%) but decreased significantly in CON (-21.2±2.1%), p< 0.05.  Post-BR orthostatic tolerance time (mean±se) decreased significantly less in EX (19.3±1.3 to 14.4±1.5 min) than in CON (17.5±0.1 to 9.1±1.5 min), p=0.03. Post-BR muscle strength decreased significantly in CON, but was preserved in EX. Post-BR bone resorption was greater than pre-BR in both groups (p<0.05).  Bone formation markers, were significantly elevated (p<0.05) in EX than in CON. Hip bone mineral density loss was less in EX compared to CON (p<0.05). CONCLUSIONS: Supine LBNP treadmill exercise along with flywheel resistive exercise maintains upright exercise capacity, orthostatic responses and muscle strength during 60-days HDT BR. Overall these results document the efficacy of the combined-exercise countermeasure protocol during microgravity as simulated by 60-days of HDT BR. (Supported by ESA, CSA, CNES; and NASA: NNJ04HF71G and NNJ04HF72G.)