Abstract
Treadmill exercise in lower body negative pressure to counteract deconditioning from spaceflight. D.E. Watenpaugh, S.M.C. Lee, W.L. Boda, D.D. O'Leary, S.M. Schneider, and A.R. Hargens. Research performed at the Department of Orthopaedics, University of California, San Diego, USA. Over the last 15 years, we developed treadmill exercise in lower body negative pressure (LBNP) as a countermeasure. We hypothesize that LBNP exercise during bed rest (simulated spaceflight) maintains muscle mass and strength, bone metabolism, gastrointestinal (GI) motility, balance, sprint speed, exercise capacity, and orthostatic tolerance. We currently study identical twins in 6 degree head-down bed rest for 30 days. One twin from each pair exercises supine in LBNP at 1.0-1.2 bodyweight and 40-80% VO2 peak 6 days per week; 5 min of resting LBNP follows exercise. The siblings serve as non-exercising controls. Preliminary findings indicate control subjects experience: reduced leg muscle strength and endurance; reduced paraspinal muscle cross-sectional area and spinal bone mineral density; increased biochemical evidence of bone catabolism; reduced GI motility; reduced balance, sprint speed, and VO2 peak; and orthostatic intolerance. The countermeasure attenuates or prevents all of these effects except GI dysmotility. Full protection of orthostatic tolerance may require longer post-exercise resting LBNP (10 min?), and resistance exercise may be needed for full maintenance of lower body musculoskeletal tissues. NASA, NIH, and the Canadian Space Agency support this work. [Jpn J Physiol 54 Suppl:S46 (2004)]
