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Influence of simulated microgravity on the VO2 max of nontrained and trained ratsHead-down suspension (HDS) of rats has evolved as a useful model for the simulation of a microgravity environment. Previous HDS experiments with rats have shown an impaired capacity to perform aerobic exercise as demonstrated by reductions in maximum oxygen consumption (VO2 max), treadmill run time (RT), and mechanical efficiency (ME) of treadmill running at submaximal conditions. To determine whether endurance training (TR) before HDS would modify exercise performance, male Sprague-Dawley rats were assigned to nontrained (NT) or TR groups for 6 wk and exposed to HDS or cage control (CC) conditions for 29 days. The rats were tested for VO2 max, RT, and ME before treatment and on days 7, 14, 21, and 28. In addition, water and electrolyte excretion was measured on days 1 and 21 of the experimental period. Before HDS, the TR rats had significantly higher measures of VO2 max (15%) and RT (22%) than the NT rats. On day 28, HDS was associated with significant reductions in absolute VO2 max (ml/min) in TR (-30%) and NT (-14%) rats. Relative VO2 max (ml.min-1.kg-1) was significantly reduced in TR (-15%) but not NT rats. Similar reductions in RT occurred in TR (-37%) and NT (-35%) rats by day 28. ME was reduced 22% in both TR and NT rats after 28 days of suspension. HDS elicited diuresis, natriuresis, and kaliuresis in TR rats after 21 days but not after 24 h. In contrast, HDS-NT rats exhibited no diuretic, natriuretic, or kaliuretic responses.(ABSTRACT TRUNCATED AT 250 WORDS).
Document ID
20050000489
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Woodman, C. R.
(School of Health Related Professions, University of Arizona Tucson 85721)
Monnin, K. A.
Sebastian, L. A.
Tipton, C. M.
Date Acquired
August 22, 2013
Publication Date
April 1, 1993
Publication Information
Publication: Journal of applied physiology (Bethesda, Md. : 1985)
Volume: 74
Issue: 4
ISSN: 8750-7587
Subject Category
Aerospace Medicine
Funding Number(s)
CONTRACT_GRANT: HL-33782
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Cardiopulmonary
NASA Discipline Number 14-10
NASA Program Space Physiology and Countermeasures

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