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Prolonged head-down tilt exposure reduces maximal cutaneous vasodilator and sweating capacity in humansCutaneous vasodilation and sweat rate are reduced during a thermal challenge after simulated and actual microgravity exposure. The effects of microgravity exposure on cutaneous vasodilator capacity and on sweat gland function are unknown. The purpose of this study was to test the hypothesis that simulated microgravity exposure, using the 6 degrees head-down tilt (HDT) bed rest model, reduces maximal forearm cutaneous vascular conductance (FVC) and sweat gland function and that exercise during HDT preserves these responses. To test these hypotheses, 20 subjects were exposed to 14 days of strict HDT bed rest. Twelve of those subjects exercised (supine cycle ergometry) at 75% of pre-bed rest heart rate maximum for 90 min/day throughout HDT bed rest. Before and after HDT bed rest, maximal FVC was measured, via plethysmography, by heating the entire forearm to 42 degrees C for 45 min. Sweat gland function was assessed by administering 1 x 10(-6) to 2 M acetylcholine (9 doses) via intradermal microdialysis while simultaneously monitoring sweat rate over the microdialysis membranes. In the nonexercise group, maximal FVC and maximal stimulated sweat rate were significantly reduced after HDT bed rest. In contrast, these responses were unchanged in the exercise group. These data suggest that 14 days of simulated microgravity exposure, using the HDT bed rest model, reduces cutaneous vasodilator and sweating capacity, whereas aerobic exercise training during HDT bed rest preserves these responses.
Document ID
Document Type
Reprint (Version printed in journal)
Crandall, C. G.
(Institute for Exercise and Environmental Medicine at Presbyterian Hospital of Dallas Dallas, Texas 75231, United States)
Shibasaki, M.
Wilson, T. E.
Cui, J.
Levine, B. D.
Date Acquired
August 21, 2013
Publication Date
June 1, 2003
Publication Information
Publication: Journal of applied physiology (Bethesda, Md. : 1985)
Volume: 94
Issue: 6
ISSN: 8750-7587
Subject Category
Aerospace Medicine
Funding Number(s)
Distribution Limits
Clinical Trial
Randomized Controlled Trial
Non-NASA Center
NASA Discipline Cardiopulmonary

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