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Exercise thermoregulation after 6 h of chair rest, 6 degrees head-down bed-rest, and water immersion deconditioning in menThe purpose was to investigate the mechanism for the excessive exercise hyperthermia following deconditioning (reduction of physical fitness). Rectal (Tre) and mean skin (Tsk) temperatures and thermoregulatory responses were measured in six men [mean (SD) age, 32 (6) years; mass, 78.26 (5.80) kg; surface area, 1.95 (0.11) m2; maximum oxygen uptake (VO2max), 48 (6) ml.min-1.kg-1; whilst supine in air at dry bulb temperature 23.2 (0.6) degree C, relative humidity 31.1 (11.1)% and air speed 5.6 (0.1) m.min-1] during 70 min of leg cycle exercise [51 (4)% VO2max] in ambulatory control (AC), or following 6 h of chair rest (CR), 6 degree head-down bed rest (BR), and 20 degree (WI20) and 80 degree (WI80) foot-down water immersion [water temperature, 35.0 (0.1) degree C]. Compared with the AC exercise delta Tre [mean (SD) 0.77 (0.13) degree C (*P < 0.05), after WI80 0.96 (0.13) degree C*, and after WI20 1.03 (0.09) degree C*. All Tsk responded similarly to exercise: they decreased (NS) by 0.5-0.7 degree C in minutes 4-8 and equilibrated at +0.1 to +0.5 degree C at 60-70. Skin heat conductance was not different among the five conditions (range = 147-159 kJ.m-2.h-1.degree C-1). Results from an intercorrelation matrix suggested that total body sweat rate was more closely related to Tre at 70 min (Tre70) than limb sweat rate or blood flow. Only 36% of the variability in Tre70 could be accounted for by total sweating, and less than 10% from total body dehydration. It would appear that multiple factors are involved which may include change in sensitivity of thermo- and osmoreceptors.
Document ID
20040173303
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Greenleaf, J. E.
(NASA Ames Research Center Moffett Field, CA United States)
Hutchinson, T.
Shaffer-Bailey, M.
Looft-Wilson, R.
Date Acquired
August 22, 2013
Publication Date
January 1, 1996
Publication Information
Publication: European journal of applied physiology and occupational physiology
Volume: 72
Issue: 4
ISSN: 0301-5548
Subject Category
Aerospace Medicine
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Regulatory Physiology
Controlled Clinical Trial
Clinical Trial
NASA Center ARC

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