HEAT ACCLIMATION, AEROBIC FITNESS, AND HYDRATION EFFECTS ON TOLERANCE DURING UNCOMPENSABLE HEAT STRESS

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Authors
  1. Cheung, S.S.
  2. McLellan, T.M.
Corporate Authors
Defence and Civil Inst of Environmental Medicine, Downsview ONT (CAN)
Abstract
The purpose of the present study was to determine the separate and combined effects of aerobic fitness, short-term heat acclimation, and hypohydration on tolerance during light exercise while wearing nuclear, biological, and chemical protective clothing in the heat (40C, 30% relative humidity). Men who were moderately fit (MF); <50 ml.kg 1(-).min 1 (-) maximal O2 consumption; n = 7) and highly fit ((HF); >55 ml.kg 1 (-) min 1(-) maximal O2 consumption; n = 81 were tested while they were euhydrated or hypohydrated by approximates to 2.5% of boyd mass through exercise and fluid restriciton the day preceding the trials. Tests were conducted before and after 2 wk of daily heat acclimation (1-h treadmill exercise at 40C, 30% relative humidity, while wearing the nuclear, biological, and chemical protection clothing). Heat acclimation increased sweat rate and decreased skin temperture and rectal temperature (Tre) in HF subjects but had no effect on tolerance time (TT). MF subjects increased sweat rate but did not alter heart rate, Tre, or TT. In both MF and HF groups, hypohydration significantly increased Tre and heart rate and decreased the respiratory exchange ratio and the TT regardless of acclimation state. TRUNCATED
Keywords
Acclimatisation;Acclimation;Adaption (physiology);Endurance (physiology);Thermal homeostasis;Temperature regulation;Hypohydration
Report Number
DCIEM-97-P-35 — Contractor Report
Date of publication
01 Feb 1997
Number of Pages
9
Reprinted from
American Physiological Society, 1998, p 1731-1739
DSTKIM No
98-01434
CANDIS No
508217
Format(s):
Hardcopy;Document Image stored on Optical Disk

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