THE THERMOPHYSIOLOGY OF UNCOMPENSABLE HEAT STRESS: INFLUENCE OF HYDRATION STATUS, FLUID REPLACEMENT, AEROBIC TRAINING, PHYSICAL FITNESS AND HEAT ACCLIMATION

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Authors
  1. Cheung, S.S.
Corporate Authors
Defence and Civil Inst of Environmental Medicine, Downsview ONT (CAN);Toronto Univ, Toronto ONT (CAN) Dept of Community Health
Abstract
The present research was developed to investigate the separate and interactive influences of hydration status, fluid replacement, short-term aerobic training, heat acclimation, and aerobic fitness during exercise in the heat. The research focused on an uncompensable heat stress environment, where the capacity for evaporative heat loss is less than the amount required to maintain thermal steady state. This was produced by either light (3.5 km-h 1(-), 0% grade, no wind; Studies 1-3) or heavy (4.8 km-h 1(-), 4% grade, no wind; Study 1) exercise in the heat (40C, 30% relative humidity) while wearing a multilayered clothing ensemble with a high insulative capacity and a low water vapour permeability. Study 1 investigated the influences of hydration status (euhydration versus hyophydration of 2.5% body mass), fluid replacement, and exercise intensity. Study 2 investigated the influences of short-term aerobic training and hydration status on unfit (LF) individuals. Study 3 investigated the influences of heat acclimation and hydration status on individuals of both LF and high fitnes (HF). Hyophydration resulted in significant increases in cardiovascular and thermal strain and a decrease in exercise tolerance regardless of other factors. Fluid replacement decreased heart rate (fc) and increased tolerance time (TT) during light exercise. TRUNCATED
Keywords
Work tolerance time;NBC clothing
Report Number
DCIEM-98-CR-01 — Contract Report
Date of publication
01 Jan 1998
Number of Pages
210
DSTKIM No
98-00521
CANDIS No
507515
Format(s):
Hardcopy;Document Image stored on Optical Disk

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