EFFECTS OF METABOLIC RATE AND AMBIENT VAPOUR PRESSURE ON HEAT STRAIN IN PROTECTIVE CLOTHING

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Authors
  1. McLellan, T.M.
  2. Pope, J.I.
  3. Cain, J.B.
  4. Cheung, S.S.
Corporate Authors
Defence and Civil Inst of Environmental Medicine, Downsview ONT (CAN)
Abstract
Studies have shown that variations in ambient water vapour pressure from 1.7 to 3.7 kPa have little effect on heat tolerance time at a metabolic rate above 450W while wearing protective clothing. With lighter exercise, where tolerance times exceed 60 min. variations in vapour pressure have a significant impact on evaporative heat loss and, therefore, heat tolerance. The present study has examined whether these findings extend to conditions with more extreme variations in vapour pressure. Twelve males performed light (l. 350W) and have (H. 500 W) exercise at 40C in a dry (D. 1.1 kPa) and humid (H.48 kPa) environment while wearing a semi-permeable nuclear, biological and chemical protective clothing ensemble (0.29m square x C 1(-) W 1(-) or 1.88 clo: Woodcock vapour permeability coefficient im = 0.33). Partitional calorimetry was used to determine the rate of heat storage (S) with evaporative heat loss from the skin (Esk) calculated from changes in dressed mass or the physical properties of the clothing and the vapour pressure gradient between the skin and the environment. Skin vapour pressure was predicted from measurements of water vapour pressure above the skin surface and in the clothing with humidity sensors coupled with thermistors. Final mean skin temperature (Tsk) was higher for the humid trials and averaged 37.4 (0.3) C. 38.9(0.4) C. 37.6 (0.5) C and 38.5 (0.4) C for LD, LH, HD and HH, respectively. TRUNCATED
Keywords
Endurance training
Report Number
DCIEM-96-RP-06 — Reprint; Research Paper
Date of publication
30 Apr 1996
Number of Pages
10
Reprinted from
Eur J Appl Physiol, vol 74; 1996, p 518-527
DSTKIM No
97-01240
CANDIS No
501517
Format(s):
Hardcopy;Document Image stored on Optical Disk

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