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Quantification of head sweating during rest and exercise in the heat.
MedLine Citation:
PMID:  22941031     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
The head's capacity for evaporative heat loss is important for design of protective helmets for use in hot environments. This study quantified head sweating rate (m (sw)) in eight males during rest and exercise at three metabolic rates (338 ± 36, 481 ± 24, 622 ± 28 W) in hot-dry (HD: 45 °C, 21 % RH) and hot-wet (HW: 35 °C, 69 % RH) conditions (matched at 31.6 °C WBGT), which were counterbalanced. Heads were shaved, and surface area was (458 ± 61 cm(2)) measured by 3D scanner. For measurement of head m (sw), dry air was passed through a sealed helmet, whereas for forearm m (sw) a capsule (15.9 cm(2)) was ventilated with ambient air. Evaporation rate was determined from the increase in vapor pressure in the exiting air. Whole-body sweat loss was calculated from the change in nude weight plus fluid intake and corrected for respiratory fluid losses. Head m (sw) increased (p = 0.001) with metabolic rate, and was lower (p = 0.018) in HD (0.4 ± 0.2 mg cm(-2) min(-1) at rest to 1.1 ± 0.6 mg cm(-2) min(-1) at 622 W), compared to HW (0.5 ± 0.3-1.4 ± 0.8 mg cm(-2) min(-1)). Forearm m (sw) increased (p < 0.001) with metabolic rate, but was higher (p = 0.002) in HD (0.4 ± 0.3-1.4 ± 0.7 mg cm(-2) min(-1)) than HW (0.1 ± 0.1-1.1 ± 0.3 mg cm(-2) min(-1)). Whole-body sweat loss was not significantly different (p = 0.06) between HD (647 ± 139 g m(-2) h(-1)) and HW (528 ± 189 g m(-2) h(-1)). This study demonstrates the importance of the head for evaporative heat loss, particularly for populations who wear protective clothing which can impair vapor transfer from the skin.
Authors:
Catherine O'Brien; Bruce S Cadarette
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-9-1
Journal Detail:
Title:  European journal of applied physiology     Volume:  -     ISSN:  1439-6327     ISO Abbreviation:  Eur. J. Appl. Physiol.     Publication Date:  2012 Sep 
Date Detail:
Created Date:  2012-9-3     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100954790     Medline TA:  Eur J Appl Physiol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Kansas Street, Building 42, Natick, MA, 01760-5007, USA, kate.obrien@us.army.mil.
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