| Skin temperature modifies the impact of hypohydration on aerobic performance. | |
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MedLine Citation:
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PMID: 20378704 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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This study determined the effects of hypohydration on aerobic performance in compensable [evaporative cooling requirement (E(req)) < maximal evaporative cooling (E(max))] conditions of 10 degrees C [7 degrees C wet bulb globe temperature (WBGT)], 20 degrees C (16 degrees C WBGT), 30 degrees C (22 degrees C WBGT), and 40 degrees C (27 degrees C WBGT) ambient temperature (T(a)). Our hypothesis was that 4% hypohydration would impair aerobic performance to a greater extent with increasing heat stress. Thirty-two men [22 +/- 4 yr old, 45 +/- 8 ml.kg(-1).min(-1) peak O(2) uptake (Vo(2 peak))] were divided into four matched cohorts (n = 8) and tested at one of four T(a) in euhydrated (EU) and hypohydrated (HYPO, -4% body mass) conditions. Subjects completed 30 min of preload exercise (cycle ergometer, 50% Vo(2 peak)) followed by a 15 min self-paced time trial. Time-trial performance (total work, change from EU) was -3% (P = 0.1), -5% (P = 0.06), -12% (P < 0.05), and -23% (P < 0.05) in 10 degrees C, 20 degrees C, 30 degrees C, and 40 degrees C T(a), respectively. During preload exercise, skin temperature (T(sk)) increased by approximately 4 degrees C per 10 degrees C T(a), while core (rectal) temperature (T(re)) values were similar within EU and HYPO conditions across all T(a). A significant relationship (P < 0.05, r = 0.61) was found between T(sk) and the percent decrement in time-trial performance. During preload exercise, hypohydration generally blunted the increases in cardiac output and blood pressure while reducing blood volume over time in 30 degrees C and 40 degrees C T(a). Our conclusions are as follows: 1) hypohydration degrades aerobic performance to a greater extent with increasing heat stress; 2) when T(sk) is >29 degrees C, 4% hypohydration degrades aerobic performance by approximately 1.6% for each additional 1 degrees C T(sk); and 3) cardiovascular strain from high skin blood flow requirements combined with blood volume reductions induced by hypohydration is an important contributor to impaired performance. |
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Authors:
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R W Kenefick; S N Cheuvront; L J Palombo; B R Ely; M N Sawka |
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Publication Detail:
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Type: Journal Article Date: 2010-04-08 |
Journal Detail:
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Title: Journal of applied physiology (Bethesda, Md. : 1985) Volume: 109 ISSN: 1522-1601 ISO Abbreviation: J. Appl. Physiol. Publication Date: 2010 Jul |
Date Detail:
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Created Date: 2010-06-30 Completed Date: 2010-10-14 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 8502536 Medline TA: J Appl Physiol Country: United States |
Other Details:
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Languages: eng Pagination: 79-86 Citation Subset: IM |
Affiliation:
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US Army Research Institute of Environmental Medicine, Thermal and Mountain Medicine Division, Kansas St., Natick, MA 01760, USA. Robert.Kenefick@us.army.mil |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Adult Blood Pressure / physiology Blood Volume / physiology Body Temperature Regulation / physiology Cardiac Output / physiology Cohort Studies Dehydration / physiopathology* Exercise / physiology* Exercise Test Heart Rate / physiology Heat-Shock Response / physiology* Hot Temperature Humans Male Oxygen Consumption / physiology Skin / blood supply Skin Temperature / physiology* Young Adult |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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