| Prior heat stress: effect on subsequent 15-min time trial performance in the heat. | |
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MedLine Citation:
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PMID: 19461533 Owner: NLM Status: In-Process |
Abstract/OtherAbstract:
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The impact of prior heat stress on subsequent aerobic exercise-heat performance has not been studied. PURPOSE: To determine whether prior heat stress degrades subsequent aerobic exercise performance in the heat. METHODS: Eighteen nonheat acclimated males were trained (four practice trials) on an aerobic exercise performance test in 22 degrees C and then divided into two (n = 8) groups. One group (EUHPH; (.)VO2peak = 44 +/- 7 mL x kg x min(-1)) was tested after 90 min of recovery (in 22 degrees C) from 3 h of intermittent light-intensity (<30% (.)VO2peak) exercise-heat (50 degrees C) stress, where sweat losses were matched with fluid intake (3.5 +/- 0.5 L) to maintain euhydration. The other group (EUH; (.)VO2peak = 45 +/- 5 mL x kg x min(-1)) was tested while euhydrated without prior exercise-heat stress. Aerobic performance was determined from a 30-min cycling preload (50% (.)VO2peak) followed by a 15-min time trial in 40 degrees C. Total work during the 15-min performance time trial in EUH and EUHPH was compared, as were the percent changes from the best practice trials. RESULTS: Volunteers were euhydrated (plasma osmolality < 290 mOsm x kg(-1)) and normothermic before each exercise-heat trial. Heart rate and core temperature were not different (P > 0.05) between groups at any time point during exercise. Total work was not different (P > 0.05) at baseline or between EUH (150.5 +/- 28.3 kJ; 2.0 +/- 0.3 kJ x kg(-1)) and EUHPH (160.3 +/- 24.0 kJ; 1.8 +/- 0.2 kJ x kg(-1)). The percent change in total work relative to baseline was not different (P > 0.05) between EUH (-18.7% +/- 9.2%) and EUHPH (-15.0% +/- 7.8%). CONCLUSIONS: If hydration and body temperatures recover, prior exercise-heat stress does not result in a greater degradation in aerobic time trial performance in the heat compared with heat exposure alone. |
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Authors:
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Robert W Kenefick; Brett R Ely; Samuel N Cheuvront; Laura J Palombo; Daniel A Goodman; Michael N Sawka |
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Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: Medicine and science in sports and exercise Volume: 41 ISSN: 1530-0315 ISO Abbreviation: Med Sci Sports Exerc Publication Date: 2009 Jun |
Date Detail:
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Created Date: 2009-05-25 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 8005433 Medline TA: Med Sci Sports Exerc Country: United States |
Other Details:
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Languages: eng Pagination: 1311-6 Citation Subset: IM; S |
Affiliation:
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US Army Research Institute of Environmental Medicine, Natick, MA 01760, USA. Robert.Kenefick@us.army.mil |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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