| Aerobic performance is degraded, despite modest hyperthermia, in hot environments. | |
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MedLine Citation:
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PMID: 20010120 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Environmental heat stress degrades aerobic performance; however, little research has focused on performance when the selected task elicits modest elevations in core body temperature (<38.5 degrees C). PURPOSE: To determine the effect of environmental heat stress, with modest hyperthermia, on aerobic performance and pacing strategies. METHODS: After a 30-min cycling preload at 50% VO2peak, eight euhydrated men performed a 15-min time trial on a cycle ergometer in temperate (TEMP; 21 degrees C, 50% RH) and hot (HOT; 40 degrees C, 25% RH) environments. Core and skin temperature (Tc and Tsk, respectively) and HR were continuously monitored. Performance was assessed by the total work (kJ) completed in 15 min. Pacing was quantified by comparing the percent difference in actual work performed in each of five 3-min blocks normalized to the mean work performed per 3-min block. Pace over the final 2 min was compared with the average pace from minutes 0 to 13 for end spurt analysis. RESULTS: Tc and HR rose continually throughout both time trials. Peak Tc remained modestly elevated in both environments [mean (range): HOT = 38.20 degrees C (37.97-38.42 degrees C); TEMP = 38.11 degrees C (38.07-38.24 degrees C)], whereas Tsk was higher in HOT (36.19 +/- 0.40 degrees C vs 31.14 +/- 1.14 degrees C), and final HR reached approximately 95% of age-predicted maximum in both environments. Total work performed in HOT (147.7 +/- 23.9 kJ) was approximately 17% less (P < 0.05) than TEMP (177.0 +/- 25.0 kJ). Pace was evenly maintained in TEMP, but in HOT, volunteers were unable to maintain initial pace, slowing progressively over time. A significant end spurt was produced in both environments. CONCLUSIONS: During a brief aerobic exercise time trial where excessive hyperthermia is avoided, total work is significantly reduced by heat stress because of a gradual slowing of pace over time. These findings demonstrate how aerobic exercise performance degrades in hot environments without marked hyperthermia. |
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Authors:
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Brett R Ely; Samuel N Cheuvront; Robert W Kenefick; Michael N Sawka |
Publication Detail:
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Type: Journal Article; Randomized Controlled Trial |
Journal Detail:
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Title: Medicine and science in sports and exercise Volume: 42 ISSN: 1530-0315 ISO Abbreviation: Med Sci Sports Exerc Publication Date: 2010 Jan |
Date Detail:
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Created Date: 2009-12-17 Completed Date: 2010-03-05 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: 135-41 Citation Subset: IM; S |
Affiliation:
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Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, MA 01760, USA. brett.ely@us.army.mil |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Analysis of Variance Athletic Performance* Body Temperature / physiology* Environment Fever / physiopathology* Heat Stress Disorders / physiopathology* Hot Temperature* Humans Male Monitoring, Physiologic Oxygen Consumption / physiology Young Adult |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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