Document Detail

Effects of environmental heat stress (35 degrees C) with simulated air movement on the thermoregulatory responses during a 4-km cycling time trial.
MedLine Citation:
PMID:  18651369     Owner:  NLM     Status:  MEDLINE    
The aim of the present investigation was to examine the influence of environmental heat stress (35 degrees C) on 4-km cycling time trial performance using simulated environmental conditions and facing air velocities that closely reflect competitive situations. Nine competitive cyclists (age 34 +/- 5 years, maximal oxygen uptake 61.7 +/- 8.6 ml . kg (-1) . min (-1)) completed a simulated 4-km cycling time trial in laboratory ambient temperatures (dry bulb temperatures) of 35 degrees C and 13 degrees C (relative humidity 60 %, air velocity 5.6 m/s). Mean performance time was reduced in 35 degrees C (390.1 +/- 19.6 s) compared to 13 degrees C (382.8 +/- 18.2 s) (95 % CI of difference = 4.0 to 10.6 s; p < 0.01). This was consistent with a decline in mean power output throughout the duration of exercise in 35 degrees C compared with 13 degrees C (p < 0.01). Mean skin temperature and mean body temperatures were elevated at rest and throughout the duration of exercise in 35 degrees C (p < 0.01). A higher level of muscle temperature was also observed at the onset and cessation of exercise in 35 degrees C (p < 0.01). The rate of heat storage (35 degrees C, 413.6 +/- 130.8 W . m (-2); 13 degrees C, 153.1 +/- 112.5 W . m (-2)) representative of the entire 4-km time trial was greater in the heat (p < 0.01). When expressed per kilometre, however, difference in the rate of heat storage between conditions declined during the final kilometre of exercise (p = 0.06). We conclude that the current decrements in self-selected work-rate in the heat are mediated to some extent through afferent feedback arising from changes in heat storage at rest and during the early stages of exercise which serve to regulate the subsequent exercise intensity in attempt to preserve thermal homeostasis.
N Altareki; B Drust; G Atkinson; T Cable; W Gregson
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Publication Detail:
Type:  Journal Article     Date:  2008-07-23
Journal Detail:
Title:  International journal of sports medicine     Volume:  30     ISSN:  0172-4622     ISO Abbreviation:  Int J Sports Med     Publication Date:  2009 Jan 
Date Detail:
Created Date:  2008-12-16     Completed Date:  2009-03-05     Revised Date:  2009-04-16    
Medline Journal Info:
Nlm Unique ID:  8008349     Medline TA:  Int J Sports Med     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  9-15     Citation Subset:  IM    
Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom.
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MeSH Terms
Air Movements
Bicycling / physiology*
Body Temperature
Body Temperature Regulation / physiology*
Exercise Test / methods
Hot Temperature / adverse effects*
Oxygen Consumption / physiology
Skin Temperature
Stress, Physiological / physiology*
Time Factors
Comment In:
Int J Sports Med. 2009 Apr;30(4):307; author reply 308-9   [PMID:  19322742 ]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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