Document Detail

Elevations in core and muscle temperature impairs repeated sprint performance.
MedLine Citation:
PMID:  15676059     Owner:  NLM     Status:  MEDLINE    
AIM: The present study investigated the effects of hyperthermia on intermittent exercise and repeated sprint performance. METHODS: Seven men completed 40 min of intermittent cycling comprising of 15 s exercise (306 +/- 22 W) and 15 s rest periods (0 W) followed by 5 x 15 s maximal sprints on a cycle ergometer in normal (approximately 20 degrees C, control) and hot (40 degrees C, hyperthermia) environments. RESULTS: Completion of the intermittent protocol in the heat elevated core and muscle temperatures (39.5 +/- 0.2 degrees C; 40.2 +/- 0.4 degrees C), heart rate (178 +/- 11 beats min(-1)), rating of perceived exertion (RPE) (18 +/- 1) and noradrenaline (38.9 +/- 13.2 micromol l(-1)) (all P < 0.05). During the first sprint (n = 6), both peak and mean power output were similar across the environmental conditions. However, mean power over the last four sprints declined to a larger extent during hyperthermia compared with the control trial (P < 0.05). Consequently, average mean power output during the five sprints was lower in hyperthermia (558.0 +/- 146.9 W) compared with control (617.5 +/- 122.6 W; P < 0.05). Power output during the repeated sprints was reduced by hyperthermia despite an elevated muscle temperature that should promote sprint performance. Venous plasma potassium concentrations (H; 5.3 +/- 0.8 mmol l(-1) vs. C; 6.3 +/- 1.0 mmol l(-1), P = 0.06) and muscle lactate levels (H; 76.6 +/- 24.3 mmol kg(-1) dry weight vs. C; 108.8 +/- 20.1 mmol kg(-1) dry weight) were lower following the hyperthermic sprints compared to control. CONCLUSION: Although an elevated muscle temperature is expected to promote sprint performance, power output during the repeated sprints was reduced by hyperthermia. The impaired performance does not seem to relate to the accumulation of recognized metabolic fatigue agents and we, therefore, suggest that it may relate to the influence of high core temperature on the function of the central nervous system.
B Drust; P Rasmussen; M Mohr; B Nielsen; L Nybo
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Acta physiologica Scandinavica     Volume:  183     ISSN:  0001-6772     ISO Abbreviation:  Acta Physiol. Scand.     Publication Date:  2005 Feb 
Date Detail:
Created Date:  2005-01-28     Completed Date:  2005-03-24     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0370362     Medline TA:  Acta Physiol Scand     Country:  England    
Other Details:
Languages:  eng     Pagination:  181-90     Citation Subset:  IM    
Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK.
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MeSH Terms
Blood Glucose / analysis
Body Temperature / physiology*
Epinephrine / blood
Ergometry / methods
Exercise / physiology*
Glycogen / metabolism
Hand Strength / physiology
Heart Rate / physiology
Lactates / analysis
Muscle, Skeletal / metabolism,  physiology*
Norepinephrine / blood
Oxygen Consumption / physiology
Potassium / blood
Reg. No./Substance:
0/Blood Glucose; 0/Lactates; 51-41-2/Norepinephrine; 51-43-4/Epinephrine; 7440-09-7/Potassium; 9005-79-2/Glycogen

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