Document Detail

Cardiorespiratory dynamics to hypoxia at the onset of cycling exercise in male endurance subjects.
MedLine Citation:
PMID:  16208284     Owner:  NLM     Status:  MEDLINE    
AIM: It is well established that altering O2 delivering to contracting skeletal muscle affects human performance. In this respect, a reduced O2 supply (e.g., hypoxia) increases the rate of muscle fatigue. This study aimed to determine the effects of moderate hypoxia and exercise intensity on oxygen uptake (VO2) and cardiac output (CO) kinetics during moderate [below the ventilatory threshold (VT)] and heavy (above VT) constant work rate cycling exercises. METHODS: Eight trained males (age, mean+/-SD, 22+/-3 years; height 182+/-5 cm; body mass 71+/-12 kg) performed at the same relative intensity in normoxic (FIO2=0.21) and hypoxic (FIO2=0.13) conditions moderate and heavy exercises during which pulmonary gas exchange was determined breath-by-breath and CO was monitored beat-by-beat with Doppler echocardiography. RESULTS: The rate of increase (t63%, corresponding to time constant and time delay of a monoexponential response) in CO was significantly faster than that of VO2 in 3 out of 4 experimental conditions (p<0.05). Moreover VO2 kinetics were significantly slowed by hypoxia and speeded by exercise intensity, while CO responses were unaffected by such conditions. A slowed CO response was apparent in hypoxia compared to normoxia (p>0.05) in heavy exercise. CONCLUSIONS: These results suggest an absence of coupling between CO and VO2 kinetics, and that cardiorespiratory O2 delivery is likely different at exercise onset as a function of exercise intensity and FIO2.
S Perrey; C Cleuziou; A M Lecoq; D Courteix; P Obert
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  The Journal of sports medicine and physical fitness     Volume:  45     ISSN:  0022-4707     ISO Abbreviation:  J Sports Med Phys Fitness     Publication Date:  2005 Mar 
Date Detail:
Created Date:  2005-10-06     Completed Date:  2006-10-13     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0376337     Medline TA:  J Sports Med Phys Fitness     Country:  Italy    
Other Details:
Languages:  eng     Pagination:  7-12     Citation Subset:  IM    
Laboratoire Efficience et Déficience Motrices EA 2991, Montpellier, France.
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MeSH Terms
Anaerobic Threshold / physiology
Analysis of Variance
Anoxia / physiopathology*
Bicycling / physiology*
Cardiac Output
Echocardiography, Doppler
Least-Squares Analysis
Muscle Fatigue / physiology
Oxygen Consumption / physiology*
Physical Endurance / physiology*
Pulmonary Gas Exchange / physiology

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