Document Detail

The effect of hypoxia on pulmonary O2 uptake, leg blood flow and muscle deoxygenation during single-leg knee-extension exercise.
MedLine Citation:
PMID:  15123565     Owner:  NLM     Status:  MEDLINE    
The effect of hypoxic breathing on pulmonary O(2) uptake (VO(2p)), leg blood flow (LBF) and O(2) delivery and deoxygenation of the vastus lateralis muscle was examined during constant-load single-leg knee-extension exercise. Seven subjects (24 +/- 4 years; mean +/-s.d.) performed two transitions from unloaded to moderate-intensity exercise (21 W) under normoxic and hypoxic (P(ET)O(2)= 60 mmHg) conditions. Breath-by-breath VO(2p) and beat-by-beat femoral artery mean blood velocity (MBV) were measured by mass spectrometer and volume turbine and Doppler ultrasound (VingMed, CFM 750), respectively. Deoxy-(HHb), oxy-, and total haemoglobin/myoglobin were measured continuously by near-infrared spectroscopy (NIRS; Hamamatsu NIRO-300). VO(2p) data were filtered and averaged to 5 s bins at 20, 40, 60, 120, 180 and 300 s. MBV data were filtered and averaged to 2 s bins (1 contraction cycle). LBF was calculated for each contraction cycle and averaged to 5 s bins at 20, 40, 60, 120, 180 and 300 s. VO(2p) was significantly lower in hypoxia throughout the period of 20, 40, 60 and 120 s of the exercise on-transient. LBF (l min(-1)) was approximately 35% higher (P > 0.05) in hypoxia during the on-transient and steady-state of KE exercise, resulting in a similar leg O(2) delivery in hypoxia and normoxia. Local muscle deoxygenation (HHb) was similar in hypoxia and normoxia. These results suggest that factors other than O(2) delivery, possibly the diffusion of O(2,) were responsible for the lower O(2) uptake during the exercise on-transient in hypoxia.
Darren S DeLorey; Colin N Shaw; J Kevin Shoemaker; John M Kowalchuk; Donald H Paterson
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't     Date:  2004-03-16
Journal Detail:
Title:  Experimental physiology     Volume:  89     ISSN:  0958-0670     ISO Abbreviation:  Exp. Physiol.     Publication Date:  2004 May 
Date Detail:
Created Date:  2004-05-04     Completed Date:  2004-12-27     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  9002940     Medline TA:  Exp Physiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  293-302     Citation Subset:  IM    
Canadian Centre for Activity and Aging, School of Kinesiology, The University of Western Ontario, London, Ontario, Canada.
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MeSH Terms
Analysis of Variance
Anoxia / physiopathology*
Exercise Test / methods
Knee / blood supply,  physiology
Leg / blood supply*,  physiology*
Muscle, Skeletal / blood supply,  physiology*
Physical Exertion / physiology*
Pulmonary Gas Exchange / physiology
Pulmonary Ventilation / physiology*

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