Document Detail

A method for estimating bicarbonate buffering of lactic acid during constant work rate exercise.
MedLine Citation:
PMID:  7851366     Owner:  NLM     Status:  MEDLINE    
A method to estimate the CO2 derived from buffering lactic acid by HCO3- during constant work rate exercise is described. It utilizes the simultaneous continuous measurement of O2 uptake (VO2) and CO2 output (VCO2), and the muscle respiratory quotient (RQm). The CO2 generated from aerobic metabolism of the contracting skeletal muscles was estimated from the product of the exercise-induced increase in VO2 and RQm calculated from gas exchange. By starting exercise from unloaded cycling, the increase in CO2 stores, not accompanied by a simultaneous decrease in O2 stores, was minimized. The total CO2 and aerobic CO2 outputs and, by difference, the millimoles (mmol) of lactate buffered by HCO3- (corrected for hyperventilation) were estimated. To test this method, ten normal subjects performed cycling exercise at each of two work rates for 6 min, one below the lactic acidosis threshold (LAT) (50 W for all subjects), and the other above the LAT, midway between LAT and peak VO2 [mean (SD), 144 (48) W]. Hyperventilation had a small effect on the calculation of mmol lactate buffered by HCO3- [6.5 (2.3)% at 6 min in four subjects who hyperventilated]. The mmol of buffer CO2 at 6 min of exercise was highly correlated (r = 0.925, P < 0.001) with the increase in venous blood lactate sampled 2 min into recovery (coefficient of variation = +/- 0.9 mmol.l-1). The reproducibility between tests done on different days was good. We conclude that the rate of release of CO2 from HCO3- can be estimated from the continuous analysis of simultaneously measured VCO2, VO2, and an estimate of muscle substrate.
Y Y Zhang; K E Sietsema; C S Sullivan; K Wasserman
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  European journal of applied physiology and occupational physiology     Volume:  69     ISSN:  0301-5548     ISO Abbreviation:  Eur J Appl Physiol Occup Physiol     Publication Date:  1994  
Date Detail:
Created Date:  1995-03-13     Completed Date:  1995-03-13     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0410266     Medline TA:  Eur J Appl Physiol Occup Physiol     Country:  GERMANY    
Other Details:
Languages:  eng     Pagination:  309-15     Citation Subset:  IM; S    
Department of Medicine, Harbor-UCLA Medical Center, Torrance 90509.
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MeSH Terms
Bicarbonates / blood,  metabolism*
Carbon Dioxide / metabolism*
Exercise Test
Heart Rate
Lactates / blood,  metabolism*
Lactic Acid
Middle Aged
Muscle, Skeletal / metabolism*
Oxygen Consumption
Physical Exertion / physiology*
Pulmonary Gas Exchange
Reg. No./Substance:
0/Bicarbonates; 0/Buffers; 0/Lactates; 124-38-9/Carbon Dioxide; 50-21-5/Lactic Acid

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

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