Document Detail


Smaller lungs in women affect exercise hyperpnea.
MedLine Citation:
PMID:  9609779     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
We subjected 29 healthy young women (age: 27 +/- 1 yr) with a wide range of fitness levels [maximal oxygen uptake (VO2 max): 57 +/- 6 ml . kg-1 . min-1; 35-70 ml . kg-1 . min-1] to a progressive treadmill running test. Our subjects had significantly smaller lung volumes and lower maximal expiratory flow rates, irrespective of fitness level, compared with predicted values for age- and height-matched men. The higher maximal workload in highly fit (VO2 max > 57 ml . kg-1 . min-1, n = 14) vs. less-fit (VO2 max < 56 ml . kg-1 . min-1, n = 15) women caused a higher maximal ventilation (VE) with increased tidal volume (VT) and breathing frequency (fb) at comparable maximal VT/vital capacity (VC). More expiratory flow limitation (EFL; 22 +/- 4% of VT) was also observed during heavy exercise in highly fit vs. less-fit women, causing higher end-expiratory and end-inspiratory lung volumes and greater usage of their maximum available ventilatory reserves. HeO2 (79% He-21% O2) vs. room air exercise trials were compared (with screens added to equalize external apparatus resistance). HeO2 increased maximal expiratory flow rates (20-38%) throughout the range of VC, which significantly reduced EFL during heavy exercise. When EFL was reduced with HeO2, VT, fb, and VE (+16 +/- 2 l/min) were significantly increased during maximal exercise. However, in the absence of EFL (during room air exercise), HeO2 had no effect on VE. We conclude that smaller lung volumes and maximal flow rates for women in general, and especially highly fit women, caused increased prevalence of EFL during heavy exercise, a relative hyperinflation, an increased reliance on fb, and a greater encroachment on the ventilatory "reserve." Consequently, VT and VE are mechanically constrained during maximal exercise in many fit women because the demand for high expiratory flow rates encroaches on the airways' maximum flow-volume envelope.
Authors:
S R McClaran; C A Harms; D F Pegelow; J A Dempsey
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Publication Detail:
Type:  Clinical Trial; Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  84     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  1998 Jun 
Date Detail:
Created Date:  1998-07-07     Completed Date:  1998-07-07     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1872-81     Citation Subset:  IM; S    
Affiliation:
John Rankin Laboratory of Pulmonary Medicine, Department of Preventive Medicine, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA.
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MeSH Terms
Descriptor/Qualifier:
Adolescent
Adult
Aerobiosis / physiology
Blood Gas Analysis
Blood Volume / physiology*
Body Height / physiology
Exercise / physiology*
Female
Humans
Hydrogen-Ion Concentration
Lactic Acid / blood
Lung / anatomy & histology*,  physiology*
Lung Volume Measurements
Peak Expiratory Flow Rate
Potassium / blood
Respiratory Function Tests
Vital Capacity / physiology
Grant Support
ID/Acronym/Agency:
HL-15469/HL/NHLBI NIH HHS
Chemical
Reg. No./Substance:
50-21-5/Lactic Acid; 7440-09-7/Potassium

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


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