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This Article Full Text Full Text (PDF) All Versions of this Article: 581/3/1309    most recent jphysiol.2006.126466v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Guenette, J. A. Articles by Sheel, A. W. Search for Related Content PubMed PubMed Citation Articles by Guenette, J. A. Articles by Sheel, A. W. Related Collections Integrative

¹ School of Human Kinetics
² Faculty of Medicine, The University of British Columbia, Vancouver, British Columbia, Canada

The purpose of this study was to compare the mechanics of breathing including the measurement of expiratory flow limitation, end-expiratory lung volume, end-inspiratory lung volume, and the work of breathing in endurance-trained men (n = 8) and women (n = 10) during cycle exercise. Expiratory flow limitation was assessed by applying a negative expiratory pressure at the mouth. End-expiratory lung volume and end-inspiratory lung volume were determined by having subjects perform inspiratory capacity manoeuvres. Transpulmonary pressure, taken as the difference between oesophageal and airway opening pressure, was plotted against volume and integrated to determine the work of breathing. Expiratory flow limitation occurred in nine females (90%) and three males (43%) during the final stage of exercise. Females had a higher relative end-expiratory lung volume (42 ± 8 versus 35 ± 5% forced vital capacity (FVC)) and end-inspiratory lung volume (88 ± 5 versus 82 ± 7% FVC) compared to males at maximal exercise (P < 0.05). Women also had a higher work of breathing compared to men across a range of ventilations. On average, women had a work of breathing that was twice that of men at ventilations above 90 l min^–1. These data suggest that expiratory flow limitation may be more common in females and that they experience greater relative increases in end-expiratory lung volume and end-inspiratory lung volume at maximal exercise compared to males. The higher work of breathing in women is probably attributed to their smaller lung volumes and smaller diameter airways. Collectively, these findings suggest that women utilize a greater majority of their ventilatory reserve compared to men and this is associated with a higher cost of breathing.

(Received 8 January 2007; accepted after revision 30 March 2007; first published online 5 April 2007)
Corresponding author A. W. Sheel: Health and Integrative Physiology Laboratory, University of British Columbia, 6108 Thunderbird Blvd, Vancouver, BC, Canada V6T-1Z3. Email: bill.sheel{at}ubc.ca