The effect of breathing an ambient low-density, hyperoxic gas on the perceived effort of breathing and maximal performance of exercise in well-trained athletes. Issue 1 (24th October 2006)

• Record Type: Journal Article
• Authors: Ansley, L; Petersen, D; Thomas, A; St Clair Gibson, A; Robson-Ansley, P; Noakes, T D
• Is Part Of: British journal of sports medicine. Volume 41:Issue 1(2007)
• Page Start: 2
• Page End: 7
• Publication Date: 2006-10-24
• Subjects: ANOVA, analysis of variance -- COPD, chronic obstructive pulmonary disease -- CR10, Category-Ratio Scale -- FiO2, fractional inspired oxygen -- PAV, pressure-assisted ventilation -- RPE15, 15-point rating of perceived exertion; Sports medicine -- Periodicals; 617.1027
• DOI: 10.1136/bjsm.2006.026989
• Languages: English
• ISSNs: 0306-3674

Abstract

Abstract : Background: The role of the perception of breathing effort in the regulation of performance of maximal exercise remains unclear. Aims: To determine whether the perceived effort of ventilation is altered through substituting a less dense gas for normal ambient air and whether this substitution affects performance of maximal incremental exercise in trained athletes. Methods: Eight highly trained cyclists (mean SD) maximal oxygen consumption (VO2 max) = 69.9 (7.9) (mlO2 /kg/min) performed two randomised maximal tests in a hyperbaric chamber breathing ambient air composed of either 35% O2 /65% N2 (nitrox) or 35% O2 /65% He (heliox). A ramp protocol was used in which power output was incremented at 0.5 W/s. The trials were separated by at least 48 h. The perceived effort of breathing was obtained via Borg Category Ratio Scales at 3-min intervals and at fatigue. Oxygen consumption (VO2 ) and minute ventilation (VE ) were monitored continuously. Results: Breathing heliox did not change the sensation of dyspnoea: there were no differences between trials for the Borg scales at any time point. Exercise performance was not different between the nitrox and heliox trials (peak power output = 451 (58) and 453 (56) W), nor was VO2 max (4.96 (0.61) and 4.88 (0.65) l/min) or maximal VE (157 (24) and 163 (22) l/min). Between-trial variability in peak power output was less than either VO2 max or maximal VE . Conclusion: Breathing a less dense gas does not improve maximal performance of exercise or reduce the perception of breathing effort in highly trained athletes, although an attenuated submaximal tidal volume and VE with a concomitant reduction in VO2 suggests an improved gas exchange and reduced O2 cost of ventilation when breathing heliox.