The effect of breathing an ambient low-density, hyperoxic gas on the perceived effort of breathing and maximal exercise performance in well-trained athletes

Les Ansley ^1*, David Petersen ², Alan Thomas ³, Alan St Clair Gibson ², Paula Robson-Ansley ⁴ and Timothy David Noakes ²

¹ Kingston University, United Kingdom
² University of Cape Town, South Africa
³ National Hyperbarics, South Africa
⁴ University of Portsmouth, United Kingdom

^* To whom correspondence should be addressed. E-mail: les{at}ansleyfamily.com.

Accepted 9 October 2006

Abstract

The role of the perception of breathing effort, in the regulation of maximal exercise performance, remains unclear. This study attempts 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. Eight highly trained cyclists (VO2max = 69.9±7.9 mLO2.kg-1.min-1) 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-1. The trials were separated by at least 48 hours. 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. 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 PO = 451±58 W and 453±56 W) nor was maximal VO2 (4.96±0.61 L.min-1 and 4.88±0.65 L.min-1) or maximal VE (157±24 L.min-1 and 163±22 L.min-1). Between trial variability in peak PO was less than either VO2max or maximal VE. Breathing a less dense gas does not improve maximal exercise performance 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.

Key Words: fatigue, muscle contraction, perception, respiration, work

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