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.
BACKGROUND
The role of the perception of breathing effort in the regulation of performance of maximal exercise remains unclear.


OBJECTIVE
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 (VO(2)max) = 69.9 (7.9) (mlO(2)/kg/min) performed two randomised maximal tests in a hyperbaric chamber breathing ambient air composed of either 35% O(2)/65% N(2) (nitrox) or 35% O(2)/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 (VO(2)) and minute ventilation (V(E)) 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 VO(2)max (4.96 (0.61) and 4.88 (0.65) l/min) or maximal V(E) (157 (24) and 163 (22) l/min). Between-trial variability in peak power output was less than either VO(2)max or maximal V(E).


CONCLUSIONS
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 V(E) with a concomitant reduction in VO(2) suggests an improved gas exchange and reduced O(2) cost of ventilation when breathing heliox.
Ansley
L
L
School of Life Sciences, Kingston University, Penrhyn Road, Kingston-upon-Thames, Surrey KT1 2EE, UK. l.ansley@kingston.ac.uk
Petersen
D
D
Thomas
A
A
St Clair Gibson
A
A
Robson-Ansley
P
P
Noakes
T D
TD
D000328:Adult; D015308:Anaerobic Threshold / Q000502:physiology; D000704:Analysis of Variance; D001642:Bicycling / Q000502:physiology*; D016552:Ergometry; D005080:Exercise Test / Q000379:methods; D006371:Helium / Q000008:administration & dosage*; D006801:Humans; D009584:Nitrogen / Q000008:administration & dosage*; D010100:Oxygen / Q000008:administration & dosage*; D010101:Oxygen Consumption / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012119:Respiration; D016037:Single-Blind Method
D006371:Helium; C041364:nitrox; C038949:heliox; D009584:Nitrogen; D010100:Oxygen