| Variables | Air | Normoxic heliox | 100% oxygen | ||
| Exhaustion | Isotime¶ | Exhaustion | Isotime¶ | Exhaustion | |
| Endurance time s | 394±35 | 637±46 | 670±43 | ||
| Pa,O2 mmHg | 67±4 | 69±4 | 68±3 | 540±14*,+ | 533±23*,+ |
| Pa,CO2 mmHg | 48±2 | 45±2 | 44±2* | 51±3*,+ | 52±3.0*,+ |
| Sa,O2 % | 89±2 | 91±2* | 91±2* | 99±1*,+ | 99±1*,+ |
| pH | 7.32±0.03 | 7.33±0.02 | 7.33±0.02 | 7.30±0.05*,+ | 7.30±0.03*,+ |
| Borg dyspnoea scores | 7.4±2.0 | 5.7±1.8* | 6.7±1.5 | 4.9±1.0* | 6.3±1.3 |
| Borg leg effort scores | 5.8±2.3 | 5.3±2.1 | 5.9±2.3 | 4.4±1.5* | 5.8±2.2 |
Data are presented as mean±sem for 12 subjects. Pa,O2: arterial oxygen tension; Pa,CO2: arterial carbon dioxide tension; Sa,O2: arterial oxygen saturation. #: peak work rate relates to the preliminary incremental test; ¶: obtained on heliox and 100% oxygen at the same time as at exhaustion on room air. *: p<0.05 versus exhaustion in room air; +: p<0.05 versus normoxic heliox at the same time-point of exercise.