Effects of Helium and 40% O<sub>2</sub> on Graded Exercise With Self-Contained Breathing Apparatus
Bibliographic record
Abstract
Maximal exercise performance is decreased when breathing from a self-contained breathing apparatus (SCBA), owing to a ventilatory limitation imposed by the increased expiratory resistance. To test the hypothesis that decreasing the density of the breathing gas would improve maximal exercise performance, we studied 15 men during four graded exercise tests with the SCBA. Participants breathed a different gas mixture during each test: normoxia (NOX; 21% O2, 79% N2), hyperoxia (HOX; 40% O2, 60% N2), normoxic helium (HE-OX; 21% O2, 79% He), and hyperoxic helium (HE-HOX; 40% O2, 60% He). Compared to NOX, power output at the ventilatory threshold and at maximal exercise significantly increased with both hyperoxic mixtures. Minute ventilation was increased at peak exercise with both helium mixtures, and maximal aerobic power (VO2max) was significantly increased by 12.9 +/- 5.6%, 10.2 +/- 6.3%, and 21.8 +/- 5.6% with HOX, HE-OX, and HE-HOX, respectively. At peak exercise, the expired breathing resistance imposed by the SCBA was significantly decreased with both helium mixtures, and perceived respiratory distress was lower with HE-HOX. The results show that HE-OX improved maximal exercise performance by minimizing the ventilation limitation. The performance-enhancing effect of HOX may be explained by increased arterial oxygen content. Moreover, HE-HOX appeared to combine the effects of helium and hyperoxia on VO2max.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".