Cerebral oxygen extraction across different exercise intensities: Role of arterial PCO2${P_{{\mathrm{C}}{{\mathrm{O}}_2}}}$
Bibliographic record
Abstract
Abstract Stability in cerebral oxygen extraction fraction (OEF) is typically determined by alterations in cerebral blood flow (CBF). At rest, arterial partial pressure of carbon dioxide () and OEF exhibit a strong inverse relationship owing to the powerful influence of on cerebral resistance, CBF and therefore oxygen delivery; however, it is unclear whether this relationship also exists during exercise, especially when supramaximal, during which marked hyperventilation‐induced reductions in induce cerebrovascular vasoconstriction and lower CBF. We determined whether: (1) supramaximal exercise yields the largest change in OEF versus lower intensities, correlated with reductions in ; and (2) declines in (independent of exercise) determine changes in OEF. Blood was sampled from the brachial/radial artery and internal jugular vein during: (1) 60 min, 34% maximal O 2 uptake (SUB; n = six males, six females); (2) 4 min, 90% maximal O 2 uptake (MAX; n = six males, six females); (3) 1−2 min of high‐intensity sprinting, ∼110% maximal O 2 uptake (HIS; n = six males, five females); and (4) resting hyperventilation‐induced hypocapnia (HYPO; n = six males, five females). OEF was calculated as: [ The ΔOEF was greatest during HIS [estimated marginal mean: 15.6% (95% confidence interval: 12.4, 18.8)] and HYPO [17.7% (14.5, 20.9)] compared with SUB [−0.9% (−4.0, 2.1); p < 0.0001 vs. HIS and vs. HYPO] and MAX [2.5% (−0.5, 5.6); p < 0.0001 vs. HIS and vs. HYPO]. Reductions in were greatest in HIS [−12.9 mmHg (−14.6, −11.2)] and HYPO [−9.2 mmHg (−10.9, −7.6)] compared with MAX [−6.2 mmHg (−7.8, −4.6)] and SUB [1.4 mmHg (−0.2, 2.9); all comparisons p < 0.0001]. The ΔOEF was inversely related to both in the pooled analysis [β = −1.65 (−2.23, −1.07); p < 0.0001] and within each of the conditions. In conclusion, probably owing to reductions in CBF, hypocapnia per se increased OEF in a similar manner to supramaximal sprinting, indicating that exercise is non‐obligatory in this process.
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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".