Muscle mass and inspired oxygen influence oxygen extraction at maximal exercise: Role of mitochondrial oxygen affinity
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Bibliographic record
Abstract
Abstract Aim We examined the Fick components together with mitochondrial O 2 affinity (p50 mito ) in defining O 2 extraction and O 2 uptake during exercise with large and small muscle mass during normoxia (NORM) and hyperoxia (HYPER). Methods Seven individuals performed 2 incremental exercise tests to exhaustion on a bicycle ergometer (BIKE) and 2 on a 1‐legged knee extension ergometer (KE) in NORM or HYPER. Leg blood flow and VO 2 were determined by thermodilution and the Fick method. Maximal ADP‐stimulated mitochondrial respiration (OXPHOS) and p50 mito were measured ex vivo in isolated mitochondria. Mitochondrial excess capacity in the leg was determined from OXPHOS in permeabilized fibres and muscle mass measured with magnetic resonance imaging in relation to peak leg O 2 delivery. Results The ex vivo p50 mito increased from 0.06 ± 0.02 to 0.17 ± 0.04 kPa with varying substrate supply and O 2 flux rates from 9.84 ± 2.91 to 16.34 ± 4.07 pmol O 2 ·s −1 ·μg −1 respectively. O 2 extraction decreased from 83% in BIKE to 67% in KE as a function of a higher O 2 delivery and lower mitochondrial excess capacity. There was a significant relationship between O 2 extraction and mitochondrial excess capacity and p50 mito that was unrelated to blood flow and mean transit time. Conclusion O 2 extraction varies with mitochondrial respiration rate, p50 mito and O 2 delivery. Mitochondrial excess capacity maintains a low p50 mito which enhances O 2 diffusion from microvessels to mitochondria during exercise.
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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 it