Slowed oxygen uptake kinetics in hypoxia correlate with the transient peak and reduced spatial distribution of absolute skeletal muscle deoxygenation
Why this work is in the frame
A frame that forgets how it found something cannot be audited. These are the routes that admitted this work.
Bibliographic record
Abstract
New findings What is the central question of the study? Does a transient overshoot in skeletal muscle deoxygenation (reflecting a kinetic mismatch of microvascular O 2 delivery to consumption) and/or its spatial distribution slow the adjustment of oxidative energy provision at the onset of exercise? What is the main finding and its importance? Slowed oxidative energy provision at the onset of exercise was correlated with the transient skeletal muscle deoxygenation peak and the reduced spatial distribution, measured by quantitative near‐infrared spectroscopy. It was not correlated with a microvascular O 2 delivery‐to‐consumption mismatch per se . This suggests that an absolute, rather than kinetic, mismatch of microvascular O 2 delivery and consumption limits the kinetics of muscular oxidative energy provision, but only when muscle deoxygenation reaches some ‘critical’ level. It remains unclear whether an overshoot in skeletal muscle deoxygenation (HHb; reflecting a microvascular kinetic mismatch of O 2 delivery to consumption) contributes to the slowed adjustment of oxidative energy provision at the onset of exercise. We progressively reduced the fractional inspired O 2 concentration ( ) to investigate the relationship between slowed pulmonary O 2 uptake ( ) kinetics and the dynamics and spatial distribution of absolute [HHb]. Seven healthy men performed 8 min cycling transitions during normoxia ( ), moderate hypoxia ( ) and severe hypoxia ( ). uptake was measured using a flowmeter and gas analyser system. Absolute [HHb] was quantified by multichannel, time‐resolved near‐infrared spectroscopy from the rectus femoris and vastus lateralis (proximal and distal regions), and corrected for adipose tissue thickness. The phase II time constant was slowed ( P < 0.05) as decreased (normoxia, 17 ± 3 s; moderate hypoxia, 22 ± 4 s; and severe hypoxia, 29 ± 9 s). The [HHb] overshoot was unaffected by hypoxia, but the transient peak [HHb] increased with the reduction in ( P < 0.05). Slowed kinetics in hypoxia were positively correlated with increased peak [HHb] in the transient ( r 2 = 0.45; P < 0.05), but poorly related to the [HHb] overshoot. A reduction of spatial heterogeneity in peak [HHb] was inversely correlated with slowed kinetics ( r 2 = 0.49; P < 0.05). These data suggest that aerobic energy provision at the onset of exercise may be limited by the following factors: (i) the absolute ratio (i.e. peak [HHb]) rather than the kinetic ratio (i.e. [HHb] overshoot) of microvascular O 2 delivery to consumption; and (ii) a reduced spatial distribution in the ratio of microvascular O 2 delivery to consumption across the muscle.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
Direct model labels (unvalidated)
Per-model category and study-design labels from the labeling rounds. They are machine output, unvalidated, and the disagreement between models ships as data. No study design here is MEDLINE-validated yet.
| Model arm | Categories | Study design | Confidence |
|---|---|---|---|
| gemma | no category Domain: not available · Genre: Empirical About the Canadian research system: no · About a Canadian topic: no | Observational | low |
| gpt | no category Domain: not available · Genre: Empirical About the Canadian research system: no · About a Canadian topic: no | Bench or experimental | low |
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) | 0.000 | 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