SKELETAL MUSCLE VO2MAX DECLINES WITH AGING INDEPENDENT OF CONVECTIVE OXYGEN DELIVERY
Bibliographic record
Abstract
It is well established that VO2max declines with age. Most studies examining this issue did so using whole body VO2. It is significant that during whole body exercise, O2 delivery to the working muscles declines from adulthood to old age and this alone can compromise aerobic performance. PURPOSE: To determine if muscle VO2max is reduced with aging independent of convective O2 delivery. METHODS: The distal muscles of a rat (Fisher 344 X Brown Norway F1 Hybrid) single hindlimb preparation perfused at matched rates of muscle convective O2 delivery, in young adult (8 mo old; mean ± SD, body mass: 416 ± 21 g) and late middle aged (28 mo old; 500 ± 58 g) animals, were electrically stimulated for 4 min (60 tetani min−1). Samples were drawn anaerobically every 30 s for measurement of O2 content in femoral arterial and venous blood. VO2max was determined by the product of blood flow and the arterio-venous O2 content difference across the hindlimb. Matching of muscle blood flow between each group was verified by examining the distribution of coloured microspheres infused after the experiment. RESULTS: Muscle O2 delivery was well matched between the 8 mo old (541 ± 96 μmol O2 min−1 100 g−1) and 28 mo old (532 ± 96 μmol O2 min−1 100 g−1) groups. VO2max was lower in the 28 mo old (308 ± 28 μmol O2 min−1 100 g−1) than the 8 mo old (388 ± 28 μmol O2, min−1 100 g−1; p < 0.05) rats. CONCLUSIONS: These results show that, at matched rates of muscle convective O2 delivery, VO2max is reduced with aging, suggesting that alterations in factors intrinsic to skeletal muscle (i.e., reduced capillarization, etc.) play a role in this response. Supported by CIHR (MOP 48185).
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".