Aerobic power declines with aging in rat skeletal muscles perfused at matched convective O<sub>2</sub> delivery
Bibliographic record
Abstract
Although it is well established that maximal O(2) uptake (Vo(2 max)) declines from adulthood to old age, the role played by alterations in skeletal muscle is unclear. Specifically, because during whole body exercise reductions in convective O(2) delivery to the working muscles from adulthood to old age compromise aerobic performance, this obscures the influence of alterations within the skeletal muscles. We sought to overcome this limitation by using an in situ pump-perfused hindlimb preparation to permit matching of muscle convective O(2) delivery in young adult (8 mo; muscle convective O(2) delivery = 569 +/- 42 micromol O(2) x min(-1) x 100 g(-1)) and late middle-aged (28-30 mo; 539 +/- 62 micromol O(2) x min(-1) x 100 g(-1)) Fischer 344 x Brown Norway F1 hybrid rats. The distal hindlimb muscles were electrically stimulated for 4 min (60 tetani/min), and Vo(2 max) was determined. Vo(2 max) normalized to the contracting muscle mass was 22% lower in the 28- to 30-mo-old (344 +/- 17 micromol O(2). min(-1) x 100 g(-1)) than the 8-mo-old (441 +/- 20 micromol O(2) x min(-1) x 100 g(-1); P < 0.05) rats. The flux through the electron transport chain complexes I-III was 45% lower in homogenates prepared from the plantaris muscles of the older animals. Coincident with these alterations, the tension at Vo(2 max) and lactate efflux were reduced in the 28- to 30-mo-old animals, whereas the percent decline in tension was greater in the 28- to 30-mo-old vs. 8-mo-old animals. Collectively, these results demonstrate that alterations within the skeletal muscles, such as a reduced mitochondrial oxidative capacity, contribute to the reduction in Vo(2 max) with aging.
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.
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 | 0.001 |
| 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".