Caffeine administration results in greater tension development in previously fatigued canine muscle <i>in situ</i>
Bibliographic record
Abstract
In isolated single skeletal myocytes undergoing long-term fatiguing contractions, caffeine (CAF) can result in nearly immediate restoration of generated tension to near-prefatigue levels by increasing Ca2+ release via activation of sarcoplasmic reticulum release channels. This study tested whether arterial CAF infusion (>5 mm) would cause a similar rapid restoration of tetanic isometric tension during contractions to fatigue in perfused canine hindlimb muscle in situ. Tetanic contractions were elicited by electrical stimulation (200 ms trains, 50 Hz, 1 contraction s(-1)), and biopsies were taken from the muscle at rest and during contractions: (1) following the onset of fatigue (tension approximately 60% of initial value); and (2) following CAF administration. Resting muscle ATP, PCr and lactate contents were 25.2 +/- 0.4, 76.9 +/- 3.3 and 14.4 +/- 3.3 mmol (kg dry weight)(-1), respectively. At fatigue, generated tetanic tension was 61.1 +/- 6.9% of initial contractions. There was a small but statistically significant recovery of tetanic tension (64.9 +/- 6.6% of initial value) with CAF infusion, after which the muscle showed incomplete relaxation. At fatigue, muscle ATP and PCr contents had fallen significantly (P < 0.05) to 18.1 +/- 1.1 and 18.9 +/- 2.1 mmol (kg dry weight)(-1), respectively, and lactate content had increased significantly to 27.7 +/- 5.4 mmol (kg dry weight)(-1). Following CAF, skeletal muscle ATP and PCr contents were significantly lower than corresponding fatigue values (15.0 +/- 1.3 and 10.9 +/- 2.2 mmol (kg dry weight)(-1), respectively), while lactate was unchanged (22.2 +/- 3.9 mmol (kg dry weight)(-1)). These results demonstrate that caffeine can result in a small, but statistically significant, recovery of isometric tension in fatigued canine hindlimb muscle in situ, although not nearly to the same degree as seen in isolated single muscle fibres. This suggests that, in this in situ isolated whole muscle model, alteration of Ca2+ metabolism is probably only one cause of fatigue.
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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) | 0.001 | 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) | 0.001 | 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".