Phosphocreatine Metabolism and Acidosis during Repeated Bouts of Heavy-Intensity Exercise Separated by 15-min Rest
Bibliographic record
Abstract
Prior heavy-intensity exercise (HVY) results in a reduced reliance on substrate-level phosphorylation during a subsequent exercise bout when the bouts are separated by 6-min rest. Proposed mechanisms for this response have been associated with acidosis and lactate accumulation. PURPOSE: To determine if a similar favourable energetic response in the second exercise is evident when the bouts are separated by 15-min of rest. In this condition intracellular acid-base status will have returned to pre-exercise resting levels prior to the second bout. METHODS: Healthy young adult male subjects (n = 7) performed a 6-min bout of HVY isotonic plantar flexion exercise (HVY1) followed by 15-min of rest, then an identical 6-min bout (HVY2). Muscle phosphocreatine (PCr) and intracellular acid-base status were measured using 3-tesla 31P-magnetic resonance spectroscopy. Each subject repeated the protocol three times. PCr was expressed as percent (%) of average pre-HVY1 resting value. RESULTS: Prior to the onset of exercise, resting intracellular hydrogen ion ([H+]i) was not different (P = 0.11) at the onset of exercise in HVY1 [94 nM (SD 4)] and HVY2 [99 nM (SD 8)]. The increase in [H+]i during exercise was reduced ∼ 45% during HVY2, with end-exercise [H+]i lower (P < 0.01) in HVY2 [139 nM (SD 38)] than HVY1 [167 nM (SD 48)]. Resting [PCr] was greater (P = 0.03) in HVY2 [101.8% (SD 2.1)] than HVY1, while at end-exercise, [PCr] was greater (P = 0.02) in HVY2 [55.1% (SD 15.1)] than HVY1 [48.7 % (SD 10.9)]. CONCLUSIONS: The lower accumulation of [H+]i (and presumably lactate accumulation) in HVY2 (delta [H+]i 40 nM) than HVY1 (delta [H+]i 73 nM), along with the decreased PCr breakdown, are consistent with reduced substrate-level phosphorylation. Therefore, these results demonstrate that the benefits of prior heavy-intensity exercise are evident after 15-min of rest, when intracellular acid-base status has returned to pre-exercise resting levels.
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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".