Exercise responses to exogenous ketone supplementation in humans: physiology, metabolism, and performance
Bibliographic record
Abstract
Ketone bodies (KB) are biologically active compounds that are increased during prolonged periods of carbohydrate restriction, e.g., in response to a ketogenic diet or after fasting. Ingestion of KB supplements is a novel method to study the effect of acutely increasing blood KB concentrations without changing diet. This thesis examined physiological, perceptual, and performance responses to acute hyperketonemia or elevated blood KB in humans. Studies 1 and 2 involved ingestion of 0.6 g/kg body mass of a commercial ketone monoester (KE) supplement 30 minutes before a 30-minute cycling bout at an intensity corresponding to ventilatory threshold. KE compared to placebo ingestion increased blood KB concentrations and decreased pH during exercise. Study 1 found that heart rate, ventilation, and rating of perceived exertion during exercise were higher after KE vs placebo ingestion. Performance during a subsequent 3 kJ/kg body mass time-trial duration was not different between treatments. Study 2 reproduced the finding of an increased heart rate and ventilation after KE vs placebo ingestion, but exercise cardiac output was not different between treatments. Peak oxygen uptake (VO2peak) was not different but peak power output at VO2peak was lower after KE vs placebo ingestion. None of the cardiorespiratory effects observed after KE vs placebo ingestion were altered when the KE-associated decrease in blood pH was normalized to placebo levels through bicarbonate co-ingestion. Study 3 showed that mean power output during a 20-min time-trial was lower after ingestion of 0.35 g/kg body mass KE vs placebo in trained cyclists. The lower self-selected workload after KE ingestion was associated with a lower mean heart rate during the time-trial and a challenge to acid-base homeostasis. In summary, acute hyperketonemia elicited by KB ingestion altered selected physiological, perceptual, and performance responses during exercise in humans.
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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 | 0.001 |
| 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".