Dietary nitrate supplementation and exercise tolerance in chronic heart failure: A double-blind, randomized, placebo-controlled, crossover trial
Bibliographic record
Abstract
Chronic heart failure (CHF) impairs skeletal muscle O2 transport and utilization leading to restricted physical capacity. Dietary nitrate supplementation has been shown to improve vascular function, reduce the O2 cost of muscle contraction and enhance exercise tolerance (Tlim) in both healthy and clinical populations (e.g., COPD). We tested the hypothesis that dietary nitrate would improve locomotor muscle O2 delivery-utilization matching and Tlim in CHF patients. Methods: Nine males with CHF (ejection fraction=33±6%) consumed either nitrate-rich (∼12 mmol nitrate; beetroot juice) or nitrate-depleted beetroot juice (placebo) for 8 days. Mean arterial pressure (MAP), central hemodynamics by impedance cardiography (stroke volume, heart rate and cardiac output), pulmonary oxygen uptake (VO2) and muscle oxygenation by near-infrared spectroscopy were determined at rest and during low- and high-intensity “step” exercise tests. Results: No differences were observed between placebo vs. beetroot juice for resting and exercising MAP, central hemodynamics or muscle oxygenation (p>0.05). The O2 cost of exercise during both low- (placebo: 0.88±0.19 vs. beetroot juice: 0.94±0.24 l/min) and high-intensity (1.33±0.30 vs. 1.36±0.31 l/min) cycling and Tlim (489±194 vs. 485±173 s) were also unaffected by beetroot juice (p>0.05). Conclusions: Contrary to the hypothesis, 8 days of dietary nitrate supplementation did not enhance skeletal muscle O2 delivery-utilization matching or exercise tolerance in CHF patients. Whether longer treatment duration and/or higher doses are therapeutically effective in this patient population remains to be determined.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.004 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.003 | 0.002 |
| Insufficient payload (model declined to judge) | 0.006 | 0.001 |
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".