Ergogenic Effect of Nitrate Supplementation: A Systematic Review and Meta-analysis
Bibliographic record
Abstract
Although over 100 studies and reviews have examined the ergogenic effects of dietary nitrate (NO3) supplementation in young, healthy men and women, it is unclear if participant and environmental factors modulate the well-described ergogenic effects-particularly relevant factors include biological sex, aerobic fitness, and fraction of inspired oxygen (FiO2) during exercise. To address this limitation, the literature was systematically reviewed for randomized, crossover, placebo-controlled studies reporting exercise performance outcome metrics with NO3 supplementation in young, healthy adults. Of the 2033 articles identified, 80 were eligible for inclusion in the meta-analysis. Random-effects meta-analysis demonstrated that exercise performance improved with NO3 supplementation compared with placebo (d = 0.174; 95% confidence interval (CI), 0.120-0.229; P < 0.001). Subgroup analyses conducted on biological sex, aerobic fitness, and FiO2 demonstrated that the ergogenic effect of NO3 supplementation was as follows: 1) not observed in studies with only women (n = 6; d = 0.116; 95% CI, -0.126 to 0.358; P = 0.347), 2) not observed in well-trained endurance athletes (≥65 mL·kg·min; n = 26; d = 0.021; 95% CI, -0.103 to 0.144; P = 0.745), and 3) not modulated by FiO2 (hypoxia vs normoxia). Together, the meta-analyses demonstrated a clear ergogenic effect of NO3 supplementation in recreationally active, young, healthy men across different exercise paradigms and NO3 supplementation parameters; however, the effect size of NO3 supplementation was objectively small (d = 0.174). NO3 supplementation has more limited utility as an ergogenic aid in participants with excellent aerobic fitness that have optimized other training parameters. Mechanistic research and studies incorporating a wide variety of subjects (e.g., women) are needed to advance the study of NO3 supplementation; however, additional descriptive studies of young, healthy men may have limited utility.
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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 | 0.009 | 0.018 |
| Meta-epidemiology (narrow) | 0.003 | 0.001 |
| Meta-epidemiology (broad) | 0.018 | 0.033 |
| Bibliometrics | 0.005 | 0.005 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.003 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.003 | 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".