References | Participants | Supplemen-tation | Concentration of nitrates mmol/day | Duration of consumption | Protocol | Findings |
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[12] | Healthy, physically active people, n = 8; placebo (P) and experimental groups (E) | 500 ml beetroot juice /day | ~ 340 mg or 11 mmol | 6 days | Time trial at 70% between the ventilation threshold and VO2max | The increase in pulmonary O2 uptake following the onset of moderate exercise was reduced by 19% in the beetroot juice condition. During severe exercise, the O2 uptake slow component was reduced, and the time-to-exhaustion was extended. Trial duration: E: 675 ± 203 s P: 583 ± 145 s (p < 0,05) |
[19] | Healthy people, n = 9; | NaNO3 | 0.033 mmol NaNO3 kg/ body WT three times daily | Randomized and double-blinded; the washout period between the two trials was at least 7 days | Maximal combined arm and leg exercise tests. | Dietary nitrate reduced VO2max from 3.72+/−0.33 to 3.62+/− 0.31 L/min, p < 0.05. Despite the reduction in VO2max the time-to-exhaustion trended towards an increase after nitrate supplementation (524+/− 31 vs 563+/− 30 s, p = 0.13). |
[10] | Healthy, physically active people; n = 7 | 500 ml beetroot juice /day | 300 mg or ~ 5,1 mmol | 6 days | Leg extension until fatigue at 30% of MVC | 20% reduced O2 cost of exercise following dietary NO3- supplementation appears to be due to a reduced ATP cost of muscle force production. Trial duration: E: 734 ± 109 s P: 586 ± 80 s (p < 0,05) |
[18] | Healthy, physically active people; n = 9 | 500 ml beetroot juice /day | 300 mg or ~ 5,1 mmol | A. 2,5 h before B. 5 days C. 15 days | Increasing exercise test | A.E: 325 ± 71 Wmax P: 322 ± 68 Wmax B. E:328 ± 68 Wmax P: 323 ± 67 Wmax C. E:331 ± 68 Wmax P: 323 ± 68 Wmax After 15 days maximal power was increased by 4% |
[16] | Healthy, physically active people; n = 9 | 500 ml of beetroot juice (BR) | 380 mg or ~ 6,1 mmol | 6 days | Subjects completed treadmill exercise tests and knee-extension exercise tests for estimation of Qmax. | The O2 cost of walking, moderate-intensity running, and severe-intensity running was reduced by BR; time-to-exhaustion during severe-intensity running was increased by 15%. Trial time: E: 8,7 ± 1,8 min P: 7,6 ± 1,5 min (p < 0,05) |
[17] | Healthy, physically active men; n = 15 | Beetroot juice | 4,4 mg or 0.07 mmol nitrate/kg body WT/day | 6 days | Increased exercise test simulating a 5000-m altitude | Short-term dietary nitrate supplementation improves arterial and muscle oxygenation status but not cerebral oxygenation status during exercise in severe hypoxia. Trial duration: E: 597 ± 22 s P: 568 ± 23 s (p < 0,05) |
[11] | Healthy, recreationally active men; n = 10 | 70, 140, or 280 ml of beetroot juice or placebo (PL) 70, 140, or 280 ml | ~ 4.2, ~ 8.4, or ~ 16.8 mmol nitrates or placebo containing ~ 0.04, ~ 0.08, or ~ 0.12 mmol nitrates | 4–5 weeks | Two, 5-min bouts of moderate-intensity exercise and one bout of severe-intensity exercise that was continued until task failure as a measure of exercise tolerance, 2.5 h post-ingestion of beetroot juice or placebo. | 8.4 and 16.8 mmol of nitrates significantly improved the time-to-task failure by 14 and 12%, respectively, during severe-intensity exercise. End-exercise VO2 during moderate-intensity exercise was reduced significantly following the ingestion of 280 ml of BR (p < 0.05). |
[23] | Healthy, physically active men; n = 16 | 500 ml beetroot juice | 5 mmol | 1.5 h before physical load | A continuous cycle exercise test involving 20-min stages at 50 and 70% VO2max and a final stage at 90% VO2 max until volitional exhaustion. | Dietary nitrate reduced VO2max by 15,63% and increased the time-to-exhaustion by 16%. Trial duration: E: 185 ± 122 s P: 160 ± 109 s (p < 0,05) |
[25] | Healthy, recreationally active participants n = 15 (males = 8, females = 7) | 1000 mg red spinach extract powder (RSE) or placebo (PBO) (maltodextrin) in gelatin capsules | ~ 90 mg | One single dose | At one occasion 65–75-min post-RSE/PBO ingestion, venipuncture was performed (PRE), after which graded exercise test - the Bruce protocol - was performed. | Significantly increased plasma NO3-. A large effect on the ventilatory threshold compared to the placebo (+ 0.12 ± 0.14 L/min) with the ventilatory threshold occurred at a significantly higher relative VO2 (+ 3.6 ± 5.2%, p < 0.05). |