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Table 3 Effects of single and long-term use of nitrates on the indicators of work capacity of healthy and physically active persons

From: The influence of amaranth (Amaranthus hypochondriacus) dietary nitrates on the aerobic capacity of physically active young persons

References

Participants

Supplemen-tation

Concentration of nitrates mmol/day

Duration of consumption

Protocol

Findings

[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).