TABLE 4

Clinical studies assessing nitrate supplementation on exercise performance during high-intensity exercise

ReferenceCohortInterventionDesignResultsOutcome
Wylie et al., 201314 male recreational team-sport playersNitrate-replete or -deplete beetroot juice as placebo (490 ml)Double blind, randomized, crossover study with juice delivered over ∼30 h preceding the completion of a Yo-Yo intermittent recovery level 1 testPerformance in the Yo-Yo IR1 was 4.2% greater with nitrate compared with the placebo.Acute nitrate supplementation improved performance during intense intermittent exercise in team sports players.
Thompson et al., 201416 male team-sport playersIntervention of nitrate-replete (140 ml/day; 12.8 mmol of nitrate) -or deplete beetroot juice as placebo (140 ml/day; 0.08 mmol nitrate)Double blind, randomized, crossover study. On day 7 of supplementation, subjects completed tests on a cycle ergometer during which cognitive tasks were simultaneously performed.Total work done during the sprints was greater with nitrate treatment (123 ± 19 kJ) compared with the placebo (119 ± 17 kJ; P < 0.05). Reaction time of response to the cognitive tasks was also improved. There was no difference in response accuracy.Nitrate supplementation enhanced repeated sprint performance and attenuated the decline in cognitive function (and specifically reaction time) that may occur during prolonged intermittent exercise.
Aucouturier et al., 201512 male subjectsIntervention of beetroot juice, 500 ml with 680 mg/l of nitrateRandomized crossover design single blinded to the subjects with a 3-day supplementationThe number of repetitions completed before reaching volitional exhaustion was significantly higher in the nitrate group than in the placebo (26.1 ± 10.7 vs. 21.8 ± 8.0 respectively, P < 0.05). In contrast during exercise performed at intensity below the peak oxygen uptake (VO2 peak), oxygen uptake (VO2) was unaffected.Nitrate supplementation enhanced tolerance to exercise at supramaximal intensity, with increased microvascular total RBC concentration in the working muscle, in the absence of effect on contractile function and resting hemodynamic parameters.
Placebo of apple-black currant juice with nitrate content <5 mg/lAUC for microvascular total hemoglobin (AUC-THb) in the vastus lateralis muscle assessed by near infrared spectroscopy during exercise was increased with nitrate.
Muggeridge et al., 2013Eight male kayakersIntervention of 70 ml nitrate-replete (5 mmol) concentrated beetroot juice or tomato juice as placeboRandomized crossover study measuring work rate during performance trials composed of 15 min of paddling at 60% of maximum work rate, five 10-s all-out sprints, and a 1-km time trial. The second and third trials were preceded by ingestion of intervention 3 h before exercise.VO2 during steady-state exercise was lower in the nitrate-treated than in the PL treated with no differences in either peak or time trial performance.Nitrate supplementation had no effect on performance.
Martin et al., 2014Team-sport athletes (9 male, age 22.3 ± 2.1 yr; 7 female, age 20.7 ± 1.3 yr)Intervention of 70 ml of nitrate-replete (0.3 g nitrate) concentrated beetroot juice orDouble blind, randomized, crossover study with participants consuming interventions 2 h prior to testsThere was no difference in overall mean power output or the mean power output for each individual sprint test.Nitrate supplementation did not improve performance.
nitrate-deplete beetroot juice as placebo
Wylie et al., 201634 healthy subjectsIntervention of nitrate-replete (3 or 6 mmol nitrate/day) concentrated beetroot juice or nitrate-deplete (0.08 mmol nitrate/day) beetroot juice as placeboRandomized counterbalanced design. Two moderate-intensity step exercise tests 2 h after the first ingestion and after 7, 28, and 30 days of supplementation, subjects completed.Compared with pre-treatment baseline, 6 mmol nitrate reduced the steady-state V˙O2 during moderate-intensity exercise by 3% at 2 h (P = 0.06), 7 days and at 28–30 days (both P < 0.05) but was unaffected by 3 mmol nitrate at all measurement points.Up to ∼4 wk supplementation with nitrate at 6 but not 3 mmol reduced submaximal exercise V˙O2.
Bescos et al., 201213 well trained endurance athletesIntervention of NaNO3, 10 mg/kg of body massRandomized, double blind, crossover study with a 40 min cycle ergometer distance-trial test after two 3 day periods of dietary supplementationThere were no differences in either the mean distance or mean power output between treatments.Nitrate supplementation did not improve a 40-min distance-trial performance.
Placebo: sodium chloride, 10 mg/kg of body mass
Coggan et al., 2015Healthy men and women (n = 12; age = 22–50 yr)Nitrate-replete (140 ml, 11.2 mmol) or -deplete beetroot juice as placeboDouble blind, placebo-controlled, randomized trialNitrate treatment increased breath NO by 61%. This was accompanied by a 4% (P < 0.01; effect size = 0.74) increase in peak knee extensor power at the highest angular velocity tested (i.e., 6.28 rad/s).Acute nitrate supplementation increased whole-body NO production and muscle speed and power in healthy men and women.
Assessments at 2 h after interventionCalculated maximal knee extensor power was greater after dietary nitrate.
Sandbakk et al., 2015Nine male elite cross-country skiers [age 18 ± 0 y, VO2max 69.3 ± 5.8 ml ⋅ min(−1) ⋅ kg(−1)]Combined supplementation with 6 g l-arginine and 614 mg nitrate against 614 mg nitrate alone and placeboRandomized, crossover, double blind study with 48 h pretreatmentThere were no differences in physiologic responses during submaximal running or in 5-km performance between treatments.There were no effects of nitrate supplementation on exercise economy or endurance running performance in endurance-trained cross-country skiers.
Haider and Folland, 201419 healthy untrained men (21 ± 3 yr)Nitrate-replete (9.7 mmol/day) or -deplete beetroot juice as placeboDouble blind, randomized, crossover study, with intervention given for seven consecutive days. After the last supplementation dose, force was recorded while participants completed a series of voluntary involuntary (electrically evoked) unilateral isometric contractions of the knee extensors.Nitrate enhanced peak force response to low-frequency electrical stimulation. Explosive force production during the first 50 ms of evoked maximal twitch and octet contractions (eight electrical impulses at 300 Hz) was 3%–15% greater after nitrate compared with placebo. Maximum voluntary force was unchanged nitrate.Nitrate supplementation enhanced the contractile properties of human skeletal muscle.
Rimer et al., 201613 trained athletesNitrate-replete (∼11.2 mmol nitrate) or -deplete beetroot juice as placebo (0.004 mmol)Double blind crossover study, with maximal inertial-load cycling trials (3 to 4 s) immediately before and after consuming intervention. Participants also performed maximal isokinetic cycling (30 s) to assess performance differences after supplementation.PMAX was increased after nitrate treatment. RP Mopt was increased with nitrate treatment.Acute nitrate supplementation enhanced maximal muscle power in trained athletes.
Lane et al., 201412 male and 12 female competitive cyclistsTrials were undertaken with a caffeinated gum (3 mg/kg body mass, 40 min prior to the TT), concentrated beetroot juice supplementation (8.4 mmol of nitrate, 2 h prior to the TT), caffeine plus beetroot juice, or a control.Cyclists each completed four experimental trials in a double blind random Latin square design.There was no effect of nitrate supplementation when used or when combined with caffeine.Nitrate supplementation was not ergogenic under the conditions of this study.
Lansley et al., 2011Nine club-level competitive male cyclistsNitrate-replete (BR) or -deplete beetroot juice (PL)Randomized, double blind, crossover study with intervention delivered 2.5 h before the completion of a 4- and a 16.1-km time trialVO2 during time trial were not different between groups but nitrate treatment significantly increased mean PO during the 4-and 16.1-km time trials.Acute nitrate supplementation improved cycling economy.
BR containing ∼6.2 mmol of nitrate
PL containing ∼0.0047 mmol of nitrate
Flueck et al., 201612 healthy, well trained menDosages were 3, 6, and 12 mmol nitrate as concentrated beetroot juice or sodium nitrate dissolved in water vs. water placebo.Placebo-controlled, single blind, crossover, randomized studyAt severe-intensity exercise, end-exercise oxygen consumption was ∼4% lower in the 6 mmol nitrate juice group compared with the 6 mmol salt ingestion or placebo.Nitrate supplementation with juice reduced O2 consumption to a greater extent compared with nitrate salt supplementation.
Measurements 3 h after ingestion. Participants cycled for 5 min at moderate intensity and a further 8 min at severe intensity. End-exercise O2 consumption at moderate intensity.
  • BR, beetroot juice; IR1, intermittent recovery test level 1; PL, placebo; RBC, red blood cell; TT, time-trial.