Exercise Performance at Moderate and Very-High Simulated Altitude.
Purpose: Nitric oxide (NO) bioavailability is reduced during acute altitude exposure, contributing toward the decline in physiological and cognitive function in this environment. This study evaluated the effects of nitrate ([Formula: see text]) supplementation on NO bioavailability, physiological and cognitive function, and exercise performance at moderate and very-high simulated altitude. Methods:Ten males (mean (SD): [Formula: see text]: 60.9 (10.1) ml·kg-1·min-1) rested and performed exercise twice at moderate (~14.0% O2; ~3,000 m) and twice at very-high (~11.7% O2; ~4,300 m) simulated altitude.
Participants ingested either 140 ml concentrated [Formula: see text]-rich (BRJ; ~12.5 mmol [Formula: see text]) or [Formula: see text]-deplete (PLA; 0.01 mmol [Formula: see text]) beetroot juice 2 h before each trial. Participants rested for 45 min in normobaric hypoxia prior to completing an exercise task. Exercise comprised a 45 min walk at 30% [Formula: see text] and a 3 km time-trial (TT), both conducted on a treadmill at a 10% gradient whilst carrying a 10 kg backpack to simulate altitude hiking. Plasma nitrite concentration ([[Formula: see text]]), peripheral oxygen saturation (SpO2), pulmonary oxygen uptake ([Formula: see text]), muscle and cerebral oxygenation, and cognitive function were measured throughout.
Results: Pre-exercise plasma [[Formula: see text]] was significantly elevated in BRJ compared with PLA (p = 0.001). Pulmonary [Formula: see text] was reduced (p = 0.020), and SpO2 was elevated (p = 0.005) during steady-state exercise in BRJ compared with PLA, with similar effects at both altitudes. BRJ supplementation enhanced 3 km TT performance relative to PLA by 3.8% [1,653.9 (261.3) vs. 1718.7 (213.0) s] and 4.2% [1,809.8 (262.0) vs. 1,889.1 (203.9) s] at 3,000 and 4,300 m, respectively (p = 0.019). Oxygenation of the gastrocnemius was elevated during the TT consequent to BRJ (p = 0.011). The number of false alarms during the Rapid Visual Information Processing Task tended to be lower with BRJ compared with PLA prior to altitude exposure (p = 0.056). Performance in all other cognitive tasks did not differ significantly between BRJ and PLA at any measurement point (p ≥ 0.141).
Conclusion: This study suggests that BRJ improves physiological function and exercise performance, but not cognitive function, at simulated moderate and very-high altitude.
Med Sci Sports Exerc. 2014 Jan;46(1):143-50. doi: 10.1249/MSS.0b013e3182a1dc51.
A single dose of beetroot juice enhances cycling performance in simulated altitude.
Increasing nitric oxide bioavailability via supplementation with nitrate-rich beetroot juice (BR) has been shown to attenuate the negative effect of hypoxia on peripheral oxygen saturation and exercise tolerance.
We investigated the effects of a single dose of concentrated BR on the physiological responses to submaximal exercise and time trial (TT) performance in trained cyclists exposed to moderate simulated altitude (approximately 2500 m).
Nine competitive amateur male cyclists (age, 28 ± 8 yr; V˙O2peak at altitude, 51.9 ± 5.8 mL·kg·min) completed four exercise trials consisting of an initial graded test to exhaustion and three performance trials on a cycle ergometer. The performance trials comprised 15 min of submaximal steady-state exercise at 60% maximum work rate and a 16.1-km TT. The second and third trials were preceded by ingestion of either 70 mL of BR or nitrate-depleted BR (PLA) 3 h before exercise.
Plasma nitrate (PLA, 39.1 ± 3.5 µM; BR, 150.5 ± 9.3 µM) and nitrite (PLA, 289.8 ± 27.9 nM; BR, 678.1 ± 103.5 nM) measured immediately before exercise were higher after ingestion of BR compared with that after PLA (P < 0.001, P = 0.004). V˙O2 during steady-state exercise was lower in the BR trial (2542 ± 114 mL·min) than that in the PLA trial (2727 ± 85 mL·min, P = 0.049). TT performance was significantly faster after BR (1664 ± 14 s) than that after PLA (1702 ± 15 s, P = 0.021).
A single dose of BR lowered V˙O2 during submaximal exercise and enhanced TT performance of trained cyclists in normobaric hypoxia. Consequently, ingestion of BR may be a practical and effective ergogenic aid for endurance exercise at altitude.
Int J Sports Physiol Perform. 2016 Oct 13:1-22. [Epub ahead of print]
The Effect of Dietary Nitrate Supplementation on Physiology and Performance in Trained Cyclists.
To determine the effect of dietary nitrate (NO3-) supplementation on physiology and performance in well-trained cyclists following six to eight-days of NO3- supplementation.
Eight competitive male cyclists (mean ± SD; age = 26 ± 8 y; body mass = 76.7 ± 6.9 kg; VO2peak = 63 ± 4 ml.kg-1.min-1) participated in a double-blind, placebo-controlled, crossover-design study in which participants ingested 70 ml beetroot juice containing ~4 mmol NO3- (NIT) or a NO3- depleted placebo (PLA), each for 8-days. Replicating pre-treatment measures, participants undertook an incremental ramp assessment to determine VO2peak, first (VT1), and second (VT2) ventilatory thresholds on day 6 (NIT6 and PLA6), moderate-intensity cycling economy on day 7 (NIT7 and PLA7), and a 4-km time-trial on day 8 (NIT8 and PLA8).
Relative to PLA, 6 days of NIT supplementation produced unclear effects for VO2peak (mean ±95%CL: 1.8 ±5.5%) and VT1 (3.7 ±12.3%) and trivial effects for both VT2 (-1.0 ±3.0%) and exercise economy on day 7 (-1.0 ±1.6%). However, effects for time-trial performance time (-0.7 ±0.9%), and power (2.4 ±2.5%), on day 8 were likely beneficial.
Despite mostly unclear outcomes for standard physiological determinants of performance, 8-days of NO3- supplementation resulted in likely beneficial improvements to 4-km time-trial performance in well-trained male endurance cyclists.
Int J Sport Nutr Exerc Metab. 2016 Oct 21:1-25. [Epub ahead of print]
Habitual Dietary Nitrate Intake in Highly Trained Athletes.
Although beetroot juice, as a nitrate carrier, is a popular ergogenic supplement amongst athletes, nitrate is consumed through the regular diet as well. We aimed to assess the habitual dietary nitrate intake and identify the main contributing food sources in a large group of highly trained athletes. Dutch highly trained athletes (226 women and 327 men) completed 2-4 web-based 24-h dietary recalls and questionnaires within a 2-4 week period. The nitrate content of food products and food groups was determined systematically based on values found in regulatory reports and scientific literature. These were then used to calculate each athlete's dietary nitrate intake from the web-based recalls. The median[IQR] habitual nitrate intake was 106[75-170] mg/d (range 19-525 mg/d). Nitrate intake correlated with energy intake (ρ=0.28, P<0.001), and strongly correlated with vegetable intake (ρ=0.78, P<0.001). In accordance, most of the dietary nitrate was consumed through vegetables, potatoes and fruit, accounting for 74% of total nitrate intake, with lettuce and spinach contributing most. When corrected for energy intake, nitrate intake was substantially higher in female vs male athletes (12.8[9.2-20.0] vs 9.4[6.2-13.8] mg/MJ; P<0.001). This difference was attributed to the higher vegetable intake in female vs male athletes (150[88-236] vs 114[61-183] g/d; P<0.001). In conclusion, median daily intake of dietary nitrate in highly trained athletes was 106 mg, with large inter-individual variation. Dietary nitrate intake was strongly associated with the intake of vegetables. Increasing the intake of nitrate-rich vegetables in the diet might serve as an alternative strategy for nitrate supplementation.
Int J Sport Nutr Exerc Metab. 2016 Nov 11:1-23. [Epub ahead of print]
Single and Combined Effects of Beetroot Crystals and Sodium Bicarbonate on 4-km Cycling Time Trial Performance.
When ingested alone, beetroot juice and sodium bicarbonate are ergogenic for high-intensity exercise performance. This study sought to determine the independent and combined effects of these supplements. Eight endurance trained (V̇O2max 65 mL·kg·min-1) male cyclists completed four x 4-km time trials (TT) in a double-blind Latin square design supplementing with beetroot crystals (BC) for 3 days (15 g.day-1+ 15 g 1 h prior to TT, containing 300 mg nitrate per 15 g), bicarbonate (Bi 0.3 g·kg-1 body mass [BM] in 5 doses every 15 min from 2.5 h prior to TT); BC+Bi or placebo (PLA). Subjects completed TTs on a Velotron cycle ergometer under standardized lab conditions. Plasma nitrite concentrations were significantly elevated only in the BC+Bi trial prior to the TT (1520 ± 786 nmol.L-1) compared to baseline (665 ± 535 nmol.L-1, p = 0.02) and the Bi and PLA conditions (Bi: 593 ± 203 nmol.L-1, p < 0.01; PLA: 543 ± 369 nmol.L-1, p< 0.01). Plasma nitrite concentrations were not elevated in the BC trial prior to the TT (1102 ± 218 nmol.L-1) compared to baseline (975 ± 607 nmol.L-1, p > 0.05). Blood bicarbonate concentrations were increased in the BC+Bi and Bi trials prior to the TT (BC+Bi: 30.9 ± 2.8 mmol.L-1; Bi: 31.7 ± 1.1 mmol.L-1). There were no differences in mean power output (386 - 394 W) or the time taken to complete the TT (335.8 - 338.1 s) between any conditions. Under the conditions of this study, supplementation was not ergogenic for 4-km TT performance.
J Clin Diagn Res. 2016 Jul;10(7):CC01-5. doi: 10.7860/JCDR/2016/20049.8113. Epub 2016 Jul 1.
Effects of a Dietary Beetroot Juice Treatment on Systemic and Cerebral Haemodynamics- A Pilot Study.
Beetroot Juice (BJ) contains dietary nitrates that increase the blood Nitric Oxide (NO) level, decrease Blood Pressure (BP), increase athletic performance and improve cognitive functions but the mechanism remains unclear. Ultrasonographic measurement of middle cerebral artery blood flow velocity with computation of Cerebral Augmentation Index (CAIx) is a measure of the reflected flow signal, modulated by changes in cerebrovascular resistance and compliance.
This pilot study tests the hypothesis that ingestion of an amount of BJ sufficient to raise the blood NO level two-to three-fold, decreases Transcranial Doppler (TCD) measured CAIx.
MATERIALS AND METHODS:
Ten healthy young-adult African-American women were studied at two levels of submaximal exercise, 40% and 80% of their predetermined peak oxygen consumptions. The subjects ingested nitrate-free orange juice (OJ, control) and an isocaloric BJ beverage (1.5 mg/mL nitrate, 220 Cal), on different days, 1-2 weeks apart.
The BJ treatment increased blood NO and decreased systolic BP at rest and at the two levels of exercise. The BJ treatment decreased CAIx only at the two levels of exercise (from 79 ± 2% to 62 ± 2% and from 80 ± 2% to 60 ± 3%, p<0.05). Exercise increased TCD-measured resistance and pulsatility indices (RIx, PIx) without changing AIx. The BJ treatment had no effect on RIx and PIx.
These findings suggest that decreased CAIx associated with aerobic exercise reflects the change in cerebral haemodynamics resulting from dietary nitrate supplementation. Future studies should determine whether the BJ-induced decrement in CAIx is correlated with an improvement in brain function.
Nutrients. 2016 Aug 31;8(9). pii: E534. doi: 10.3390/nu8090534.
Effects of a Short-Term High-Nitrate Diet on Exercise Performance.
It has been reported that nitrate supplementation can improve exercise performance. Most of the studies have used either beetroot juice or sodium nitrate as a supplement; there is lack of data on the potential ergogenic benefits of an increased dietary nitrate intake from a diet based on fruits and vegetables. Our aim was to assess whether a high-nitrate diet increases nitric oxide bioavailability and to evaluate the effects of this nutritional intervention on exercise performance. Seven healthy male subjects participated in a randomized cross-over study. They were tested before and after 6 days of a high (HND) or control (CD) nitrate diet (~8.2 mmol∙day(-1) or ~2.9 mmol∙day(-1), respectively).
Plasma nitrate and nitrite concentrations were significantly higher in HND (127 ± 64 µM and 350 ± 120 nM, respectively) compared to CD (23 ± 10 µM and 240 ± 100 nM, respectively). In HND (vs. CD) were observed: (a) a significant reduction of oxygen consumption during moderate-intensity constant work-rate cycling exercise (1.178 ± 0.141 vs. 1.269 ± 0.136 L·min(-1)); (b) a significantly higher total muscle work during fatiguing, intermittent sub-maximal isometric knee extension (357.3 ± 176.1 vs. 253.6 ± 149.0 Nm·s·kg(-1)); (c) an improved performance in Repeated Sprint Ability test.
These findings suggest that a high-nitrate diet could be a feasible and effective strategy to improve exercise performance.
Nitric Oxide. 2016 Dec 30;61:55-61. doi: 10.1016/j.niox.2016.10.006. Epub 2016 Oct 21.
Dietary nitrate supplementation improves sprint and high-intensity intermittent running performance.
The influence of dietary nitrate (NO3-) supplementation on indices of maximal sprint and intermittent exercise performance is unclear.
To investigate the effects of NO3- supplementation on sprint running performance, and cognitive function and exerciseperformance during the sport-specific Yo-Yo Intermittent Recovery level 1 test (IR1).
In a double-blind, randomized, crossover study, 36 male team-sport players received NO3--rich (BR; 70 mL·day-1; 6.4 mmol of NO3-), and NO3--depleted (PL; 70 mL·day-1; 0.04 mmol NO3-) beetroot juice for 5 days. On day 5 of supplementation, subjects completed a series of maximal 20-m sprints followed by the Yo-Yo IR1. Cognitive tasks were completed prior to, during and immediately following the Yo-Yo IR1.
BR improved sprint split times relative to PL at 20 m (1.2%; BR 3.98 ± 0.18 vs. PL 4.03 ± 0.19 s; P < 0.05), 10 m (1.6%; BR 2.53 ± 0.12 vs. PL 2.57 ± 0.19 s; P < 0.05) and 5 m (2.3%; BR 1.73 ± 0.09 vs. PL 1.77 ± 0.09 s; P < 0.05). The distance covered in the Yo-Yo IR1 test improved by 3.9% (BR 1422 ± 502 vs. PL 1369 ± 505 m; P < 0.05). The reaction time to the cognitive tasks was shorter in BR (615 ± 98 ms) than PL (645 ± 120 ms; P < 0.05) at rest but not during the Yo-Yo IR1. There was no difference in response accuracy.
Dietary NO3- supplementation enhances maximal sprint and high-intensity intermittent running performance in competitive team sport players. Our findings suggest that NO3- supplementation has the potential to improve performance in single-sprint or multiple-sprint (team) sports.
Nutr Res. 2016 Dec;36(12):1361-1369. doi: 10.1016/j.nutres.2016.11.004. Epub 2016 Nov 14.
Dietary nitrate does not affect physical activity or outcomes in healthy older adults in a randomized, cross-over trial.
Although dietary nitrate (NO3-) ingestion appears to enhance exercise capacity and performance in young individuals, inconclusive findings have been reported in older people. Therefore, we conducted a double-blind, crossover randomized clinical trial using beetroot juice in older healthy participants, who were classified as normal weight and overweight. We tested whether consumption of beetroot juice (a rich source of NO3-) for 1 week would increase nitric oxide bioavailability via the nonenzymatic pathway and enhance (1) exercise capacity during an incremental exercise test, (2) physical capability, and (3) free-living physical activity. Twenty nonsmoking, healthy participants between 60 and 75 years of age and with a body mass index of 20.0 to 29.9 kg/m2 were included. Presupplementation and postsupplementation resting, submaximal, maximal, and recovery gas exchanges were measured. Physical capability was measured by hand-grip strength, time-up-and-go, repeated chair rising test, and 10-m walking speed. Free-living physical activity was assessed by triaxal accelerometry. Changes in urinary and plasmaNO3-concentrations were measured by gas chromatography-mass spectrometry. Nineteen participants (male-to-female ratio, 9:10) completed the study.Beetroot juice increased significantly both plasma and urinary NO3-concentrations (P<.001) when compared with placebo. Beetroot juice did not influence resting or submaximal and maximal oxygen consumption during the incremental exercise test. In addition, measures of physical capability and physical activity levels measured in free-living conditions were not modified by beetroot juice ingestion. The positive effects of beetroot juice ingestion on exercise performance seen in young individuals were not replicated in healthy, older adults. Whether aging represents a modifier of the effects of dietary NO3-on muscular performance is not known, and mechanistic studies and larger trials are needed to test this hypothesis.