Dietary nitrate supplementation improves sprint and high-intensity intermittent running performance

Dietary Nitrate Supplementation and Exercise-Related Performance

Over the last decade, there has been a growing interest in the utility of nitrate (NO3^-) supplementation to improve exercise-related performance. After consumption, dietary NO3^- can be reduced to nitric oxide, a free radical gas involved in numerous physiological actions including blood vessel vasodilation, mitochondrial respiration, and skeletal muscle contractile function. Emerging evidence indicates that dietary NO3^- supplementation has a small but nevertheless significant beneficial effect on endurance performance through the combined effects of enhanced tissue oxygenation and metabolic efficiency in active skeletal muscle. There is further evidence to suggest that dietary NO3^- exerts a direct influence on contractile mechanisms within the skeletal muscle through alterations in calcium availability and sensitivity. Response heterogeneity and sizeable variability in the nitrate content of beetroot juice products influence the effectiveness of dietary NO3^- for exercise performance, and so dosing and product quality, as well as training history, sex, and individual-specific characteristics, should be considered.

Effects of Dietary Nitrate Supplementation on Weightlifting Exercise Performance in Healthy Adults: A Systematic Review

Dietary nitrate (NO3-) supplementation has been evidenced to induce an ergogenic effect in endurance and sprint-type exercise, which may be underpinned by enhanced muscle contractility and perfusion, particularly in type II muscle fibers. However, limited data are available to evaluate the ergogenic potential of NO3- supplementation during other exercise modalities that mandate type II fiber recruitment, such as weightlifting exercise (i.e., resistance exercise). In this systematic review, we examine the existing evidence basis for NO3- supplementation to improve muscular power, velocity of contraction, and muscular endurance during weightlifting exercise in healthy adults. We also discuss the potential mechanistic bases for any positive effects of NO3- supplementation on resistance exercise performance. Dialnet, Directory of Open Access Journals, Medline, Pubmed, Scielo, Scopus and SPORT Discus databases were searched for articles using the keywords: nitrate or beetroot and supplement or nut*r or diet and strength or "resistance exercise" or "resistance training" or "muscular power". Four articles fulfilling the inclusion criteria were identified. Two of the four studies indicated that NO3- supplementation could increase aspects of upper body weightlifting exercise (i.e., bench press) performance (increases in mean power/velocity of contraction/number of repetitions to failure), whereas another study observed an increase in the number of repetitions to failure during lower limb weightlifting exercise (i.e., back squat). Although these preliminary observations are encouraging, further research is required for the ergogenic potential of NO3- supplementation on weightlifting exercise performance to be determined.

Effectiveness of beetroot juice derived nitrates supplementation on fatigue resistance during repeated-sprints: a systematic review

In recent decades, the search for non-doping substances that enhance sports performance has increased. Ergogenic aids such as beetroot juice (BRJ) and BRJ rich in nitrates (NO₃^-) are widely used to cause physiological benefits that may lead to physical improvements. Therefore, the purpose of this systematic review was to explore the knowledge reported to date on the NO₃^- derived from BRJ intake effect on fatigue resistance during repeated sprints. A digital search was conducted following systematic review guidelines, and 18 studies met inclusion criteria from a total of 209 articles. In a third of the selected studies, the consumption of beet juice rich in NO₃^- contributes to an increase in nitrites in plasma that led to the rise in peak power, mean power, number of sprint repetitions, total work and time to task failure, and causes a decrease in fatigue index and sprints times. Some different dose has been proposed for both chronic and acute protocols. It seems that a chronic intake of ∼5-6 mmol of NO₃^- in 70 ml of BRJ, twice a day, for a minimum of 3-6 days could lead to a fatigue resistance improvement during repeated sprints. Besides, acute intake of NO₃^- 2.5-3 h before physical exertion or a dose of 250 ml/d to 500 ml/d of BRJ could lead to similar effective results. This systematic review presents some improvements (1.2-5.38%) in fatigue resistance during repeated sprints when consuming BRJ derived NO₃^-. The in-field practical meaning of these results should be explored.

Could intramuscular storage of dietary nitrate contribute to its ergogenic effect? A mini-review

Extensive research performed over the past 10 years has resulted in dietary nitrate being considered a nutritional supplement that can improve exercise performance. However, there is still limited insight in the metabolic fate of dietary nitrate following the appearance of nitrate and nitrite in the circulation. Recent observations in humans suggest the storage of nitrate in skeletal muscle tissue. This short review discusses the possibility of nitrate being stored and utilized in human skeletal muscle tissue, and why confirming this may increase our understanding of how the nitrate-nitrite-NO pathway improves exercise performance. Further insight in skeletal muscle nitrate storage and metabolism may provide answers to current gaps in knowledge, such as the ergogenic benefit of acute vs multiday dietary nitrate supplementation, as well as the suggested muscle fiber-type specific effects on exercise performance. In this mini-review, specific questions that need further exploration are also discussed.

The benefits and risks of beetroot juice consumption: a systematic review

Beetroot juice (BRJ) has become increasingly popular amongst athletes aiming to improve sport performances. BRJ contains high concentrations of nitrate, which can be converted into nitric oxide (NO) after consumption. NO has various functions in the human body, including a vasodilatory effect, which reduces blood pressure and increases oxygen- and nutrient delivery to various organs. These effects indicate that BRJ may have relevant applications in prevention and treatment of cardiovascular disease. Furthermore, the consumption of BRJ also has an impact on oxygen delivery to skeletal muscles, muscle efficiency, tolerance and endurance and may thus have a positive impact on sports performances. Aside from the beneficial aspects of BRJ consumption, there may also be potential health risks. Drinking BRJ may easily increase nitrate intake above the acceptable daily intake, which is known to stimulate the endogenous formation of N-nitroso compounds (NOC's), a class of compounds that is known to be carcinogenic and that may also induce several other adverse effects. Compared to studies on the beneficial effects, the amount of data and literature on the negative effects of BRJ is rather limited, and should be increased in order to perform a balanced risk assessment.

Effects of Beetroot Juice Ingestion on Physical Performance in Highly Competitive Tennis Players

Beetroot juice (BJ) contains high levels of inorganic nitrate (NO₃⁻) and its intake has good evidence in increasing blood nitrate/nitrite concentrations. The ingestion of BJ has been associated with improvements in physical performance of endurance sports, however the literature in intermittent sports is scarce. The aim of this study was to investigate whether BJ could improve physical performance in tennis players. Thirteen well-trained tennis players (25.4 ± 5.1 years) participated in the study during their preparatory period for the tennis season. Subjects were randomly divided into two groups and performed a neuromuscular test battery after either BJ or placebo (PLA) consumption. Both trials were executed on two separate days, in randomized order, with one week of wash out period. The test battery consisted of serve velocity test (SVT), countermovement jump (CMJ), isometric handgrip strength (IHS), 5-0-5 agility test (5-0-5), and 10 m sprint (10-m). No significant differences were found in SVT (1.19%; p = 0.536), CMJ (0.96%; p = 0.327), IHS (4.06%; p = 0.069), 5-0-5 dominant and nondominant side (1.11–2.02%; p = 0.071–0.191) and 10-m (1.05%; p = 0.277) when comparing BJ and PLA ingestion. Thus, our data suggest that low doses of BJ (70 mL) consumption do not enhance tennis physical performance.

Does Acute Beetroot Juice Supplementation Improve Neuromuscular Performance and Match Activity in Young Basketball Players? A Randomized, Placebo-Controlled Study

Whereas beetroot juice (BJ) supplementation is shown to increase physical performance in endurance activities, its benefits in team sports has been barely studied. In this randomized placebo-controlled study, we investigated the effects of BJ acute supplementation in improving neuromuscular performance and physical match activity in basketball. Ten young male competitive basketball players aged 15–16 years received 140 mL of BJ or placebo (PLA) on two separated days in a balanced cross-over design. Testing sessions comprised a neuromuscular test battery consisting of a countermovement jump (CMJ), isometric handgrip strength, 10-m/20-m sprint and agility T-test, followed by a 40-minute simulated basketball match. Physical match activity (distances, speeds, accelerations, and decelerations) was monitored using an inertial tracking system (Wimu Pro^TM) Results revealed no significant effects of BJ on CMJ (p = 0.304, ES = 0.13), isometric handgrip strength (p = 0.777, ES = 0.06), 10-m (p = 0.820, ES = 0.10), and 20-m sprint (p = 0.540, ES = 0.13), agility T-test (p = 0.979, ES ≤ 0.01) and any physical match demands (p > 0.151, ES = 0.13–0.48). Acute moderate doses of BJ (12.8 mmol of NO₃⁻) was not effective in improving neuromuscular performance (jump height, isometric handgrip strength, sprint, and agility) or physical match requirements in young trained basketball players the day of the competition.

Dietary Nitrate and Physical Performance

Nitric oxide (NO) plays a plethora of important roles in the human body. Insufficient production of NO (for example, during older age and in various disease conditions) can adversely impact health and physical performance. In addition to its endogenous production through the oxidation of l-arginine, NO can be formed nonenzymatically via the reduction of nitrate and nitrite, and the storage of these anions can be augmented by the consumption of nitrate-rich foodstuffs such as green leafy vegetables. Recent studies indicate that dietary nitrate supplementation, administered most commonly in the form of beetroot juice, can ( a) improve muscle efficiency by reducing the O₂ cost of submaximal exercise and thereby improve endurance exercise performance and ( b) enhance skeletal muscle contractile function and thereby improve muscle power and sprint exercise performance. This review describes the physiological mechanisms potentially responsible for these effects, outlines the circumstances in which ergogenic effects are most likely to be evident, and discusses the effects of dietary nitrate supplementation on physical performance in a range of human populations.

A Single Dose of Beetroot Juice Does Not Change Blood Pressure Response Mediated by Acute Aerobic Exercise in Hypertensive Postmenopausal Women

OBJECTIVE

To verify if acute intake of beetroot juice potentiates post-exercise hypotension (PEH) in hypertensive postmenopausal women.

METHODS

Thirteen hypertensive postmenopausal women (58.1 ± 4.62 years and 27.4 ± 4.25 kg/m²) were recruited to participate in three experimental sessions, taking three different beverages: Beetroot juice (BJ), placebo nitrate-depleted BJ (PLA), and orange flavored non-caloric drink (OFD). The participants performed moderate aerobic exercise training on a treadmill, at 65-70% of heart rate reserve (HRR), for 40 min. After an overnight fast, the protocol started at 07h when the first resting blood pressure (BP) was measured. The beverage was ingested at 07h30 and BP was monitored until the exercise training started, at 09h30. After the end of the exercise session, BP was measured every 15 min over a 90-min period. Saliva samples were collected at rest, immediately before and after exercise, and 90 min after exercise for nitrite (NO₂^-) analysis.

RESULTS

There was an increase in salivary NO₂^- with BJ intake when compared to OFD and PLA. A slight increase in salivary NO₂^- was observed with PLA when compared to OFD (p < 0.05), however, PLA resulted in lower salivary NO₂^- when compared to BJ (p < 0.001). There were no changes in salivary NO₂^- with the OFD. Systolic and diastolic BP decreased (p < 0.001) on all post exercise time points after all interventions, with no difference between the three beverages.

CONCLUSION

Acute BJ intake does not change PEH responses in hypertensive postmenopausal women, even though there is an increase in salivary NO₂^-.

Nitrate supplementation improves physical performance specifically in non-athletes during prolonged open-ended tests: a systematic review and meta-analysis

Nitrate (NO3 -) is an ergogenic nutritional supplement that is widely used to improve physical performance. However, the effectiveness of NO3 - supplementation has not been systematically investigated in individuals with different physical fitness levels. The present study analysed whether different fitness levels (non-athletes v. athletes or classification of performance levels), duration of the test used to measure performance (short v. long duration) and the test protocol (time trials v. open-ended tests v. graded-exercise tests) influence the effects of NO3 - supplementation on performance. This systematic review and meta-analysis was conducted and reported according to the guidelines outlined in the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement. A systematic search of electronic databases, including PubMed, Web of Science, SPORTDiscus and ProQuest, was performed in August 2017. On the basis of the search and inclusion criteria, fifty-four and fifty-three placebo-controlled studies evaluating the effects of NO3 - supplementation on performance in humans were included in the systematic review and meta-analysis, respectively. NO3 - supplementation was ergogenic in non-athletes (mean effect size (ES) 0·25; 95 % CI 0·11, 0·38), particularly in evaluations of performance using long-duration open-ended tests (ES 0·47; 95 % CI 0·23, 0·71). In contrast, NO3 - supplementation did not enhance the performance of athletes (ES 0·04; 95 % CI -0·05, 0·15). After objectively classifying the participants into different performance levels, the frequency of trials showing ergogenic effects in individuals classified at lower levels was higher than that in individuals classified at higher levels. Thus, the present study indicates that dietary NO3 - supplementation improves physical performance in non-athletes, particularly during long-duration open-ended tests.

SPRINTING. . . Dietary Approaches to Optimize Training Adaptation and Performance

Although sprint athletes are assumed to primarily be interested in promoting muscle hypertrophy, it is the ability to generate explosive muscle power, optimization of power-to-weight ratio, and enhancement of anaerobic energy generation that are key outcomes of sprint training. This reflects the physique of track sprinters, being characterized as ecto-mesomorphs. Although there is little contemporary data on sprinters dietary habits, given their moderate energy requirements relative to body mass, a carbohydrate intake within the range of 3-6 g·kg^-1·day^-1 appears reasonable, while ensuring carbohydrate availability is optimized around training. Similarly, although protein needs may be twice general population recommendations, sprint athletes should consume meals containing ∼0.4 g/kg high biological value protein (i.e., easily digested, rich in essential amino acids) every 3-5 hr. Despite the short duration of competitions and relative long-recovery periods between races, nutrition still plays an important role in sprint performance. As energy expenditure moderates during competition, so too should intake of energy and macronutrients to prevent unwanted weight gain. Further adjustments in macronutrient intake may be warranted among athletes contemplating optimization of power-to-weight ratio through reductions in body fat prior to the competitive season. Other novel acute methods of weight loss have also been proposed to enhance power-to-weight ratio, but their implementation should only be considered under professional guidance. Given the metabolic demands of sprinting, a few supplements may be of benefit to athletes in training and/or competition. Their use in competition should be preceded with trialing in training to confirm tolerance and perceived ergogenic potential.

Evaluation and Behavior of Spanish Bodybuilders: Doping and Sports Supplements

The use of doping agents has these days become a public health problem, as it also affects young and non-competitive amateurs in different sports. To prepare for competition, bodybuilders perform aggressive dietary protocols, so, bodybuilders frequently consume nutritional supplements (NS) and banned substances in large dosages. Thus, the aim of this study is to analyze the prevalence of banned substances consumption and NS intake in competitive level bodybuilders. A total of 48 bodybuilders (44 males and 4 females) completed a validated online questionnaire on NS consumption. The quantitative data was presented as a mean (M) ± standard deviation (SD), as well as having minimum and maximum values. The categorical variables were expressed using frequencies and percentages. 83.3% of the participants declared that they had consumed or would consume banned substances, the most consumed being anabolic steroids (72.9%). One hundred percent of those sampled use NS. Whey protein (96%), branched-chain amino acids (BCAA) (94%), creatine (85%) and vitamin complexes (83%) were the most consumed, however, there is a low consumption of certain NS which could also increase athletic performance.

Sports Foods and Dietary Supplements for Optimal Function and Performance Enhancement in Track-and-Field Athletes

Athletes are exposed to numerous nutritional products, attractively marketed with claims of optimizing health, function, and performance. However, there is limited evidence to support many of these claims, and the efficacy and safety of many products is questionable. The variety of nutritional aids considered for use by track-and-field athletes includes sports foods, performance supplements, and therapeutic nutritional aids. Support for sports foods and five evidence-based performance supplements (caffeine, creatine, nitrate/beetroot juice, β-alanine, and bicarbonate) varies according to the event, the specific scenario of use, and the individual athlete's goals and responsiveness. Specific challenges include developing protocols to manage repeated use of performance supplements in multievent or heat-final competitions or the interaction between several products which are used concurrently. Potential disadvantages of supplement use include expense, false expectancy, and the risk of ingesting banned substances sometimes present as contaminants. However, a pragmatic approach to the decision-making process for supplement use is recommended. The authors conclude that it is pertinent for sports foods and nutritional supplements to be considered only where a strong evidence base supports their use as safe, legal, and effective and that such supplements are trialed thoroughly by the individual before committing to use in a competition setting.

Enhancement of Exercise Performance by 48 Hours, and 15-Day Supplementation with Mangiferin and Luteolin in Men

The natural polyphenols mangiferin and luteolin have free radical-scavenging properties, induce the antioxidant gene program and down-regulate the expression of superoxide-producing enzymes. However, the effects of these two polyphenols on exercise capacity remains mostly unknown. To determine whether a combination of luteolin (peanut husk extract containing 95% luteolin, PHE) and mangiferin (mango leave extract (MLE), Zynamite^®) at low (PHE: 50 mg/day; and 140 mg/day of MLE containing 100 mg of mangiferin; L) and high doses (PHE: 100 mg/day; MLE: 420 mg/day; H) may enhance exercise performance, twelve physically active men performed incremental exercise to exhaustion, followed by sprint and endurance exercise after 48 h (acute effects) and 15 days of supplementation (prolonged effects) with polyphenols or placebo, following a double-blind crossover design. During sprint exercise, mangiferin + luteolin supplementation enhanced exercise performance, facilitated muscle oxygen extraction, and improved brain oxygenation, without increasing the VO₂. Compared to placebo, mangiferin + luteolin increased muscle O₂ extraction during post-exercise ischemia, and improved sprint performance after ischemia-reperfusion likely by increasing glycolytic energy production, as reflected by higher blood lactate concentrations after the sprints. Similar responses were elicited by the two doses tested. In conclusion, acute and prolonged supplementation with mangiferin combined with luteolin enhances performance, muscle O₂ extraction, and brain oxygenation during sprint exercise, at high and low doses.

An acute dose of inorganic dietary nitrate does not improve high-intensity, intermittent exercise performance in temperate or hot and humid conditions

Purpose

Dietary nitrate (NO₃⁻) has repeatedly been shown to improve endurance and intermittent, high-intensity events in temperate conditions. However, the ergogenic effects of dietary NO₃⁻ on intermittent exercise performance in hot conditions have yet to be investigated.

Methods

In a randomised, counterbalanced, double-blind crossover study, 12 recreationally trained males ingested a nitrate-rich beetroot juice shot (BRJ) (6.2 mmol NO₃⁻) or a nitrate-depleted placebo (PLA) (< 0.004 mmol NO₃⁻) 3 h prior to an intermittent sprint test (IST) in temperate (22 °C, 35% RH) and hot conditions (30 °C, 70% RH). The cycle ergometer IST consisted of twenty maximal 6 s sprints interspersed by 114 s of active recovery. Work done, power output, heart rate and RPE were measured throughout; tympanic temperature was measured prior to and upon completion.

Results

There were no significant effects of supplement on sprint performance in either temperate or hot, humid conditions (p > 0.05). There was a reduced peak (BRJ: 659 ± 100W vs. PLA: 693 ± 139W; p = 0.056) and mean power (BRJ: 543 ± 29W vs. PLA: 575 ± 38W; p = 0.081) following BRJ compared to PLA in the hot and humid condition, but this was not statistically significant. There was no effect of supplement on total work done irrespective of environmental condition. However, ~ 75% of participants experienced performance decreases following BRJ in the hot and humid environment. No differences were observed between trials for tympanic temperature measured at the conclusion of the exercise trial.

Conclusion

In conclusion, an acute dose of inorganic dietary NO₃⁻ does not improve repeated-sprint performance in either temperate, or hot and humid conditions.

Dietary Nitrate Enhances the Contractile Properties of Human Skeletal Muscle

We review recent studies of the effects of dietary nitrate on human muscle contractile function and discuss possible underlying mechanisms.

Dietary nitrate, a source of nitric oxide (NO), improves the contractile properties of human muscle. We present the hypothesis that this is due to nitrosylation of the ryanodine receptor and increased NO signaling via the soluble guanyl cyclase-cyclic guanosine monophosphate-protein kinase G pathway, which together increase the free intracellular Ca²⁺ concentration along with the Ca²⁺ sensitivity of the myofilaments themselves.

Effects of a single dose of beetroot juice on cycling time trial performance at ventilatory thresholds intensity in male triathletes

Background

Beetroot juice (BJ) is classified as a high-level supplement for improving sports performance. There is some controversy over the benefits of BJ supplementation for endurance exercise performance, especially when referring to well-trained athletes. This study examines the effects of acute BJ supplementation on cardioventilatory responses, exercise economy/efficiency, slow component of oxygen uptake, time trial performance, blood lactate, energy consumption, and carbohydrate and fat oxidation.

Methods

Twelve well-trained, male triathletes (aged 21–47 yr) were assigned in a randomized, double-blind, crossover design to receive 70 ml of BJ (6.5 mmol NO₃⁻) or placebo (PL). Three hours after taking the supplement, participants completed an endurance test on a cycle ergometer at a constant work rate (W) corresponding to first ventilatory threshold (VT1) (30 min) and second ventilatory threshold (VT2) time trial (~ 15 min).

Results

Maximal oxygen uptake was 54.78 ± 3.13 mL·min^− 1·kg^− 1, and gross efficiency was > 22% at each load intensity and experimental condition. No significant interaction effect (supplement*intensity) was observed on any of the cardioventilatory variables, efficiency/economy, VT2 time trial, energy expenditure, carbohydrate oxidation and fat oxidation (p > 0.05).

Conclusion

Our findings do not support an improvement in the variables examined in response to acute BJ supplementation. Probably, higher doses are needed for improving time trial performance in male triathletes during a cycle ergometer test conducted at a load intensity equivalent to the first and second ventilatory threshold.

Effects of Beetroot Juice Supplementation on Performance and Fatigue in a 30-s All-Out Sprint Exercise: A Randomized, Double-Blind Cross-Over Study

As a nitric oxide precursor, beetroot juice (BJ) is known to enhance high-intensity exercise performance (80⁻100% VO2max) yet its impacts on higher intensity sprint exercise (>100% VO2max) remain to be established. This study sought to examine the effects of BJ supplementation on performance and subsequent fatigue during an all-out sprint exercise. Using a randomized cross-over, double-blind, placebo-controlled design, 15 healthy resistance-trained men (22.4 ± 1.6 years) ingested 70 mL of either BJ or placebo. Three hours later, participants undertook a 30-s all-out Wingate test. Before and after the sprint exercise and at 30 s and 180 s post-exercise, three countermovement jumps (CMJ) were performed and blood lactate samples were obtained. Compared to placebo, BJ consumption improved peak (placebo vs. BJ, 848 ± 134 vs. 881 ± 135 W; p = 0.049) and mean (641 ± 91 vs. 666 ± 100 W; p = 0.023) power output and also reduced the time taken to reach Wpeak in the Wingate test (8.9 ± 1.4 vs. 7.3 ± 0.9 s; p = 0.003). No differences were detected in the fatigue index. In addition, while over time CMJ height and power diminished (ANOVA p < 0.001) and blood lactate levels increased (ANOVA p < 0.001), no supplementation effect was observed. Our findings indicate that while BJ supplementation improved performance at the 30-s cycling sprint, this improvement was not accompanied by differences in fatigue during or after this type of exercise.

The Effect of Beetroot Juice Supplementation on Dynamic Apnea and Intermittent Sprint Performance in Elite Female Water Polo Players

Nitrate-rich beetroot juice is thought to have ergogenic effects, particularly in conditions where oxygen availability is limited. Whether these effects also apply to elite athletes is currently unknown. The aim of this study was to assess the effects of beetroot juice supplementation on dynamic apnea and intermittent sprint performance in elite female water polo players. In a double-blinded, randomized, crossover manner, the Dutch National female water polo team (N = 14) was subjected to two 6-day supplementation periods (1 and 2), with either 140 ml/day of nitrate-rich (BR; ∼800 mg/day nitrate) or nitrate-depleted (PLA) beetroot juice. Following blood sampling on Day 6, the athletes performed a maximal-distance front crawl swimming test without breathing (dynamic apnea test). In addition, intermittent sprint performance was assessed by performing 16 swim sprints of 15 m, in a 4 × 4 block with 30-s recovery between blocks (intermittent test). Distance covered during the dynamic apnea test did not differ between BR (49.5 ± 7.8 m) and PLA (46.9 ± 9.1 m, p = .178). However, when correcting for test order, the distance covered was significantly larger in BR versus PLA when BR was ingested in Period 2 (50.1 ± 8.5 vs. 42.8 ± 5.7 m, p = .002), whereas no difference was observed when BR was ingested in Period 1 (48.8 ± 7.4 vs. 52.3 ± 10.4 m, p = .10). The time to complete the intermittent test was not different between BR and PLA (316.0 ± 7.9 vs. 316.3 ± 6.9 s, p = .73). In conclusion, beetroot juice supplementation does not improve intermittent performance in elite female water polo players, but there may be a potential for ergogenic effects during dynamic apnea.

Acute beetroot juice administration improves peak isometric force production in adolescent males

The purpose of this study was to examine the effects of acute beetroot juice (BR) administration on repeated sprint performance and isometric force production in adolescent males. Twelve male adolescents (age, 16.8 ± 1.0 years; height, 178.8 ± 9.2 cm; mass, 74.8 ± 12.5 kg; peak height velocity, 2.53 ± 1.2 years) participated in this double-blind, placebo-controlled, crossover designed study. Participants consumed 2 × 70 mL of BR (∼12.9 mmol NO3−; Beet It Sport) or a nitrate-depleted placebo (PL) at 2.5 h prior to performing isometric mid-thigh pulls (IMTP) and 4 repeated 20-s Wingate sprints interspersed with 4 min of rest. Sprint data were analyzed by a 2 × 4 (group × time) repeated-measures ANOVA while a dependent t test was used to compare conditions for IMTP peak force. A significant main effect for time (p < 0.05) was observed for peak power (PP), average power (Pavg), and fatigue index (FI) across sprints. Compared with sprint 1, sprint 4 resulted in significant decreases in PP (p < 0.000; −16.6%) and Pavg (p = 0.000; −21.8%) and FI was significantly elevated (p < 0.000; 15.2%). No significant group × time interactions were observed between conditions for PP (p = 0.402), Pavg (p = 0.479), or FI (p = 0.37). IMTP peak force was significantly higher (p = 0.004; 13.9%) following BR consumption compared with PL. The repeated sprint protocol resulted in significant fatigue while BR did not influence sprint performance. However, it appears BR administration may improve peak force production in adolescent males.

Effects of inorganic nitrate and nitrite consumption on cognitive function and cerebral blood flow: A systematic review and meta-analysis of randomized clinical trials

We conducted a systematic review and meta-analysis of randomized clinical trials examining the effect of inorganic nitrate or nitrite supplementation on cognitive function (CF) and cerebral blood flow (CBF). Two databases (PubMed, Embase) were searched for articles from inception until May 2017. Inclusion criteria were: randomized clinical trials; participants >18 years old; trials comparing a nitrate/nitrite intervention with a control. Thirteen and nine trials were included in the meta-analysis to assess CF and CBF, respectively. Random-effects models were used and the effect size described as standardized mean differences (SMDs). A total of 297 participants (median of 23 per trial) were included for CF; 163 participants (median of 16 per trial) were included for CBF. Nitrate/nitrite supplementation did not influence CF (SMD +0.06, 95% CI: -0.06, 0.18, P = 0.32) or CBF under resting (SMD +0.14, 95% CI: -0.13, 0.41, P = 0.31), or stimulated conditions (SMD + 0.23, 95% CI: -0.11, 0.56, P = 0.19). The meta-regression showed an inverse association between duration of the intervention and CBF (P = 0.02) but no influence of age, BMI or dose (P < 0.05). Nitrate and nitrite supplementation did not modify CBF or CF. Further trials employing larger samples sizes and interventions with longer duration are warranted.

No individual or combined effects of caffeine and beetroot-juice supplementation during submaximal or maximal running

Dietary supplements such as caffeine and beetroot juice are used by athletes in an attempt to optimize performance and therefore gain an advantage in competition. The aim of this study was to investigate the individual and combined effects of caffeine and beetroot-juice supplementation during submaximal and maximal treadmill running. Seven males (maximal oxygen uptake: 59.0 ± 2.9 mL·kg–1·min–1) and 2 females (maximal oxygen uptake: 53.1 ± 11.4 mL·kg–1·min–1) performed a preliminary trial followed by 4 experimental test sessions. Each test session consisted of two 5-min submaximal running bouts (at ∼70% and 80% of maximal oxygen uptake) and a maximal 1-km time trial (TT) in a laboratory. Participants ingested 70 mL of concentrated beetroot juice containing either 7.3 mmol of nitrate (BR) or no nitrate (PBR) 2.5 h prior to each test session, then either caffeine (C) at 4.8 ± 0.4 (4.3–5.6) mg/kg of body mass or a caffeine placebo (PC) 45 min before each test session. The 4 test sessions (BR-C, BR-PC, PBR-C, and PBR-PC) were presented in a counterbalanced and double-blind manner. No significant differences were identified between the 4 interventions regarding relative oxygen uptake, running economy, respiratory exchange ratio, heart rate (HR), or rating of perceived exertion (RPE) at the 2 submaximal intensities (P > 0.05). Moreover, there were no significant differences in performance, maximum HR, peak blood lactate concentration, or RPE during the maximal TT when comparing the interventions (P > 0.05). In conclusion, no beneficial effects of supplementing with typical doses of caffeine, beetroot juice, or a combination of the two were observed for physiological, perceptual, or performance responses during submaximal or maximal treadmill running exercise.

Discrete physiological effects of beetroot juice and potassium nitrate supplementation following 4-wk sprint interval training

The physiological and exercise performance adaptations to sprint interval training (SIT) may be modified by dietary nitrate ([Formula: see text]) supplementation. However, it is possible that different types of [Formula: see text] supplementation evoke divergent physiological and performance adaptations to SIT. The purpose of this study was to compare the effects of 4-wk SIT with and without concurrent dietary [Formula: see text] supplementation administered as either [Formula: see text]-rich beetroot juice (BR) or potassium [Formula: see text] (KNO3). Thirty recreationally active subjects completed a battery of exercise tests before and after a 4-wk intervention in which they were allocated to one of three groups: 1) SIT undertaken without dietary [Formula: see text] supplementation (SIT); 2) SIT accompanied by concurrent BR supplementation (SIT + BR); or 3) SIT accompanied by concurrent KNO3 supplementation (SIT + KNO3). During severe-intensity exercise, V̇o2peak and time to task failure were improved to a greater extent with SIT + BR than SIT and SIT + KNO3 ( P < 0.05). There was also a greater reduction in the accumulation of muscle lactate at 3 min of severe-intensity exercise in SIT + BR compared with SIT + KNO3 ( P < 0.05). Plasma [Formula: see text] concentration fell to a greater extent during severe-intensity exercise in SIT + BR compared with SIT and SIT + KNO3 ( P < 0.05). There were no differences between groups in the reduction in the muscle phosphocreatine recovery time constant from pre- to postintervention ( P > 0.05). These findings indicate that 4-wk SIT with concurrent BR supplementation results in greater exercise capacity adaptations compared with SIT alone and SIT with concurrent KNO3 supplementation. This may be the result of greater NO-mediated signaling in SIT + BR compared with SIT + KNO3.

NEW & NOTEWORTHY We compared the influence of different forms of dietary nitrate supplementation on the physiological and performance adaptations to sprint interval training (SIT). Compared with SIT alone, supplementation with nitrate-rich beetroot juice, but not potassium [Formula: see text], enhanced some physiological adaptations to training.

Beetroot juice ingestion during prolonged moderate-intensity exercise attenuates progressive rise in O2 uptake

Nitrate-rich beetroot juice (BR) supplementation has been shown to increase biomarkers of nitric oxide availability with implications for the physiological responses to exercise. We hypothesized that BR supplementation before and during prolonged moderate-intensity exercise would maintain an elevated plasma nitrite concentration ([[Formula: see text]]), attenuate the expected progressive increase in V̇o2 over time, and improve performance in a subsequent time trial (TT). In a double-blind, randomized, crossover design, 12 men completed 2 h of moderate-intensity cycle exercise followed by a 100-kJ TT in three conditions: 1) BR before and 1 h into exercise (BR + BR); 2) BR before and placebo (PL) 1 h into exercise (BR + PL); and 3) PL before and 1 h into exercise (PL + PL). During the 2-h moderate-intensity exercise bout, plasma [[Formula: see text]] declined by ~17% in BR + PL but increased by ~8% in BR + BR such that, at 2 h, plasma [[Formula: see text]] was greater in BR + BR than both BR + PL and PL + PL ( P < 0.05). V̇o2 was not different among conditions over the first 90 min of exercise but was lower at 120 min in BR + BR (1.73 ± 0.24 l/min) compared with BR + PL (1.80 ± 0.21 l/min; P = 0.08) and PL + PL (1.83 ± 0.27 l/min; P < 0.01). The decline in muscle glycogen concentration over the 2-h exercise bout was attenuated in BR + BR (~28% decline) compared with BR + PL (~44% decline) and PL + PL (~44% decline; n = 9, P < 0.05). TT performance was not different among conditions ( P > 0.05). BR supplementation before and during prolonged moderate-intensity exercise attenuated the progressive rise in V̇o2 over time and appeared to reduce muscle glycogen depletion but did not enhance subsequent TT performance.

NEW & NOTEWORTHY We show for the first time that ingestion of nitrate during exercise preserves elevated plasma [nitrite] and negates the progressive rise in O2 uptake during prolonged moderate-intensity exercise.

IOC consensus statement: dietary supplements and the high-performance athlete

Nutrition usually makes a small but potentially valuable contribution to successful performance in elite athletes, and dietary supplements can make a minor contribution to this nutrition programme. Nonetheless, supplement use is widespread at all levels of sport. Products described as supplements target different issues, including (1) the management of micronutrient deficiencies, (2) supply of convenient forms of energy and macronutrients, and (3) provision of direct benefits to performance or (4) indirect benefits such as supporting intense training regimens. The appropriate use of some supplements can benefit the athlete, but others may harm the athlete's health, performance, and/or livelihood and reputation (if an antidoping rule violation results). A complete nutritional assessment should be undertaken before decisions regarding supplement use are made. Supplements claiming to directly or indirectly enhance performance are typically the largest group of products marketed to athletes, but only a few (including caffeine, creatine, specific buffering agents and nitrate) have good evidence of benefits. However, responses are affected by the scenario of use and may vary widely between individuals because of factors that include genetics, the microbiome and habitual diet. Supplements intended to enhance performance should be thoroughly trialled in training or simulated competition before being used in competition. Inadvertent ingestion of substances prohibited under the antidoping codes that govern elite sport is a known risk of taking some supplements. Protection of the athlete's health and awareness of the potential for harm must be paramount; expert professional opinion and assistance is strongly advised before an athlete embarks on supplement use.

IOC Consensus Statement: Dietary Supplements and the High-Performance Athlete

Nutrition usually makes a small but potentially valuable contribution to successful performance in elite athletes, and dietary supplements can make a minor contribution to this nutrition program. Nonetheless, supplement use is widespread at all levels of sport. Products described as supplements target different issues, including the management of micronutrient deficiencies, supply of convenient forms of energy and macronutrients, and provision of direct benefits to performance or indirect benefits such as supporting intense training regimens. The appropriate use of some supplements can offer benefits to the athlete, but others may be harmful to the athlete's health, performance, and/or livelihood and reputation if an anti-doping rule violation results. A complete nutritional assessment should be undertaken before decisions regarding supplement use are made. Supplements claiming to directly or indirectly enhance performance are typically the largest group of products marketed to athletes, but only a few (including caffeine, creatine, specific buffering agents and nitrate) have good evidence of benefits. However, responses are affected by the scenario of use and may vary widely between individuals because of factors that include genetics, the microbiome, and habitual diet. Supplements intended to enhance performance should be thoroughly trialed in training or simulated competition before implementation in competition. Inadvertent ingestion of substances prohibited under the anti-doping codes that govern elite sport is a known risk of taking some supplements. Protection of the athlete's health and awareness of the potential for harm must be paramount, and expert professional opinion and assistance is strongly advised before embarking on supplement use.

Potential benefits of dietary nitrate ingestion in healthy and clinical populations: A brief review

This article provides an overview of the current literature relating to the efficacy of dietary nitrate (NO₃^-) ingestion in altering aspects of cardiovascular and metabolic health and exercise capacity in healthy and diseased individuals. The consumption of NO₃^--rich vegetables, such as spinach and beetroot, have been variously shown to promote nitric oxide bioavailability, reduce systemic blood pressure, enhance tissue blood flow, modulate muscle O₂ utilisation and improve exercise tolerance both in normoxia and in hypoxia, as is commonly observed in a number of disease states. NO₃^- ingestion may, therefore, act as a natural means for augmenting performance and attenuating complications associated with limited O₂ availability or transport, hypertension and the metabolic syndrome. Recent studies indicate that dietary NO₃^- might also augment intrinsic skeletal muscle contractility and improve the speed and power of muscle contraction. Moreover, several investigations suggest that NO₃^- supplementation may improve aspects of cognitive performance both at rest and during exercise. Collectively, these observations position NO₃^- as more than a putative ergogenic aid and suggest that increasing natural dietary NO₃^- intake may act as a prophylactic in countering the predations of senescence and certain cardiovascular-metabolic diseases.

Evidence-Based Supplements for the Enhancement of Athletic Performance

A strong foundation in physical conditioning and sport-specific experience, in addition to a bespoke and periodized training and nutrition program, are essential for athlete development. Once these underpinning factors are accounted for, and the athlete reaches a training maturity and competition level where marginal gains determine success, a role may exist for the use of evidence-based performance supplements. However, it is important that any decisions surrounding performance supplements are made in consideration of robust information that suggests the use of a product is safe, legal, and effective. The following review focuses on the current evidence-base for a number of common (and emerging) performance supplements used in sport. The supplements discussed here are separated into three categories based on the level of evidence supporting their use for enhancing sports performance: (1) established (caffeine, creatine, nitrate, beta-alanine, bicarbonate); (2) equivocal (citrate, phosphate, carnitine); and (3) developing. Within each section, the relevant performance type, the potential mechanisms of action, and the most common protocols used in the supplement dosing schedule are summarized.

Repeated-sprint performance and plasma responses following beetroot juice supplementation do not differ between recreational, competitive and elite sprint athletes

PURPOSE

There is an ongoing debate whether highly trained athletes are less responsive to the ergogenic properties of nitrate. We assessed the effects of nitrate supplementation on plasma nitrate and nitrite concentrations and repeated-sprint performance in recreational, competitive and elite sprint athletes.

METHODS

In a randomized double-blinded cross-over design, recreational cyclists (n = 20), national talent speed-skaters (n = 22) and Olympic-level track cyclists (n = 10) underwent two 6-day supplementation periods; 140 mL/d nitrate-rich (BR; ∼800 mg/d) and nitrate-depleted (PLA; ∼0.5 mg/d) beetroot juice. Blood samples were collected and three 30-s Wingate tests were performed.

RESULTS

Plasma nitrate and nitrite concentrations were higher following BR vs PLA (P < .001), with no differences between sport levels (all P > .10). Peak power over the three Wingates was not different between BR and PLA (1338 ± 30 vs 1333 ± 30 W; P = .62), and there was no interaction between treatment (BR-PLA) and Wingate number (1-2-3; P = .48). Likewise, mean power did not differ between BR and PLA (P = .86). In contrast, time to peak power improved by ∼2.8% following BR vs PLA (P = .007). This improvement in BR vs PLA was not different between Wingate 1, 2 and 3. Moreover, the effects of BR vs PLA did not differ between sport levels for any Wingate parameter (all P > .30).

CONCLUSION

The plasma and repeated-sprint performance responses to beetroot juice supplementation do not differ between recreational, competitive and elite sprint athletes. Beetroot juice supplementation reduces time to reach peak power, which may improve the capacity to accelerate during high-intensity and sprint tasks in recreational as well as elite athletes.

Dietary nitrate supplementation in cardiovascular health: an ergogenic aid or exercise therapeutic?

Oral consumption of inorganic nitrate, which is abundant in green leafy vegetables and roots, has been shown to increase circulating plasma nitrite concentration, which can be converted to nitric oxide in low oxygen conditions. The associated beneficial physiological effects include a reduction in blood pressure, modification of platelet aggregation, and increases in limb blood flow. There have been numerous studies of nitrate supplementation in healthy recreational and competitive athletes; however, the ergogenic benefits are currently unclear due to a variety of factors including small sample sizes, different dosing regimens, variable nitrate conversion rates, the heterogeneity of participants’ initial fitness levels, and the types of exercise tests used. In clinical populations, the study results seem more promising, particularly in patients with cardiovascular diseases who typically present with disruptions in the ability to transport oxygen from the atmosphere to working tissues and reduced exercise tolerance. Many of these disease-related, physiological maladaptations, including endothelial dysfunction, increased reactive oxygen species, reduced tissue perfusion, and muscle mitochondrial dysfunction, have been previously identified as potential targets for nitric oxide restorative effects. This review is the first of its kind to outline the current evidence for inorganic nitrate supplementation as a therapeutic intervention to restore exercise tolerance and improve quality of life in patients with cardiovascular diseases. We summarize the factors that appear to limit or maximize its effectiveness and present a case for why it may be more effective in patients with cardiovascular disease than as ergogenic aid in healthy populations.

Hematological and Hemodynamic Responses to Acute and Short-Term Creatine Nitrate Supplementation

In a double-blind, crossover, randomized and placebo-controlled trial; 28 men and women ingested a placebo (PLA), 3 g of creatine nitrate (CNL), and 6 g of creatine nitrate (CNH) for 6 days. Participants repeated the experiment with the alternate supplements after a 7-day washout. Hemodynamic responses to a postural challenge, fasting blood samples, and bench press, leg press, and cycling time trial performance and recovery were assessed. Data were analyzed by univariate, multivariate, and repeated measures general linear models (GLM). No significant differences were found among treatments for hemodynamic responses, clinical blood markers or self-reported side effects. After 5 days of supplementation, one repetition maximum (1RM) bench press improved significantly for CNH (mean change, 95% CI; 6.1 [3.5, 8.7] kg) but not PLA (0.7 [-1.6, 3.0] kg or CNL (2.0 [-0.9, 4.9] kg, CNH, p = 0.01). CNH participants also tended to experience an attenuated loss in 1RM strength during the recovery performance tests following supplementation on day 5 (PLA: -9.3 [-13.5, -5.0], CNL: -9.3 [-13.5, -5.1], CNH: -3.9 [-6.6, -1.2] kg, p = 0.07). After 5 days, pre-supplementation 1RM leg press values increased significantly, only with CNH (24.7 [8.8, 40.6] kg, but not PLA (13.9 [-15.7, 43.5] or CNL (14.6 [-0.5, 29.7]). Further, post-supplementation 1RM leg press recovery did not decrease significantly for CNH (-13.3 [-31.9, 5.3], but did for PLA (-30.5 [-53.4, -7.7] and CNL (-29.0 [-49.5, -8.4]). CNL treatment promoted an increase in bench press repetitions at 70% of 1RM during recovery on day 5 (PLA: 0.4 [-0.8, 1.6], CNL: 0.9 [0.35, 1.5], CNH: 0.5 [-0.2, 0.3], p = 0.56), greater leg press endurance prior to supplementation on day 5 (PLA: -0.2 [-1.6, 1.2], CNL: 0.9 [0.2, 1.6], CNH: 0.2 [-0.5, 0.9], p = 0.25) and greater leg press endurance during recovery on day 5 (PLA: -0.03 [-1.2, 1.1], CNL: 1.1 [0.3, 1.9], CNH: 0.4 [-0.4, 1.2], p = 0.23). Cycling time trial performance (4 km) was not affected. Results indicate that creatine nitrate supplementation, up to a 6 g dose, for 6 days, appears to be safe and provide some ergogenic benefit.

Dietary nitrate as modulator of physical performance and cardiovascular health

PURPOSE OF REVIEW

Early interventional trials reported improvements in cardiac and exercise outcomes with inorganic nitrate ingestion. The current review aims to provide a brief update of recent evidence regarding ergogenic and cardiovascular effects of dietary nitrate and practical recommendations.

RECENT FINDINGS

Recent evidence has been inconsistent and questions remain regarding effective dose, duration, and source of nitrate and cohorts likely to benefit. Dietary nitrate may be most relevant to those with vascular/metabolic impairments, those engaging in short-term, intense exercise, deconditioned individuals, and those with a low dietary nitrate intake.

SUMMARY

The evidence for cardiovascular/exercise benefit is plausible but inconsistent. However, dietary nitrate, in contrast to pharmacological nitrate, has a high benefit-risk ratio. Although nitrate supplementation has grown in popularity, it is suggested that increased green vegetables consumption may provide similar/superior benefits to nitrate supplementation in a cheaper, safer, and potentially tastier context.

A time-course evaluation of inflammatory and oxidative markers following high-intensity exercise in horses: a pilot study

Exercise is a physiological stress resulting in reactive oxygen species and inflammatory mediators, the accumulation of which are thought to contribute to degenerative articular diseases. The horse is of particular interest in this regard as equine athletes are frequently exposed to repetitive bouts of high-intensity exercise. The purpose of this study was to provide a detailed description of the response of articular and systemic oxidative and inflammatory biomarkers following high-intensity, exhaustive exercise in horses. A group of horses (Ex) underwent repeated bouts of high-intensity exercise, at a target heart rate of 180 beats/min, until voluntary exhaustion. Baseline plasma and synovial fluid (SF) samples were taken 24 h before exercise and then at 0.5, 1, 2, 4, 8, and 24 h following exercise cessation. This time course was repeated in a group of nonexercised control horses (Co). Plasma and SF samples were analyzed for prostaglandin E₂ (PGE₂), nitric oxide (NO), total antioxidant status (TAS), and glycosaminoglycans (GAG). The Ex group had significantly higher plasma NO at 0.5, 1, and 2 h; and higher plasma PGE₂ at 0.5 and 1 h compared with Co. SF PGE₂ and GAG were also higher in Ex horses at 8 h compared with Co. It is concluded that high-intensity exercise in horses results in a rapid increase in systemic oxidative and inflammatory markers from 0.5 to 2 h after exercise, which is followed by local articular inflammation and cartilage turnover at 8 h postexercise. NEW & NOTEWORTHY In horses, the influence of exercise systemically and within the articular space remains unclear and requires further detailed characterization. In this study, we identify that an acute bout of high-intensity exercise in horses induces systemic inflammation and oxidative stress within 30 min of exercise cessation, which lasts for ~2 h. Articular inflammation and cartilage turnover were also be observed within the equine carpal joint 8 h following exercise completion.

Effects of Dietary Nitrate Supplementation on Physiological Responses, Cognitive Function, and 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 (NO3−) supplementation on NO bioavailability, physiological and cognitive function, and exercise performance at moderate and very-high simulated altitude.

Methods:Ten males (mean (SD): V˙O2max: 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 NO3−-rich (BRJ; ~12.5 mmol NO3−) or NO3−-deplete (PLA; 0.01 mmol NO3−) 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% V˙O2max 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 ([NO2−]), peripheral oxygen saturation (SpO₂), pulmonary oxygen uptake (V˙O2), muscle and cerebral oxygenation, and cognitive function were measured throughout.

Results: Pre-exercise plasma [NO2−] was significantly elevated in BRJ compared with PLA (p = 0.001). Pulmonary V˙O2 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.

Nutrition and Supplementation in Soccer

Contemporary elite soccer features increased physical demands during match-play, as well as a larger number of matches per season. Now more than ever, aspects related to performance optimization are highly regarded by both players and soccer coaches. Here, nutrition takes a special role as most elite teams try to provide an adequate diet to guarantee maximum performance while ensuring a faster recovery from matches and training exertions. It is currently known that manipulation and periodization of macronutrients, as well as sound hydration practices, have the potential to interfere with training adaptation and recovery. A careful monitoring of micronutrient status is also relevant to prevent undue fatigue and immune impairment secondary to a deficiency status. Furthermore, the sensible use of evidence-based dietary supplements may also play a role in soccer performance optimization. In this sense, several nutritional recommendations have been issued. This detailed and comprehensive review addresses the most relevant and up-to-date nutritional recommendations for elite soccer players, covering from macro and micronutrients to hydration and selected supplements in different contexts (daily requirements, pre, peri and post training/match and competition).

Beetroot Juice Supplementation Improves High-Intensity Intermittent Type Exercise Performance in Trained Soccer Players

It has been shown that nitrate supplementation can enhance endurance exercise performance. Recent work suggests that nitrate ingestion can also increase intermittent type exercise performance in recreational athletes. We hypothesized that six days of nitrate supplementation can improve high-intensity intermittent type exercise performance in trained soccer players. Thirty-two male soccer players (age: 23 ± 1 years, height: 181 ± 1 m, weight: 77 ± 1 kg, playing experience: 15.2 ± 0.5 years, playing in the first team of a 2nd or 3rd Dutch amateur league club) participated in this randomized, double-blind cross-over study. All subjects participated in two test days in which high-intensity intermittent running performance was assessed using the Yo-Yo IR1 test. Subjects ingested nitrate-rich (140 mL; ~800 mg nitrate/day; BR) or a nitrate-depleted beetroot juice (PLA) for six subsequent days, with at least eight days of wash-out between trials. The distance covered during the Yo-Yo IR1 was the primary outcome measure, while heart rate (HR) was measured continuously throughout the test, and a single blood and saliva sample were collected just prior to the test. Six days of BR ingestion increased plasma and salivary nitrate and nitrite concentrations in comparison to PLA (p < 0.001), and enhanced Yo-Yo IR1 test performance by 3.4 ± 1.3% (from 1574 ± 47 to 1623 ± 48 m; p = 0.027). Mean HR was lower in the BR (172 ± 2) vs. PLA trial (175 ± 2; p = 0.014). Six days of BR ingestion effectively improves high-intensity intermittent type exercise performance in trained soccer players.