Athletes use nutritional supplementation to enhance the effects of training and achieve improvements in their athletic performance. Beetroot juice increases levels of nitric oxide (NO), which serves multiple functions related to increased blood flow, gas exchange, mitochondrial biogenesis and efficiency, and strengthening of muscle contraction. These biomarker improvements indicate that supplementation with beetroot juice could have ergogenic effects on cardiorespiratory endurance that would benefit athletic performance. The aim of this literature review was to determine the effects of beetroot juice supplementation and the combination of beetroot juice with other supplements on cardiorespiratory endurance in athletes. A keyword search of DialNet, MedLine, PubMed, Scopus and Web of Science databases covered publications from 2010 to 2016. After excluding reviews/meta-analyses, animal studies, inaccessible full-text, and studies that did not supplement with beetroot juice and adequately assess cardiorespiratory endurance, 23 articles were selected for analysis. The available results suggest that supplementation with beetroot juice can improve cardiorespiratory endurance in athletes by increasing efficiency, which improves performance at various distances, increases time to exhaustion at submaximal intensities, and may improve the cardiorespiratory performance at anaerobic threshold intensities and maximum oxygen uptake (VO2max). Although the literature shows contradictory data, the findings of other studies lead us to hypothesize that supplementing with beetroot juice could mitigate the ergolytic effects of hypoxia on cardiorespiratory endurance in athletes. It cannot be stated that the combination of beetroot juice with other supplements has a positive or negative effect on cardiorespiratory endurance, but it is possible that the effects of supplementation with beetroot juice can be undermined by interaction with other supplements such as caffeine.

Background: Beetroot juice (BJ) is rich in inorganic nitrates and has proved effective at increasing blood nitric oxide (NO) levels. When used as a supplement BJ has shown an ergogenic effect on cardiorespiratory resistance exercise modalities, yet few studies have examined its impact on high intensity efforts. Objective: To assess the effects of BJ intake on anaerobic performance in a Wingate test. Methods: Fifteen trained men (age 21.46 ± 1.72 years, height 1.78 ± 0.07 cm and weight 76.90 ± 8.67 kg) undertook a 30-s maximum intensity test on an inertial cycle ergometer after drinking 70 mL of BJ (5.6 mmol NO3−) or placebo. Results: Despite no impacts of BJ on the mean power recorded during the test, improvements were produced in peak power (6%) (p = 0.034), average power 0–15 s (6.7%) (p = 0.048) and final blood lactate levels (82.6%) (p < 0.001), and there was a trend towards a shorter time taken to attain peak power (−8.4%) (p = 0.055). Conclusions: Supplementation with BJ has an ergonomic effect on maximum power output and on average power during the first 15 s of a 30-s maximum intensity inertial cycle ergometer test.

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.

Word Count: 247 28 Text Only Word Count: 2564 29 30 Abstract 2 Purpose: Dietary supplementation with inorganic nitrate (NO 3 -) can enhance high-3intensity exercise performance by improving skeletal muscle contractility and 4 metabolism, but the extent to which this might be linked to altered psychophysiological 5 processes is presently unclear. The purpose of this study was to assess the effects of 6 NO 3 --rich beetroot juice (BJ) supplementation on profile of mood states (POMS), 7 ratings of perceived exertion (RPE) and performance in a 30 s Wingate cycle test. 8 Methods: In a double blind, randomized, crossover study, 15 subjects completed two 9 laboratory sessions after ingesting NO 3 --rich or NO 3 --depleted (placebo) BJ. Participants 10 initially completed the POMS questionnaire. Subsequently, participants completed a 11 warm-up followed by a 30 s all-out Wingate cycling test. After the Wingate test, 12 participants immediately indicated the RPE of their leg muscles (RPE muscular ), 13 cardiovascular system (RPE cardio ) and general RPE (RPE general ). Results: Compared to 14the placebo condition, supplementation with BJ increased peak power output (W peak ) 15 (+4.4%, 11.5 ± 0.7 vs. 11.1 ± 1.0 W·kg -1 , p = 0.039) and lowered the time taken to 16 reach W peak (7.3 ± 0.9 vs. 8.7 ± 1.5 s, p = 0.002) during the Wingate test. The POMS 17 score linked to tension was increased prior to the Wingate test (4.8 ± 3.0 vs. 3.4 ± 2.4, p 18 = 0.040), and RPE muscular was lowered immediately following the Wingate test (17.7 ± 19 1.6 vs. 18.3 ± 1.0, p = 0.031), after BJ compared to placebo ingestion. Conclusions: 20 Acute BJ supplementation improved pre-exercise tension, and 30 s Wingate test 21 performance, and lowered post-exercise RPE muscular . 22 23 states 25 26 30However, although many commercially available supplements claim to improve sports 31 performance, such claims are not always supported by a firm foundation of robust 32 scientific evidence. To overcome this ambiguity, and to provide evidence-based 33 recommendations for dietary supplementation to enhance sports performance, the 34 International Olympic Committee has recently published a classification for nutritional 35 supplements based on the scientific evidence to support their ergogenic efficacy 1 . One 36 dietary supplement classified as having a high level of scientific evidence to support an 37 ergogenic effect was inorganic nitrate (NO 3 -). 38The ergogenic effects of NO 3supplementation, which is typically administered in 39 the form of NO 3 --rich beetroot juice (BJ), is attributed to its stepwise reduction to nitrite 40 and subsequently nitric oxide (NO) as NO 3is considered biologically inert 2 . After 41 NO 3supplementation, the increase in plasma [nitrite] serves as a circulating substrate 42 for O 2 -independent NO generation 2 , with the reduction of nitrite to NO enhanced in 43 conditions of hypoxia and acidosis 23 . Some of the physiological processes that have 44 been reported to be enhanced by increase NO exposure, which might underpi...

Background Caffeine supplementation (CAFF) has an established ergogenic effect on physical performance and the psychological response to exercise. However, few studies have compared the response to CAFF intake among athletes of different competition level. This study compares the acute effects of CAFF on anaerobic performance, mood and perceived effort in elite and moderately-trained recreational athletes. Methods Participants for this randomized, controlled, crossover study were 8 elite athletes (in the senior boxing national team) and 10 trained-recreational athletes. Under two experimental conditions, CAFF supplementation (6 mg/kg) or placebo (PLAC), the athletes completed a Wingate test. Subjective exertion during the test was recorded as the rating of perceived exertion (RPE) both at the general level (RPEgeneral) and at the levels muscular (RPEmuscular) and cardiorespiratory (RPEcardio). Before the Wingate test, participants completed the questionnaires Profiles of Moods States (POMS) and Subjective Vitality Scale (SVS). Results In response to CAFF intake, improvements were noted in Wpeak (11.22 ± 0.65 vs 10.70 ± 0.84; p = 0.003; $$ {\eta}_p^2 $$ηp2=0.44), Wavg (8.75 ± 0.55 vs 8.41 0.46; p = 0.001; $$ {\eta}_p^2 $$ηp2 =0.53) and time taken to reach Wpeak (7.56 ± 1.58 vs 9.11 ± 1.53; p <  0.001; $$ {\eta}_p^2 $$ηp2 =0.57) both in the elite and trained-recreational athletes. However, only the elite athletes showed significant increases in tension (+ 325%), vigor (+ 31%) and SVS (+ 28%) scores after the intake of CAFF compared to levels recorded under the condition PLAC (p <  0.05). Similarly, levels of vigor after consuming CAFF were significantly higher in the elite than the trained-recreational athletes (+ 5.8%). Conclusions CAFF supplementation improved anaerobic performance in both the elite and recreational athletes. However, the ergogenic effect of CAFF on several mood dimensions and subjective vitality was greater in the elite athletes.