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Acute Dietary Nitrate Supplementation Improves Cycling Time Trial Performance
Abstract
Dietary nitrate supplementation has been shown to reduce the O2 cost of submaximal exercise and to improve high-intensity exercise tolerance. However, it is presently unknown whether it may enhance performance during simulated competition. The present study investigated the effects of acute dietary nitrate supplementation on power output (PO), VO2, and performance during 4- and 16.1-km cycling time trials (TT).
After familiarization, nine club-level competitive male cyclists were assigned in a randomized, crossover design to consume 0.5 L of beetroot juice (BR; containing ∼ 6.2 mmol of nitrate) or 0.5 L of nitrate-depleted BR (placebo, PL; containing ∼ 0.0047 mmol of nitrate), ∼ 2.5 h before the completion of a 4- and a 16.1-km TT.
BR supplementation elevated plasma [nitrite] (PL = 241 ± 125 vs BR = 575 ± 199 nM, P < 0.05). The VO2 values during the TT were not significantly different between the BR and PL conditions at any elapsed distance (P > 0.05), but BR significantly increased mean PO during the 4-km (PL = 279 ± 51 vs BR = 292 ± 44 W, P < 0.05) and 16.1-km TT (PL = 233 ± 43 vs BR = 247 ± 44 W, P < 0.01). Consequently, BR improved 4-km performance by 2.8% (PL = 6.45 ± 0.42 vs BR = 6.27 ± 0.35 min, P < 0.05) and 16.1-km performance by 2.7% (PL = 27.7 ± 2.1 vs BR = 26.9 ± 1.8 min, P < 0.01).
These results suggest that acute dietary nitrate supplementation with 0.5 L of BR improves cycling economy, as demonstrated by a higher PO for the same VO2 and enhances both 4- and 16.1-km cycling TT performance.
... It has been shown that ingested nitrate, such as in the form of beetroot juice (BRJ), can lead to reduced oxygen cost during exercise, altered oxygen uptake kinetics [15][16][17][18][19][20][21], and improved exercise tolerance [15][16][17]20,22,23]. Studies suggest that increased NO bioavailability may also improve lipid metabolism [24,25] or reduce the utilization of muscle glycogen [26]. ...
... It has been shown that ingested nitrate, such as in the form of beetroot juice (BRJ), can lead to reduced oxygen cost during exercise, altered oxygen uptake kinetics [15][16][17][18][19][20][21], and improved exercise tolerance [15][16][17]20,22,23]. Studies suggest that increased NO bioavailability may also improve lipid metabolism [24,25] or reduce the utilization of muscle glycogen [26]. ...
... During HIHVT, differences in TG and NH 3 were found between the two supplementation groups. Contrary to the prevailing hypothesis of NO 3 − inducing a reduction in VO 2 during exercise in the participants supplemented with NO 3 − [6, [15][16][17][18][19][20][21], no differences in VO 2 were found between the N and P groups in the present study. ...
The aim of this study was to investigate the possible effects of chronic nitrate supplementation on the metabolites of energy metabolism during high-intensity, high-volume intermittent training (HIHVT). In this placebo-controlled double-blind study, 17 participants exercised 3 times a week on a cycle ergometer. Sodium nitrate or sodium chloride as the placebo was supplemented daily at 8.5 mg/kg body weight for 10 days. The training exercise consisted of a warm-up, a 45-min interval period, and a post-exercise period. Oxygen uptake, respiratory exchange ratio, and various parameters were measured in the venous blood and plasma. During training, the oxygen uptake and respiratory exchange ratio did not differ between the nitrate and the placebo group. Venous plasma concentrations of nitrate and nitrite were significantly increased in the nitrate group (p < 0.001 and p = 0.007, respectively). Triglyceride concentrations were significantly lower in the nitrate group than in the placebo group (p = 0.010). The concentration of free fatty acids in the plasma did not change upon nitrate supplementation and no significant differences were observed in the contribution of fat to energy metabolism during exercise. An increase in plasma ammonia concentration was observed in the nitrate group during and after exercise (p = 0.048). Metabolites of energy-rich phosphates did not differ between the nitrate and chloride groups, suggesting no improvement in efficiency through the supplemented nitrate. It was concluded that nitrate supplementation did not reduce oxygen uptake and adenosine triphosphate resynthesis by hydrolysis or through creatine kinase activity during high-intensity, high-volume intermittent exercise. Although, lipid metabolism as well as amino acid metabolism might be affected by nitrate supplementation during HIHVT.
... The plasma levels of nitrate and nitrite are dose-dependent, where higher doses result in higher systemic concentrations 54 Importantly, this has been shown to translate to improvements in time trial performance 55,63,64 . Interestingly, the plasma concentrations of nitrate and nitrite have been shown to decrease dramatically following a bout of maximal exercise 56 , suggesting that the nitrate and nitrite are utilized during exercise. ...
... However, in these cohorts, as little as a 1% improvement could be the difference between a podium finish or not, and this may be difficult to detect statistically 5,6 . A critical example of this stems from dietary nitrate research, where a growing body of evidence suggests that the ergogenic benefits are predominantly isolated to recreationally active individuals 54,55,57 and there may be minimal to no beneficial effect in elite athletes [110][111][112][113] . However, this is not always the case, as some ergogenic aids favour adaptations in trained individuals. ...
... Evidence suggests that men and women obtain similar benefits from creatine [120][121][122] and β-alanine 122-124 supplementation. However, there is emerging evidence that recreationally active and trained women do not experience the ergogenic effects of dietary nitrate supplementation 61,119,[125][126][127] , despite a higher relative dose, whereas the ergogenic benefits are consistently reported in recreationally active men 54,55,57 . This highlights the complexity of sex-specific responses in human physiology and metabolism and supports the ongoing calls for greater inclusion of female participants in sports science and ergogenic aid research 128,129 . ...
Top-class athletes have optimized their athletic performance largely through adequate training, nutrition, recovery, and sleep. A key component of sports nutrition is the utilization of nutritional ergogenic aids, which may provide a small but significant increase in athletic performance. Over the last decade, there has been an exponential increase in the consumption of nutritional ergogenic aids, where over 80% of young athletes report using at least one nutritional ergogenic aid for training and/or competition. Accordingly, due to their extensive use, there is a growing need for strong scientific investigations validating or invalidating the efficacy of novel nutritional ergogenic aids. Notably, an overview of the physiological considerations that play key roles in determining ergogenic efficacy is currently lacking. Therefore, in this brief review, we discuss important physiological considerations that contribute to ergogenic efficacy for nutritional ergogenic aids that are orally ingested including: (1) the impact of first pass metabolism, (2) rises in systemic concentrations, and (3) interactions with the target tissue. In addition, we explore mouth rinsing as an alternate route of ergogenic efficacy that bypasses the physiological hurdles of first pass metabolism via direct stimulation of the central nervous system. Moreover, we provide real world examples and discuss several practical factors that can alter the efficacy of nutritional ergogenic aids including human variability, dosing protocols, training status, sex differences, and the placebo effect. Taking these physiological considerations into account will strengthen the quality and impact of the literature regarding the efficacy of potential ergogenic aids for top-class athletes.
... [76] In contrast, other studies have now reported that NO 3 -(given mainly through beetroot juice) [Beet Root Juice, BRJ] can improve end times, exercise time to exhaustion, and increase maximal strength and exercise rate. [77][78][79][80][81][82] Many of these studies have also been conducted by elite cycling athletes and highlight the use of NO 3 supplementation to improve athletic performance in various sports (e.g. cycling, running, rowing, static apnea testing). ...
... cycling, running, rowing, static apnea testing). [77][78][79][80][81][82] Overall, chronic (3-15 days) and acute (2-3 h) nitrate administration either as NO 3 rich beetroot juice (5.1-18.1 mmol NO 3 per dose) or as NaNO 3 -(0.1 mmol/kg is associated with improvements in maximal exercise in walking, running, rowing and cycling and to improve tolerance to more intense exercise rates in almost all age groups of both sexes in trained and untrained populations. Most studies use doses of 70 ml BRJ. ...
... Most studies use doses of 70 ml BRJ. [77][78][79][80][81][82] Also, it is of great concern the findings of a recent review study speculated that although women are underrepresented in dietary NO 3 supplementation investigation, there are sex differences in response to NO 3 supplementation. [83] Regarding the NO 3 supplementation dose issues, a study by Wylie et al., (2016) showed that no improvement in the physiological response to exercise was achieved with NO 3 doses below ~5 mmol. ...
Branched-chain amino acids (BCAA) and nitrate have become increasingly popular mainly for their potential effect on individuals' health and secondary as ergogenic aids. The purpose of this narrative review was to incorporate the current scientific evidence of BCAA and nitrate supplementation on athletic performance and health. The current recommendations of BCAA and nitrate supplementation are discussed, as well as possible health complications associated with its intake. Pubmed, Scopus, and Web of Science were searched for articles on the effects of BCAA and nitrate supplementation in humans. The positive effect of BCAAs supplementation on athletic performance does not appear to be fully established. BCAAs supplementation seems to be recommended for all athletes who exercise vigorously daily, as it enhances their recovery after causing exercise-induced muscle damage. BCAAs supplementation reduces the feeling of delayed muscle pain, which follows because of muscle damage. Limited scientific data suggest a potentially beneficial effect of BCAAs on reducing central fatigue. Several clinical conditions could benefit from BCAAs' consumption. However, there are no reliable markers to evaluate or quantify their requirements. There are no exact consumption protocols and absolute recommendations, mainly because BCAAs are also obtained through the consumption of animal protein. Dietary nitrates lower blood pressure, reduce the cost of exercise oxygen, and, at least sometimes, enhance exercise capacity. Taking supplements for 2-6 days (or up to 15 days) can increase athletic performance during high-intensity exercise. The duration of continuous maximum exercise for which nitrates appear to be ergogenic is between 5-30 min. There is limited evidence that nitrates are beneficial in prolonged exercise performance (40 min), at least when administered short term. Supplementation of approximately 5-9 mmol of nitrate/day for 1-15 days may have beneficial effects on normal exercise responses, although the exact dose-response relationship has not yet been established. Five to 9 mmol of nitrates can be easily consumed in the normal diet and there is currently no evidence to adequately document that taking additional nitrates produces greater benefits. The effectiveness of acute nitrate supplementation is likely to depend on many factors, such as sex, health, hypoxia, diet, and level of fitness/training experience of the subjects. Nitrate needs are most likely met by ingesting approximately 250-500 g of leafy and root vegetables per day; however, dietary supplements might represent a more convenient and accurate way of covering an athlete's nitrate needs.
... Despite some controversy (1,2), dietary nitrate supplementation (DNS) has been suggested to enhance endurance performance during both single joint (3,4) and locomotor (5,6) exercise. The formation of nitric oxide (NO) from nitrate (NO 3 À ) and nitrite (NO 2 À ) (7) is thought to contribute to this potential ergogenic effect by enhancing peripheral hemodynamics and, therefore, oxygen (O 2 ) transport to muscle (7,8), a key determinant of athletic performance (9). ...
... DNS did not affect the time to task failure during high-intensity cycling exercise (Fig. 3). Although this lack of an effect confirms several earlier studies utilizing locomotor (44,45) and single joint (24) investigations documenting a positive effect of DNS on endurance performance during various events, including cycling (5,40), running (46), and knee-extensor (3) exercise. The reasons for the discrepancy between the performancerelated outcomes in these investigations remain unclear. ...
... In fact, it could be argued that, compared with other studies using 5 þ days of dietary nitrate in well-trained endurance athletes, the current supplementation protocol (3 days, 4.1 mmol NO 3 À /day; untrained individuals) could potentially have been too short to alter the cardiopulmonary and neuromuscular fatigue response to exercise and, consequently, cycling performance. However, according to previously established dose-response curves, plasma [NO 2 À ] and [NO 3 À ] usually peaks between 2 and 4 days of consistent DNS (28), and significant performance enhancements have been reported as early as 2.5 h after acute oral nitrate supplementation (5). Thus, despite efforts to ensure a supplementation regime consistent with successful earlier protocols (28,50) and investigations documenting enhanced endurance performance following DNS (7,16,44,51), the current group mean time to task failure was very similar following DNS and PLA (Fig. 3). ...
This study investigated the impact of dietary nitrate supplementation on peripheral hemodynamics, the development of neuromuscular fatigue, and time to task failure during cycling exercise. Eleven recreationally active male participants (27±5 years, VO 2 max: 42±2ml/kg/min) performed two experimental trials following 3 days of either dietary nitrate-rich beetroot juice (4.1mmol NO 3 ⁻ /day; DNS) or placebo (PLA) supplementation in a blinded, counterbalanced order. Exercise consisted of constant-load cycling at 50, 75, and 100 W (4-min each) and, at ~80% of peak power output (218±12W), to task-failure. All participants returned to repeat the shorter of the two trials performed to task-failure, but with the opposite supplementation regime (ISO-time comparison). Mean arterial pressure (MAP), leg blood flow (Q L ; Doppler ultrasound), leg vascular conductance (LVC), and pulmonary gas exchange were continuously assessed during exercise. Locomotor muscle fatigue was determined by the change in pre- to post-exercise quadriceps twitch-torque (∆Q tw ) and voluntary activation (∆VA; electrical femoral nerve stimulation). Following DNS, plasma [nitrate] (~670 vs ~180 nmol) and [nitrite] (~775 vs ~11 nmol) were significantly elevated compared to PLA. Unlike PLA, DNS lowered both Q L and MAP by ~8% (P<0.05), but did not alter LVC (P=0.31). VO 2 across work rates, as well as cycling time to task-failure (~7min) and locomotor muscle fatigue following the ISO-time comparison were not different between the two conditions (∆Q tw ~42%, ∆VA ~4%). Thus, despite significant hemodynamic changes, DNS did not alter the development of locomotor muscle fatigue and, ultimately, cycling time to task failure.
... Several studies have reported the effects of consuming beetroot juice (BRJ), a source of dietary nitrate, on exercise performance. Supplementation of BRJ has been shown to reduce the oxygen cost of low-, moderate-, and vigorous-intensity aerobic exercise (9,18,20,29), attenuate the slow component of VO 2 kinetics (17,28), increase time-to-exhaustion during vigorous-intensity cycling (19), and improve cycling time trial (TT) performance (9). However, previous research has demonstrated that the subjects' level of aerobic fitness may affect the efficacy of BRJ supplementation (7). ...
... Cermak et al. (9) showed that chronic BRJ supplementation improved 10-km TT performance and reduced the oxygen cost of both moderate-and vigorous-intensity cycling compared to PL in well-trained cyclists. Lansley et al. (19) showed improvements in 4-km and 10.1-km cycling TT performance after acute consumption of BRJ in well-trained cyclists, but no difference in the rate of oxygen consumption during either TT compared to PL. Bond et al. (4) demonstrated that chronic supplementation of BRJ improved 500-m rowing TT repeatability in well-trained rowers. ...
... However, studies have shown that an acute dose of concentrated BRJ can significantly increase plasma NO 2 levels. For example, Lansley et al. (19), showed that 2.5 hrs after consuming ~6.2 mmoL of dietary NO 3 from BRJ, plasma NO 2 increased by 138%. Wylie et al. (30) showed that 2.5 hrs after consumption of ~4.2 mmoL of dietary NO 3 from BRJ, plasma NO 2 increased by 250%. ...
Fiddler R, Fiddler J, Ashton N, Lind E. The Effects of Beetroot Juice Supplementation on Oxygen Cost of Vigorous Intensity Aerobic Exercise in Trained Endurance Athletes. JEPonline 2018; 21(6):134-142. Nitric oxide (NO) regulates many physiological processes critical to exercise performance. Beetroot juice (BRJ) supplementation has been shown to increase plasma nitrate, increasing NO availability. The present study investigated the effects of BRJ supplementation during vigorous intensity aerobic exercise. Using a repeated measures crossover design with a 1-wk washout period, 11 Division III collegiate distance runners (mean ± SD: age = 20.3 ± 1.1 yr; VO 2 peak = 55.5 ± 8.1 mL·kg-1 ·min-1) consumed 120 mL·d-1 of BRJ or placebo (PL) for 4 consecutive days. On day 5 the subjects completed 5 min of treadmill running at 65%, 85%, and 100% of volume of oxygen uptake reserve (VO 2 R) separated by 2 min each. There were no statistically significant interactions between treatment and exercise intensity for VO 2 , HR, RER, and RPE. The main effect of treatment was statistically significant for VO 2 , where BRJ (2.43 ± 0.18 L·min-1) was lower compared to PL (2.49 ± 0.17 L·min-1), P=0.029. The main effect of treatment was not statistically significant for HR, P = 0.490; RER, P=0.462; or RPE, P=0.471. These results suggest that a 4-day treatment of 120 mL·d-1 of BRJ reduces VO 2 during vigorous intensity aerobic exercise in well-trained endurance athletes.
... Over the last decade, studies have shown that oral beet nitrate supplementation improves performance between 2 and 16% across various exercise modalities (Cermak et al., 2012;Lansley et al., 2011;Murphy et al., 2012). Oral beet nitrate supplementation elevates plasma nitrate [NO 3 − ] and nitrite [NO 2 − ] consequently enhancing nitric oxide (NO) production using an O 2 − independent stepwise reduction of inorganic NO 3 − to NO 2 − and then to NO (Lundberg et al., 2008;Wylie et al., 2013). ...
... Previous health and sports performance research show oral nitrate supplementation enhances skeletal muscle blood flow, lowers blood pressure, improves vascular conductance, increases metabolic efficiency, and improves oxygen diffusive conductance in exercising muscles (Breese et al., 2013;Ferguson et al., 2013;Larsen et al., 2006;Larsen et al., 2011;Larsen et al., 2010). In turn, nitrate supplementation appears to improve exercise performance and metabolic efficiency across various exercise durations, intensities, and populations (Aucouturier et al., 2015;Bailey et al., 2015;Bailey et al., 2009;Coggan and Peterson, 2016;Lansley et al., 2011;Lee et al., 2015;Rimer et al., 2016;Shannon et al., 2017; C. Thompson et al., 2017;Wylie et al., 2016). While many studies show nitrate supplementation improves exercise performance and metabolic efficiency, meta-analysis research also suggests that non-elite athletes are most likely to experience positive physiological and performance benefits (Braakhuis and Hopkins, 2015). ...
... These data support the concept that in order to generate the same degree of glycolytic metabolic demand observed under placebo conditions, additional power was required until the point in which the cyclists reached their upper sustainable aerobic power requirements, i. e., FTP or 4 mmol lactate concentration. This concept is supported by previous cycling related studies (Lansley et al., 2011;Lee et al., 2015). In the study by Lansley et al. (2011), they observed during both a 4 k and 16 k simulation time trial races that nitrate supplementation improved performance by 2.4% and 2.7%, respectively. ...
Introduction
This study investigated the effects of a beet nitric oxide enhancing (NOE) supplement comprised of nitrite and nitrate on cycling performance indices in trained cyclists. Methods: Subjects completed a lactate threshold test and a high-intensity interval (HIIT) protocol at 50% above functional threshold power with or without oral NOE supplement. Results: NOE supplementation enhanced lactate threshold by 7.2% (Placebo = 191.6 ± 37.3 watts, NOE = 205.3 ± 39.9; p =0.01; Effect Size (ES) = 0.40). During the HIIT protocol, NOE supplementation improved time to exhaustion 18% (Placebo = 1,251 ± 562s, NOE = 1,474 ± 504s; p = 0.02; ES = 0.42) and total energy expended 22.3% (Placebo = 251 ± 48.6 kJ, NOE = 306.6 ± 55.2 kJ; p = 0.01; ES = 1.079). NOE supplementation increased the intervals completed (Placebo = 7.00 ± 2.5, NOE = 8.14 ± 2.4; p = 0.03; ES = 0.42) and distance cycled (Placebo = 10.9 ± 4.0 km, NOE = 13.5 ±3.9 km; p = 0.01; ES = 0.65). Also, target power was achieved at a higher cadence during the HIIT work and rest periods (p=0.02), which enhanced muscle oxygen saturation (SmO2) recovery. Time-to-fatigue was negatively correlated with the degree of SmO2, desaturation during the HIIT work interval segment (r = -0.67; p 0.008), while both SmO2 desaturation and the SmO2 starting work segment saturation level correlated with a cyclist’s kJ expended (SmO2 desaturation: r = -0.51, p = 0.06; SmO2 starting saturation: r = 0.59, p = 0.03). Conclusion: NOE supplementation containing beet nitrite and nitrate enhanced submaximal (lactate threshold) and HIIT maximal effort work. The NOE supplementation resulted in a cyclist riding at higher cadence rates with lower absolute torque values at the same power during both the work and rest periods, which in-turn delayed over-all fatigue and improved total work output.
... Blood pressure has previously been shown to decrease following acute and chronic dietary nitrate supplementation (primarily BRJ), with more pronounced reductions observed in systolic vs. diastolic blood pressure (Webb et al., 2008;Kapil et al., 2010;Vanhatalo et al., 2010;Siervo et al., 2013;Ashor et al., 2017). However, others have reported no change in blood pressure after acute (Lansley et al., 2011;Casey et al., 2015;Curtis et al., 2015;Kroll et al., 2018) and chronic (Blekkenhorst et al., 2018;Oggioni Dgj et al., 2018;Fan et al., 2019) dietary nitrate ingestion (i.e., BRJ, sodium nitrate, and nitraterich vegetables). More specifically, BRJ ingestion (140-500 mL) did not alter blood pressure ∼2.5-3 h post-ingestion in healthy adults (Lansley et al., 2011;Casey et al., 2015;Curtis et al., 2015), which is in line with our findings. ...
... However, others have reported no change in blood pressure after acute (Lansley et al., 2011;Casey et al., 2015;Curtis et al., 2015;Kroll et al., 2018) and chronic (Blekkenhorst et al., 2018;Oggioni Dgj et al., 2018;Fan et al., 2019) dietary nitrate ingestion (i.e., BRJ, sodium nitrate, and nitraterich vegetables). More specifically, BRJ ingestion (140-500 mL) did not alter blood pressure ∼2.5-3 h post-ingestion in healthy adults (Lansley et al., 2011;Casey et al., 2015;Curtis et al., 2015), which is in line with our findings. Our participants exhibited an average change of −2 ± 5 mmHg, and range from −13 mmHg to 8 mmHg. ...
Introduction
Beetroot juice (BRJ) improves peripheral endothelial function and vascular compliance, likely due to increased nitric oxide bioavailability. It is unknown if BRJ alters cerebrovascular function and cardiovagal baroreflex control in healthy individuals.
Purpose
We tested the hypotheses that BRJ consumption improves cerebral autoregulation (CA) and cardiovagal baroreflex sensitivity (cBRS) during lower-body negative pressure (LBNP).
Methods
Thirteen healthy adults (age: 26 ± 4 years; 5 women) performed oscillatory (O-LBNP) and static LBNP (S-LBNP) before (PRE) and 3 h after consuming 500 mL of BRJ (POST). Participants inhaled 3% CO 2 (21% O 2 , 76% N 2 ) during a 5 min baseline and throughout LBNP to attenuate reductions in end-tidal CO 2 tension (PETCO 2 ). O-LBNP was conducted at ∼0.02 Hz for six cycles (−70 mmHg), followed by a 3-min recovery before S-LBNP (−40 mmHg) for 7 min. Beat-to-beat middle cerebral artery blood velocity (MCAv) (transcranial Doppler) and blood pressure were continuously recorded. CA was assessed using transfer function analysis to calculate coherence, gain, and phase in the very-low-frequency (VLF; 0.020–0.070 Hz) and low-frequency bands (LF; 0.07–0.20 Hz). cBRS was calculated using the sequence method. Comparisons between POST vs. PRE are reported as mean ± SD.
Results
During O-LBNP, coherence VLF was greater at POST (0.55 ± 0.06 vs. 0.46 ± 0.08; P < 0.01), but phase VLF ( P = 0.17) and gain VLF ( P = 0.69) were not different. Coherence LF and phase LF were not different, but gain LF was lower at POST (1.03 ± 0.20 vs. 1.12 ± 0.30 cm/s/mmHg; P = 0.05). During S-LBNP, CA was not different in the VLF or LF bands (all P > 0.10). Up-cBRS and Down-cBRS were not different during both LBNP protocols.
Conclusion
These preliminary data indicate that CA and cBRS during LBNP in healthy, young adults is largely unaffected by an acute bolus of BRJ.
... Then, at the stomach, NO 2 is decomposed into nitric oxide (NO) and finally reaches the plasma and systemic circulation [5,6]. In sport performance, the physiological effects of BJ supplementation and NO could be summed up in a dilation of the vascular endothelium [7,8], causing a vasodilator effect and reducing the blood pressure (BP) [9,10]. In addition, these physiological effects are interesting for sport performance because it could increase muscle blood flow [11], alter and improve lactate removal in the exercise [12]. ...
... In addition, these physiological effects are interesting for sport performance because it could increase muscle blood flow [11], alter and improve lactate removal in the exercise [12]. In addition, the intake of NO 3 − effects has been proved in different endurance sports, where cardiovascular system has an important role in performance [1,7,13], showing a lower oxygen consumption (VO2) during exercise [1] with an improvement in adenosine triphosphate (ATP) synthesis [14]. ...
Beetroot juice (BJ) has been used as a sport supplement, improving performance in resistance training (RT). However, its effect on the modulation of the autonomic nervous system has not yet been widely studied. Therefore, the objective of this randomized double-blind crossover study was to assess the effect of acute BJ supplementation compared to placebo in blood pressure (BP), heart rate (HR), heart rate variability (HRV) and internal load during RT measure as Root Mean Square of the Successive Differences between adjacent RR intervals Slope (RMSSD and RMSSD-Slope, respectively). Eleven men performed an incremental RT test (three sets at 60%, 70% and 80% of their repetition maximum) composed by back squat and bench press with. HR, HRV and RMSSD-Slope were measured during and post exercise. As the main results, RMSSD during exercise decrease in the BJ group compared to placebo (p = 0.023; ES = 0.999), there were no differences in RMSSD post-exercise, and there were differences in RMSSD-Slope between groups in favor of the BJ group (p = 0.025; ES = 1.104) with a lower internal load. In conclusion, BJ supplementation seems to be a valuable tool for the reduction in the internal load of exercise during RT measured as RMSSD-Slope while enhancing performance.
... Although inorganic nitrate itself is relatively inert, metabolic pathways have been identified in humans that convert this compound into bioactive nitrite and nitric oxide (NO), which have the potential to elicit a wide range of physiological effects [3,4]. Research from several independent groups has shown that both acute and chronic consumption of inorganic nitrate, which increases NO bioavailability, can improve performance across various time-trial [5][6][7][8][9], time-to-exhaustion [10,11], high-intensity intermittent [12,13] and strengthbased [14,15] exercise tasks, as well as exercise tolerance in certain clinical populations [16]. However, dietary nitrate ingestion does not enhance exercise performance under all conditions (e.g. ...
... The Delphi technique has previously been employed in various areas of sport and exercise science and specifically in determining best practice for the administration of different nutritional supplements and ergogenic aids [45,46]. The current study aims to use this technique to derive a consensus on the use of dietary inorganic nitrate as an ergogenic aid, focusing on seven key areas of interest, including the following: (1) identifying the specific types of sport/exercise for which dietary nitrate is ergogenic (Activity); (2) characterizing the specific populations for whom dietary nitrate is ergogenic (Population); (3) identifying which dietary nitrate supplementation strategies are ergogenic (Supplementation strategy); (4) elucidating the physiological changes that underpin the ergogenic effects of dietary nitrate (Physiological effects); (5) clarifying whether dietary nitrate is safe to consume (Safety and toxicity); (6) appraising the quality of the evidence for dietary nitrate as an ergogenic aid (Quality of available evidence); (7) determining whether supplementation with dietary inorganic nitrate for ergogenic purposes is consistent with the ethos of Olympic sport (Ethos of Olympic sport). ...
Introduction
Dietary inorganic nitrate is a popular nutritional supplement, which increases nitric oxide bioavailability and may improve exercise performance. Despite over a decade of research into the effects of dietary nitrate supplementation during exercise there is currently no expert consensus on how, when and for whom this compound could be recommended as an ergogenic aid. Moreover, there is no consensus on the safe administration of dietary nitrate as an ergogenic aid. This study aimed to address these research gaps.
Methods
The modified Delphi technique was used to establish the views of 12 expert panel members on the use of dietary nitrate as an ergogenic aid. Over three iterative rounds (two via questionnaire and one via videoconferencing), the expert panel members voted on 222 statements relating to dietary nitrate as an ergogenic aid. Consensus was reached when > 80% of the panel provided the same answer (i.e. yes or no). Statements for which > 80% of the panel cast a vote of insufficient evidence were categorised as such and removed from further voting. These statements were subsequently used to identify directions for future research.
Results
The 12 panel members contributed to voting in all three rounds. A total of 39 statements (17.6%) reached consensus across the three rounds (20 yes, 19 no). In round one, 21 statements reached consensus (11 yes, 10 no). In round two, seven further statements reached consensus (4 yes, 3 no). In round three, an additional 11 statements reached consensus (5 yes, 6 no). The panel agreed that there was insufficient evidence for 134 (60.4%) of the statements, and were unable to agree on the outcome of the remaining statements.
Conclusions
This study provides information on the current expert consensus on dietary nitrate, which may be of value to athletes, coaches, practitioners and researchers. The effects of dietary nitrate appear to be diminished in individuals with a higher aerobic fitness (peak oxygen consumption [V̇O2peak] > 60 ml/kg/min), and therefore, aerobic fitness should be taken into account when considering use of dietary nitrate as an ergogenic aid. It is recommended that athletes looking to benefit from dietary nitrate supplementation should consume 8–16 mmol nitrate acutely or 4–16 mmol/day nitrate chronically (with the final dose ingested 2–4 h pre-exercise) to maximise ergogenic effects, taking into consideration that, from a safety perspective, athletes may be best advised to increase their intake of nitrate via vegetables and vegetable juices. Acute nitrate supplementation up to ~ 16 mmol is believed to be safe, although the safety of chronic nitrate supplementation requires further investigation. The expert panel agreed that there was insufficient evidence for most of the appraised statements, highlighting the need for future research in this area.
Graphical Abstract
... This time frame includes a potentially wide range of exercises with different requirements in terms of energy metabolism, though, in general, they might be considered moderate-intensity exercises that are predominantly fueled by aerobic energy sources (21). These may include exercise tasks such as 4 km cycling (56), 2000 m rowing (59), and 3 km running (69). Conversely, nitrate was ineffective for short-duration exercises. ...
... Surprisingly, considering the beneficial effects of nitrates on aerobic exercise lasting 2-10 min, exercise lasting >10 min was not improved with nitrate ingestion. Nonetheless, some individual studies have shown beneficial effects of nitrate on longer duration exercise, such as 10 (74) and 16 km cycling (56). Higher nitrate doses (∼12.4 mmol·d −1 ) may be necessary during prolonged endurance exercise to attenuate the increase in oxygen consumption and spare muscle glycogen (75). ...
To identify how variables such as exercise condition, supplementation strategy, participant characteristics and demographics, and practices that control oral microbiota diversity could modify the effect of inorganic nitrate ingestion (as nitrate salt supplements, beetroot juice, and nitrate-rich vegetables) on exercise performance, we conducted a systematic review with meta-analysis. Studies were identified in PubMed, Embase, and Cochrane databases. Eligibility criteria included randomized controlled trials assessing inorganic nitrate on exercise performance in healthy adults. To assess the variation in effect size, we used meta-regression models for continuous variables and subgroup analysis for categorical variables. One hundred and twenty-three studies were included in this meta-analysis totaling 1705 participants. Nitrate was effective for improving exercise performance (Standardized Mean Difference (SMD):0.101; 95% confidence intervals (95%CI):0.051,0.151, P < 0.001, I2 = 0%), although nitrate salts supplementation was not as effective (P = 0.629) as ingestion via beetroot juice (P < 0.001) or a high nitrate diet (P = 0.005). Practices that control oral microbiota diversity influenced the nitrate effect, with practices harmful to oral bacteria decreasing the ergogenic effect of nitrate. Nitrate ingestion was most effective for exercise lasting between 2 and 10min (P < 0.001). An inverse dose-response relationship between the fraction of inspired oxygen and the effect size (coefficient: -0.045;95%CI: -0.085, -0.005, P = 0.028) suggests that nitrate was more effective in increasingly hypoxic conditions. There was a dose-response relation for acute administration (P = 0.049). The most effective acute dose was between 5–14.9mmol provided ≥150min prior to exercise (P < 0.001). An inverse dose-response for protocols ≥ 2days was observed (P = 0.025), with the optimal dose between 5–9.9mmol∙day−1 (P < 0.001). Nitrate, via beetroot juice or a high nitrate diet, improved exercise performance, particular those lasting between 2–10min. Ingestion of 5–14.9mmol⋅day−1 taken at least 150min prior to exercise appears optimal for performance gains, while athletes should be aware that practices which control oral microbiota diversity may decrease the effect of nitrate.
... Given this, it seems that nitrate supplementation may be especially effective in the absence of the use of antibacterial mouthwash, and preferably other practices that reduce oral microbiota diversity (e.g., using antibacterial toothpaste, tongue scraping, chewing gum), when performed with 5.0-9.9 mmol nitrate from vegetables, beetroot gel, or beetroot juice provided at least 150 min before exercise tasks lasting 120-600 s (3); there is also the possibility that dietary nitrate may be ergogenic in continuous exercise lasting up to approximately 30 min (16). Based on this evidence, most studies that have investigated the ergogenic effect of nitrate in women have at least one suboptimal methodological aspect that may have contributed to a lack of benefit (3). ...
... One final consideration from a convenience standpoint relates to the consumption of dietary nitrate prior to or during exercise to elicit ergogenic effects. In the days leading up to a competitive sporting event, research indicates that it is possible to elevate habitual nitrate intake and achieve ergogenic effects using both concentrated beetroot juice and whole vegetables [50][51][52][53]. Nevertheless, consumption of a nitrate-rich salad in the hours prior to exercise (e.g., to provide a final 'top up' dose of nitrate pre-competition), and during exercise, may be logistically difficult, due to the challenges of transporting enough of the vegetables to, or around, a sporting event. ...
In recent years, a number of studies have explored the potential salutary effects of dietary nitrate, with promising findings emerging. Indeed, numerous investigations have now demonstrated that increasing intake of dietary nitrate can reduce blood pressure, improve endothelial function, decrease platelet aggregation, increase cognitive function and brain perfusion, and enhance exercise performance. Most researchers have explored the health and/or performance effects of dietary nitrate by providing participants with concentrated beetroot juice, which is rich in this compound. Another strategy for increasing/optimising dietary nitrate intake, which could be embraced alongside or instead of nitrate-rich supplements in research and non-research settings, is the consumption of whole nitrate-rich vegetables. In this review, we explore the potential advantages and disadvantages of increasing consumption of various whole nitrate-rich vegetables to augment dietary nitrate intake. We compare the cost, convenience, availability, feasibility/acceptability, and efficacy of consumption of nitrate via whole nitrate-rich vegetables against concentrated beetroot juice ‘shots’ as defined supplements. We also discuss possible strategies that could be used to help individuals maximise their intake of nitrate via whole vegetables, and outline potential avenues for future research.
... Moreover, beetroot juice also led to a significant increase in power output during the last 10 min of an incremental cycle ergometer test in young men. Similarly, Lansley et al. [185] investigated the effect of beetroot juice consumed 2.5 h prior to completing a 4 km cycling time trial in elite male cyclists. The authors found that the cyclists completed the time trial significantly faster after consuming the beetroot juice supplement compared to the placebo supplement. ...
Citation: Clemente-Suárez, V.J.; Bustamante-Sanchez, Á.; Mielgo-Ayuso, J.; Martínez-Guardado, I.; Martín-Rodríguez, A.; Tornero-Aguilera, J.F. Antioxidants and Sports Performance. Nutrients 2023, 15, 2371. https://doi. Abstract: The role of reactive oxygen species and antioxidant response in training adaptations and sports performance has been a large issue investigated in the last few years. The present review aims to analyze the role of reactive oxygen species and antioxidant response in sports performance. For this aim, the production of reactive oxygen species in physical activities, the effect of reactive oxygen species on sports performance, the relationship between reactive oxygen species and training adaptations, inflammation, and the microbiota, the effect of antioxidants on recovery and sports performance, and strategies to use antioxidants supplementations will be discussed. Finally, practical applications derived from this information are discussed. The reactive oxygen species (ROS) production during physical activity greatly influences sports performance. This review concludes that ROS play a critical role in the processes of training adaptation induced by resistance training through a reduction in inflammatory mediators and oxidative stress, as well as appropriate molecular signaling. Additionally, it has been established that micronutrients play an important role in counteracting free radicals, such as reactive oxygen species, which cause oxidative stress, and the effects of antioxidants on recovery, sports performance, and strategies for using antioxidant supplements, such as vitamin C, vitamin E, resveratrol, coenzyme Q10, selenium, and curcumin to enhance physical and mental well-being.
... According to Murphy et al. (2014), beetroot juice is used as a supplement because of its high inorganic nitrate (NO 3 − ) content, a compound found naturally in vegetables and in processed meats, where it is used as a preservative. The findings reflect the importance of supplementation with NO 3 − or nitrate salts to increase the bioavailability of NO in order to influence muscle function improving exercise performance, mainly in aerobic metabolism state Lansley et al. (2011). ...
Nutrition is increasingly recognized as a key component of optimal sporting performance, with both the science and practice of sports nutrition developing rapidly. The sports nutrition market has witnessed robust growth in the past few years; it is gaining pace due to the increase in health awareness among the population, new product development, the rapid increase in urbanization, and growth in a number of sales outlets, health clubs, fitness centers and gyms. Athletes use a range of nutritional and diet strategies to improve sports performance. Nutrition plans need to be personalized to the individual athlete to take into account the specificity and uniqueness of the event, performance goals, practical challenges, food preferences, and responses to various strategies. A key factor is the related marketing used to reach the core aim of the athletes for specific sports nutrition so they can meet their energy and nutrient requirements, whether that is speed, endurance, recovery, or strength. The marketing strategies in the sports nutrition industry are wide. Companies understand the power of sports endorsement, the trending on social media, and after all the factors of advertisement, through the different marketing communication channels impacting the athletes’ behavior for the final decision-making process of purchasing the product. In this paper the purpose is to investigate the effect of sport-related nutritional marketing as a communication strategy reaching athletes, and, its second relationship, the effect of the marketed sport-related nutritional products impact on athlete’s performance, from the athlete’s aspect. The importance of this paper is to examine a new topic of a connection between sports nutritional marketing and the eventual performance effect on a particular sub-category of athletes because very little research is being conducted on this topic of interest. The research framework used in this paper will help to guide future research and improve marketing communication strategies with great insight on what are the key methods to reach out to short and distance athletes from a marketing point of view, as well as the key factors that make marketed sport nutritional products impact on athlete’s performance.
... These phenotypes suggest that factors other than V̇O 2 max, such as exercise economy, lactate threshold, and power, affect exercise performance (35). Consistent with our results, prior studies have shown that free radical scavengers (36), nitrates (37), and L-citrulline (38) supplementation can improve time trial performance without affecting V̇O 2 max. Unidentified gut microbes other than B. uniformis affected by αCD may also explain the improved cycling time trial performance in the αCD group. ...
Although gut microbiota has been linked to exercise, whether alterations in the abundance of specific bacteria improve exercise performance remains ambiguous. In a cross-sectional study involving 25 male long-distance runners, we found a correlation between Bacteroides uniformis abundance in feces and the 3000-m race time. In addition, we administered flaxseed lignan or α-cyclodextrin as a test tablet to healthy, active males who regularly exercised in a randomized, double-blind, placebo-controlled study to increase B. uniformis in the gut (UMIN000033748). The results indicated that α-cyclodextrin supplementation improved human endurance exercise performance. Moreover, B. uniformis administration in mice increased swimming time to exhaustion, cecal short-chain fatty acid concentrations, and the gene expression of enzymes associated with gluconeogenesis in the liver while decreasing hepatic glycogen content. These findings indicate that B. uniformis enhances endurance exercise performance, which may be mediated by facilitating hepatic endogenous glucose production.
... Beetroot contains a number of bioactive compounds, including phenolic compounds, ascorbic acid, carotenoids, flavonoids and betalain pigments, the group of antioxidant compounds responsible for its violet colour, which have been shown to attenuate oxidative stress-induced injury and upregulate endogenous antioxidant production [85]. In addition, beetroot consumption has been associated with improvements in oxygen use and performance during submaximal endurance and resistance exercise in low to moderately-trained athletes, a phenomenon that has been attributed to its high nitrate content [86][87][88][89][90]. However, whether BJ can also invoke improvements in post-exercise recovery is under debate. ...
The metabolic and mechanical stresses associated with muscle-fatiguing exercise result in perturbations to bodily tissues that lead to exercise-induced muscle damage (EIMD), a state of fatigue involving oxidative stress and inflammation that is accompanied by muscle weakness, pain and a reduced ability to perform subsequent training sessions or competitions. This review collates evidence from previous research on a wide range of nutritional compounds that have the potential to speed up post-exercise recovery. We show that of the numerous compounds investigated thus far, only two—tart cherry and omega-3 fatty acids—are supported by substantial research evidence. Further studies are required to clarify the potential effects of other compounds presented here, many of which have been used since ancient times to treat conditions associated with inflammation and disease.
... It is difficult to compare our results with those of other studies because the protocols differ in terms of the supplements used, the exercise assessment, and the study population. Some studies on nitrate supplementation in beet juice and physical performance have shown some beneficial changes [27,28], but others have shown no effect [29]. ...
Background and objectives: The purpose of this study was to evaluate the effect of Opuntia ficus-indica juice (OFIJ) on performance and biochemical and physiological responses to a 6 min walking test (6MWT) in diabetic patients. Materials and Methods: Twenty diabetic patients performed a 6MWT at 07:00 h. During each test session, they were asked to drink 70 mL/day of natural OFIJ or placebo (PLA) for 4 days. Results: the results showed that cardiovascular parameters increased significantly after the 6MWT under both conditions. While, cortisol, HbA1c, cholesterol total (CT), triglycerides (TG), as well as low-density lipoprotein (LDL) were not modified between without and with supplementation. Likewise, no significant variation in performance was observed for PLA and OFIJ (p > 0.05). The cardiovascular parameters (heart rate max (HRmax), diastolic blood pressure (DBP), and systolic blood pressure (SBP)), lipid profile (CT, TG, LDL, and high-density lipoprotein HDL), hormonal parameters (insulin and glucagon), HbA1c and lactate ([La]) did not present any significant modification either between PLA or OFIJ (p > 0.05). Muscle-damage markers (creatine kinase (CK) and lactate dehydrogenase (LDH)], cortisol, and liver parameters (i.e., oxidative stress marker, γGT, and total bilirubin) as well as glucose (GLC) were affected by supplementation (p < 0.05) before and after the 6MWT, but this change was significant only for OFIJ (p < 0.05). Conclusion: OFIJ had an antioxidant capacity, improved performance of the 6MWT, and reduced muscle-damage markers and glucose level in type 2 diabetic patients.
... They gave a single dose of beetroot juice (500 mL beetroot juice equivalent to 434 mg sodium nitrate) to subjects 2.5 hours prior to a cycle-based ergometer test involving two moderate work-loads with 90% gas exchange threshold, followed by the ramp test [7]. In another study, Lansley et al. used the same dose of beetroot juice 2.5 hours prior to exercise and observed significant improvement in mean completion time (2.8%) and average power output (5%) during 4-16.1 km of cycle ergometer time trials, with respect to the placebo group [37]. ...
Nitric oxide (NO) is an essential component of the human body, involved in blood vessel dilation, stimulation of hormone release, signaling and regulation of neurotransmission. Nitric oxide is synthesized by nitric-oxide-synthase-dependent and -independent pathways. Nitric oxide supplementation improves cardiac health, enhances performance during exercise, reduces high blood pressure during pregnancy, reduces erectile dysfunction and improves healing processes and respiratory response. Nitric-oxide-associated benefits are mostly apparent in untrained or moderately trained individuals. L-arginine and L-citrulline supplementation contributes to nitric oxide levels because L-arginine is directly involved in NO synthesis, whereas L-citrulline acts as an L-arginine precursor that is further converted to NO by a reaction catalyzed by NO synthase. L-arginine supplements increase respiratory response and enhance performance during exercise, while L-citrulline with malate and other molecules increase working capacity. Various studies involving beetroot juice have reported a significant increase in plasma nitrite levels, regarded as markers of NO, after intake of beetroot juice. Although NO supplementation may have mild to moderate side-effects, using smaller or divided doses could avoid some of these side-effects. Since nitric oxide supplementation may worsen certain health conditions and may interfere with certain medicines, it should only be taken under medical supervision.
... Therefore, a direct comparison between these findings and other taekwondo-specific studies is not possible. In contrast to our results, previous studies with other sports and exercise modes reported improvements for the incremental cycle test [57] and the 4 km time trial by NO3 − supplementation [58]. Kelly et al. [55] reported improvement with BJ (8.2 mmol NO3 − ) at intensities of 60%, 70%, and 80% peak power during incremental tests. ...
Studies have shown that Nitrate (NO3-) rich beetroot juice (BJ) supplementation improves endurance and high-intensity intermittent exercise. The dose-response effect on taekwondo of BJ supplementation are yet to be determined. This study aimed to investigate two acute doses of 400 mg of NO3-(BJ-400) and (800 mg NO3- (BJ-800) on taekwondo-specific performance tests compared with a placebo (PL) and control (CON) conditions. Eight trained male taekwondo athletes (age: 20±4 years, height: 180±2 cm, weight: 64.8±4.0 kg) completed four experimental trials using a randomized, double‐blind placebo‐controlled design: BJ-400, BJ-800, PL, and CON. Countermovement jump (CMJ) was performed before the Multiple Frequency Speed of Kick Test (FSKT) and Progressive Specific Taekwondo Test (PSTT), respectively, whereas cognitive function was assessed (via the Stroop test) before and after supplementation and 10 minutes following PSTT. Blood lactate was collected before the CMJ tests, immediately, and 3 minutes after the FSKT and PSST, with rating of perceived exertion (RPE) was recorded during and after specific taekwondo tests. Nosignificant difference between conditions were observed (p> 0.05)for PSTT and FSKT performances. In addition, blood lactate, RPE, heart rate, and CMJ height and performance during the specific taekwondo tests were not significantly different among conditions (p> 0.05). However, after the PSTT test, cognitive function was higher in BJ-400 compared to other treatments (p< 0.05). In conclusion, acute intake of 400 and 800 mg of NO3-rich BJ did not improve taekwondo-specific performance tests in trained male taekwondo athletes.
... Nitric oxide (NO) is an important physiological signalling molecule for skeletal muscle perfusion, metabolism, contractility, and fatigue resistance [1,2], and it is attracting much interest in sport physiology and nutrition as an ergogenic aid [3]. To date, many studies have shown that dietary NO related supplements, such as nitrate-rich beetroot juice or watermelon juice, enhance athletic performance [4][5][6]. NO has been suggested to improve exercise performance primarily by enhancing exercise induced vasodilation and increasing the oxygenation status in the working muscles [7]. ...
The effects of L-citrulline or L-arginine supplementation on exercise performance are
equivocal, and the effects on swimming performance are unclear. We aimed to assess whether 8-day supplementation with L-arginine or L-citrulline supplementation would improve 200 m and 100 m freestyle swimming time-trial performances. After the baseline trial (first visit), in a double-blind, randomised design, 15 trained/developmental (5 females) swimmers and triathletes were assigned to three groups and underwent an 8-day supplementation period, with a daily dose of either 8 gr L-arginine (Arg, n = 5) or L-citrulline (Cit, n = 5) or placebo (Pla, n = 5). On day 9, participants completed experimental trial (second visit). In each trial, after blood sampling, participants performed both 200m and 100 m freestyle swimming time-trials, with 30 min recovery between trials. Plasma nitric oxide (NOx) and blood lactate concentrations (BLa) were collected immediately before and after 200 m and 100 m TTs, respectively. No significant difference was observed in NOx between groups (p = 0.201). There was no significant difference in 200 m (p = 0.226) and 100 m swimming time-trials (p = 0.993) between groups. There was a main effect of time on BLa concentration (p < 0.001), but no trial x group (p = 0.243) and trial x lactate x group interaction effect (p = 0.276) was present. Furthermore, 8-day either L-citrulline or L-arginine supplementation did not enhance middle (200 m) and short distance (100 m) swimming performance in trained/developmental swimmers and triathletes. These findings do not support the use of L-citrulline or L-arginine supplementation as ergogenic aids for swimming performance.
... Nitraterich vegetables and vegetable extracts can, in turn, stimulate nitrate reduction by the oral microbiota resulting in a lowering of blood pressure 118,119 . This oral microbiota dependent pathway (i.e., the nitrate-nitrite-nitric oxide pathway) can also increase sport performance, improve vascular endothelial function, inhibit platelet aggregation and promote the release of circulating angiogenic cells from the bone marrow 118,120,121 . Additionally, nitrate can reverse metabolic syndrome and have anti-diabetic effects in animal models 122 . ...
It has been estimated that we obtain over three quarters of dietary nitrate from vegetables and fruits. Nitrate-rich vegetable types include leafy greens and certain root vegetables (e.g., beetroots and radishes). The salivary glands actively concentrate plasma nitrate, leading to high salivary nitrate concentrations (5–8 mM) after a nitrate-rich meal. Nitrate is an ecological factor that can induce rapid changes in structure and function of polymicrobial communities. However, the effects on the oral microbiota have not been clarified, whilst a limited number of previous studies did indicate that nitrate is likely to be beneficial for oral health. The aim of this thesis was therefore to study nitrate-induced microbiome changes and identify potential mechanisms for nitrate-induced homeostasis, in order to determine if nitrate can be considered a prebiotic compound for oral health. A second aim was to isolate nitrate-reducing isolates and test their probiotic potential in vitro. In chapter 1, an in vitro study was set up testing the effect of 6.5 mM nitrate on oral communities grown from saliva of 12 healthy individuals. In chapter 2, fifty-three nitrate-reducing isolates were obtained and the effect of six probiotic candidates was tested on healthy oral communities grown from saliva of different donors with or without 6.5 mM nitrate. In chapter 3, the effects of nitrate-rich beetroot extracts on oral acidification after sugar rinsing was tested in 24 individuals without active caries. Supernatants (chapters 1 and 2) or saliva samples (chapter 3) were taken for nitrate, nitrite, ammonium, lactate and pH measurements. Additionally, the bacterial composition of in vitro biofilms and salivary pellets were determined using 16S rRNA gene Illumina sequencing and/or qPCR of the nitrate-reducing genus Rothia. We showed that nitrate stimulates the growth of the beneficial genera Rothia and Neisseria in our in vitro model, while potentially decreasing caries-, halitosis- and periodontal disease-associated bacteria. Additionally, the in vitro and in vivo data presented in this thesis indicate that nitrate can limit or prevent pH drops when sugars are fermented by the oral microbiota – a mechanism of resilience that could be stimulated by the consumption of nitrate-rich vegetable extracts. The main pH buffering mechanisms of nitrate were lactic acid usage during denitrification (observed both in vivo and in vitro) and during the reduction of nitrite to ammonium, as well as the potential production of ammonia (observed in vitro). In this thesis, the effects of nitrate were observed after short periods, i.e., after 5-9 h incubation in vitro and/or after 1-4 hours after nitrate supplement intake in vivo. Future studies should focus on the longitudinal effects of daily nitrate intake. In chapter 2, nitrate-reducing species belonging to the genera Rothia and Actinomyces were isolated. A selection of Rothia isolates increased lactate usage and nitrate reduction capacities of oral communities, potentially benefitting dental health and systemic health, respectively. The in vitro and in vivo data presented in the current thesis suggest that nitrate can modulate the oral microbiota in ways that are beneficial for the host and could thus be considered a prebiotic substance for the oral microbiota. Additionally, nitrate-reducing isolates can stimulate certain beneficial effects of nitrate metabolism. Nitrate and nitrate-reducing bacteria are thus promising components for future oral care products to prevent or treat oral diseases and this should be further investigated.
... Although we used the 30-s Wingate test to evaluate exercise performance in this study, which is a widely used method for measuring anaerobic sprint performance 2,38,39) , there are several other methods for evaluating exercise performance whose exercise intensity differs from that of the 30-s Wingate test. For example, a time trial performance [40][41][42][43] or a timeto-exhaustion test 1,[44][45][46] is often used as the evaluation method for moderate-to-high intensity exercise performance. It is possible that different results regarding the effects of the AA mixture supplement may be obtained with different exercise intensity protocols. ...
The aim of the present study was to examine the effect of an amino acid (AA) mixture of arginine, valine, and serine on exercise performance after prolonged exercise in humans. In a randomized, double-blinded, placebo-controlled crossover trial, nineteen recreationally active healthy males ingested an AA mixture of 1.8 g of arginine, 1.1 g of valine, and 0.1 g of serine or a placebo twice a day for 3 days and carried out a cycling exercise at 50% VO2max for 90 min with a 15-min rest at the midpoint. After the exercise, subjects performed a 30-s Wingate test. Their leg and grip strength, rating scale of perceived exertion (RPE), and blood biochemical parameters were also evaluated. There were no significant differences between the two conditions in the Wingate test performance (peak power: AA 650.9 ± 80.8 vs placebo 644.7 ± 78.0, p = 0.585; mean power: AA 491.6 ± 58.8 vs placebo 490.8 ± 63.7, p = 0.907), leg and grip strength, or RPE score during exercise. The plasma noradrenaline concentrations in the AA condition were significantly higher than those in the placebo condition during exercise (p < 0.05). Moreover, strong correlations were found between the Wingate test performance and level of plasma noradrenaline (p < 0.001). These results indicated that the AA mixture supplement significantly elevated the plasma noradrenaline level during exercise, while sprint performance after prolonged exercise was not improved by the AA mixture supplement in the study.
... Similarly, Cook, Myers [13] examined the effects of a seven-day New Zealand blackcurrant (NZBK) extract supplementation (105 mg anthocyanin·day −1 ), on 14 trained cyclists' performance (16.1 km time-trial). In close agreement to the aforementioned meta-analysis [45], cyclists showed a 2.4% improvement with blackcurrants [13], and 2.7% with beetroot [46] in 16.1 km cycling time trial performance. Additionally, Murphy, Cook [47] reported a performance increase of 0.82% with NZBK following two, 4 km cycling time-trials separated by 10 min. ...
Background:
Food high in (poly)phenolic compounds, such as anthocyanins, have the potential to improve exercise recovery and exercise performance. Haskap berries are rich in anthocyanins, but no research has examined the potential to improve human performance. The aim of this study was to determine the influence of Haskap berry on parameters of endurance running performance.
Methods:
Using a double-blind, placebo controlled, independent groups design, 30 male recreational runners (mean ± SD age, 33 ± 7 years; stature, 178.2 ± 7.2 cm; mass, 77.7 ± 10.6 kg; V˙O2peak, 52.2 ± 6.6 mL/kg/min) volunteered to participate. Following familiarisation, volunteers visited the laboratory twice (separated by seven days) to assess submaximal, maximal and 5 km time trial running performance. After the first visit, volunteers were randomly assigned to consume either the Haskap berry intervention or an isocaloric placebo control.
Results:
There were modest changes in heart rate and V˙O2 at submaximal intensities (p < 0.05). Time to exhaustion during the V˙O2peak test was longer in the Haskap group by 20 s (p = 0.031). Additionally, 5 km time trial performance was improved in the Haskap group by ~21 s (p = 0.016), which equated to a 0.25 km/h increase in mean running speed compared to the placebo control; this represented a >2% improvement in running performance.
Conclusions:
The application of this newly identified functional food to athletes has the capacity to improve endurance running performance.
... Most of the studies reporting that the ingestion of acute or chronic NO3 gives positive effects on TT performances included tests with a duration of less than minutes of moderate or high intensity 18 21 showed significant improvement in 10-km TT after BRJ supplementation in recreational endurance runners compared to PLA condition (performance improvement: 1.9%). These improvements in TT performance after acute or chronic BRJ supplementation were comparable and greater than those reported in studies with endurance running training protocols prescribed with VO2max and Vpeak (improvement of performance in 3-km and 10-km TT: 1% and 1.4%, respectively) 24,25 (Smith et al. 2003;Manoel et al. 2017). "Besides, most studies that have examined these effects have used the time to-exhaustion protocols with exercise being performed at a constant work rate 12 (Lansley et al. 2011), which do not turn to the normal athletic competition. ...
Objective: To find out the effect of 15 days of beetroot juice (BRJ) supplementation on 10 km time trial performance in trained distance runners of University level.Methods: Thirty trained athletes,15 males age = 26.3 y ± 1.52, height 170.5 ± 0.2 cm, and 15 females, age = 25.2 y ± 1.30, height 157.8 ± 0.3 cm were selected for the present study. Two experimental and two control groups were made consisting of males and females separately. The first group of male and female (Experimental Group) consumed the BRJdaily 250 ml/dayand the second group (Control Group) did not consume beetroot juice. Both groups underwent a regular athletics training programme. All the subjects were tested on Ten Km Time Trial (TT)performance before supplementation of BRJ and after 15 days of supplementation of BRJ. Results: The significant effect of BRJ supplementationwas observed (p < 0.05) between pre and post measures of 10 km TT in experimental group. BRJ supplementation significantly improved performance in 10 km TT in both groups (respectively male; P< 0.006; F=11.09, ES = .480, female; P < 0.000, F=40.45, ES = .771.Conclusion: Consumption of BRJ250 ml/day in improved 10 km time trial performance in traineddistance runners.
... de CrossFit ou praticantes de treinos intermitentes de alta intensidade, e privilegiou estudos com utilização do teste Wingate, uma vez que, este avalia a capacidade de gerar potência explosiva de curta duração, uma caraterística fundamental em determinados exercícios de CrossFit. Devido à natureza complexa deste tipo de treinos, os participantes seguem diferentes regimes e rotinas, daí a dificuldade, em alguns estudos, de quantificar e comparar componentes do regime de treino mais detalhadamente, tais como intensidade e volume, dando origem a resultados enviesados.A análise dos estudos apresentados (Tabela 1) revela a inconsistência de resultados em relação à influência do nitrato dietético nas várias componentes que influenciam a performance.DISCUSSÃO DOS RESULTADOSEm exercícios intermitentes de alta intensidade, a suplementação com nitratos poderá traduzir-se em maior tolerância ao exercício e aumento do tempo até à exaustão, uma vez que a contração muscular é mais eficiente com menor custo energético total, permitindo poupar energia.Também se poderá traduzir na redução do consumo de oxigênio (VO 2 ) sem efeito na frequência cardíaca ou acumulação de lactato sanguíneo; na redução da pressão arterial em repouso, na melhoria da função cardiorrespiratória e do desempenho no limiar anaeróbio(9, 15,(18)(19)(20)(21)(22)(23). ...
INTRODUÇÃO:
O CrossFit é uma prática desportiva predominantemente intermitente de alta intensidade e com uma forte componente de endurance. No sentido de melhorar a performance, o sumo de beterraba é um dos alimentos que tem sido amplamente utilizado como suplemento alimentar, no sentido de melhorar a performance. Várias investigações têm demonstrado melhorias na performance em modalidades que envolvam exercícios de endurance intensos e em exercícios de força e potência. Isto deve-se ao seu conteúdo em nitratos cuja evidência científica sugere apresentarem efeitos benéficos ao nível da vasodilatação, aumento do fluxo sanguíneo para as fibras musculares e promoção de trocas gasosas e regulação da eficiência da fosforilação oxidativa, para além de promoverem rápida recuperação muscular.
OBJETIVOS:
O presente artigo de revisão tem por objetivos perceber quais são as variáveis da performance (força, potência ou
endurance) influenciadas pelo sumo de beterraba, bem como as diferenças entre suplementação crónica ou aguda.
METODOLOGIA: Foi realizada pesquisa bibliográfica, nas bases de dados SCIELO e PUBMED, usando como critérios de inclusão: artigos publicados a partir de 2012 e redigidos em português ou inglês. Foram excluídos artigos cuja amostra era constituída por crianças ou idosos, realizados in vitro ou em animais, estudos em que não foram determinados os efeitos diretos do sumo de beterraba e em que não tenha sido reconhecida credibilidade académica.
RESULTADOS:
A análise dos estudos revela a inconsistência de resultados em relação à influência do nitrato dietético nas várias componentes que influenciam a performance.
CONCLUSÕES:
Sendo o CrossFit um exercício físico de minutos, no qual cada variável pode fazer a diferença, a utilização de nitratos em indivíduos responsivos, pode ser uma mais valia, apesar de não ter ficado comprovada a sua eficácia.
... Similarly, [151] Trexler et al. found significant TTE improvements at 90% and 100%, but not 110%, of peak aerobic velocity following pomegranate extract consumption. Two studies conducted multiple distance TTs following NO 3 consumption, with Shannon et al. [85] noting positive effects in a 1.5 km but not 10 km running TT, whereas no differences between improvements were seen between 4 and 16.1 km cycling TT performance by Lansley et al. [71]. Regarding intermittent performance, Wylie et al. [95] found significant increases in mean power output during 24 repeated sixsecond sprints, but no effect on exercise performance across six 60-second efforts. ...
Background
Increasing nitric oxide bioavailability may induce physiological effects that enhance endurance exercise performance. This review sought to evaluate the performance effects of consuming foods containing compounds that may promote nitric oxide bioavailability.
Methods
Scopus, Web of Science, Ovid Medline, EMBASE and SportDiscus were searched, with included studies assessing endurance performance following consumption of foods containing nitrate, L-arginine, L-citrulline or polyphenols. Random effects meta-analysis was conducted, with subgroup analyses performed based on food sources, sex, fitness, performance test type and supplementation protocol (e.g. duration).
Results
One hundred and eighteen studies were included in the meta-analysis, which encompassed 59 polyphenol studies, 56 nitrate studies and three L-citrulline studies. No effect on exercise performance following consumption of foods rich in L-citrulline was identified (SMD=-0.03, p=0.24). Trivial but significant benefits were demonstrated for consumption of nitrate and polyphenol-rich foods (SMD=0.15 and 0.17, respectively, p <0.001), including performance in time-trial, time-to-exhaustion and intermittent-type tests, and following both acute and multiple-day supplementation, but no effect of nitrate or polyphenol consumption was found in females. Among nitrate-rich foods, beneficial effects were seen for beetroot, but not red spinach or Swiss chard and rhubarb. For polyphenol-rich foods, benefits were found for grape, (nitrate-depleted) beetroot, French maritime pine, Montmorency cherry and pomegranate, while no significant effects were evident for New Zealand blackcurrant, cocoa, ginseng, green tea or raisins. Considerable heterogeneity between polyphenol studies may reflect food-specific effects or differences in study designs and subject characteristics. Well-trained males (V̇O 2max ≥65 ml.kg.min ⁻¹ ) exhibited small, significant benefits following polyphenol, but not nitrate consumption.
Conclusion
Foods rich in polyphenols and nitrate provide trivial benefits for endurance exercise performance, although these effects may be food dependent. Highly trained endurance athletes do not appear to benefit from consuming nitrate-rich foods but may benefit from polyphenol consumption. Further research into food sources, dosage and supplementation duration to optimise the ergogenic response to polyphenol consumption is warranted. Further studies should evaluate whether differential sex-based responses to nitrate and polyphenol consumption are attributable to physiological differences or sample size limitations.
Other
The review protocol was registered on the Open Science Framework ( https://osf.io/u7nsj ) and no funding was provided.
... A potential candidate nutrient that might affect blood supply to the target tissue is nitrate [12,13]. Dietary nitrate has been shown to improve endurance exercise performance in human athletes [20][21][22]. Nitrate (NO 3 ) in itself is inert, but after conversion to nitrite (NO 2 ), mainly facilitated by bacteria in the mouth [23], it is further reduced to nitric oxide (NO, by denitrifying anaerobic bacteria or periodontal acidity [19,24]), which is a vasoactive component. The NO 3 -NO 2 -NO pathway is suggested to be very important in the regulation of blood flow [25], as shown by Larsen et al. [26]. ...
The objective of the current experiment was to investigate whether or not maternal dietary nitrate supplementation, a nitric oxide (NO) precursor, could reduce piglet losses under commercial circumstances. In the current experiment, 120 hyper prolific gilts and sows (Landrace x Yorkshire: Danbred) on a commercial farm in Denmark received either a control lactation diet or a lactation diet containing 0.1% of calcium nitrate (containing 63.1% of nitrate) from approximately 5 days pre-farrowing until day 4 of lactation. The number of piglets born total, alive, and stillborn, as well as birth weights, weights after cross-fostering (approximately 1 day of age), 24 h after cross-fostering, day 3 of age, and at weaning was recorded. Placentas of sows were collected after expulsion and scored on redness. No effect of nitrate supplementation was found on piglet weight, piglet growth, placental redness score, and pre-weaning mortality during lactation. Maternal dietary nitrate supplementation decreased stillbirth percentage with 2.5% (9.9 vs. 7.4%; p = 0.05). It can be concluded that maternal dietary nitrate supplementation shows the potential to decrease the incidence of stillbirth in hyper prolific sows.
... These include extending time to exhaustion in endurance exercise, improving time trials <40 min in duration, enhanced type II muscle fibre function during high intensity exercise, and improving intermittent team sport activities [5][6][7][8][9][10]. To date, most studies examining exercise performance have been conducted in trained athletes and have used beetroot juice as the supplemental source of dietary nitrate [6,[11][12][13][14][15], although spinach, arugula, and celery are other sources. Rather than dietary nitrate sources, some studies have directly supplemented sodium or potassium nitrate-as this represents a one rather than two-step reduction to NO with a higher conversion efficiency-but these failed to show ergogenic effects on exercise performance [12,[16][17][18][19][20]. ...
Dietary nitrate supplementation has shown promising ergogenic effects on endurance exercise. However, at present there is no systematic analysis evaluating the effects of acute or chronic nitrate supplementation on performance measures during high-intensity interval training (HIIT) and sprint interval training (SIT). The main aim of this systematic review and meta-analysis was to evaluate the evidence for supplementation of dietary beetroot—a common source of nitrate—to improve peak and mean power output during HIIT and SIT. A systematic literature search was carried out following PRISMA guidelines and the PICOS framework within the following databases: PubMed, ProQuest, ScienceDirect, and SPORTDiscus. Search terms used were: ((nitrate OR nitrite OR beetroot) AND (HIIT or high intensity or sprint interval or SIT) AND (performance)). A total of 17 studies were included and reviewed independently. Seven studies applied an acute supplementation strategy and ten studies applied chronic supplementation. The standardised mean difference for mean power output showed an overall trivial, non-significant effect in favour of placebo (Hedges’ g = −0.05, 95% CI −0.32 to 0.21, Z = 0.39, p = 0.69). The standardised mean difference for peak power output showed a trivial, non-significant effect in favour of the beetroot juice intervention (Hedges’ g = 0.08, 95% CI -0.14 to 0.30, Z = 0.72, p = 0.47). The present meta-analysis showed trivial statistical heterogeneity in power output, but the variation in the exercise protocols, nitrate dosage, type of beetroot products, supplementation strategy, and duration among studies restricted a firm conclusion of the effect of beetroot supplementation on HIIT performance. Our findings suggest that beetroot supplementation offers no significant improvement to peak or mean power output during HIIT or SIT. Future research could further examine the ergogenic potential by optimising the beetroot supplementation strategy in terms of dosage, timing, and type of beetroot product. The potential combined effect of other ingredients in the beetroot products should not be undermined. Finally, a chronic supplementation protocol with a higher beetroot dosage (>12.9 mmol/day for 6 days) is recommended for future HIIT and SIT study.
... Therefore, a direct comparison between these findings and other taekwondo-specific studies is not possible. In contrast to our results, previous studies with other sports and exercise modes reported improvements for the incremental cycle test [57] and the 4 km time trial by NO3 − supplementation [58]. Kelly et al. [55] reported improvement with BJ (8.2 mmol NO3 − ) at intensities of 60%, 70%, and 80% peak power during incremental tests. ...
Studies have shown that nitrate (NO3 −)-rich beetroot juice (BJ) supplementation improves endurance and high-intensity intermittent exercise. The dose-response effects on taekwondo following BJ supplementation are yet to be determined. This study aimed to investigate two acute doses of 400 mg of NO3 − (BJ-400) and 800 mg of NO3 − (BJ-800) on taekwondo-specific performance and cognitive function tests compared with a placebo (PL) and control (CON) conditions. Eight trained male taekwondo athletes (age: 20 ± 4 years, height: 180 ± 2 cm, body mass: 64.8 ± 4.0 kg) completed four experimental trials using a randomized, double-blind placebo-controlled design: BJ-400, BJ-800, PL, and CON. Participants consumed two doses of BJ-400 and BJ-800 or nitrate-depleted PL at 2.5 h prior to performing the Multiple Frequency Speed of Kick Test (FSKT). Countermovement jump (CMJ) was performed before the (FSKT) and PSTT, whereas cognitive function was assessed (via the Stroop test) before and after supplementation and 10 min following PSTT. Blood lactate was collected before the CMJ tests immediately and 3 min after the FSKT and PSST; rating of perceived exertion (RPE) was recorded during and after both specific taekwondo tests. No significant differences (p > 0.05), with moderate and large effect sizes, between conditions were observed for PSTT and FSKT performances. In addition, blood lactate, RPE, heart rate, and CMJ height were not significantly different among conditions (p > 0.05). However, after the PSTT test, cognitive function was higher in BJ-400 compared to other treatments (p < 0.05). It was concluded that acute intake of 400 and 800 mg of NO3 − rich BJ reported a moderate to large effect size in anaerobic and aerobic; however, no statistical differences were found in taekwondo-specific performance.
... Several other studies report positive benefits of NO 3 − intake, such as lowering blood pressure [17,18], reduced use of ATP and reduced degradation of phosphocreatine (PCr), improved muscle contractile efficiency [16], reduced oxygen consumption during submaximal exercise [19][20][21], and improved performance [16,19,[22][23][24]. Conversely, many other studies do not report the above-mentioned positive effects [25][26][27][28][29][30][31]. ...
Nitrates have become increasingly popular for their potential role as an ergogenic aid. The purpose of this article was to review the current scientific evidence of nitrate supplementation on human performance. The current recommendation of nitrate supplementation is discussed, as well as possible health complications associated with nitrate intake for athletes, and dietary strategies of covering nitrate needs through sufficient intake of nitrate-rich foods alone are presented. Pubmed, Scopus, and Web of Science were searched for articles on the effects of nitrate supplementation in humans. Nitrates are an effective ergogenic aid when taken acutely or chronically in the range of ~5–16.8 mmol (~300–1041 mg) 2–3 h before exercise and primarily in the case of exercise duration of ~10–17 min in less trained individuals (VO2max < 65 mL/kg/min). Nitrate needs are most likely meet by ingesting approximately 250–500 g of leafy and root vegetables per day; however, dietary supplements might represent a more convenient and accurate way of covering an athlete’s nitrate needs. Athletes should refrain from mouthwash usage when nitrate supplementation benefits are desired. Future research should focus on the potential beneficial effects of nitrate supplementation on brain function, possible negative impacts of chronic nitrate supplementation through different nitrate sources, and the effectiveness of nitrate supplementation on strength and high-intensity intermittent exercise.
... Later, studies that met the following criteria were selected: (1) study subjects were healthy and free of cardiovascular diseases, (2) the observed cardiovascular benefits were statistically significant, and (3) plasma nitrate or nitrite levels were reported. Finally, a total of 14 studies that met the criteria were selected (Ashworth et al., 2015;Bailey et al., 2010Bailey et al., , 2009DeVan et al., 2016;Kapil et al., 2010;Kelly et al., 2013;Lansley et al., 2011;Larsen et al., 2007Larsen et al., , 2006Schneider et al., 2018;Sobko et al., 2010;van der Avoort et al., 2020;Vanhatalo et al., 2010;Webb et al., 2008) (Table 1). ...
The impacts of dietary nitrates and nitrites on human health have been a controversial topic for many years. However, the risk and benefit assessment of nitrates and nitrites is complicated by the large variation in nitrate and nitrite intake among people and the endogenous nitrite formation in the body. This study conducted a probabilistic risk–benefit assessment of dietary nitrates and nitrites based on internal dose by integrating exogenous and endogenous exposures with human trial data on cardiovascular benefits. A total diet study was carried out to quantify the age-specific dietary intakes of nitrates and nitrites. A previously well-validated human toxicokinetic model was used to predict internal doses for different age groups. In addition, the integrated approach was applied to different populations from different countries/regions based on reported exposure estimates to conduct a comprehensive risk–benefit assessment of dietary nitrates and nitrites. The results demonstrated that vegetable consumption was the main contributor to the internal nitrate and nitrite levels in all age groups. Exposure to nitrates and nitrites exceeding acceptable daily intakes in a variety of foods showed cardiovascular benefits. The probabilistic risk assessment showed that the exposure to nitrates and nitrites did not pose an appreciable health and safety risk. Therefore, the present results suggest that dietary nitrates and nitrites have clear cardiovascular benefits that may outweigh potential risks. Our analysis contributes significantly to addressing the controversy regarding risks and benefits from dietary nitrates and nitrites, and our approach could be applied to other dietary constituents with the potential for both risks and benefits.
... Beetroot juice is used as a supplement because it may serve as a precursor of NO due to its high nitrate content (1). Numerous studies investigated beetroot juice and its effects on intensive endurance exercise modalities and concluded it does in fact enhance performance when the dominant type of energy metabolism is oxidative (3,13,17,19,25). In addition, there is reason to believe that enhanced NO bioavailability may influence muscle function (MF) and exercise performance by modulating skeletal MF through its role in the regulation of blood flow, contractility, and glucose and calcium homeostasis (1,21). ...
Anderson, OK, Martinez-Ferran, M, Lorenzo-Calvo, J, Jiménez, SL, and Pareja-Galeano, H. Effects of nitrate supplementation on muscle strength and mass: a systematic review. J Strength Cond Res XX(X): 000–000, 2021—This systematic review examines the effect of dietary nitrate supplementation (SUP) on muscle strength and hypertrophy when combined with physical exercise. The databases PubMed, Web of Science, and MEDLINE were searched for full-text articles published between January 2000 and June 2020. For inclusion, studies had to report on the effects of SUP administered as acute or chronic doses together with a standardized exercise protocol on muscle strength and hypertrophy compared with placebo in healthy adults who were sedentary, physically active, or professional athletes. Twelve studies (1,571 subjects) were finally selected. In 5 studies, the SUP regime was acute, and in 7, it was chronic. SUP was nitrate-rich beetroot juice in 9 studies, a potassium nitrate capsule in 1, and increased dietary nitrate in 2. Ingested nitrate was 64–1,200 mg. Of the 12 studies, 6 observed an ergogenic effect of SUP compared with placebo. These findings indicate that muscle strength gains are possible provided the dose, format, frequency, period, and exercise test are appropriate. Best results were observed with a minimum acute dose of 400 mg of nitrate provided as beetroot juice/shot taken 2–2.5 hours before exercise involving low- and high-intensity muscle contractions. This SUP regime seems to improve muscle efficiency in terms of reduced phosphocreatine and energy costs (P-magnetic resonance spectroscopy) and improved time to exhaustion.
Objective
To evaluate the effects of acute nitrate supplementation on the performance of athletes in a time trial test.
News
Nitrate supplementation has been used by elite athletes as an ergogenic tool. Most studies investigate the effects of chronic nitrate supplementation. However, there is no consensus on whether nitrate can improve the performance of athletes after acute ingestion.
Prospects and projects
This study is a systematic review and meta-analysis which evaluated the available evidence on the effects of acute nitrate supplementation on the performance of athletes in a time trial test. From 137 articles retrieved, seventeen studies were eligible for qualitative and quantitative syntheses.
Conclusion
The time in the against-the-clock test of supplemented athletes was lower compared to the placebo group (τ² = 135.59; P < 0.18; 95% CI of −37.23, −16.61). The acute use of beetroot juice significantly reduced the cyclists’ time by 28.46 seconds (τ² = 111.06; P = 0.21; 95% CI of −39.01, −17.90). In general, the studies showed a low to uncertain risk of bias by the Cochrane tool, despite not clearly reporting the blinding of the outcome evaluators and randomization/allocation concealment procedures.
Nitric oxide can interact with a wide range of proteins including many that are involved in metabolism. In this review we have summarized the effects of NO on glycolysis, fatty acid metabolism, the TCA cycle, and oxidative phosphorylation with reference to skeletal muscle. Low to moderate NO concentrations upregulate glucose and fatty acid oxidation, while higher NO concentrations shift cellular reliance toward a fully glycolytic phenotype. Moderate NO production directly inhibits pyruvate dehydrogenase activity, reducing glucose-derived carbon entry into the TCA cycle and subsequently increasing anaploretic reactions. NO directly inhibits aconitase activity, increasing reliance on glutamine for continued energy production. At higher or prolonged NO exposure, citrate accumulation can inhibit multiple ATP-producing pathways. Reduced TCA flux slows NADH/FADH entry into the ETC. NO can also inhibit the ETC directly, further limiting oxidative phosphorylation. Moderate NO production improves mitochondrial efficiency while improving O2 utilization increasing whole-body energy production. Long-term bioenergetic capacity may be increased because of NO-derived ROS, which participate in adaptive cellular redox signaling through AMPK, PCG1-α, HIF-1, and NF-κB. However, prolonged exposure or high concentrations of NO can result in membrane depolarization and opening of the MPT. In this way NO may serve as a biochemical rheostat matching energy supply with demand for optimal respiratory function.
Background and Purpose: Red beet juice is a rich source of nitrate. Nitric oxide has the ability to stimulate vasodilation; Which increases blood flow to the muscle. Due to the involvement of aerobic and anaer-obic systems in karate, the aim of this study was to investigate the effect of red beet juice on aerobic and anaerobic power of karate girls. Materials and Methods: For this purpose, 10 club-level female karate players in the black belt category , two and three, were voluntarily studied in a cross-sectional, randomized, double-blind study. Subjects arrived at the gym at 7:30 a.m. and rested for 90 minutes after consuming red beetroot juice (100 ml) or placebo (blueberry juice) and taking the test at 9:00 a.m. First, 10 minutes of dynamic warm-up including walking and stretching movements were performed, then 4×9 test, RAST test and finally karate aerobic test was performed. In this aerobic test, the subjects guarded the punching bag consecutively. They were moving like a real combat during the recovery. The test ended when the subject was no longer able to continue the blows. In this case, the time was kept constant and the obtained number was recorded as fatigue time and test stage. Three minutes of active rest were determined between each test. After one week, the groups of subjects were transferred and the mentioned tests were performed again. Statistical analysis was reported using paired t-test and SPSS software version 26. Results: HFD The results showed that with consumption of red beet juice compared to placebo maximum power (P = 0.014), minimum power (P = 0.025), average power (P = 0.011), fatigue index (P = 0.022) and Speed drop index (P = 0.020) improved significantly in RAST test. There was also a significant decrease in agility test time (P = 0.039). But there was no significant difference in karate specific aerobic test (P = 0.099) and perceived exertion (P = 0.685). Conclusion: According to the results of the present study, consumption of red beet juice is effective in anaerobic performance and agility of karateka. But the amount of change in aerobic performance in the special karate test was not significant. Therefore, according to the results, it seems that consuming red beet juice can be useful for these athletes. How to cite this article: Hashemi fard E, Ebrahimi M. The effect of acute consumption of red beet juice on aerobic and anaerobic power of amateur karate girls. Journal of Sport and Exercise Physiology. 2022;15(3):102-111.
Background and Purpose: Red beet juice is a rich source of nitrate. Nitric oxide has the ability to stimulate vasodilation; Which increases blood flow to the muscle. Due to the involvement of aerobic and anaer-obic systems in karate, the aim of this study was to investigate the effect of red beet juice on aerobic and anaerobic power of karate girls. Materials and Methods: For this purpose, 10 club-level female karate players in the black belt category , two and three, were voluntarily studied in a cross-sectional, randomized, double-blind study. Subjects arrived at the gym at 7:30 a.m. and rested for 90 minutes after consuming red beetroot juice (100 ml) or placebo (blueberry juice) and taking the test at 9:00 a.m. First, 10 minutes of dynamic warm-up including walking and stretching movements were performed, then 4×9 test, RAST test and finally karate aerobic test was performed. In this aerobic test, the subjects guarded the punching bag consecutively. They were moving like a real combat during the recovery. The test ended when the subject was no longer able to continue the blows. In this case, the time was kept constant and the obtained number was recorded as fatigue time and test stage. Three minutes of active rest were determined between each test. After one week, the groups of subjects were transferred and the mentioned tests were performed again. Statistical analysis was reported using paired t-test and SPSS software version 26. Results: HFD The results showed that with consumption of red beet juice compared to placebo maximum power (P = 0.014), minimum power (P = 0.025), average power (P = 0.011), fatigue index (P = 0.022) and Speed drop index (P = 0.020) improved significantly in RAST test. There was also a significant decrease in agility test time (P = 0.039). But there was no significant difference in karate specific aerobic test (P = 0.099) and perceived exertion (P = 0.685). Conclusion: According to the results of the present study, consumption of red beet juice is effective in anaerobic performance and agility of karateka. But the amount of change in aerobic performance in the special karate test was not significant. Therefore, according to the results, it seems that consuming red beet juice can be useful for these athletes. How to cite this article: Hashemi fard E, Ebrahimi M. The effect of acute consumption of red beet juice on aerobic and anaerobic power of amateur karate girls. Journal of Sport and Exercise Physiology. 2022;15(3):102-111.
Intense and prolonged physical exercise can lead to oxidative stress. Therefore, many sport supplements can prevent the exercise-induced oxidative stress. The aim of this study was to investigate the effect of short-term supplementation of caffeine-beet juice on antioxidants and exercise performance in endurance athletes.
Methods
This study was performed in a short-term, counterbalanced, double-blind, cross-over and randomized study that included 7-day supplementation-placebo. Ten male runners (age: 27.5±83.8, weight: 69.9±7.8, height: 176.77±7 were divided in: 1-placebo (beetroot juice without nitrate); 2-BRJX (140ml beet juice+4.8mmol nitrate+200mg caffeine); 3-BRJX (140ml beet juice+9.6mmol nitrate+400mg caffeine). The Trials were performed during 8 days with 14 days washout. Exercise protocol included running 5km with maximum effort. Lactate, perceived exertion, heart rate and performance were measured before and after trials.
Results
The results showed that BRJX supplementation caused a significant increase in antioxidative enzymes (SOD, CAT, GPx) (p<0.05). Also, high and low doses of supplementation had a significant effect on endurance performance (p<0.05). RPE at 4500m, was significantly higher than 1500m point in all three trials (p<0.05). The results also showed that blood lactate level decreased with increasing recovery time (p<0.001).
Conclusion
It can be concluded that high and low doses beetroot-caffeine juice supplementation has a beneficial effect on antioxidants enzymes and exercise performance in endurance athletes. Therefore, it is recommended to use this supplement before endurance exercise to prevent exercise-related oxidative damage and faster reduction of blood lactate and improve performance.
Background/Objective
Dietary nitrate ingestion extends endurance capacity, but data supporting endurance time-trial performance are unclear. This systematic review and meta-analysis evaluated the evidence for dietary nitrate supplementation to improve high-intensity endurance time-trial performance over 5–30 minutes on the premise that nitrate may alleviate peripheral fatigue over shorter durations.
Methods
A systematic literature search and data extraction was carried out following PRISMA guidelines and the PICOS framework within five databases: PubMed, ProQuest, ScienceDirect, Scopus and SPORTDiscus. Search terms used were: (nitrate OR nitrite OR beetroot) AND (high intensity OR all out) AND (time trial or total work done) AND performance.
Results
Twenty-four studies were included. Fifteen studies applied an acute supplementation strategy (4.1 mmol–15.2 mmol serving on one day), eight chronic supplementation (4.0 mmol–13.0 mmol per day over 3–15 days), and one applied both acute and chronic supplementation (8.0 mmol on one day and over 15 days). Standardised mean difference for time-trial ranging from 5 to 30 minutes showed an overall trivial effect in favour of nitrate (Hedges'g = 0.15, 95% CI -0.00 to 0.31, Z = 1.95, p = 0.05). Subgroup analysis revealed a small, borderline effect in favour of chronic nitrate intervention (Hedges'g = 0.30, 95% CI -0.00 to 0.59, Z = 1.94, p = 0.05), and a non-significant effect for acute nitrate intervention (Hedges'g = 0.10, 95% CI -0.08 to 0.28, Z = 1.11, p = 0.27).
Conclusion
Chronic nitrate supplementation improves time-trial performance ranging from 5 to 30 minutes.
In this chapter is presented part of the results of a project of the Greek Ministry of Rural Development and Foods (MRDF). This project aimed at the investigation of the freshwater quality (surface and groundwater) in River Water Basins EL07 and ELO4 located in Sterea Hellas, central Greece. This includes the identification of pollution sources as well as the proposal of measures for protection and restoration of water quality, according to the provisions of Community Directive 2000/60 and national regulations. The water properties discussed in this chapter are pH, electrical conductivity, and the inorganic nitrogen ions nitrite, nitrate, and ammonium. The entire area was divided into 11 catchments from which, for two consecutive years (2017–2018), water samples were taken at specified intervals from rivers, lakes, canals, and wells. These samples were analyzed in situ and in the laboratory, evaluated as to their suitability for drinking and irrigation, according to European Union and national regulations. The values of the parameters studied ranged widely among rivers, lakes, groundwater, and drainage canals, reflecting the various prevailing conditions in the different water sources and the special characteristics of the sampling positions. The median values of all the properties studied are lying within the normal and acceptable levels. However, in some places, extreme values, unacceptable for any use were recorded. The pH was higher in lake water, followed by rivers, canals, and groundwaters; electrical conductivity was found to be higher in river and canal waters, followed by canals and groundwaters; nitrite was higher in groundwaters followed by canals, rivers, and lake waters, while nitrate was higher in groundwaters followed by all other categories, and ammonium was higher in canals, followed by lakes, rivers, and groundwaters.
The sources of contamination on a case-by-case basis appear to be anthropogenic, such as poor agricultural practices and, in particular, unsound management of inputs (fertilizers and pesticides), the dumping into drainage canals of untreated municipal or/and industrial waste, livestock farming (as it was found in the catchments, Sperceios – C1, Kifisos – C5, and Asopos – C6). And there are natural sources, such as seawater intrusion and the chemical composition of the rocks of the study area (especially in the catchments: Sperceios – C1, Amfissa – C4, Messapios-Lilantas – C8, Nireas-Kireas-Voudoros-Kimasi – C9, Kallas – C10). The most significant suggested measurement of water contamination are the tracing of contamination sources to identify their origin (agricultural, livestock, urban, industrial), the implementation of good agricultural practices (especially in applying appropriate irrigation methods that reduce nutrient leaching into the aquifer), and the estimation of the nutrient needs by soil and plant analysis or by using precision agriculture practices, both of which permit the differentiation of the amount of nitrogen fertilizers needs by taking into account the significant variability of the soil properties. Furthermore, suggestions include the continuous monitoring of surface and groundwater through certain environmental indicators (for example nitrate content), and taking protection measures of water drilling and application of their protection zones following the River Basin Management Plans, which propose detailed measures based on the article 4 of the Water Framework Directive 2000/60.
Objective:
The impact of high-nitrate beetroot juice (BRJ) supplementation has seen a recent explosion of interest in sports science. This study examined the potential influence of 7-day BRJ supplementation on the endurance performance of winter triathletes.
Methods:
Eighty young active winter triathletes (44 males, age = 21.50 ± 1.15 yrs; 36 females, age = 20.66 ± 1.45 yrs) participated in this study and were provided with either BRJ (6.5 mmol NO3-/70 mL) or a placebo (PL, 0.065 mmol NO3-/70 mL) for 7 days (a dose of ×3 per day) in a randomized, double-blind design. The athletes then completed a submaximal treadmill run, intraday cycling exhaustion testing, and a 10-km cross country (XC) skiing competition on the second day.
Results:
There was a significant decrease in the oxygen uptake, respiratory exchange ratio, and blood lactic acid level (p < 0.05) between the BRJ and PL treatment groups during V3 speed running (males: 13.3 km·h-1, females: 11.6 km·h-1). BRJ treatment also remarkably increased the time to exhaustion (TTE) during cycling exhaustion testing (males: p = 0.02, females: p = 0.04). No significant differences were observed in medium- or low-speed submaximal treadmill runs and 10-km XC skiing performance.
Conclusions:
One week of daily nitrate-rich BRJ supplementation improved running economy at high speed during the submaximal treadmill running test and extended the TTE of athletes during cycling exhaustion testing. However, BRJ supplementation did not improve the performance in 10-km on-snow time trials in XC skiing. Regarding nutritional strategies to improve endurance performance in exercise training and competition, these results should be carefully considered owing to the different motor skill levels and competitive abilities of participants.
El objetivo fue analizar los efectos de la suplementación con zumo de remolacha (ZR) sobre el rendimiento deportivo en triatletas amateur, medido mediante un protocolo de media sentadilla bilateral y unilateral, y con una prueba de salto con contramovimiento (CMJ), en situación de fatiga. Doce triatletas amateurs participaron en este estudio aleatorizado, a doble ciego y con un diseño cruzado compuesto por dos sesiones de evaluación que consistían en un test incremental hasta la extenuación ejecutado entre dos CMJ y dos pruebas de media sentadilla con 30 y 40 kg de manera bilateral y unilateral. La intervención nutricional consistía en ingerir 140 mL de ZR o placebo 2,5 h antes de la prueba. La suplementación con ZR mejoró el consumo máximo de oxígeno (VO2max) absoluto (p = 0,033) y relativo (p = 0,011) obtenido en la prueba incremental en comparación con placebo (4,12 ± 0,70 vs. 3,72 ± 0,90 ml·kg·min-1 y 54,82 ± 7,72 vs. 44,48 ± 15,84 ml·kg·min-1). Por otro lado, no se encontró una interacción significativa (p > 0,05, n2p = 0,03-0,30) para ninguna de las variables estudiadas en relación con el rendimiento bilateral y unilateral en media sentadilla ni CMJ entre la condición (placebo y ZR) y el tiempo (antes, PRE y después, POST). Estos resultados ponen de manifiesto que la suplementación con ZR ayuda a exhibir un mayor VO2max en triatletas amateurs pero no reduce la fatiga en comparación con la condición de placebo.
Dietary nitrate supplementation has been shown to reduce pulmonary O 2 uptake during submaximal exercise and enhance exercise performance. However, the effects of nitrate supplementation on local metabolic and haemodynamic regulation in contracting human skeletal muscle remain unclear. To address this, eight healthy young male sedentary subjects were assigned in a randomized, double‐blind, crossover design to receive nitrate‐rich beetroot juice (NO3, 9 mmol) and placebo (PLA) 2.5 h prior to the completion of a double‐step knee‐extensor exercise protocol that included a transition from unloaded to moderate‐intensity exercise (MOD) followed immediately by a transition to intense exercise (HIGH). Compared with PLA, NO3 increased plasma levels of nitrate and nitrite. During MOD, leg and leg blood flow (LBF) were reduced to a similar extent (∼9%–15%) in NO3. During HIGH, leg was reduced by ∼6%–10% and LBF by ∼5%–9% (did not reach significance) in NO3. Leg kinetics was markedly faster in the transition from passive to MOD compared with the transition from MOD to HIGH both in NO3 and PLA with no difference between PLA and NO3. In NO3, a reduction in nitrate and nitrite concentration was detected between arterial and venous samples. No difference in the time to exhaustion was observed between conditions. In conclusion, elevation of plasma nitrate and nitrate reduces leg skeletal muscle and blood flow during exercise. However, nitrate supplementation does not enhance muscle kinetics during exercise, nor does it improve time to exhaustion when exercising with a small muscle mass. image
Key points
Dietary nitrate supplementation has been shown to reduce systemic O 2 uptake during exercise and improve exercise performance.
The effects of nitrate supplementation on local metabolism and blood flow regulation in contracting human skeletal muscle remain unclear.
By using leg exercise engaging a small muscle mass, we show that O 2 uptake and blood flow are similarly reduced in contracting skeletal muscle of humans during exercise.
Despite slower kinetics in the transition from moderate to intense exercise, no effects of nitrate supplementation were observed for kinetics and time to exhaustion.
Nitrate and nitrite concentrations are reduced across the exercising leg, suggesting that these ions are extracted from the arterial blood by contracting skeletal muscle.
Background. Nitrate-rich supplements such as beetroot extract could improve aerobic performance by increasing neuromuscular functioning. However, little is known about the effects of beetroot extract on combat sports, such as taekwondo. Problem and aim. This study investigated the acute effect of beetroot extract supplementation (1g) on taekwondo athletes under-going a maximal aerobic test. Methods. Twelve athletes (26.8±8.8 yrs.; 77.8±11.7 kg; 1.8±0.1 m; 25.3±3.2 kg/m2; 10.0±5.3 Fat%) were submitted to a specific Taek-wondo aerobic protocol. All participants performed an alternated kick (bandal-chagi) maximal protocol under two randomized conditions: a) beetroot extract; and b) Placebo. Results. Beetroot condition showed a higher absolute VO2Peak (4.0±0.6 vs. 3.6±0.5 L/min; p=0.048), absolute VO2max at anaerobic threshold (3.7±0.6 vs. 3.2±0.6 L/min; p=0.044), and complete stages (10.9±2.6 vs. 8.3±1.7 L/min; p=0.009). Lactate concentration increased significantly between measurements taken before, after and 3 min after (p≤0.001) the test, without differences between conditions (p=0.46). Conclusion. Our results suggest an ergogenic effect of beetroot extract supplementation (1 g) on aerobic capacity and specific test performance in taekwondo athletes.
Nutrition plays a key role in training for, and competing in, competitive sport, and is essential for reducing risk of injury and illness, recovering and adapting between bouts of activity, and enhancing performance. Consumption of a Mediterranean diet (MedDiet) has been demonstrated to reduce risk of various non-communicable diseases and increase longevity. Following the key principles of a MedDiet could also represent a useful framework for good nutrition in competitive athletes under most circumstances, with potential benefits for health and performance parameters. In this review, we discuss the potential effects of a MedDiet, or individual foods and compounds readily available in this dietary pattern, on oxidative stress and inflammation, injury and illness risk, vascular and cognitive function, and exercise performance in competitive athletes. We also highlight potential modifications which could be made to the MedDiet (whilst otherwise adhering to the key principles of this dietary pattern) in accordance with contemporary sports nutrition practices, to maximise health and performance effects. In addition, we discuss potential directions for future research.
The plasma level of NO(x), i.e., the sum of NO(2)- and NO(3)-, is frequently used to assess NO bioavailability in vivo. However, little is known about the kinetics of NO conversion to these metabolites under physiological conditions. Moreover, plasma nitrite recently has been proposed to represent a delivery source for intravascular NO. We therefore sought to investigate in humans whether changes in NO(x) concentration are a reliable marker for endothelial NO production and whether physiological concentrations of nitrite are vasoactive. NO(2)- and NO(3)- concentrations were measured in blood sampled from the antecubital vein and brachial artery of 24 healthy volunteers. No significant arterial-venous gradient was observed for either NO(2)- or NO(3)-. Endothelial NO synthase (eNOS) stimulation with acetylcholine (1-10 microg/min) dose-dependently augmented venous NO(2)- levels by maximally 71%. This effect was paralleled by an almost 4-fold increase in forearm blood flow (FBF), whereas an equieffective dose of papaverine produced no change in venous NO(2)-. Intraarterial infusion of NO(2)- had no effect on FBF. NOS inhibition (N(G)-monomethyl-l-arginine; 4-12 micromol/min) dose-dependently reduced basal NO(2)- and FBF and blunted acetylcholine-induced vasodilation and NO release by more than 80% and 90%, respectively. In contrast, venous NO(3)- and total NO(x) remained unchanged as did systemic arterial NO(2)- and NO(3)- levels during all these interventions. FBF and NO release showed a positive association (r = 0.85; P < 0.001). These results contradict the current paradigm that plasma NO(3)- and/or total NO(x) are generally useful markers of endogenous NO production and demonstrate that only NO(2)- reflects acute changes in regional eNOS activity. Our results further demonstrate that physiological levels of nitrite are vasodilator-inactive.
Background: The RacerMate Inc. CompuTrainer is an increasingly popular ergometer in Sport Science laboratories, yet there is little information on the characteristics and validity of the CompuTrainer calibration procedure.
Aim: To investigate the effect of a range of environmental temperatures on the CompuTrainer calibration procedure and validate the power output against an SRM powermeter.
Methods: A bicycle fitted with an SRM Training System was attached to a CompuTrainer ergometer. The calibration procedure was repeated (up to 5 occasions) interspaced with 2min cycling at 200W and ∼90rpm. The cyclist then cycled for a further 2min at 200W for a direct comparison with the SRM training system. This process was repeated at seven different random calibration values at a range of environmental temperatures (15, 20, 28 and 38°C).
Results: At all temperatures there was a large decline in calibration pressure after the first 2min of cycling, with no further decline after 6min of cycling. This decline was inversely correlated with the temperature (r2 = 0.7). In low temperatures (15° and 20°C) the CompuTrainer significantly underestimated SRM power by 7.3 ± 5.8 W (95%CI: 4.2-10.4W; Range 1-18W; p = 0.0002) but was similar (-0.3 ± 4.4W) in high temperatures (28° and 38°C) (95%CI: -2.7-2.0W; Range -9-5W; p = 0.78).
Conclusions: Both temperature and calibration procedure were shown to affect power measurement and thus these authors have suggested an alternative procedure to enhance the reliability and validity of the CompuTrainer ergometer.
The race-to-race variation in performance of a top athlete determines the smallest change in performance affecting the athlete's chances of winning. We report here the typical variation in competition times of elite cyclists in various race series. Repeated-measures analysis of log-transformed official race times provided the typical variation in a cyclist's performance as a coefficient of variation. The typical variation of a top cyclist (and its 95% likely limits) was 0.4% (0.3–0.5%) in World Cup road races, 0.7% (0.7–0.8%) in Tour de France road races, 1.2% (0.8–2.2%) in the Kilo, 1.3% (0.9–2.4%) in road time trials, 1.7% (1.2–2.6%) in Tour de France time trials, and 2.4% (2.1–2.8%) in World Cup mountain biking. Cyclist interdependence arising from team tactics and pack riding probably accounts for the lower variability in performance of cyclists in road races and precludes estimation of the smallest worthwhile change in performance time for cyclists in these events. The substantial differences in variability between the remaining events, where riders act independently of each other, arise from various event-specific aspects. For these events the smallest worthwhile changes in performance time (~0.5×typical variation) are ~0.5% in the Kilo, ~0.6% in road time trials, and ~1.2% in mountain-bike races.
Abstract
Background
We investigated the ergogenic effects of betaine (B) supplementation on strength and power performance.
Methods
Twelve men (mean ± SD age, 21 ± 3 yr; mass, 79.1 ± 10.7 kg) with a minimum of 3 months resistance training completed two 14-day experimental trials separated by a 14-day washout period, in a balanced, randomized, double-blind, repeated measures, crossover design. Prior to and following 14 days of twice daily B or placebo (P) supplementation, subjects completed two consecutive days (D1 and D2) of a standardized high intensity strength/power resistance exercise challenge (REC). Performance included bench, squat, and jump tests.
Results
Following 14-days of B supplementation, D1 and D2 bench throw power (1779 ± 90 and 1788 ± 34 W, respectively) and isometric bench press force (2922 ± 297 and 2503 ± 28 N, respectively) were increased (p < 0.05) during REC compared to pre-supplementation values (1534 ± 30 and 1498 ± 29 W, respectively; 2345 ± 64 and 2423 ± 84 N, respectively) and corresponding P values (1374 ± 128 and 1523 ± 39 W; 2175 ± 92 and 2128 ± 56 N, respectively). Compared to pre-supplementation, vertical jump power and isometric squat force increased (p < 0.05) on D1 and D2 following B supplementation. However, there were no differences in jump squat power or the number of bench press or squat repetitions.
Conclusion
B supplementation increased power, force and maintenance of these measures in selected performance measures, and these were more apparent in the smaller upper-body muscle groups.
We investigated the ergogenic effects of betaine (B) supplementation on strength and power performance.
Twelve men (mean +/- SD age, 21 +/- 3 yr; mass, 79.1 +/- 10.7 kg) with a minimum of 3 months resistance training completed two 14-day experimental trials separated by a 14-day washout period, in a balanced, randomized, double-blind, repeated measures, crossover design. Prior to and following 14 days of twice daily B or placebo (P) supplementation, subjects completed two consecutive days (D1 and D2) of a standardized high intensity strength/power resistance exercise challenge (REC). Performance included bench, squat, and jump tests.
Following 14-days of B supplementation, D1 and D2 bench throw power (1779 +/- 90 and 1788 +/- 34 W, respectively) and isometric bench press force (2922 +/- 297 and 2503 +/- 28 N, respectively) were increased (p < 0.05) during REC compared to pre-supplementation values (1534 +/- 30 and 1498 +/- 29 W, respectively; 2345 +/- 64 and 2423 +/- 84 N, respectively) and corresponding P values (1374 +/- 128 and 1523 +/- 39 W; 2175 +/- 92 and 2128 +/- 56 N, respectively). Compared to pre-supplementation, vertical jump power and isometric squat force increased (p < 0.05) on D1 and D2 following B supplementation. However, there were no differences in jump squat power or the number of bench press or squat repetitions.
B supplementation increased power, force and maintenance of these measures in selected performance measures, and these were more apparent in the smaller upper-body muscle groups.
Pharmacological sodium nitrate supplementation has been reported to reduce the O2 cost of submaximal exercise in humans. In this study, we hypothesized that dietary supplementation with inorganic nitrate in the form of beetroot juice (BR) would reduce the O2 cost of submaximal exercise and enhance the tolerance to high-intensity exercise. In a double-blind, placebo (PL)-controlled, crossover study, eight men (aged 19-38 yr) consumed 500 ml/day of either BR (containing 11.2 +/- 0.6 mM of nitrate) or blackcurrant cordial (as a PL, with negligible nitrate content) for 6 consecutive days and completed a series of "step" moderate-intensity and severe-intensity exercise tests on the last 3 days. On days 4-6, plasma nitrite concentration was significantly greater following dietary nitrate supplementation compared with PL (BR: 273 +/- 44 vs. PL: 140 +/- 50 nM; P < 0.05), and systolic blood pressure was significantly reduced (BR: 124 +/- 2 vs. PL: 132 +/- 5 mmHg; P < 0.01). During moderate exercise, nitrate supplementation reduced muscle fractional O2 extraction (as estimated using near-infrared spectroscopy). The gain of the increase in pulmonary O2 uptake following the onset of moderate exercise was reduced by 19% in the BR condition (BR: 8.6 +/- 0.7 vs. PL: 10.8 +/- 1.6 ml.min(-1).W(-1); P < 0.05). During severe exercise, the O2 uptake slow component was reduced (BR: 0.57 +/- 0.20 vs. PL: 0.74 +/- 0.24 l/min; P < 0.05), and the time-to-exhaustion was extended (BR: 675 +/- 203 vs. PL: 583 +/- 145 s; P < 0.05). The reduced O2 cost of exercise following increased dietary nitrate intake has important implications for our understanding of the factors that regulate mitochondrial respiration and muscle contractile energetics in humans.
The purpose of this study was to examine the efficacy of 15 days of betaine supplementation on muscle endurance, power performance and rate of fatigue in active college-aged men.
Twenty-four male subjects were randomly assigned to one of two groups. The first group (BET; 20.4 +/- 1.3 years; height: 176.8 +/- 6.6 cm; body mass: 77.8 +/- 13.4 kg) consumed the supplement daily, and the second group (PL; 21.4 +/- 4.7 years; height: 181.3 +/- 5.9 cm; body mass: 83.3 +/- 5.2 kg) consumed a placebo. Subjects were tested prior to the onset of supplementation (T1) and 7 (T2) and 14 days (T3) following supplementation. Each testing period occurred over a 2-day period. During day one of testing subjects performed a vertical jump power (VJP) and a bench press throw (BPT) power test. In addition, subjects were required to perform as many repetitions as possible with 75% of their 1-RM in both the squat and bench press exercises. Both peak and mean power was assessed on each repetition. On day two of testing subjects performed two 30-sec Wingate anaerobic power tests (WAnT), each test separated by a 5-min active rest.
No differences were seen at T2 or T3 in the repetitions performed to exhaustion or in the number of repetitions performed at 90% of both peak and mean power between the groups in the bench press exercise. The number of repetitions performed in the squat exercise for BET was significantly greater (p < 0.05) than that seen for PL at T2. The number of repetitions performed at 90% or greater of peak power in the squat exercise was significantly greater for BET at both T2 and T3 than PL. No differences in any power assessment (VJP, BPT, WAnT) was seen between the groups
Two-weeks of betaine supplementation in active, college males appeared to improve muscle endurance of the squat exercise, and increase the quality of repetitions performed.
Quercetin is one of a broad group of natural polyphenolic flavonoid substances that are being investigated for their widespread health benefits. These benefits have generally been ascribed to its combination of antioxidant and anti-inflammatory activity, but recent in vitro evidence suggests that improved mitochondrial biogenesis could play an important role. In addition, the in vivo effects of quercetin on mitochondrial biogenesis exercise tolerance are unknown. We examined the effects of 7 days of quercetin feedings in mice on markers of mitochondrial biogenesis in skeletal muscle and brain, and on endurance exercise tolerance. Mice were randomly assigned to one of the following three treatment groups: placebo, 12.5 mg/kg quercetin, or 25 mg/kg quercetin. Following 7 days of treatment, mice were killed, and soleus muscle and brain were analyzed for mRNA expression of peroxisome proliferator-activated receptor-gamma coactivator (PGC-1alpha) and sirtuin 1 (SIRT1), and mitochondrial DNA (mtDNA) and cytochrome c. Additional mice underwent a treadmill performance run to fatigue or were placed in voluntary activity wheel cages, and their voluntary activity (distance, time, and peak speed) was recorded. Quercetin increased mRNA expression of PGC-1alpha and SIRT1 (P < 0.05), mtDNA (P < 0.05) and cytochrome c concentration (P < 0.05). These changes in markers of mitochondrial biogenesis were associated with an increase in both maximal endurance capacity (P < 0.05) and voluntary wheel-running activity (P < 0.05). These benefits of querectin on fitness without exercise training may have important implications for enhancement of athletic and military performance and may also extend to prevention and/or treatment of chronic diseases.
Endothelial nitric oxide (nitrogen monoxide) is synthesized at the intravascular/extravascular interface. We previously have reported the intravascular half-life of NO, as a result of consumption by erythrocytes, as approximately 2 ms. We report here studies designed to estimate the lifetime of NO in the parenchymal (extravascular) tissue and describe the implications of these results for the distribution of NO and oxygen concentration gradients away from the blood vessel. The rate of consumption of NO by parenchymal cells (hepatocytes) linearly depends on both NO and O(2) concentration. We estimate that the extravascular half-life of NO will range from 0.09 to > 2 s, depending on O2 concentration and thus distance from the vessel. Computer modeling reveals that this phenomenon, coupled with reversible NO inhibition of cellular mitochondrial oxygen consumption, substantially extends the zone of adequate tissue cellular oxygenation away from the blood vessel, with an especially dramatic effect during conditions of increased tissue work (oxygen consumption). This represents a second action of NO, in addition to vasodilation, in enhancing tissue cellular respiration and provides a possible physiological function for the known reversible inhibition of mitochondrial respiration by low concentrations of NO.
The plasma level of NO(x), i.e., the sum of NO(2)- and NO(3)-, is frequently used to assess NO bioavailability in vivo. However, little is known about the kinetics of NO conversion to these metabolites under physiological conditions. Moreover, plasma nitrite recently has been proposed to represent a delivery source for intravascular NO. We therefore sought to investigate in humans whether changes in NO(x) concentration are a reliable marker for endothelial NO production and whether physiological concentrations of nitrite are vasoactive. NO(2)- and NO(3)- concentrations were measured in blood sampled from the antecubital vein and brachial artery of 24 healthy volunteers. No significant arterial-venous gradient was observed for either NO(2)- or NO(3)-. Endothelial NO synthase (eNOS) stimulation with acetylcholine (1-10 microg/min) dose-dependently augmented venous NO(2)- levels by maximally 71%. This effect was paralleled by an almost 4-fold increase in forearm blood flow (FBF), whereas an equieffective dose of papaverine produced no change in venous NO(2)-. Intraarterial infusion of NO(2)- had no effect on FBF. NOS inhibition (N(G)-monomethyl-l-arginine; 4-12 micromol/min) dose-dependently reduced basal NO(2)- and FBF and blunted acetylcholine-induced vasodilation and NO release by more than 80% and 90%, respectively. In contrast, venous NO(3)- and total NO(x) remained unchanged as did systemic arterial NO(2)- and NO(3)- levels during all these interventions. FBF and NO release showed a positive association (r = 0.85; P < 0.001). These results contradict the current paradigm that plasma NO(3)- and/or total NO(x) are generally useful markers of endogenous NO production and demonstrate that only NO(2)- reflects acute changes in regional eNOS activity. Our results further demonstrate that physiological levels of nitrite are vasodilator-inactive.
The effects of the nitric oxide (NO) donor spermine NONOate (Sp-NO, 1.0 mM) on cross-bridge recruitment and cross-bridge cycling kinetics were studied in permeabilized rabbit psoas muscle fibers. Fibers were activated at various Ca2+ concentrations (pCa, negative logarithm of Ca2+ concentration), and the pCa at which force was maximal (pCa 4.0) and approximately 50% of maximal (pCa50 5.6) were determined. Fiber stiffness was determined using 1-kHz sinusoidal length perturbations, and the fraction of cross bridges in the force-generating state was estimated by the ratio of stiffness during maximal (pCa 4.0) and submaximal (pCa 5.6) Ca2+ activation to stiffness during rigor (at pCa 4.0). Cross-bridge cycling kinetics were evaluated by measuring the rate constant for force redevelopment after quick release (by 15% of optimal fiber length, L(o)) and restretch of the fiber to L(o). Exposing fibers to Sp-NO for 10 min reduced force and the fraction of cross bridges in the force-generating state at maximal and submaximal (pCa50) Ca2+ activation. However, the effects of Sp-NO were more pronounced during submaximal Ca2+ activation. Sp-NO also reduced the rate constant for force redevelopment but only during submaximal Ca2+ activation. We conclude that Sp-NO reduces Ca2+ sensitivity by decreasing the number of cross bridges in the strongly bound state and also impairs cross-bridge cycling kinetics during submaximal activation.
The purpose of this study was, firstly, to investigate the intensity of exercise performance of highly trained ultra-endurance triathletes during the cycling portion of an Ironman triathlon, and, secondly, to examine the anaerobic threshold and its relationship to this performance. Following a peak oxygen consumption (VO(2peak)) test on a cycle ergometer to determine the heart rate (HR(Th,vent)) and power output (PO(Th,vent)) at the ventilatory threshold (Th(vent)), 11 highly trained male triathletes [mean (SEM) age 35.8 (1.6) years, body fat 11.7 (1.2)%. VO(2peak) 67.5 (1.0) ml x kg(-1) x min(-1)] who were participating in an Ironman triathlon, in random order: (1) cycled at their PO(Th,vent) (Bi(Th,vent)) until they were exhausted, and (2) cycled for 5 h at a self-selected intensity (Bi(SSI)). Cycling power output (PO), oxygen uptake (VO(2)), heart rate (HR) and blood lactate concentration ([La(-)](b)) were recorded at regular intervals during these trials, while performance HR was recorded during the cycling phase of the Ironman triathlon. Significantly greater (P < 0.05) values were attained during Bi(Th,vent) than during Bi(SSI) for PO [274 (9) compared to 188 (9) W], VO(2) [3.61 (0.15) compared to 2.64 (0.09) l x min(-1)], and [La(-)](b) [6.7 (0.8) compared to 2.8 (0.4) mmol x l(-1)]. Moreover, mean HR during the Ironman triathlon cycle phase [146.3 (2.4) beats.min(-1); n=7] was significantly greater than mean HR during Bi(SSI) [130 (4) beats x min(-1)], and significantly less than mean HR during Bi(Th,vent) [159 (3) beats x min(-1); all P < 0.05]. However, HR during the cycle portion of the Ironman triathlon was highly related to (r = 0.873; P < 0.05) and not significantly different to HR(Th,vent) [150 (4) beats x min(-1)]. These data suggest that ultra-endurance triathletes cycle during the Ironman triathlon at a HR intensity that approximates to HR(Th,vent), but at a PO that is significantly below PO(Th,vent).
Disturbances of nitric oxide (NO) bioavailability may play a key role in vascular dysfunction and in the development of atherosclerotic lesions. Thus assessment of a reduced NO bioavailability in human circulation is of particular interest. Here we summarize potential biomarkers of NO availability in human blood and critically discuss their respective significance and application fields.
Nitrite anions comprise the largest vascular storage pool of nitric oxide (NO), provided that physiological mechanisms exist to reduce nitrite to NO. We evaluated the vasodilator properties and mechanisms for bioactivation of nitrite in the human forearm. Nitrite infusions of 36 and 0.36 micromol/min into the forearm brachial artery resulted in supra- and near-physiologic intravascular nitrite concentrations, respectively, and increased forearm blood flow before and during exercise, with or without NO synthase inhibition. Nitrite infusions were associated with rapid formation of erythrocyte iron-nitrosylated hemoglobin and, to a lesser extent, S-nitroso-hemoglobin. NO-modified hemoglobin formation was inversely proportional to oxyhemoglobin saturation. Vasodilation of rat aortic rings and formation of both NO gas and NO-modified hemoglobin resulted from the nitrite reductase activity of deoxyhemoglobin and deoxygenated erythrocytes. This finding links tissue hypoxia, hemoglobin allostery and nitrite bioactivation. These results suggest that nitrite represents a major bioavailable pool of NO, and describe a new physiological function for hemoglobin as a nitrite reductase, potentially contributing to hypoxic vasodilation.
We have studied the effect of nitric oxide (NO) and potassium cyanide (KCN) on oxidative phosphorylation efficiency. Concentrations of NO or KCN that decrease resting oxygen consumption by 10-20% increased oxidative phosphorylation efficiency in mitochondria oxidizing succinate or palmitoyl-L-carnitine, but not in mitochondria oxidizing malate plus glutamate. When compared to malate plus glutamate, succinate or palmitoyl-L-carnitine reduced the redox state of cytochrome oxidase. The relationship between membrane potential and oxygen consumption rates was measured at different degrees of ATP synthesis. The use of malate plus glutamate instead of succinate (that changes the H(+)/2e(-) stoichiometry of the respiratory chain) affected the relationship, whereas a change in membrane permeability did not affect it. NO or KCN also affected the relationship, suggesting that they change the H(+)/2e(-) stoichiometry of the respiratory chain. We propose that NO may be a natural short-term regulator of mitochondrial physiology that increases oxidative phosphorylation efficiency in a redox-sensitive manner by decreasing the slipping in the proton pumps.
Nitrite is the main oxidation product of nitric oxide (NO) in plasma. It sensitively reflects changes in endothelial NO synthase (eNOS) activity under fasting conditions and serves as an endocrine NO donor, contributing to the regulation of blood flow through reaction with haemoglobin. As NO is necessary to maintain an adequate vascular response to the increased demands of blood flow, it is believed to be important for vasodilation induced by exercise.
To investigate whether the capacity of the vasculature to produce nitrite is associated with exercise performance.
With the use of chemiluminescence detection, nitrite concentrations in 55 healthy subjects (mean (SEM) age 40 (2) years; 22 men) were studied before and after an exercise test, and endothelial function was determined by measuring flow-mediated dilation of the brachial artery using high-resolution ultrasound. In a subset of subjects, the NOS inhibitor, N(G)-monomethyl-L-arginine, was applied to elucidate the effect of eNOS on changes in nitrite.
Exercise significantly (p<0.001) increased plasma nitrite from 97 (6) to 125 (8) nM. The relative increase in plasma nitrite was related to flow-mediated dilation (6.1 (0.3)%; r = 0.36; p = 0.01). N(G)-Monomethyl-L-arginine blocked increases in nitrite. Post-exercise nitrite concentration correlated with exercise performance, as determined by maximally reached stress power (r = 0.37; p<0.007), and inversely with age. Multivariate analysis showed that both age and post-exercise nitrite concentration were independent predictors of stress endurance and power.
The results suggest a role for plasma nitrite in the adaptation of haemodynamics during exercise. An impaired increase in plasma nitrite may limit exercise capacity.
Performance testing is one of the most common and important measures used in sports science and physiology. Performance tests allow for a controlled simulation of sports and exercise performance for research or applied science purposes. There are three factors that contribute to a good performance test: (i) validity; (ii) reliability; and (iii) sensitivity. A valid protocol is one that resembles the performance that is being simulated as closely as possible. When investigating race-type events, the two most common protocols are time to exhaustion and time trials. Time trials have greater validity than time to exhaustion because they provide a good physiological simulation of actual performance and correlate with actual performance. Sports such as soccer are more difficult to simulate. While shuttle-running protocols such as the Loughborough Intermittent Shuttle Test may simulate physiology of soccer using time to exhaustion or distance covered, it is not a valid measure of soccer performance. There is a need to include measures of skill in such protocols. Reliability is the variation of a protocol. Research has shown that time-to-exhaustion protocols have a coefficient of variation (CV) of >10%, whereas time trials are more reliable as they have been shown to have a CV of <5%. A sensitive protocol is one that is able to detect small, but important, changes in performance. The difference between finishing first and second in a sporting event is <1%. Therefore, it is important to be able to detect small changes with performance protocols. A quantitative value of sensitivity may be accomplished through the signal : noise ratio, where the signal is the percentage improvement in performance and the noise is the CV.
Purpose:
The purpose of this study was to assess research aimed at measuring performance enhancements that affect success of individual elite athletes in competitive events.
Analysis:
Simulations show that the smallest worthwhile enhancement of performance for an athlete in an international event is 0.7-0.4 of the typical within-athlete random variation in performance between events. Using change in performance in events as the outcome measure in a crossover study, researchers could delimit such enhancements with a sample of 16-65 athletes, or with 65-260 in a fully controlled study. Sample size for a study using a valid laboratory or field test is proportional to the square of the within-athlete variation in performance in the test relative to the event; estimates of these variations are therefore crucial and should be determined by repeated-measures analysis of data from reliability studies for the test and event. Enhancements in test and event may differ when factors that affect performance differ between test and event; overall effects of these factors can be determined with a validity study that combines reliability data for test and event. A test should be used only if it is valid, more reliable than the event, allows estimation of performance enhancement in the event, and if the subjects replicate their usual training and dietary practices for the study; otherwise the event itself provides the only dependable estimate of performance enhancement. Publication of enhancement as a percent change with confidence limits along with an analysis for individual differences will make the study more applicable to athletes. Outcomes can be generalized only to athletes with abilities and practices represented in the study.
Conclusion:
estimates of enhancement of performance in laboratory or field tests in most previous studies may not apply to elite athletes in competitive events.
Nitrate and nitrite have been considered stable inactive end products of nitric oxide (NO). While several recent studies now imply that nitrite can be reduced to bioactive NO again, the more stable anion nitrate is still considered to be biologically inert. Nitrate is concentrated in saliva, where a part of it is reduced to nitrite by bacterial nitrate reductases. We tested if ingestion of inorganic nitrate would affect the salivary and systemic levels of nitrite and S-nitrosothiols, both considered to be circulating storage pools for NO. Levels of nitrate, nitrite, and S-nitrosothiols were measured in plasma, saliva, and urine before and after ingestion of sodium nitrate (10 mg/kg). Nitrate levels increased greatly in saliva, plasma, and urine after the nitrate load. Salivary S-nitrosothiols also increased, but plasma levels remained unchanged. A 4-fold increase in plasma nitrite was observed after nitrate ingestion. If, however, the test persons avoided swallowing after the nitrate load, the increase in plasma nitrite was prevented, thereby illustrating its salivary origin. We show that nitrate is a substrate for systemic generation of nitrite. There are several pathways to further reduce this nitrite to NO. These results challenge the dogma that nitrate is biologically inert and instead suggest that a complete reverse pathway for generation of NO from nitrate exists.
Recent studies surprisingly show that dietary inorganic nitrate, abundant in vegetables, can be metabolized in vivo to form nitrite and then bioactive nitric oxide. A reduction in blood pressure was recently noted in healthy volunteers after dietary supplementation with nitrate; an effect consistent with formation of vasodilatory nitric oxide. Oral bacteria have been suggested to play a role in bioactivation of nitrate by first reducing it to the more reactive anion nitrite. In a cross-over designed study in seven healthy volunteers we examined the effects of a commercially available chlorhexidine-containing antibacterial mouthwash on salivary and plasma levels of nitrite measured after an oral intake of sodium nitrate (10mg/kg dissolved in water). In the control situation the salivary and plasma levels of nitrate and nitrite increased greatly after the nitrate load. Rinsing the mouth with the antibacterial mouthwash prior to the nitrate load had no effect on nitrate accumulation in saliva or plasma but abolished its conversion to nitrite in saliva and markedly attenuated the rise in plasma nitrite. We conclude that the acute increase in plasma nitrite seen after a nitrate load is critically dependent on nitrate reduction in the oral cavity by commensal bacteria. The removal of these bacteria with an antibacterial mouthwash will very likely attenuate the NO-dependent biological effects of dietary nitrate.