***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: It is possible that dietary nitrate ( NO3− ) supplementation may improve both physical and cognitive performance via its influence on blood flow and cellular energetics . Purpose To investigate the effects of dietary NO3− supplementation on exercise performance and cognitive function during a prolonged intermittent sprint test ( IST ) protocol , which was design ed to reflect typical work patterns during team sports . Methods In a double-blind r and omised crossover study , 16 male team-sport players received NO3−-rich ( BR ; 140 mL day−1 ; 12.8 mmol of NO3− ) , and NO3−-depleted ( PL ; 140 mL day−1 ; 0.08 mmol NO3− ) beetroot juice for 7 days . On day 7 of supplementation , subjects completed the IST ( two 40-min “ halves ” of repeated 2-min blocks consisting of a 6-s “ all-out ” sprint , 100-s active recovery and 20 s of rest ) , on a cycle ergometer during which cognitive tasks were simultaneously performed . Results Total work done during the sprints of the IST was greater in BR ( 123 ± 19 kJ ) compared to PL ( 119 ± 17 kJ ; P < 0.05 ) . Reaction time of response to the cognitive tasks in the second half of the IST was improved in BR compared to PL ( BR first half : 820 ± 96 vs. second half : 817 ± 86 ms ; PL first half : 824 ± 114 vs. second half : 847 ± 118 ms ; P < 0.05 ) . There was no difference in response accuracy . Conclusions These findings suggest that dietary NO3−  enhances repeated sprint performance and may attenuate the decline in cognitive function ( and specifically reaction time ) that may occur during prolonged intermittent exercise INTRODUCTION Dietary nitrate supplementation has received much attention in the literature due to its proposed ergogenic properties . Recently , the ingestion of a single bolus of nitrate-rich beetroot juice ( 500 ml , ~6.2 mmol NO3- ) was reported to improve subsequent time-trial performance . However , this large volume of ingested beetroot juice does not represent a realistic dietary strategy for athletes to follow in a practical , performance-based setting . Therefore , we investigated the impact of ingesting a single bolus of concentrated nitrate-rich beetroot juice ( 140 ml , ~8.7 mmol NO3- ) on subsequent 1-hr time-trial performance in well-trained cyclists . METHODS Using a double-blind , repeated- measures crossover design ( 1-wk washout period ) , 20 trained male cyclists ( 26 ± 1 yr , VO(2peak ) 60 ± 1 ml · kg(-1 ) · min(-1 ) , Wmax 398 ± 7.7 W )  ingested 140 ml of concentrated beetroot juice ( 8.7 mmol NO3- ; BEET ) or a placebo ( nitrate-depleted beetroot juice ; PLAC ) with breakfast 2.5 hr before an ~1-hr cycling time trial ( 1,073 ± 21 kJ ) . Resting blood sample s were collected every 30 min after BEET or PLAC ingestion and immediately after the time trial . RESULTS Plasma nitrite concentration was higher in BEET than PLAC before the onset of the time trial ( 532 ± 32 vs. 271 ± 13 nM , respectively ; p < .001 ) , but subsequent time-trial performance ( 65.5 ± 1.1 vs. 65 ± 1.1 s ) , power output ( 275 ± 7 vs. 278 ± 7 W ) , and heart rate ( 170 ± 2 vs. 170 ± 2 beats/min ) did not differ between BEET and PLAC treatments ( all p > .05 ) . CONCLUSION Ingestion of a single bolus of concentrated ( 140 ml ) beetroot juice ( 8.7 mmol NO3- ) does not improve subsequent 1-hr time-trial performance in well-trained cyclists Recent studies have suggested that dietary inorganic nitrate ( NO3− ) supplementation may improve muscle efficiency and endurance exercise tolerance but possible effects during team sport-specific intense intermittent exercise have not been examined . We hypothesized that NO3− supplementation would enhance high-intensity intermittent exercise performance . Fourteen male recreational team-sport players were assigned in a double-blind , r and omized , crossover design to consume 490 mL of concentrated , nitrate-rich beetroot juice ( BR ) and nitrate-depleted placebo juice ( PL ) over ~30 h preceding the completion of a Yo – Yo intermittent recovery level 1 test ( Yo – Yo IR1 ) . Resting plasma nitrite concentration ( [ NO2− ] ) was ~400 % greater in BR compared to PL . Plasma [ NO2− ] declined by 20 % in PL ( P < 0.05 ) and by 54 % in BR ( P < 0.05 ) from pre-exercise to end-exercise . Performance in the Yo – Yo IR1 was 4.2 % greater ( P < 0.05 ) with BR ( 1,704 ± 304 m ) compared to PL ( 1,636 ± 288 m ) . Blood [ lactate ] was not different between BR and PL , but the mean blood [ glucose ] was lower ( 3.8 ± 0.8 vs. 4.2 ± 1.1 mM , P < 0.05 ) and the rise in plasma [ K+ ] tended to be reduced in BR compared to PL ( P = 0.08 ) . These findings suggest that NO3− supplementation may promote NO production via the nitrate-nitrite-NO pathway and enhance Yo – Yo IR1 test performance , perhaps by facilitating greater muscle glucose uptake or by better maintaining muscle excitability . Dietary NO3− supplementation improves performance during intense intermittent exercise and may be a useful ergogenic aid for team sports players The anion nitrate-abundant in our diet-has recently emerged as a major pool of nitric oxide ( NO ) synthase-independent NO production . Nitrate is reduced stepwise in vivo to nitrite and then NO and possibly other bioactive nitrogen oxides . This reductive pathway is enhanced during low oxygen tension and acidosis . A recent study shows a reduction in oxygen consumption during submaximal exercise attributable to dietary nitrate . We went on to study the effects of dietary nitrate on various physiological and biochemical parameters during maximal exercise . Nine healthy , nonsmoking volunteers ( age 30+/-2.3 years , VO(2max ) 3.72+/-0.33 L/min ) participated in this study , which had a r and omized , double-blind crossover design . Subjects received dietary supplementation with sodium nitrate ( 0.1 mmol/kg/day ) or placebo ( NaCl ) for 2 days before the test . This dose corresponds to the amount found in 100 - 300 g of a nitrate-rich vegetable such as spinach or beetroot . The maximal exercise tests consisted of an incremental exercise to exhaustion with combined arm and leg cranking on two separate ergometers . Dietary nitrate reduced VO(2max ) from 3.72+/-0.33 to 3.62+/-0.31 L/min , P<0.05 . Despite the reduction in VO(2max ) the time to exhaustion trended to an increase after nitrate supplementation ( 524+/-31 vs 563+/-30 s , P=0.13 ) . There was a correlation between the change in time to exhaustion and the change in VO(2max ) ( R(2)=0.47 , P=0.04 ) . A moderate dietary dose of nitrate significantly reduces VO(2max ) during maximal exercise using a large active muscle mass . This reduction occurred with a trend toward increased time to exhaustion implying that two separate mechanisms are involved : one that reduces VO(2max ) and another that improves the energetic function of the working muscles Six days of dietary nitrate supplementation in the form of beetroot juice ( ~0.5 L/d ) has been reported to reduce pulmonary oxygen uptake ( VO₂ ) during submaximal exercise and increase tolerance of high-intensity work rates , suggesting that nitrate can be a potent ergogenic aid . Limited data are available regarding the effect of nitrate ingestion on athletic performance , and no study has investigated the potential ergogenic effects of a small-volume , concentrated dose of beetroot juice . The authors tested the hypothesis that 6 d of nitrate ingestion would improve time-trial performance in trained cyclists . Using a double-blind , repeated- measures crossover design , 12 male cyclists ( 31±3 yr , VO2peak=58±2 ml·kg⁻¹·min⁻¹ , maximal power [Wmax]=342±10 W ) ingested 140 ml/d of concentrated beetroot ( ~8 mmol/d nitrate ) juice ( BEET ) or a placebo ( nitrate-depleted beetroot juice ; PLAC ) for 6 d , separated by a 14-d washout . After supplementation on Day 6 , subjects performed 60 min of submaximal cycling ( 2 × 30 min at 45 % and 65 % Wmax , respectively ) , followed by a 10-km time trial . Time-trial performance ( 953±18 vs. 965±18 s , p<.005 ) and power output ( 294±12 vs. 288±12 W , p<.05 ) improved after BEET compared with PLAC supplementation . Submaximal VO₂ was lower after BEET ( 45 % Wmax=1.92±0.06 vs. 2.02±0.09 L/min , 65 % Wmax 2.94±0.12 vs. 3.11±0.12 L/min ) than with PLAC ( main effect , p<.05 ) . Whole-body fuel selection and plasma lactate , glucose , and insulin concentrations did not differ between treatments . Six days of nitrate supplementation reduced VO₂ during submaximal exercise and improved time-trial performance in trained cyclists PURPOSE 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 ) . METHODS After familiarization , nine club-level competitive male cyclists were assigned in a r and omized , 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 . RESULTS 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 ) . CONCLUSIONS 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 Purpose To examine the effect of betaine supplementation on cycling sprint performance . Methods Sixteen recreationally active subjects ( 7 females and 9 males ) completed three sprint tests , each consisting of four 12 sec efforts against a resistance equal to 5.5 % of body weight ; efforts were separated by 2.5 min of cycling at zero resistance . Test one established baseline ; test two and three were preceded by seven days of daily consumption of 591 ml of a carbohydrate-electrolyte beverage as a placebo or a carbohydrate-electrolyte beverage containing 0.42 % betaine ( approximately 2.5 grams of betaine a day ) ; half the beverage was consumed in the morning and the other half in the afternoon . We used a double blind r and om order cross-over design ; there was a 3 wk washout between trials two and three . Average and maximum peak and mean power were analyzed with one-way repeated measures ANOVA and , where indicated , a Student Newman-Ke 
    Output:
    
Nitrate supplementation is likely to improve exercise tolerance and capacity that may improve exercise performance .