***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 Abstract . The purpose of this study was , firstly , to investigate the intensity of exercise performanceof 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 ( VO2peak ) test on a cycle ergometer to determine the heart rate ( HRTh , vent ) and power output ( POTh , vent ) at the ventilatory threshold ( Thvent ) , 11 highly trained male triathletes [ mean ( SEM ) age 35.8 ( 1.6 ) years , body fat 11.7 (1.2)% . VO2peak 67.5 ( 1.0 ) ml·kg–1·min–1 ] who were participating in an Ironman triathlon , in r and om order : ( 1 ) cycled at their POTh , vent ( BiTh , vent ) until they were exhausted , and ( 2 ) cycled for 5 h at a self-selected intensity ( BiSSI ) . Cycling power output ( PO ) , oxygen uptake ( VO2 ) , 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 BiTh , vent than during BiSSI for PO [ 274 ( 9 ) compared to 188 ( 9 ) W ] , VO2 [ 3.61 ( 0.15 ) compared to 2.64 ( 0.09 ) l·min–1 ] , and [La–]b [ 6.7 ( 0.8 ) compared to 2.8 ( 0.4 ) mmol·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 BiSSI [ 130 ( 4 ) beats·min–1 ] , and significantly less than mean HR during BiTh , vent [ 159 ( 3 ) beats·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 HRTh , vent [ 150 ( 4 ) beats·min–1 ] . These data suggest that  ultra-endurance triathletes cycle during the Ironman triathlon at a HR intensity that approximates to HRTh , vent , but at a PO that is significantly below POTh , vent Recent research has shown that dietary nitrate has favorable effects on blood flow and exercise performance . The purpose of this r and omized , double-blind , placebo-controlled crossover study was to investigate the acute effects of pomegranate extract on blood flow , vessel diameter , and exercise performance in active individuals . Nineteen men and women ( mean ± SD : age , 22.2 ± 2.2 years ; height , 174.8 ± 10.7 cm ; body mass , 71.9 ± 13.5 kg ) were r and omly assigned to a placebo ( PL ) or pomegranate extract ( PE ) group . Participants performed a maximal oxygen consumption treadmill test to determine peak velocity ( PV ) . Participants returned after 24 - 48 h and ingested either PL or PE . Brachial artery blood flow was assessed using ultrasound at baseline and 30 min post-ingestion ( 30minPI ) . Three treadmill runs to exhaustion were performed at 90 % , 100 % , and 110 % PV . Blood flow was assessed immediately after each exercise bout and 30 min postexercise ( 30minPEx ) . After a 7 - 10 day washout , participants repeated the same procedures , ingesting the opposite supplement . Separate repeated measures ANOVAs were performed for blood flow , vessel diameter , and time to exhaustion ( TTE ) . Blood flow was significantly augmented ( p = 0.033 ) 30minPI with PE in comparison with PL . Vessel diameter was significantly larger ( p = 0.036 ) 30minPEx with PE . Ingestion of PE was found to significantly augment TTE at 90 % ( p = 0.009 ) and 100 % PV ( p = 0.027 ) . Acute ingestion of PE 30 min before exercise may enhance vessel diameter and blood flow and delay fatigue during exercise . Results of the current study indicate that PE is ergogenic for intermittent running , eliciting beneficial effects on blood flow 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 This study examined the effects of acute supplementation with L-arginine and nitrate on running economy , endurance and sprint performance in endurance-trained athletes . In a r and omised cross-over , double-blinded design we compared the effects of combined supplementation with 6 g L-arginine and 614 mg nitrate against 614 mg nitrate alone and placebo in nine male elite cross-country skiers ( age 18 ± 0 years , VO2max 69.3 ± 5.8 ml ⋅ min(-1 ) ⋅ kg(-1 ) ) . After a 48-hour st and ardisation of nutrition and exercise the athletes were tested for plasma nitrate and nitrite concentrations , blood pressure , submaximal running economy at 10 km ⋅ h(-1 ) and 14 km ⋅ h(-1 ) at 1 % incline and 180 m as well as 5-km time-trial running performances . Plasma nitrite concentration  following L-arginine + nitrate supplementation ( 319 ± 54 nmol ⋅ L(-1 ) ) did not differ from nitrate alone ( 328 ± 107 nmol ⋅ L(-1 ) ) , and both were higher than placebo ( 149 ± 64 nmol ⋅ L(-1 ) , p < 0.01 ) . There were no differences in physiological responses during submaximal running or in 5-km performance between treatments . The plasma nitrite concentrations indicate greater nitric oxide availability both following acute supplementation of L-arginine + nitrate and with nitrate alone compared to placebo , but no additional effect was revealed when L-arginine was added to nitrate . Still , there were no effects of supplementation on exercise economy or endurance running performance in endurance-trained cross-country skiers 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 Nitric oxide ( NO ) has been demonstrated to enhance the maximal shortening velocity and maximal power of rodent muscle . Dietary nitrate ( NO3(- ) ) intake has been demonstrated to increase NO bioavailability in humans . We therefore hypothesized that acute dietary NO3(- ) intake ( in the form of a concentrated beetroot juice ( BRJ ) supplement ) would improve muscle speed and power in humans . To test this hypothesis , healthy men and women ( n = 12 ; age = 22 - 50 y ) were studied using a r and omized , double-blind , placebo-controlled crossover design . After an overnight fast , subjects ingested 140 mL of BRJ either containing or devoid of 11.2 mmol of NO3(- ) . After 2 h , knee extensor contractile function was assessed using a Biodex 4 isokinetic dynamometer . Breath NO levels were also measured periodically using a Niox Mino analyzer as a biomarker of whole-body NO production . No significant changes in breath NO were observed in the placebo trial , whereas breath NO rose by 61 % ( P < 0.001 ; effect size = 1.19 ) after dietary NO3(- ) 
    Output:
    
No statistically significant effects were observed from the meta-regression analysis .
Conclusion Dietary NO3− supplementation is likely to elicit a positive outcome when testing endurance exercise capacity , whereas dietary NO3− supplementation is less likely to be effective for time-trial performance .