***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: The aim of the study was to examine prevalence and duration /seriousness of gastrointestinal ( GI ) problems  as a function of carbohydrate-rich ( CHO ) supplements and mode of exercise . The relationship between GI problems and a variety of physiological and personal factors ( age , exercise experience ) was also examined . Thirty-two male tri-athletes performed three experimental trials at 1-wk intervals , each trial on a different supplement : a conventional , semisolid supplement ( S ; 1.2 g CHO , 0.1 g protein , and 0.02 g fat.kg BW-1 x h-1 ) ; an almost isocaloric fluid supplement ( F ; 1.3 g CHO.kg BW-1 x h-1 , no fat , no protein ) ; and a fluid placebo ( P ) . The 3 h of exercise started at 75 % VO2max and consisted of alternately cycling ( bouts 1 and 3 ) and running ( bouts 2 and 4 ) . GI symptoms were monitored by a question naire . Analysis of variance revealed that nausea lasted longer with P as compared with S ( P < 0.05 ) . Bloating lasted longer during bout 3 with P as compared with F and S ( P < 0.05 ) . Accounting for confounding factors , most GI symptoms occurred more frequently and lasted longer during running than during cycling . Multiple regression analysis revealed significant relationships between nausea and urge to defecate , between an urge to defecate , GI cramps and flatulence , and between belching and side ache . From all other factors energy depletion , CHO malabsorption , exercise intensity , exercise experience , and age were significantly related to GI symptoms during the exercise The presence of carbohydrate in the mouth can immediately improve physical performance . How this occurs is not well understood . Here we used transcranial magnetic stimulation of primary motor cortex ( M1 ) to investigate the effects of non-sweet carbohydrate on corticomotor excitability and voluntary force production . In Experiment 1 , 16 participants performed a fatiguing isometric elbow flexion exercise for 30 min , and Motor evoked potentials ( MEPs ) were recorded from the biceps brachii during maximal voluntary force ( MVF ) produced every 2 min . After 11 min participants drank a carbohydrate solution ( CHO ) or an energy-free placebo solution ( PLA ) , in a double-blind , cross-over protocol . MEP amplitude increased by 30 % , and MVF increased by 2 % , immediately after carbohydrate ingestion . There was no relationship between the facilitation of MEP amplitude and plasma glucose or magnitude of fatigue . In a control experiment , 17 participants alternately mouth-rinsed CHO and PLA , in a r and omized , double-blind protocol . MEPs were recorded from right first dorsal interosseous at rest or during isometric contraction . MEP amplitude increased by 9 % with CHO , when the muscle was voluntarily activated . In both experiments , there were no effects on silent period duration , indicating that MEP facilitation was not due to reduced inhibition within M1 . This is the first demonstration that carbohydrate in the mouth immediately increases the excitability of the corticomotor pathway , prior to its ingestion . Afference from oral receptors is integrated with descending motor output , perhaps via nuclei in the brainstem . This novel form of sensorimotor integration facilitates corticomotor output to both fatigued and fresh muscle It is presently unclear whether the reported ergogenic effect of a carbohydrate ( CHO ) mouth rinse on cycling time-trial performance is affected by the acute nutritional status of an individual . Hence , the aim of this study was to investigate the effect of a CHO mouth rinse on a 60-min simulated cycling time-trial performance commenced in a fed or fasted state . Twelve competitive male cyclists each completed 4 experimental trials using a double-blinded Latin square design . Two trials were commenced 2 h after a meal that contained 2.5 g·kg(-1 ) body mass of CHO ( FED ) and 2 after an overnight fast ( FST ) . Prior to and after every 12.5 % of total time during a performance ride , either a 10 % maltodextrin ( CHO ) or a taste-matched placebo ( PLB ) solution was mouth rinsed for 10 s then immediately expectorated . There were significant main effects for both pre-ride nutritional status ( FED vs. FST ; p < 0.01 ) and CHO mouth rinse ( CHO vs. PLB ; p < 0.01 ) on power output with an interaction evident between the interventions ( p < 0.05 ) . The CHO mouth rinse improved mean power to a greater extent after an overnight fast ( 282 vs. 273 W , 3.4 % ; p < 0.01 ) compared with a fed state ( 286 vs. 281 W , 1.8 % ; p < 0.05 ) . We concluded that a CHO mouth rinse  improved performance to a greater extent in a fasted compared with a fed state ; however , optimal performance was achieved in a fed state with the addition of a CHO mouth rinse Studies have reported that rinsing the mouth with a carbohydrate ( CHO ) solution improves cycling time-trial performance compared with rinsing with a placebo solution . However , no studies have compared the effect of mouth rinsing with a no-mouth-rinse control condition . The aim of this study was to compare the effects of a CHO mouth rinse with those of a placebo rinse and a no-rinse condition .  Ten male cyclists completed three 1,000-kJ cycling time trials in a r and omized , counterbalanced order . At every 12.5 % of the time trial completed , participants were required to rinse their mouths for 5 s with either a 6.4 % maltodextrin solution ( CHO ) , water ( WA ) , or no solution ( CON ) . Heart rate and ratings of perceived exertion ( RPE ) were recorded every 25 % of the time trial completed . Time to completion was faster in both CHO ( 65.7 ± 11.07 min ) and CON ( 67.6 ± 12.68 min ) than in WA ( 69.4 ± 13.81 min ; p = .013 and p = .042 , respectively ) . The difference between CHO and CON approached significance ( p = .086 ) . There were no differences in heart rate or RPE between any conditions . In summary , repeated mouth rinsing with water results in decreased performance relative to not rinsing at all . Adding CHO to the rinse solution appears to oppose this fall in performance , possibly providing additional benefits to performance compared with not rinsing the mouth at all . This brings into question the magnitude of the effect of CHO mouth rinsing reported in previous studies that did not include a no-rinse condition PURPOSE To investigate the influence of ingesting versus mouth rinsing a carbohydrate-electrolyte solution on 1-h running performance . METHODS After a 14- to 15-h fast , 10 endurance-trained male runners ( mean ± SD : VO2peak = 65.0 ± 4.4 mL·kg(-1)·min(-1 ) ) completed three 1-h performance runs separated by 1 wk . In r and om order , runners ingested either a 8-mL·kg(-1 ) body mass of either a 6.4 % carbohydrate-electrolyte solution ( CHO ) or a placebo solution ( P ) 30 min before or a 2-mL·kg(-1 ) body mass at 15-min intervals throughout the 1-h run . On a separate occasion , runners mouth rinsed ( R ) a 6.4 % CHO , i.e. , without ingestion , at the same times as in the ingestion trials . RESULTS Total distances covered in the CHO , P , and R trials were 14,515 ± 756 , 14,190 ± 800 , and 14,283 ± 758 m , respectively . Runners covered 320 m more ( 90 % confidence interval = 140 - 510 m , P = 0.01 ) during the CHO trial compared with the P trial and 230 m more ( 90 % confidence interval = 83 - 380 m , P = 0.019 ) in comparison with the R trial . There was no difference in n distance covered between the R and P trials ( P = 1.0 ) . CONCLUSIONS A greater distance was covered after the mouth rinse and ingestion of a 6.4 % CHO during a 1-h performance run than when mouth rinsing the same solution or mouth rinsing followed by the ingestion of the same volume of a placebo solution PURPOSE AND METHODS To investigate the effect of glucose infusion on glucose kinetics and performance , six endurance cyclists ( VO2max = 61.7 + /- 2.0 ( mean + /- SE ) mL x kg(-1 ) x min(-1 ) ) completed two performance trials in which they had to accomplish a set amount of work as quickly as possible ( 991 + /- 41 kJ ) . Subjects were infused with either glucose ( 20 % in saline ; carbohydrate ( CHO ) ) at a rate of 1 g x min(-1 ) or saline ( 0.9 % saline ; placebo ( PLA ) ) . It was hypothesized that time trial performance would be unaffected by the infusion of glucose , as endogenous stores of CHO would not be limiting in the PLA trial . RESULTS Plasma glucose concentration increased from 4.8 + /- 0.1 mmol x L(-1 ) to 5.9 + /- 0.3 mmol x L(-1 ) during the PLA trial and from 4.9 + /- 0.1 mmol x L(-1 ) at rest to 12.4 + /- 1.1 mmol x L(-1 ) during the CHO trial . These values were significantly higher at all time points during the CHO trial compared with PLA ( P < 0.001 ) . In the final stages of the time trial , Rd in the PLA trial was 49 + /- 5 micromol x kg(-1 ) x min(-1 ) compared with 88 + /- 7 micromol x kg(-1 ) x min(-1 ) in the CHO trial ( P < 0.05 ) . Despite these differences , there was no difference in performance time between PLA and CHO ( 60.04 + /- 1.47 min , PLA , vs 59.90 + /- 1.49 min , CHO , respectively ) . Infused carbohydrate oxidation in the last 25 % of the CHO trial was at least 675 + /- 120 micromol x kg(-1 ) and contributed 17 + /- 4 % to total carbohydrate oxidation . CONCLUSION The results demonstrate that glucose infusion had no effect on 1-h cycle time-trial performance , despite an increased availability of plasma glucose for oxidation and evidence of increased glucose uptake into the tissues PURPOSE AND METHOD To investigate the possible role of carbohydrate ( CHO ) receptors in the mouth in influencing exercise performance , seven male and two female endurance cyclists ( VO(2max ) 63.2 + /- 2.7 ( mean + /- SE ) mL.kg*(-1).min(-1 ) ) completed two performance trials in which they had to accomplish a set amount of work as quickly as possible ( 914 + /- 40 kJ ) . On one occasion a 6.4 % maltodextrin solution ( CHO ) was rinsed around the mouth for every 12.5 % of the trial completed . On the other occasion , water ( PLA ) was rinsed . Subjects were not allowed to swallow either the CHO solution or water , and each mouthful was spat out after a 5-s rinse . RESULTS Performance time was significantly improved with CHO compared with PLA ( 59.57 + /- 1.50 min vs 61.37 + /- 1.56 min , respectively , P = 0.011 ) . This improvement result ed in a significantly higher average power output during the CHO compared with the PLA trial ( 259 + /- 16 W and 252 + /- 16 W , respectively , P = 0.003 ) . There were no differences in heart rate or rating of perceived exertion ( RPE ) between the two trials ( P > 0.05 ) . CONCLUSION The results demonstrate that carbohydrate mouth rinse has a positive effect on 1-h time trial performance . The mechanism responsible for the improvement in high-intensity exercise performance with exogenous carbohydrate appears to involve an increase in central drive or motivation rather than having any metabolic cause . The nature and role of putative CHO receptors in the mouth warrants further investigation Carbohydrate-electrolyte ( CE ) feedings have been shown to improve endurance performance at moderate intensities ( 60 - 75 % VO2max ) and or more than 2 h duration . The effects of CE feedings during high intensity exercise ( i.e. > or = 80 % VO2 max ) of shorter duration ( approximately 1 h ) are less clear . Therefore the purpose of the present study was to investigate the effect of the ingestion of a 7.6 % CE solution during exercise on time trial cycling performance of approximately 1 h. This type of performance testing has been shown to be more reproducible ( coefficient of variation 3.35 % ) than the traditional exercise test to exhaustion . On two occasions and in r and om order nineteen endurance trained cyclists completed an exercise test requiring the accomplishment of a set amount of work as fast as possible ( time trial ) under strictly st and ardized conditions . As the start and during the trials they drank in total 14 ml/kg of either a 7.6 % CE solution or artificially flavored and colored water ( placebo ) .  Time to complete the 
    Output:
    
An activation of the oral receptors and consequently brain areas involved with reward ( insula/operculum frontal , orbitofrontal cortex , and striatum ) is suggested as a possible physiological mechanism responsible for the improved performance with CHO mouth rinse .