***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: INTRODUCTION Caffeine enhances performance of single bouts of endurance exercise , but its effects on repeated bouts typical of those in high-intensity team sports are unclear . PURPOSE To investigate effects of caffeine in a performance test simulating physical and skill dem and s of a rugby union game . METHODS The study was a double-blind , r and omized , crossover design in which nine competitive male rugby players ingested either caffeine ( 6 mg.kg(-1 ) body mass ) or placebo ( dextrose ) 70 min before performing a rugby test . Each test consisted of seven circuits in each of two 40-min halves with a 10-min half-time rest . Each circuit included stations for measurement of sprint time ( two straight-line and three agility sprints ) , power generation in two consecutive drives , and accuracy for passing balls rapidly . Interstitial fluid was sample d transdermally by electrosonophoresis before ingestion of caffeine or placebo and then before testing , at half-time , and immediately after testing ; sample s were assayed chromatographically for caffeine and epinephrine concentrations . RESULTS The effects of caffeine on mean performance ( + /-90 % confidence limits ) over all 14 circuits were : sprint speeds , 0.5 % ( + /-1.7 % ) through 2.9 % ( + /-1.3 % ) ; first-drive power , 5.0 % ( + /-2.5 % ) ; second-drive power , -1.2 % ( + /-6.8 % ) ; and passing accuracy , 9.6 % ( + /-6.1 % ) . The enhancements were mediated partly through a reduction of fatigue that developed throughout the test and partly by enhanced performance for some measures from the first circuit . Caffeine produced a 51 % ( + /-11 % ) increase in mean epinephrine concentration ; correlations between individual changes in epinephrine concentration and changes in performance were mostly unclear , but there were some strong positive correlations with sprint speeds and a strong negative correlation with passing accuracy . CONCLUSION Caffeine is likely to produce substantial enhancement of several aspects of high-intensity team-sport performance PURPOSE This study was design ed to examine the effect of carbohydrate ( CHO ) feedings on physical and central nervous system ( CNS ) function during intermittent high-intensity exercise with physical dem and s similar to those of team sports such as basketball . METHODS Twenty active men ( N = 10 ) and women ( N = 10 ) , with experience competing in team sports , performed three practice sessions before two experimental trials during which they were fed either a 6 % CHO solution or a flavored placebo ( PBO ) . Experimental trials consisted of four 15-min quarters of shuttle running with variable intensities ranging from walking ( 30 % VO(2max ) ) , to running ( 120 % VO(2max ) ) , to maximal sprinting , and 40 jumps at a target hanging at 80 % of their maximum vertical jump height . Subjects received 5 mL.kg(-1 ) of fluid before exercise and 3 mL.kg(-1 ) after exercise , in addition to 3 mL.kg(-1 ) over a 5-min span after the first and third quarters , and 8 mL.kg(-1 ) during a 20-min halftime . During each break , the subjects performed a battery of tests measuring peripheral and CNS function , including 20-m sprints , a 60-s maximal jumping test , internal and external mood evaluation , cognitive function , force sensation , tests of motor skills , and target-jumping accuracy . RESULTS Compared with PBO , CHO feedings during exercise result ed in faster 20-m sprint times and higher average jump height in the fourth quarter ( P < 0.05 ) . CHO feedings also reduced force sensation , enhanced motor skills , and improved mood late in exercise versus PBO ( P < 0.05 ) . CONCLUSION These results suggest that CHO feedings during intermittent high-intensity exercise similar to that of team sports benefited both peripheral and CNS function late in exercise compared with a flavored placebo BACKGROUND AND PURPOSE Prolonged wakefulness impairs sustained vigilant attention , measured with the psychomotor vigilance task ( PVT ) , and induces a compensatory increase in sleep intensity in recovery sleep , quantified by slow‐wave activity ( SWA ) in the sleep electroencephalogram ( EEG ) . These effects of sleep deprivation are counteracted by the adenosine receptor antagonist caffeine , implying involvement of the adenosine neuromodulator/receptor system . To examine a role for adenosine A2A receptors , we investigated whether variation of the A2A receptor gene ( ADORA2A ) modified effects of caffeine on PVT and SWA after sleep deprivation To examine the effects of aerobic interval training on the decline in short-passing ability caused by a short bout of high-intensity intermittent activities . For this r and omized controlled trial , 26 junior soccer players ( mean age , 17.8 + /- 0.6 years ; mean height , 178 + /- 5 cm ; mean body mass , 74.5 + /- 6.9 kg ) were recruited . After baseline measurements , subjects were r and omly allocated to 1 of 2 groups : the control group ( CG ) or the aerobic interval training group ( ITG ) . The ITG completed 4 weeks of high-intensity aerobic training , consisting of 4 bouts of running for 4 min at 90%-95 % of maximal heart rate , with 3 min of active recovery between sets , in addition to normal training .  Maximum oxygen uptake , Yo-Yo Intermittent Recovery Test level 1 ( YYIRT ) , and short-passing ability ( measured using the Loughborough Soccer Passing Test ( LSPT ) ) were measured before and after a 5 min high-intensity simulation ( HIS ) , reproducing the most intense phase of a match . The ITG ( n = 11 ) , but not the CG ( n = 10 ) , showed a significant 12 % and 4 % increase in YYIRT and maximal oxygen consumption after training , respectively , and reduced the worsening in LSPT penalty time after the HIS ( p < 0.05 ) . The relative exercise intensity during HIS decreased in the ITG only ( p < 0.01 ) . Our results demonstrated that junior soccer players may benefit from aerobic training to attenuate the decline in short-passing ability caused by a short bout of intermittent activities completed at the same pretraining workload PURPOSE This study was design ed to examine the effects of carbohydrate-electrolyte ingestion on physical and mental function associated with the performance of  intermittent high-intensity ( IHI ) exercise  similar to many common competitive sporting events . METHODS Physically active men ( N = 5 ) and women ( N = 5 ) , experienced in competitive soccer or basketball , completed three practice sessions and two experimental trials of an IHI shuttle running protocol design ed to closely stimulate the dem and s of an actual competitive sporting event such as basketball . The experimental trials consisted of four 15-min quarters ( QTR ) of intermittent shuttle running at various percentages of .VO(2max ) ( walking , jogging , running , sprinting and jumping ) , separated by a 20-min halftime rest period ( HALF ) and followed by a shuttle run to fatigue . Various tests of physical and mental function ( shuttle run to fatigue , 20-m maximal sprint , 10-repetition maximal vertical jumping , whole body motor skill test ( MS-Test ) , profile of mood states ( POMS ) , and Stroop Color-Word Test ) were performed throughout the experimental trial . Carbohydrate-electrolyte ( CHO ) or placebo ( P ) drinks were consumed before exercise ( 5 mL.kg(-1 ) ; 6 % solution ) and at halftime ( 5 mL.kg(-1 ) ; 18 % solution ) . Smaller volumes ( 3 mL.kg(-1 ) ; 6 % solution ) were given after QTR-1 , HALF , QTR-3 , and QTR-4 . RESULTS CHO ingestion result ed in a 37 % longer run time to fatigue and faster 20-m sprint time during QTR-4 ( P < 0.05 ) . MS-Test performance was also improved during the latter stages of exercise along with self-reported perceptions of fatigue ( subscale of POMS ) ( P < 0.05 ) in CHO versus P. CONCLUSION These results suggest a beneficial role of carbohydrate-electrolyte ingestion on physical and mental function during intermittent exercise similar to that of many competitive team sports This study examined the effects of ingesting a glucose-polymer ( GP ) solution on the motor skill proficiencies of association football ( soccer ) players from two teams playing during two matches in a cool environment . Fifteen minutes before each match and at halftime , players from both teams ingested 5 ml/kg of either placebo or a 6.9 % GP solution . GP ingestion did not improve tackling , heading , dribbling , or shooting ability . On the contrary , the mean of successful tackles was lower with GP ingestion than with placebo .  The success rate for heading , dribbling , and shooting also tended to be lower in the GP than in the placebo condition . In contrast , success in passing and ball control was similar in the two conditions . Improvements in passing and ball control may have been related to a decrease in the intensity of play in the second half of the game . These data indicate that there are no measurable benefits of GP ingestion for the motor skill proficiencies of soccer players during games played in a cool environment 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 The effects of high-intensity , short- duration , re-warm-ups on team-sport-related performance were investigated . In a r and omised , cross-over study , participants performed 2 × 26-min periods of an intermittent activity protocol ( IAP ) on a non-motorized treadmill , interspersed by 15-min of passive recovery ( CON ) ; 3-min small-sided game ( SSG ) ; or a 5RM leg-press . Measures included counter-movement jump , repeated-sprint , the Loughborough soccer passing test ( LSPT ) , blood lactate concentration , heart-rate , and perceptual measures . Data were analyzed using effect size ( 90 % confidence intervals ) , and percentage change ; determining magnitudes of effects . A 5RM re-warm-up improved flight-time to contraction-time ratio when compared to SSG ( 9.8 % , ES ; 0.5±0.3 ) and CON ( ES : 9.4 % , 0.7±0.5 ) re-warm-ups , remaining higher following the second IAP ( 8.8 % , ES ; 0.5±0.3 and 10.2 % , ES ; 0.6±0.6 , respectively ) . Relative-maximum rate-of-force development was greater in the 5RM condition following the second IAP compared to SSG ( 29.3 % , ES ; 0.7±0.5 ) and CON ( 16.2 % , ES ; 0.6±0.6 ) . Repeated-sprint ability during the second IAP improved in the 5RM re-warm-up ; peak velocity , mean velocity , and acceleration were 4 , 3 , and 18 % greater , respectively . Within groups , the SSG re-warm-up improved LSPT performance post-intervention ; 6.4 % ( ES : 0.6±0.8 ) and following the second IAP 6.2 % ( ES : 0.6±0.6 ) , compared to pre-intervention . A 5RM leg-press re-warm-up improved physical performance , while a SSG re-warm-up enhanced skill execution following st and ardized intermittent exercise OBJECTIVES To examine the effect of a high carbohydrate meal on serum caffeine concentration following caffeine intake . DESIGN R and omised , double-blind , crossover . METHODS Fourteen healthy males r and omly completed 4 trials , each separated by 5 days . Participants either remained fasted ( on 2 occasions ) or ingested a high carbohydrate meal ( 2.0gkg(-1 ) carbo 
    Output:
    
Conclusions The findings from this systematic review suggest that nutritional interventions , which provide carbohydrate , caffeine and fluid , have potential to preserve skills performed under conditions that induce soccer-specific fatigue .
The weight of current evidence supports the consumption of carbohydrate , but is less conclusive with respect to caffeine and fluid provision .