***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: Background Studies involving chronic creatine supplementation in elite soccer players are scarce . Therefore , the aim of this study was to examine the effects of creatine monohydrate supplementation on lower-limb muscle power in Brazilian elite soccer players ( n = 14 males ) during pre-season training . Findings This was a r and omized , double-blind , placebo-controlled parallel-group study . Brazilian professional elite soccer players participated in this study . During the pre-season ( 7 weeks ) , all the subjects underwent a st and ardized physical and specific soccer training . Prior to and after either creatine monohydrate or placebo supplementation , the lower-limb muscle power was measured by countermovement jump performance . The Jumping performance was compared between groups at baseline ( p = 0.99 ) . After the intervention , jumping performance was lower in the placebo group ( percent change = - 0.7 % ; ES = - 0.3 ) than in the creatine group ( percent change = + 2.4 % ; ES = + 0.1 ) , but it did not reach statistical significance ( p = 0.23 for time x group interaction ) . Fisher ’s exact test revealed that the proportion of subjects that experienced a reduction in jumping performance was significantly greater in the placebo group than in the creatine group ( 5 and 1 , respectively ; p = 0.05 ) after the training . The magnitude-based inferences demonstrated that placebo result ed in a possible negative effect ( 50 % ) in jumping performance , whereas creatine supplementation led to a very likely trivial effect ( 96 % ) in jumping performance in the creatine group . Conclusions Creatine monohydrate supplementation prevented the decrement in lower-limb muscle power in elite soccer players during a pre-season progressive training PURPOSE This investigation examined the effects of creatine ( Cr ) supplementation on intermittent high-intensity exercise activities specific to competitive soccer . METHODS On two occasions 7 d apart , 17 highly trained male soccer players performed a counter-movement jump test ( CMJT ) , a repeated sprint test ( RST ) consisting of six maximal 15-m runs with a 30-s recovery , an intermittent endurance test ( IET ) consisting of forty 15-s bouts of high-intensity running interspersed by 10-s bouts of low-intensity running , and a recovery CMJT consisting of three jumps . After the initial testing session , players were evenly and r and omly included in a CREATINE ( 5 g of Cr , four times per day for 6 d ) or a PLACEBO group ( same dosage of maltodextrins ) using a double-blind research design . RESULTS The CREATINE group 's average 5-m and 15-m times during the RST were consistently faster after the intervention ( 0.95 + /- 0.03 vs 0.97 + /- 0.02 s , P < 0.05 and 2.29 + /- 0.08 vs 2.32 + /- 0.07 s , P = 0.07 , respectively ) . Neither group showed significant changes in the CMJT or the IET . The CREATINE group 's recovery CMJT performance relative to the resting CMJT remained unchanged postsupplementation , whereas it tended to decrease in the PLACEBO group . CONCLUSION In conclusion , acute Cr supplementation favorably affected repeated sprint performance and limited the decay in jumping ability after the IET in highly trained soccer players . Intermittent endurance performance was not affected by Cr Muscle glycogen availability can limit endurance exercise performance . We previously demonstrated 5 days of creatine ( Cr ) and carbohydrate ( CHO ) ingestion augmented post-exercise muscle glycogen storage compared to CHO feeding alone in healthy volunteers . Here , we aim ed to characterise the time-course of this Cr-induced response under more stringent and controlled experimental conditions and identify potential mechanisms underpinning this phenomenon . Fourteen healthy , male volunteers cycled to exhaustion at 70 % VO2peak . Muscle biopsies were obtained at rest immediately post-exercise and after 1 , 3 and 6 days of recovery , during which Cr or placebo supplements ( 20 g day−1 ) were ingested along with a prescribed high CHO diet ( 37.5 kcal kg body mass−1 day−1 , > 80 % calories CHO ) . Oral-glucose tolerance tests ( oral-GTT ) were performed pre-exercise and after 1 , 3 and 6 days of Cr and placebo supplementation . Exercise depleted muscle glycogen content to the same extent in both treatment groups . Creatine supplementation  increased muscle total-Cr , free-Cr and phosphocreatine ( PCr ) content  above placebo following 1 , 3 and 6 days of supplementation ( all P < 0.05 ) . Creatine supplementation also increased muscle glycogen content noticeably above placebo after 1 day of supplementation ( P < 0.05 ) , which was sustained thereafter . This study confirmed dietary Cr augments post-exercise muscle glycogen super-compensation , and demonstrates this occurred during the initial 24 h of post-exercise recovery ( when muscle total-Cr had increased by < 10 % ) . This marked response ensued without apparent treatment differences in muscle insulin sensitivity ( oral-GTT , muscle GLUT4 mRNA ) , osmotic stress ( muscle c-fos and HSP72 mRNA ) or muscle cell volume ( muscle water content ) responses , such that another mechanism must be causative Background To determine the effects of a low dose , short-term Creatine monohydrate ( Cr ) supplementation ( 0.03 g.kg.d−1 during 14 d ) on muscle power output in elite youth soccer players . Methods Using a two-group matched , double blind , placebo-controlled design , nineteen male soccer players ( mean age = 17.0 ± 0.5 years ) were r and omly assigned to either Cr ( N = 9 ) or placebo ( N = 10 ) group . Before and after supplementation , participants performed a 30s Wingate Anaerobic Test ( WAnT ) to assess peak power output ( PPO ) , mean power output ( MPO ) , fatigue index ( FI ) , and total work . Results There were significant increases in both PPO and MPO after the Cr supplementation period ( P ≤ 0.05 ) but not the placebo period . There were also significant increases in total work , but not FI , after the Cr supplementation and placebo periods ( P ≤ 0.05 ) . Notably , there were differences in total work between the Cr and placebo groups after ( P ≤ 0.05 ) but not before the 14 d supplementation period . Conclusion There is substantial evidence to indicate that a low-dose , short-term oral Cr supplementation beneficially affected muscle power output in elite youth soccer players The purpose of this study was to examine the effects of acute creatine-monohydrate supplementation on soccer-specific performance in young soccer players . Twenty young male soccer players ( 16.6 + /- 1.9 years ) participated in the study and were matched and allocated to 2 r and omly assigned trials : ingesting creatine-monohydrate supplement ( 3 x 10-g doses ) or placebo for 7 days . Before and after the supplementation protocol , each subject underwent a series of soccer-specific skill tests : dribble test , sprint-power test , endurance test , and vertical jump test . Specific dribble test times improved significantly in the creatine group ( 13.0 + /- 1.5 vs. 10.2 + /- 1.8 s ; p < .05 ) after supplementation protocol . Sprint-power test times were significantly improved after creatine-monohydrate supplementation ( 2.7 + /- 0.4 vs. 2.2 + /- 0.5 s ; p < .05 ) as well as vertical jump height ( 49.2 + /- 5.9 vs. 55.1 + /- 6.3 cm ; p < .05 ) in creatine trial . Furthermore , dribble and power test times , along with vertical jump height , were superior in creatine versus placebo trial ( p < .05 ) at post-supplementation performance . There were no changes in specific endurance test results within or between trials ( p > .05 ) . There were no between-trial differences in the placebo trial ( p > .05 ) . The main finding of the present study indicates that supplementation with creatine in young soccer players improved soccer-specific skill performance compared with ingestion of placebo Abstract It has been suggested that assessment of high-intensity activities during a match is a valid measure of physical performance in elite soccer . Recently , sprinting activities have been analysed in more depth . The aim of this study was to develop a detailed analysis of the sprinting activities of different playing positions during European Champions League and UEFA Cup competitions . Altogether , 717 elite outfield soccer players were evaluated throughout 2002–2006 using ProZone ® ( Leeds , UK ) .  Sprinting ( explosive and leading )  was analysed for each playing position . To compare positional differences , a Kruskal-Wallis analysis was performed . Differences were found among positions for total number of sprints and total sprint distance covered : wide midfielders > ( attackers = wide defenders ) > central midfielders > central defenders ( P < 0.001 ) , as well as for explosive sprints :  ( wide midfielders = attackers = wide defenders ) > central defenders , wide midfielders > central midfielders > central defenders and attackers = wide defenders = central midfielders ( P < 0.001 ) , and leading sprints : wide midfielders > ( attackers = wide defenders ) > central midfielders > central defenders ( P < 0.001 ) . For each group , there were no differences in ratio of explosive to leading sprints . Wide midfielders performed a higher number of sprints in all five distance categories than all other positions . This study showed that sprinting characteristics are influenced by position . Wide midfielders have to complete additional high-intensity activities during training sessions compared with the other positions to achieve the performance level required during the match PURPOSE To compare the change in muscle creatine , fiber morphology , body composition , hydration status , and exercise performance between vegetarians and nonvegetarians with 8 wk of creatine supplementation and resistance training . METHODS Eighteen VG and 24 NV subjects ( 19 - 55 yr ) were r and omly assigned ( double blind ) to four groups : VG + creatine ( VGCr , N=10 ) , VG + placebo ( VGPl , N=8 ) , NV + creatine ( NVCr , N=12 ) , and NV + placebo ( NVPl , N=12 ) . Before and at the end of the study , muscle biopsies were taken from the vastus lateralis m , body composition was assessed by DXA , and strength was assessed using 1-RM bench press and leg press . Subjects participated in the same 8-wk resistance-training program . Creatine dosage was based on lean tissue mass ( 0.25 g.kg(-1 ) LTM.d(-1 ) x 7 d ; 0.0625 g.kg(-1 ) LTM.d(-1 ) x 49 d ) . RESULTS Biopsy sample s indicated that total creatine ( TCr = free Cr + PCr ) was significantly lower in VG compared with NV at baseline ( VG=117 mmol.kg(-1 ) ; NV=130 mmol.kg(-1 ) ; P<0.05 ) . For Cr subjects , there was a greater increase in PCr , TCr , bench-press strength , isokinetic work , Type II fiber area , and whole-body lean tissue compared with subjects on placebo ( P<0.05 ) . Vegetarians who took Cr had a greater increase in TCr , PCr , lean tissue , and total work performance than nonvegetarians who took Cr ( P<0.05 ) . The change in muscle TCr was significantly correlated with initial muscle TCr , and the change in lean tissue mass and exercise performance . These findings confirm an ergogenic effect of Cr during resistance training and suggest that subjects with initially low levels of intramuscular Cr ( vegetarians ) are more responsive to supplementation This study investigated the effects of acute creatine ( Cr ) supplementation on the performance of elite female soccer players undertaking an exercise protocol simulating match play . On two occasions , 7 days apart , 12 players performed 5 x 11-min exercise testing blocks interspersed with 1 min of rest . Each block consisted of 11 all-out 20-m running sprints , 2 agility runs , and 1 precision ball-kicking drill , separated by recovery 20-m walks , jogs , and runs . After the initial testing session , subjects were assigned to either a CREATINE ( 5 g of Cr , 4 times per day for 6 days ) or a PLACEBO group ( same dosage of a glucose polymer ) using a double-blind research design . Body mass ( BM ) increased ( 61.7 + /- 8.9 to 62.5 < or = 8.9 kg , p < .01 ) in the CREATINE group ; however , no change was observed in the PLACEBO group ( 63.4 < or = 2.9 kg to 63.7 + /- 2.5 kg ) . No overall change in 20-m sprint times and agility run times were observed , although the CREATINE group achieved faster post-supplementation times in sprints 11 , 13 , 14 , 16 , 21 , 23 , 25 , 32 , and 39 ( p < .05 ) , and agility runs 3 , 5 , and 8 ( 
    Output:
    
In conclusion , creatine supplementation with a loading dose of 20⁻30 g/day , divided 3⁻4 times per day , ingested for 6 to 7 days , and followed by 5 g/day for 9 weeks or with a low dose of 3 mg/kg/day for 14 days presents positive effects on improving physical performance tests related to anaerobic metabolism , especially anaerobic power , in soccer players