***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 
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    Input: Background Knee injuries in football are common regardless of age , gender or playing level , but adolescent females seem to have the highest risk . The consequences after severe knee injury , for example anterior cruciate ligament ( ACL ) injury , are well-known , but less is known about knee injury prevention . We have design ed a cluster r and omized controlled trial ( RCT ) to evaluate the effect of a warm-up program aim ed at preventing acute knee injury in adolescent female football . Methods In this cluster r and omized trial 516 teams ( 309 clusters ) in eight regional football districts in Sweden with female players aged 13–17 years were r and omized into an intervention group  ( 260 teams ) or a  control group  ( 256 teams ) . The teams in the intervention group were instructed to do a structured warm-up program at two training sessions per week throughout the 2009 competitive season ( April to October ) and those in the control group were informed to train and play as usual . Sixty-eight sports physical therapists are assigned to the clubs to assist both groups in data collection and to examine the players ' acute knee injuries during the study period . Three different forms are used in the trial : ( 1 ) baseline player data form collected at the start of the trial , ( 2 ) computer-based registration form collected every month , on which one of the coaches/team leaders documents individual player exposure , and ( 3 ) injury report form on which the study therapists report acute knee injuries result ing in time loss from training or match play . The primary outcome is the incidence of ACL injury and the secondary outcomes are the incidence of any acute knee injury ( except contusion ) and incidence of severe knee injury ( defined as injury result ing in absence of more than 4 weeks ) . Outcome measures are assessed after the end of the 2009 season . Discussion Prevention of knee injury is beneficial for players , clubs , insurance companies , and society . If the warm-up program is proven to be effective in reducing the incidence of knee injury , it can have a major impact by reducing the future knee injury burden in female football as well as the negative long-term disabilities associated with knee injury . Trial registration Objective To evaluate the effectiveness of neuromuscular training in reducing the rate of acute knee injury  in adolescent female football players . Design Stratified cluster r and omised controlled trial with clubs as the unit of r and omisation . Setting 230 Swedish football clubs ( 121 in the intervention group , 109 in the control group ) were followed for one season ( 2009 , seven months ) . Participants 4564 players aged 12 - 17 years ( 2479 in the intervention group , 2085 in the control group ) completed the study . Intervention 15 minute neuromuscular warm-up programme ( targeting core stability , balance , and proper knee alignment ) to be carried out twice a week throughout the season . Main outcome measures The primary outcome was rate of anterior cruciate ligament injury ; secondary outcomes were rates of severe knee injury ( > 4 weeks ’ absence ) and any acute knee injury . Results Seven players ( 0.28 % ) in the intervention group , and 14 ( 0.67 % ) in the control group had an anterior cruciate ligament injury . By Cox regression analysis according to intention to treat , a 64 % reduction in the rate of anterior cruciate ligament injury was seen in the intervention group ( rate ratio 0.36 , 95 % confidence interval 0.15 to 0.85 ) . The absolute rate difference was −0.07 ( 95 % confidence interval −0.13 to 0.001 ) per 1000 playing hours in favour of the intervention group . No significant rate reductions were seen for secondary outcomes . Conclusions A neuromuscular warm-up programme significantly reduced the rate of anterior cruciate ligament injury in adolescent female football players . However , the absolute rate difference did not reach statistical significance , possibly owing to the small number of events . Trial registration Clinical trials NCT00894595 Background Participants ' compliance , attitudes and beliefs have the potential to influence the efficacy of an intervention greatly . Objective To characterise team and player compliance with a comprehensive injury prevention warm-up programme for football ( The 11 + ) , and to assess attitudes towards injury prevention among coaches and their association with compliance and injury risk . Study Design A prospect i ve cohort study and retrospective survey based on a cluster-r and omised controlled trial with teams as the unit of r and omisation . Methods Compliance , exposure and injuries were registered prospect ively in 65 of 125 football teams ( 1055 of 1892 female Norwegian players aged 13–17 years and 65 of 125 coaches ) throughout one football season ( March – October 2007 ) . St and ardised telephone interviews were conducted to assess coaches ' attitudes towards injury prevention . Results Teams completed the injury prevention programme in 77 % ( mean 1.3 sessions per week ) of all training and match sessions , and players in 79 % ( mean 0.8 sessions per week ) of the sessions they attended . Compared with players with intermediate compliance , players with high compliance with the programme had a 35 % lower risk of all injuries ( RR 0.65 , 95 % CI 0.46 to 0.91 , p=0.011 ) . Coaches who had previously utilised injury prevention training coached teams with a 46 % lower risk of injury ( OR 0.54 , 95 % CI 0.33 to 0.87 , p=0.011 ) . Conclusions Compliance with the injury prevention programme was high , and players with high compliance had significantly lower injury risk than players with intermediate compliance . Positive attitudes towards injury prevention correlated with high compliance and lower injury risk Background Injury prevention programme delivery on adherence and injury risk , specifically involving regular supervisions with coaches and players on programme execution on field , has not been examined . Aim The objective of this cluster-r and omised study was to evaluate different delivery methods of an effective injury prevention programme ( FIFA 11 + ) on adherence and injury risk among female youth football teams . Method During the 4-month 2011 football season , coaches and 13-year-old to 18-year-old players from 31 tier 1–3 level teams were introduced to the 11 + through either an unsupervised website ( ‘ control ’ ) or a coach-focused workshop with ( ‘ comprehensive ’ ) and without ( ‘ regular ’ ) additional supervisions by a physiotherapist .  Team and player adherence to the 11 + , playing exposure , history and injuries were recorded . Results Teams in the comprehensive and regular intervention groups demonstrated adherence to the 11 + programme of 85.6 % and 81.3 % completion of total possible sessions , compared to 73.5 % for teams in the control group . These differences were not statistically significant , after adjustment for cluster by team , age , level and injury history . Compared to players with low adherence , players with high adherence to the 11 + had a 57 % lower injury risk ( IRR 0.43 , 95 % CI 0.19 to 1.00 ) . However , adjusting for covariates , this between-group difference was not statistically significant ( IRR=0.44 , 95 % CI 0.18 to 1.06 ) . Conclusion Following a coach workshop , coach-led delivery of the FIFA 11 + was equally successful with or without the additional field involvement of a physiotherapist . Proper education of coaches during an extensive preseason workshop was more effective in terms of team adherence than an unsupervised delivery of the 11 + programme to the team . Trial registration IS RCT N67835569 The long-term development of injury risk in Swedish male elite football was studied . Two prospect i ve cohort studies from seasons 1982 and 2001 were compared with respect to exposure to  football , injury incidence and injury severity . The mean number of training sessions during the season had increased by 68 % between 1982 and 2001 ( 142 vs. 238 , P<0.001 ) , whereas teams played more matches in 1982 ( 49 vs. 41 , P=0.02 ) . The total exposure to football had increased by 27 % . Three out of four players incurred an injury in both seasons . In 2001 , players suffered more training injuries due to an increased training exposure . Accounting for risk exposure , there was no difference in injury incidence or severity between the two seasons . The incidence was 8.3 injuries/1000 h of total exposure ( 4.6 in training and 20.6 in matches ) in 1982 , compared to 7.8/1000 h-1 ( 5.2 in training and 25.9 in matches ) in 2001 . Major injuries accounted for 9 % of all injuries , corresponding to an incidence of 0.8/1000 h of football , in both seasons . A trend from semi-professionalism to full professionalism in Swedish elite football was seen during the last two decades . The injury risk did not change over the same period Background : Risk factors for soccer injuries and possibilities for prevention have been discussed by several authors , but only a few have investigated the effectiveness of preventive interventions . Purpose : The aim of the present study was to evaluate the effects of a prevention program on the incidence of soccer injuries in male youth amateur players . Study Design : Prospect i ve controlled intervention study . Methods : Seven soccer teams took part in a  prevention program that focused on education and supervision of coaches and players , while seven other teams were instructed to train and play soccer as usual . Over 1 year all injuries were documented weekly by physicians . Complete weekly injury reports were available for 194 players . Results : The incidence of injury per 1000 hours of training and playing soccer was 6.7 in the intervention group and 8.5 in the control group , which equates to 21 % fewer injuries in the intervention group . The greatest effects were observed for mild injuries , overuse injuries , and injuries incurred during training . The prevention program had greater effects in low-skill than in high-skill teams . Conclusions : The incidence of soccer injuries can be reduced by preventive interventions , especially in low skill level youth teams . Coaches and players need better education regarding injury prevention strategies and should include such interventions as part of their regular training A set of exercises -- the " 11"--have been selected to prevent football injuries . The purpose of this cluster-r and omized controlled trial was to investigate the effect of the " 11 " on injury risk in female youth football . Teams were r and omized to an  intervention ( n=59 teams , 1091 players ) or a control group ( n=54 teams , 1001 players ) . The intervention group was taught the " 11 , " exercises for core stability , lower extremity strength , neuromuscular control and agility , to be used as a 15-min warm-up program for football training over an 8-month season . A total of 396 players ( 20 % ) sustained 483 injuries . No difference was observed in the overall injury rate between the intervention ( 3.6 injuries/1000 h , confidence interval ( CI ) 3.2 - 4.1 ) and control group ( 3.7 , CI 3.2 - 4.1 ; RR=1.0 , CI 0.8 - 1.2 ; P=0.94 ) nor in the incidence for any type of injury . During the first 4 months of the season , the training program was used during 60 % of the football training sessions , but only 14 out of 58 intervention teams completed more than 20 prevention training sessions . In conclusion , we observed no effect of the injury prevention program on the injury rate , most likely because the compliance with the program was low OBJECTIVE To determine the effectiveness of coach-led neuromuscular warm-up on reducing  lower extremity ( LE ) injuries in female athletes in a mixed-ethnicity , predominantly low-income , urban population . DESIGN Cluster r and omized controlled trial . SETTING Chicago public high schools . PARTICIPANTS Of 258 coaches invited to participate , 95 ( 36.8 % ) enrolled ( 1558 athletes ) . Ninety coaches and 1492 athletes completed the study . INTERVENTIONS We r and omized schools to intervention and control groups . We trained intervention coaches to implement a 20-minute neuromuscular warm-up . Control coaches used their usual warm-up . MAIN OUTCOME MEASURES Coach compliance was tracked by self-report and direct observation . Coaches reported weekly athlete exposures ( AEs ) and LE injuries causing a missed practice or game . Research assistants interviewed injured athletes . Injury rates were compared between the control and intervention groups using χ(2 ) and Fisher exact tests . Significance was set at P < .05 . Poisson regression analysis adjusted for clustering and covariates in an athlete subset reporting personal information ( n = 855 ; 57.3 % ) . RESULTS There were 28 023 intervention AEs and 22 925 control AEs . Intervention coaches used prescribed warm-up in 1425 of 1773 practice s ( 80.4 % ) . Intervention athletes had lower rates per 1000 AEs of gradual-onset LE injuries ( 0.43 vs 1.22 , P < .01 ) , acute-onset noncontact LE injuries ( 0.71 vs 1.61 , P < .01 ) , noncontact ankle sprains ( 0.25 vs 0.74 , P = .01 ) , and LE injuries treated surgically ( 0 vs 0.17 , P = .04 ) . Regression analysis showed significant incidence rate ratios for acute-onset noncontact LE injuries ( 0.33 ; 95 % CI , 0.17 - 0.61 ) , noncontact ankle spra 
    Output:
    
DISCUSSION Several method ological weaknesses were observed , but it seems that there is a trend toward a warm-up that contains basic stretching , strengthening and balance exercises , which performed for more than three months and regularly , could prevent injuries .
" FIFA 11 + " program might be a good preventive measure of injuries by implementing its program of structured warm- up .