***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 A protective effect on injury risk in youth sports through neuromuscular warm-up training routines has consistently been demonstrated . However , there is a paucity of information regarding the quantity and quality of coach-led injury prevention programmes and its impact on the physical performance of players . Objective The aim of this cluster-r and omised controlled trial was to assess whether different delivery methods of an injury prevention programme ( FIFA 11 + ) to coaches could improve player performance , and to examine the effect of player adherence on performance and injury risk . Method During the 2011 football season ( May – August ) , coaches of 31 tiers 1–3 level teams were introduced to the 11 + through either an unsupervised website or a coach-focused workshop with and without additional on-field supervisions . Playing exposure , adherence to the 11 + , and injuries were recorded for female 13-year-old to 18-year-old players . Performance testing included the Star Excursion Balance Test ( SEBT ) , single-leg balance , triple hop and jumping-over-a-bar tests . Results Complete preseason and postseason performance tests were available for 226 players ( 66.5 % ) . Compared to the unsupervised group , single-leg balance ( OR=2.8 ; 95 % CI 1.1 to 4.6 ) and the anterior direction of the SEBT improved significantly in the onfield supervised group of players ( OR=4.7 ; 95 % CI 2.2 to 7.1 ) , while 2-leg jumping performance decreased ( OR=−5.1 ; 95 % CI −9.9 to −0.2 ) . However , significant improvements in 5 of 6 reach distances in the SEBT were found , favouring players who highly adhered to the 11 + . Also , injury risk was lower for those players ( injury rate ratio , IRR=0.28 , 95 % CI 0.10 to 0.79 ) . Conclusions Different delivery methods of the FIFA 11 + to coaches influenced players ’ physical performance minimally . However , high player adherence to the 11 + result ed in significant improvements in functional balance and reduced injury risk Background This study was conducted to investigate whether the most common injuries in soccer could be prevented , and to determine if a simple question naire could identify players at increased risk . Hypothesis Introduction of targeted exercise programs to male soccer players with a history of previous injury or reduced function in the ankle , knee , hamstring , or groin will prevent injuries . Study Design R and omized controlled trial ; Level of evidence , 2 . Methods A total of 508 players representing 31 teams were included in the study . A question naire indicating previous injury and /or reduced function as inclusion criteria was used to divide the players into high-risk ( HR ) ( 76 % ) and low-risk ( LR ) groups . The HR players were r and omized individually into an HR intervention group or HR control group . Results A total of 505 injuries were reported , sustained by 56 % of the players . The total injury incidence was a mean of 3.2 ( 95 % confidence interval [ CI ] , 2.5–3.9 ) in the LR control group , 5.3 ( 95 % Cl , 4.6–6.0 ) in the HR control group ( P = .0001 vs the LR control group ) , and 4.9 ( 95 % Cl , 4.3–5.6 ) in the HR intervention group ( P = .50 vs the HR control group ) . For the main outcome measure , the sum of injuries to the ankle , knee , hamstring , and groin , there was also a significantly lower injury risk in the LR control group compared with the 2 other groups , but no difference between the HR intervention group and the HR control group . Compliance with the training programs in the HR intervention group was poor , with only 27.5 % in the ankle group , 29.2 % in the knee group , 21.1 % in the hamstring group , and 19.4 % in the groin defined as having carried out the minimum recommended training volume . Conclusion The players with a significantly increased risk of injury were able to be identified through the use of a question naire , but player compliance with the training programs prescribed was low and any effect of the intervention on injury risk could not be detected The purpose of the present study was to examine the incidence rates of acute hamstring injuries in Danish elite football sustained during training or match play .  Furthermore , it was our intention to document details about the recurrence , severity and the injury seasonal distribution . Hamstring injuries among 374 elite football players were registered prospect ively during a 12-month period . A total of 46 first-time and eight recurrent hamstring injuries were registered . The incidence rates for incurring a first-time hamstring injury showed a significantly ( P<0.01 ) greater incidence rate per 1000 h during match play compared with training . Of 32 players who reported a hamstring injury in the 12-month period before the study , eight ( 25 % ) incurred an injury that fulfilled the criteria for a recurrent injury . In 69 % of the injuries , the severity of injury was categorized as moderate ( 8 - 28 days from injury to injury free ) and 18 % as severe ( > 28 days from injury to injury free ) . Each team sustained a mean of 3.4 hamstring injuries per season , with a mean of 21.5 days missed per injury ( range 3 - 136 ; median 16 days per injury ) . The seasonal distribution showed an accumulation of injuries in the first 2 months after a 3.5-month mid-season winter break Background : No previous study on adult football involving several different countries has investigated the incidence and pattern of injuries at the highest club competitive level . Objective : To investigate the risk exposure , risk of injury , and injury pattern of footballers involved in UEFA Champions League and international matches during a full football season . Method : Eleven top clubs ( 266 players ) in five European countries were followed prospect ively throughout the season of 2001–2002 . Time-lost injuries and individual exposure times were recorded during all club and national team training sessions and matches . Results : A total of 658 injuries were recorded . The mean ( SD ) injury incidence was 9.4 ( 3.2 ) injuries per 1000 hours ( 30.5 ( 11.0 ) injuries per 1000 match hours and 5.8 ( 2.1 ) injuries per 1000 training hours ) . The risk of match injury was significantly higher in the English and Dutch teams than in the teams from France , Italy , and Spain ( 41.8 ( 3.3 ) v 24.0 ( 7.9 ) injuries per 1000 hours ; p = 0.008 ) . Major injuries ( absence > 4 weeks ) constituted 15 % of all injuries , and the risk of major injury was also significantly higher among the English and Dutch teams ( p = 0.04 ) . National team players had a higher match exposure , with a tendency towards a lower training injury incidence than the rest of the players ( p = 0.051 ) . Thigh strain was the most common injury ( 16 % ) , with posterior strains being significantly more common than anterior ones ( 67 v 36 ; p<0.0001 ) . Conclusions : The risk of injury in European professional football is high . The most common injury is the thigh strain typically involving the hamstrings . The results suggest that regional differences may influence injury epidemiology and traumatology , but the factors involved are unclear . National team players have a higher match exposure , but no higher risk of injury than other top level players Background The incidence rate of soccer injuries is among the highest in sports , particularly for adult male soccer players . Purpose To investigate the effect of the ‘ The11 ’ injury prevention programme on injury incidence and injury severity in adult male amateur soccer players . Study design Cluster-r and omised controlled trial . Methods Teams from two high-level amateur soccer competitions were r and omly assigned to an intervention ( n=11 teams , 223 players ) or control group ( n=12 teams , 233 players ) . The intervention group was instructed to perform The11 in each practice session during one soccer season . The11 focuses on core stability , eccentric training of thigh muscles , proprioceptive training , dynamic stabilisation and plyometrics with straight leg alignment . All participants of the control group continued their practice sessions as usual . Results In total , 427 injuries were recorded , affecting 274 of 456 players ( 60.1 % ) .  Compliance with the intervention programme was good ( team compliance=73 % , player compliance=71 % ) . Contrary to the hypothesis , injury incidences were almost equal between the two study groups : 9.6 per 1000 sports hours ( 8.4–11.0 ) for the intervention group and 9.7 ( 8.5–11.1 ) for the control group . No significant differences were found in injury severity , but a significant difference was observed in the location of the injuries : players in the intervention group sustained significantly less knee injuries . Conclusions This study did not find significant differences in the overall injury incidence or injury severity between the intervention and control group of adult male soccer players . More research is recommended , focusing on injury aetiology and risk factors in adult male amateur soccer players PURPOSE The purpose of this study was to evaluate differences in hamstring activation during lower body resistance training exercises . This study also sought to assess differences in hamstring-to-quadriceps muscle activation ratios and gender differences therein . METHODS A r and omized repeated measures design was used to compare six resistance training exercises that are commonly believed to train the hamstrings , including the squat , seated leg curl , stiff leg dead lift , single leg stiff leg dead lift , good morning , and Russian curl .  Subjects included 34 college athletes . Outcome measures included the biceps femoris ( H ) and rectus femoris ( Q ) electromyography ( EMG ) and the H-to-Q EMG ratio , for each exercise . RESULTS Main effects were found for the H ( P < 0.001 ) and Q ( P < 0.001 ) . Post hoc analysis identified the specific differences between exercises . In addition , main effects were found for the H-to-Q ratio when analyzed for all subjects ( P < 0.001 ) . Further analysis revealed that women achieved between 53.9 to 89.5 % of the H-to-Q activation ratios of men , for the exercises assessed . In a separate analysis of strength matched women and men , women achieved between 35.9 to 76.0 % of the H-to-Q ratios of men , for these exercises . CONCLUSIONS Hamstring resistance training exercises offer differing degrees of H and Q activation and ratios . Women compared with men , are less able to activate the hamstrings and /or more able to activate the quadriceps . Women may require disproportionately greater training for the hamstrings compared with the quadriceps Background : Hamstring injuries are the second most common injury causing missed days in professional baseball field players . Recent studies have shown the preventive benefit of eccentric conditioning on the hamstring muscle group in injury prevention . Specifically , Nordic-type exercises have been shown to decrease the incidence of acute hamstring injuries in professional athletes . Purpose : This was a prospect i ve study performed in coordination with a single Major League Baseball ( MLB ) organization ( major and minor league teams ) that targeted the effects of Nordic exercises on the incidence of acute hamstring injuries in the professional-level baseball player . Study Design : Prospect i ve cohort study ; Level of evidence , 2 . Methods : The daily workouts of 283 professional baseball players throughout all levels of a single MLB organization were prospect ively recorded . The intervention group participated in the Nordic exercise program and was compared with a r and omly selected control group of professional athletes within the organization not participating in the exercise program . The incidence of hamstring injuries in both groups was compared , and the total number of days missed due to injury was compared with the 2 previous seasons . Results : There were 10 hamstring injuries that occurred during the 2012 season among the 283 professional athletes that required removal from play . There were no injuries that occurred in the intervention group ( n = 65 , 0.00 % ; P = .0381 ) . The number needed to treat ( NNT ) to prevent 1 hamstring injury was 11.3 . The average repetitions per week of the injured group were assessed at multiple time points ( 2 , 4 , 6 , and total weeks ) prior to injury . There were significantly fewer repetitions per week performed in the injured group at all time points compared with overall average repetitions per week in the noninjured group ( P = .0459 , .0127 , .0164 , and .0299 , respectively ) . After beginning the Nordic exercise program , there were 136 total days missed due to a hamstring injury during the 2012 season . This number was less than the 2011 season ( 273 days missed ) and the 2010 season ( 309 days missed ) . Conclusion : Study results indicate the initiation of Nordic hamstring exercises may decrease the incidence of acute hamstring injuries and potentially decrease the total number of days missed due to injury in professional baseball players . Clinical Relevance : The financial and competitive interest in professional baseball players is of large importance to the player , team , and fans . Prevention of injuries is as important to all parties involved as the treatment and rehabilitation following an injury . This prospect i ve study shows the initiation of a simple , free exercise can reduce the incidence of hamstring injury in the professional-level baseball player Objective To examine the effect of a comprehensive warm-up programme design ed to reduce the risk of injuries in female youth football . Design Cluster r and omised controlled trial with clubs as the unit of r and omisation . Setting 125 football clubs from the south , east , and middle of Norway ( 65 clusters in the intervention group ; 60 in the control group ) followed for one league season ( eight months ) . Participants 1892 female players aged 13 - 17 ( 1055 players in the intervention group ; 837 players in the control group ) . Intervention A comprehensive warm-up programme 
    Output:
    
Teams using injury prevention programs that included the NH exercise  reduced hamstring injury rates up to 51 % in the long term compared with the teams that did not use any injury prevention measures .
Conclusions This systematic review and meta- analysis demonstrates that injury prevention programs that include NH exercises decrease the risk of hamstring injuries among soccer players .