***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: 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 : Anterior knee pain ( AKP ) is the most common activity-related injury of the knee . The authors investigated the effect of an exercise intervention on the incidence of AKP in UK army recruits undergoing a 14-week physically arduous training program . Hypothesis : Modifying military training to include targeted preventative exercises may reduce the incidence of AKP in a young recruit population . Study Design : R and omized controlled trial ; Level of evidence , 1 . Methods : A single-blind cluster r and omized controlled trial was performed in 39 male and 11 female training groups ( median age : 19.7 years ; interquartile range , 17 - 25 ) undergoing phase 1 of army recruit training . Each group was r and omly assigned to either an intervention ( n = 759 ) or control ( n = 743 ) protocol . The intervention consisted of 4 strengthening and 4 stretching exercises completed during supervised physical training lessons ( 7 per week ) . The control group followed the existing training syllabus warm-up exercises . The primary outcome was a diagnosis of AKP during the 14-week training program . Results : Forty-six participants ( 3.1 % ; 95 % confidence interval [ CI ] , 2.3 - 4.1 ) were diagnosed with AKP . There were 36 ( 4.8 % ; 95%CI , 3.5 - 6.7 ) new cases of AKP in the control group and 10 ( 1.3 % ; 0.7 - 2.4 ) in the intervention group . There was a 75 % reduction in AKP risk in the intervention group ( unadjusted hazard ratio = 0.25 ; 95 % CI , 0.13 - 0.52 ; P < .001 ) . Three participants ( 0.4 % ) from the intervention group were discharged from the military for medical reasons compared to 25 ( 3.4 % ) in the control group . Conclusion : A simple set of lower limb stretching and strengthening exercises result ed in a substantial and safe reduction in the incidence of AKP in a young military population undertaking a physical conditioning program . Such exercises could also be beneficial for preventing this common injury among nonmilitary participants in recreational physical activity Abstract Zouita , S , Zouita , ABM , Kebsi , W , Dupont , G , Ben Abderrahman , A , Ben Salah , FZ , and Zouhal , H. Strength training reduces injury rate in elite young soccer players during one season . J Strength Cond Res 30(5 ) : 1295–1307 , 2016—The purpose of this study was to examine the effect of strength training on physical fitness parameters and injuries occurrence in young elite soccer players . Fifty-two elite young soccer players ( 13–14 years ) were divided on a r and omized order into experimental group ( EG , n = 26 ) and control group ( CG , n = 26 ) . For EG , 2 to 3 sessions of strength training ( 90 minutes ) were introduced weekly in their training program for 12 weeks ( 4 × 3 weeks separated by 1-week recovery ) . Sprint tests ( 10 - 20 - 30 m ) , T-test time , and jumping tests were measured at the start ( T0 ) , at the middle ( T1 ) , and at the end of the experiment period ( T2 ) . The injury rate was recorded by the medical and fitness training staff throughout the soccer season . Compared to CG , EG performed significantly better in sprint running and T-test time at T2 ( p < 0.01 ) . Similarly , the improvement amount for jumping tests was significantly greater ( p ⩽ 0.05 ) in EG than in CG . A total of 17 injuries were recorded over the soccer season . The rate was higher in CG ( 13 injuries ) than in training group ( 4 injuries ) . This study showed that strength training accurately and efficiently scheduled in youth soccer players , induced performance improvement , and reduced the rate of injuries BACKGROUND The risk of musculoskeletal injury with the introduction of moderate-to-vigorous exercise in sedentary adults is not well established . The purpose of this report is to examine the effect of a 12-month exercise intervention on musculoskeletal injury and bodily pain in predominately overweight , sedentary men ( n = 102 ) and women ( n = 100 ) , ages 40 to 75 years . METHODS Participants were r and omized to a moderate-to-vigorous aerobic exercise intervention ( EX )  ( 6 d/wk , 60 min/d , 60 % to 85 % max . heart rate ) or usual lifestyle control ( CON ) . Participants completed a self-report of musculoskeletal injury and body pain at baseline and 12-months . RESULTS The number of individuals reporting an injury ( CON ; 28 % vs. EX ; 28 % , P = .95 ) did not differ by group . The most commonly injured site was lower leg/ankle/foot . The most common causes of injury were sports/physical activity , home maintenance , or " other . " In the control group , bodily pain increased over the 12 months compared with the exercise group ( CON -7.9 , EX -1.4 , P = .05 ) . Baseline demographics and volume of exercise were not associated with injury risk . CONCLUSIONS Previously sedentary men and women r and omized to a 12-month aerobic exercise intervention with a goal of 360 min/wk reported the same number of injuries as those in the control group and less bodily pain Sometimes interventions in r and omized clinical trials are not allocated to individual patients , but rather to patients in groups . This is called cluster allocation , or cluster r and omization , and is particularly common in health services research . Similarly , in some types of observational studies , patients ( or observations ) are found in naturally occurring groups , such as neighborhoods . In either situation , observations within a cluster tend to be more alike than observations selected entirely at r and om . This violates the assumption of independence that is at the heart of common methods of statistical estimation and hypothesis testing . Failure to account for the dependence between individual observations and the cluster to which they belong can have profound implication s on the design and analysis of such studies . Their p-values will be too small , confidence intervals too narrow , and sample size estimates too small , sometimes to a dramatic degree . This problem is similar to that caused by the more familiar " unit of analysis error " seen when observations are repeated on the same subjects , but are treated as independent . The purpose of this paper is to provide an introduction to the problem of  clustered data in clinical research . It provides guidance and examples of methods for analyzing clustered data and calculating sample sizes when planning studies . The article concludes with some general comments on statistical software for cluster data and principles for planning , analyzing , and presenting such studies STUDY DESIGN An explorative , 1-year prospect i ve cohort study . Objective To examine whether an association between a sudden change in weekly running distance and running-related injury varies according to injury type . BACKGROUND It is widely accepted that a sudden increase in running distance is strongly related to injury in runners . But the scientific knowledge supporting this assumption is limited . METHODS A volunteer sample of 874 healthy novice runners who started a self-structured running regimen were provided a global-positioning-system watch . After each running session during the study period , participants were categorized into 1 of the following exposure groups , based on the progression of their weekly running distance : less than 10 % or regression , 10 % to 30 % , or more than 30 % . The primary outcome was running-related injury . RESULTS A total of 202 runners sustained a running-related injury .  Using Cox regression analysis , no statistically significant differences in injury rates were found across the 3 exposure groups . An increased rate of distance-related injuries ( patellofemoral pain , iliotibial b and syndrome , medial tibial stress syndrome , gluteus medius injury , greater trochanteric bursitis , injury to the tensor fascia latae , and patellar tendinopathy ) existed in those who progressed their weekly running distance by more than 30 % compared with those who progressed less than 10 % ( hazard ratio = 1.59 ; 95 % confidence interval : 0.96 , 2.66 ; P = .07 ) . CONCLUSION Novice runners who progressed their running distance by more than 30 % over a 2-week period seem to be more vulnerable to distance-related injuries than runners who increase their running distance by less than 10 % . Owing to the exploratory nature of the present study , r and omized controlled trials are needed to verify these results , and more experimental studies are needed to vali date the assumptions . Still , novice runners may be well advised to progress their weekly distances by less than 30 % per week over a 2-week period Background : The incidence of acute hamstring injuries is high in several sports , including the different forms of football . Purpose : The authors investigated the preventive effect of eccentric strengthening of the hamstring muscles using the Nordic hamstring exercise compared with no additional hamstring exercise on the rate of acute hamstring injuries in male soccer players . Study Design : R and omized controlled trial ; Level of evidence , 1 . Methods : Fifty Danish male professional and amateur soccer teams ( 942 players ) were allocated to an intervention group ( 461 players ) or a control group ( 481 players ) . Players in the intervention group conducted a 10-week progressive eccentric training program followed by a weekly seasonal program , whereas players in the control group followed their usual training program . The main outcome measures were numbers of overall , new , and recurrent acute hamstring injuries during 1 full soccer season . Results : Fifty-two acute hamstring injuries in the control group compared with 15 injuries in the intervention group were registered . Comparing intervention versus the control group , overall acute hamstring injury rates per 100 player seasons were 3.8 versus 13.1 ( adjusted rate ratio [ RR ] , 0.293 ; 95 % confidence interval [ CI ] , 0.150 - 0.572 ; P < .001 ) . New injury rates per 100 player seasons were 3.1 versus 8.1 ( RR , 0.410 ; 95 % CI , 0.180 - 0.933 ; P = .034 ) , whereas recurrent injury rates per 100 player seasons were 7.1 versus 45.8 ( RR , 0.137 ; 95 % CI , 0.037 - 0.509 ; P = .003 ) . Number needed to treat [ NNT ] to prevent 1 acute hamstring injury ( new or recurrent ) is 13 ( 95 % CI , 9 - 23 ) players . The NNT to prevent 1 new injury is 25 ( 95 % CI , 15 - 72 ) players , and NNT to prevent 1 recurrent injury is 3 ( 95 % CI , 2 - 6 ) players . Conclusion : In male professional and amateur soccer players , additional eccentric hamstring exercise decreased the rate of overall , new , and recurrent acute hamstring injuries Abstract Pedersen , MT , And ersen , LL , Jørgensen , MB , Søgaard , K , and Sjøgaard , G. Effect of specific resistance training on musculoskeletal pain symptoms : Dose-response relationship . J Strength Cond Res 27(1 ) : 229–235 , 2013—The purpose of this study was to investigate the dose-response of strength training for relieving  musculoskeletal pain in female office workers . The relation between the dose of training in terms of total training volume ( sets × repetitions × load reported in training diaries ) during a 16-week strength training program and changes in pain ( calculated as pain index , 0–100 % , from self-reported intensities and duration s of pain in the upper body and low back ) was determined by regression analysis . The women were part of a r and omized controlled trial with specific strength training ( SRT ) , all-round physical exercise ( APE ) , and a reference group ( REF ) . Results showed that pain index in SRT and APE decreased significantly from baseline to follow-up 
    Output:
    
Conclusion The included studies were generally well design ed and executed , had high compliance rates , were safe , and attained consistently favourable results across four different acute and overuse injury outcomes despite considerable differences in population s and interventions .
Increasing strength training volume and intensity were associated with sports injury risk reduction .
Three characteristically different approaches to prevention mechanisms were identified and incorporated into contemporary strength training recommendations