***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 Muscle injuries are one of the commonest injuries affecting athletes . It often leads to significant pain and disability causing loss of training and competition time . With current treatment , the duration to return-to-play ranges form six weeks to never , depending on injury severity . Recent research es have suggested that autologous platelet-rich plasma ( PRP ) injection into the injured site may hasten soft tissues healing . To- date , there has been no r and omised clinical trials to evaluate the effects of PRP on muscle healing . The aim of this study is to examine the effects of autologous PRP on duration to return-to-play after muscle injury . Methods and design A r and omised , single blind controlled trial will be conducted . Twenty-eight patients aged 18 years and above with a recent grade -2 hamstring injury will be invited to take part . Participants will be r and omised to receive either autologous PRP injection with rehabilitation programme , or rehabilitation programme only . Participants will be followed up at day three of study and then weekly for 16 weeks . At each follow up visit , participants will be assessed on readiness to return-to-play using a set of criteria . The primary end-point is when participants have fulfilled the return-to-play criteria or end of 16 weeks . The main outcome measure of this study is the duration to return-to-play after injury . Conclusion This study protocol proposes a rigorous and potential significant evaluation of PRP use for grade -2 hamstring injury . If proven effective such findings could be of great benefit for patients with similar injuries . Trial registration Current Controlled Trials Background : Groin injury is a common injury in football and a complicated area when it comes to diagnosis and therapy . There is a lack of comprehensive epidemiological data on groin injuries in professional football . Objective : To investigate the incidence , pattern and severity of hip and groin injuries in professional footballers over seven consecutive seasons . Study design : Prospect i ve cohort study . Setting : European professional football . Methods : During the 2001/2 to 2007/8 seasons , between nine and 17 clubs per season ( 23 clubs in total ) were investigated , accounting for 88 club seasons in total .  Time loss injuries and individual exposure during club and national team training sessions and matches were recorded . Main outcome measure : Injury incidence . Results : A total of 628 hip/groin injuries were recorded , accounting for 12–16 % of all injuries per season . The total injury incidence was 1.1/1000 h ( 3.5/1000 match hours vs 0.6/1000 training hours , p<0.001 ) and was consistent over the seasons studied . Eighteen different diagnostic entities were registered , adductor ( n = 399 ) and iliopsoas ( n = 52 ) related injuries being the most common . More than half of the injuries ( 53 % ) were classified as moderate or severe ( absence of more than a week ) , the mean absence per injury being 15 days . Reinjuries accounted for 15 % of all registered injuries . In the 2005/6 to 2007/8 seasons , 41 % of all diagnoses relied solely on clinical examination . Conclusions : Hip/groin injuries are common in professional football , and the incidence over consecutive seasons is consistent . Hip/groin injuries are associated with long absences . Many hip/groin diagnoses are based only on clinical examination Background Previous studies on the prognostic value of clinical and MRI parameters for the time to return to play ( TTRTP ) in acute hamstring injuries showed only limited to moderate evidence for the various investigated parameters . Some studies had multiple method ological limitations , including retrospective design s and the use of univariate analysis only . The aim of this study was to assess the prognostic value of clinical and MRI parameters for TTRTP using multivariate analysis . Methods 28 clinical and MRI parameters were prospect ively investigated for an association with TTRTP in 80 non-professional athletes with MRI positive hamstring injuries undergoing a st and ardised rehabilitation programme . The association between possible prognostic parameters and TTRTP was assessed with a multivariate linear regression model . Parameters that had a p value < 0.2 on univariate testing were included in this model . Results 74 athletes were available for analysis . A total of nine variables met the criteria for the multivariate analysis : intensity of sports , level of sports , self-predicted TTRTP by the athlete , length of discomfort on palpation , deficit in passive straight leg raise , pain score on isometric knee flexion , isometric knee flexion strength deficit and distance of the proximal pole of the MRI hyperintensity to the tuber ischiadicum . Of these , only self-predicted TTRTP by the athlete and a passive straight leg raise deficit remained significantly associated with TTRTP after stepwise logistic regression . Conclusions The clinical parameters self-predicted TTRTP and passive straight leg raise deficit are independently associated with the TTRTP . MRI parameters in grade 1 and 2 hamstring injuries , as described in the literature , are not associated with TTRTP . For clinical practice , prognosis of the TTRTP in these injuries should better be based on clinical parameters Background : Muscle injuries constitute a large percentage of all injuries in football . Purpose : To investigate the incidence and nature of muscle injuries in male professional footballers . Study Design : Cohort study ; Level of evidence , 2 . Methods : Fifty-one football teams , comprising 2299 players , were followed prospect ively during the years 2001 to 2009 . Team medical staff recorded individual player exposure and time-loss injuries . The first-team squads of 24 clubs selected by the Union of European Football Associations as belonging to the best European teams , 15 teams of the Swedish First League , and another 15 European teams playing their home matches on artificial turf pitches were included . A muscle injury was defined as “ a traumatic distraction or overuse injury to the muscle leading to a player being unable to fully participate in training or match play . ” Results : In total , 2908 muscle injuries were registered . On average , a player sustained 0.6 muscle injuries per season . A squad of 25 players can thus expect about 15 muscle injuries per season . Muscle injuries constituted 31 % of all injuries and caused 27 % of the total injury absence . Ninety-two percent of all muscle injuries affected the 4 major muscle groups of the lower limbs : hamstrings ( 37 % ) , adductors ( 23 % ) , quadriceps ( 19 % ) , and calf muscles ( 13 % ) . Sixteen percent of the muscle injuries were reinjuries . These reinjuries caused significantly longer absences than did index injuries . The incidence of muscle injury increased with age . When separated into different muscle groups , however , an increased incidence with age was found only for calf muscle injuries and not for hamstring , quadriceps , or hip/groin strains . Conclusion : Muscle injuries are a substantial problem for players and their clubs . They constitute almost one third of all time-loss injuries in men ’s professional football , and 92 % of all injuries affect the 4 big muscle groups in the lower limbs A study was conducted to estimate the accuracy and reliability of  review ers when screening records for relevant trials for a systematic review . A sensitive search of ten electronic bibliographic data bases yielded 22 571 records of potentially relevant trials . Records were allocated to four review ers such that two review ers examined each record and so that identification of trials by each review er could be compared with those identified by each of the other review ers . Agreement between review ers was assessed using Cohen 's kappa statistic . Ascertainment intersection methods were used to estimate the likely number of trials missed by review ers . Full copies of reports were obtained and assessed independently by two research ers for eligibility for the review . Eligible reports formed the ' gold st and ard ' against which an assessment was made about the accuracy of screening by review ers . After screening , 301 of 22 571 records were identified by at least one review er as potentially relevant . Agreement was ' almost perfect ' ( kappa>0.8 ) within two pairs , ' substantial ' ( kappa>0.6 ) within three pairs and ' moderate ' ( kappa>0.4 ) within one pair . Of the 301 records selected , 273 complete reports were available . When pairs of review ers agreed on the potential relevance of records , 81 per cent were eligible ( range 69 to 91 per cent ) . If review ers disagreed , 22 per cent were eligible ( range 12 to 45 per cent ) . Single review ers missed on average 8 per cent of eligible reports ( range 0 to 24 per cent ) , whereas pairs of review ers did not miss any ( range 0 to 1 per cent ) . The use of two review ers to screen records increased the number of r and omized trials identified by an average of 9 per cent ( range 0 to 32 per cent ) . Review ers can reliably identify potentially relevant records when screening thous and s of records for eligibility . Two review ers should screen records for eligibility , whenever possible , in order to maximize ascertainment of relevant trials In order to study the incidence and mechanisms of injury in soccer and to recommend prophylactic measures , 180 players in a senior male soccer division were followed prospect ively for 1 yr . Attendance records for games and practice sessions were kept , and all injuries were examined and treated by the same orthopaedic surgeon . One hundred twenty-four players incurred 256 injuries , mostly sprains and strains of the lower extremities . Of these , 62 % were considered minor with ankle sprains being the most common ( 17 % ) , while 11 % were considered major with knee ligament sprains being the most frequent ( 32 % ) . Overuse injuries were most frequent in the preseason training period . Traumatic leg injuries involved players with inadequate or no shin guards . Of the traumatic knee injuries , 11 of 18 ( 61 % ) occurred during a collision ; non-contact knee injuries were frequently seen in those players with a history of knee injury and existing instability . Study of injury sequence disclosed that a minor injury was often followed within two months by a major one . In addition , with severe injuries incurred during fouls , the individual causing the penalty was injured . This prospect i ve study suggested that those with knee instability and those allowed to resume play with poorly rehabilitated or clinical ly unhealed injuries are more apt to sustain further injury . Some injuries can be avoided by using better equipment and by observance of the rules Background Following publication of the PRISMA statement , the UK Centre for Review s and Dissemination ( CRD ) at the University of York in Engl and began to develop an international prospect i ve register of systematic review s with health-related outcomes . The objectives were to reduce unplanned duplication of review s and provide transparency in the review process , with the aim of minimizing reporting bias . Methods An international advisory group was formed and a consultation undertaken to establish the key items necessary for inclusion in the register and to gather views on various aspects of functionality . This article describes the development of the register , now called PROSPERO , and the process of registration . Results PROSPERO offers free registration and free public access to a unique prospect i ve register of systematic review s across all areas of health from all around the world . The dedicated web-based interface is electronically search able and available to all prospect i ve registrants . At the moment , inclusion in PROSPERO is restricted to systematic review s of the effects of interventions and strategies to prevent , diagnose , treat , and monitor health conditions , for which there is a health-related outcome .Ideally , registration should take place before the research ers have started formal screening against inclusion criteria but review s are eligible as long as they have not progressed beyond the point of completing data extraction .The required data set captures the key attributes of review design as well as the administrative details necessary for registration .Su bmi tted registration forms are checked against the scope for inclusion in PROSPERO and for clarity of content before being made publicly available on the register , rejected , or returned to the applicant for clarification . The public records include an audit trail of major changes to planned methods , details of when the review has been completed , and links to result ing publications when provided by the authors . Conclusions There has been international support and an enthusiastic response to the principle of prospect i ve registration of protocol s for systematic review s and to the development of PROSPERO .In October 2011 , PROSPERO contained 200 records of systematic review s being undertaken in 26 countries around the world on a diverse range of interventions Abstract This prospect i ve cohort study described return-to-play ( RTP ) data for different types of muscle injuries in male elite-level football players in Europe . Eighty-nine European professional teams were followed between 2001 and 2013 . Team medical staff recorded individual player exposure and time-loss injuries . A total of 17,371 injuries occurred , including 5603 ( 32 % ) muscle injuries . From 2007 , we received results from 386 magnetic resonance imaging ( MRI ) examinations , and radiological grading was performed . A negative MRI was associated with shorter recovery time ( 6 ± 7 days ) . Lay-off days were correlated with MRI grading of thigh muscle injuries ( P < 0.001 ) . Among hamstring injuries , 83 % occurred to the biceps femoris , 12 % affected the semimembranosus and 5 % the semitendinosus . Recurrence rate was higher among biceps femoris injuries ( 18 % ) compared with semitendinosus and semimembranosus injuries ( 2 % together ) . Groin muscle injuries caused shorter median absence ( 9 days ) than hamstring ( 13 days ; P < 0.001 ) , quadriceps ( 12 days ; P < 0.001 ) and calf muscle ( 13 days ; P < 0.001 ) injuries . Overall , we found that MRI was valuable for prognosticating RTP , with radiological grading associated with lay-off times after injury . Re-injuries were common in b 
    Output:
    
Conclusion Only half of the included studies provided some definition of RTP after hamstring injury , of which reaching the athlete ’s pre-injury level and being able to perform full sport activities were the most important .