***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: The present study analyzed the impact of the running style and the morphologic and functional characteristics of the foot on the incidence of non-traumatic foot and lower limb disorders in runners . From January 2004 to December 2008 , we prospect ively examined 166 runners , both recreational and competitive , involved in various running specialities , from three athletics clubs in Northern Italy . They were 86 males and 80 females , with a mean age of 31.1 ± 12.2 years . We considered non-traumatic foot and lower limb diseases reported during the follow-up period , which result ed in a minimum sport rest of two weeks . The incidence of these diseases was examined with respect to general characteristics , type of activity , foot morphology , running style . 59 % of athletes reported one or more diseases . The most common were plantar fasciitis ( 31 % of athletes ) and Achilles tendinopathies ( 24 % ) . Overall , the more prone to injuries were males ( 60.9 % of cases ) , competitive runners ( 70.9 % ) , middle-distance runners ( 51.7 % ) , and those using spike shoes ( 80.3 % ) . Age , body weight and height were not important predictors of running injuries in general . Considering the morphological characteristics of the foot , the most prone to injury were the varus hindfoot ( 87.5 % of cases ) and the cavus arch ( 71.4 % ) . In conclusion , a deep knowledge of the factors predisposing runners to specific diseases , often chronic and highly debilitating for the athlete , may allow implementing effective therapeutic measures . Key pointsExamination of 166 runners during a period of five years of activity . The incidence of these diseases was examined with respect to general characteristics , type of activity , foot morphology , running style.59 % of athletes reported one or more diseases . The most common were plantar fascitis ( 31 % of athletes ) and Achilles tendinopathies (24%).Overall , the more prone to injuries were males ( 60.9 % of cases ) , competitive runners ( 70.9 % ) , middle-distance runners ( 51.7 % ) , and those using spike shoes (80.3%).Age , body weight and height were not important predictors of running injuries in general . The most prone to injury were the varus hindfoot ( 87.5 % of cases ) and the cavus arch ( 71.4 % ) Prognosis studies are investigations of future events or the evaluation of associations between risk factors and health outcomes in population s of patients ( 1 ) . The results of such studies improve our underst and ing of the clinical course of a disease and assist clinicians in making informed decisions about how best to manage patients . Prognostic research also informs the design of intervention studies by helping define subgroups of patients who may benefit from a new treatment and by providing necessary information about the natural history of a disorder ( 2 ) . There has recently been a rapid increase in the use of systematic review methods to synthesize the evidence on research questions related to prognosis . It is essential that investigators conducting systematic review s thoroughly appraise the method ologic quality of included studies to be confident that a study 's design , conduct , analysis , and interpretation have adequately reduced the opportunity for bias ( 3 , 4 ) . Caution is warranted , however , because inclusion of method ologically weak studies can threaten the internal validity of a systematic review ( 4 ) . This follows abundant empirical evidence that inadequate attention to biases can cause invalid results and inferences ( 5 - 9 ) . However , there is limited consensus on how to appraise the quality of prognosis studies ( 1 ) . A useful framework to assess bias in such studies follows the basic principles of epidemiologic research ( 10 , 11 ) . We focus on 6 areas of potential bias : study participation , study attrition , prognostic factor measurement , confounding measurement and account , outcome measurement , and analysis . The main objectives of our review of review s are to describe methods used to assess the quality of prognosis studies and to describe how well current practice s assess potential biases . Our secondary objective is to develop recommendations to guide future quality appraisal , both within single studies of prognostic factors and within systematic review s of the evidence . We hope this work facilitates future discussion and research on biases in prognosis studies and systematic review s. Methods Literature Search and Study Selection We identified systematic review s of prognosis studies by search ing MEDLINE ( 1966 to October 2005 ) using the search strategy recommended by McKibbon and colleagues ( 12 ) . This strategy combines broad search terms for systematic review s ( systematic review .mp ; meta- analysis .mp ) and a sensitive search strategy for prognosis studies ( cohort , incidence , mortality , follow-up studies , prognos * , predict * , or course ) . We also search ed the reference lists of included review s and method ologic papers to identify other relevant publications . We restricted our search to English- language publications . One review er conducted the search and selected the studies . Systematic review s , defined as review s of published studies with a comprehensive search and systematic selection , were included if they assessed the method ologic quality of the included studies by using 1 or more explicit criteria . We excluded studies if they were meta-analyses of independent patient data only , if their primary goal was to investigate the effectiveness of an intervention or specific diagnostic or screening tests , or if they included studies that were not done on humans . Data Extraction and Synthesis Individual items included in the quality assessment of the systematic review s were recorded as they were reported in the publication ( that is , the information that would be available to readers and future review ers ) . We review ed journal Web sites and contacted the authors of the systematic review s for additional information when authors made such an offer in their original papers . When review s assessed different study design s by using different sets of quality items , we extracted only those items used to assess cohort studies . We constructed a comprehensive list of distinct items that the review s used to assess the quality of their included studies . The full text of each review was screened . All items used by the review authors to assess the quality of studies were extracted into a computerized spreadsheet by 1 review er . Two experienced review ers , a clinical epidemiologist and an epidemiologist , independently synthesized the quality items extracted from the prognosis review s to determine how well the systematic review s assessed potential biases . We did this in 3 steps : 1 ) identified distinct concepts or domains addressed by the quality items ; 2 ) grouped each extracted quality item into the appropriate domain or domains ; and 3 ) identified the domains necessary to assess potential biases in prognosis studies . We then used this information to assess how well the review s ' quality assessment included items from the domains necessary to assess potential biases . After completing each of the first 3 steps , the review ers met to attempt to reach a consensus . The consensus process involved each review er presenting his or her observations and results , followed by discussion and debate . A third review er was available in cases of persistent disagreement or uncertainty . In the first step , all domains addressed by the quality items were identified . The first review er iteratively and progressively defined the domains as items were extracted from the included review s. The second review er defined domains from a r and om list of all extracted quality items . Limited guidance was provided to the review ers so that their assessment s and definitions of domains would be independent . The review ers agreed on a final set of domains that adequately and completely defined all of the extracted items . In the second step , review ers independently grouped each extracted item into the appropriate domains . Review ers considered each extracted item by asking , What is each particular quality item addressing ? or What are the review 's authors getting at with the particular quality assessment item ? . Items were grouped into the domain or domains that best represented the concepts being addressed . For example , the extracted items at least 80 % of the group originally identified was located for follow-up and follow-up was sufficiently complete or does n't jeopardize validity were each independently classified by both review ers as assessing the domain completeness of follow-up adequate , whereas the extracted item quantification and description of all subjects lost to follow-up was classified as assessing the domain completeness of follow-up described . In the third step , we identified the domains necessary to assess potential biases . Each review er considered the ability of the identified domains to adequately address , at least in part , 1 of the following 6 potential biases : 1 ) study participation , 2 ) study attrition , 3 ) prognostic factor measurement , 4 ) confounding measurement and account , 5 ) outcome measurement , and 6 ) analysis . Domains were considered to adequately address part of the framework if information garnered from that domain would inform the assessment of potential bias . For example , both review ers judged that the identified domain study population represents source population or population of interest assessed potential bias in a prognosis study , whereas the domain research question definition did not , although the latter is an important consideration in assessing the inclusion of studies in a systematic review . Finally , on the basis of our previous ratings , we looked at whether each review included items from the domains necessary to assess the 6 potential biases . We calculated the frequency of systematic review s by assessing each potential bias and the number of review s that adequately assessed bias overall . From this systematic synthesis , we developed recommendations for improving quality appraisal in future systematic review s of prognosis studies . We used Microsoft Access and Excel 2002 ( Microsoft Corp. , Redmond , Washington ) for data management and SAS for Windows , version 9.1 ( SAS Institute , Inc. , Cary , North Carolina ) for descriptive statistics . Role of the Funding Sources The funding sources , the Canadian Institutes of Health Research , the Canadian Chiropractic Research Foundation , the Ontario Chiropractic Association , and the Ontario Ministry of Health and Long Term Care , did not have a role in the collection , analysis , or interpretation of the data or in the decision to su bmi t the manuscript for publication . Results We identified 1384 potentially relevant articles . Figure 1 shows a flow chart of studies that were included and excluded . Figure 2 shows the number of review s identified by year of publication . We excluded 131 systematic review s of prognosis studies that did not seem to include any quality assessment of the included studies ; this represented 44 % of prognosis review s. We included 163 review s of prognosis studies in our analysis ( 13 - 175 ) . The most common topics were cancer ( 15 % ) , musculoskeletal disorders and rheumatology ( 13 % ) , cardiovascular ( 10 % ) , neurology ( 10 % ) , and obstetrics ( 10 % ) . Other review s included a wide range of health and health care topics . Sixty-three percent of the review s investigated the association between a specific prognostic factor and a particular outcome ; the remainder investigated multiple prognostic factors or models . The number of primary studies included in each systematic review ranged from 3 to 167 ( median , 18 [ interquartile range , 12 to 31 ] ) . A complete description of the included review s is available from the authors on request . Figure 1 . Flow diagram of inclusion and exclusion criteria of systematic review s. Figure 2 . Number of systematic review s of prognosis studies identified over time . Quality Items One hundred fifty-three review s provided adequate detail to allow extraction of quality items . Eight hundred eighty-two distinct quality items were extracted from the review s. Most review s developed their own set of quality items , with only a few applying criteria from previous review s. Most quality items Background : Several risk factors have been suggested in the development of Achilles tendinopathy , but large-scale prospect i ve studies are limited . Purpose : To investigate the role of the vascular response to activity of the Achilles tendon , tendon thickness , ultrasound tissue characterization ( UTC ) of tendon structure , and foot posture as possible risk factors in the development of Achilles tendinopathy . Study Design : Cohort study ; Level of evidence , 2 . Methods : The study began with 351 first-year students at Ghent University . After 51 students were excluded , 300 were tested in the academic years 2013 - 2014 and 2014 - 2015 and were followed prospect ively for 2 consecutive years by use of a multilevel registration method . Of those , 250 students were included in the statistical analysis . At baseline , foot posture index and UTC were investigated bilaterally . Blood flow and tendon thickness were measured before and after a running activity . Cox regression analyses were performed to identify significant contributors to the development of Achilles tendinopathy . Results : During the 2-year follow-up , 27 of the included 250 participants developed Achilles tendinopathy ( 11 % ) . Significant predictive effects were found for female sex and blood flow response after running ( P = .022 and P = .019 , respectively ) . The risk of developing Achilles tendinopathy increased if the blood flow increase after running was reduced , regardless of sex , foot pronation , and timing of flow measurements . The model had a predictive accuracy of 81.5 % regarding the development of Achilles tendinopathy , with a specificity of 85.0 % and a sensitivity of 50.0 % . Conclusion : This prospect i ve study identified both female sex and the diminished blood flow response after running as significant risk factors for the development of Achilles tendinopathy . UTC of tendon structure , Achilles tendon thickness , and foot posture did not significantly contribute to the prediction of Achilles tendinopathy . A general evaluation of tendon structure by UTC , measurement of tendon thickness , or determination of the foot posture index will not allow clinicians to identify patients at risk for developing Achilles tendinopathy . Furthermore , it may be possible to improve blood flow after activity by using noninvasive techniques ( such as prostagl and ins , compression stockings , heat , massage , and vibration techniques ) . These techniques may be useful in the prevention and management of Achilles tendinopathy , but further research is needed Background A recent study published in The American Journal of Sports Medicine showed that asymptomatic soccer players with an increased risk of developing Achilles and patellar tendon injuries within the next 12 months can be identified with use of ultrasonography . Hypothesis Prophylactic eccentric training and stretching can reduce both the frequency of asymptomatic ultrasonographic changes in Achilles and patellar tendons in soccer players and the risk of these asymptomatic intratendinous changes becoming symptomatic . Study Design R and omized controlled trial ; Level of evidence , 
    Output:
    
CONCLUSION From an ocean of studies with high levels of bias , we extracted nine clinical risk factors that may increase a person 's risk of Achilles tendinopathy .