***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 : The ThinkFirst Canada Smart Hockey program is an educational injury prevention video that teaches the mechanisms , consequences , and prevention of brain and spinal cord injury in ice hockey . This study evaluates knowledge transfer and behavioural outcomes in 11–12 year old hockey players who viewed the video . Design : R and omized controlled design . Setting : Greater Toronto Minor Hockey League , Toronto Ontario . Subjects : Minor , competitive 11–12 year old male ice hockey players and hockey team coaches . Interventions : The Smart Hockey video was shown to experimental teams at mid-season . An interview was conducted with coaches to underst and reasons to accept or refuse the injury prevention video . Main outcome measures : A test of concussion knowledge was administered before , immediately after , and three months after exposure to the video . The incidence of aggressive penalties was measured before and after viewing the video . Results : The number of causes and mechanisms of concussion named by players increased from 1.13 to 2.47 and from 0.67 to 1.22 respectively . This effect was maintained at three months . There was no significant change in control teams . There was no significant change in total penalties after video exposure ; however , specific body checking related penalties were significantly reduced in the experimental group . Conclusion : This study showed some improvements in knowledge and behaviours after a single viewing of a video ; however , these findings require confirmation with a larger sample to underst and the sociobehavioural aspects of sport that determine the effectiveness and acceptance of injury prevention interventions OBJECTIVE To prospect ively document the incidence of game injury rates in youth ice hockey tournaments to compare with season-long game injury rates and to analyze the injuries occurring at tournaments by mechanism , type , body location , severity , player position , and period of play . DESIGN A prospect i ve injury report form completed for injured players by the tournament athletic trainer . SETTING  Four boys ' tournaments  and one girls ' tournament  during the 1993 - 94 season . PARTICIPANTS 807 boys and girls , ages 9 - 19 . MEASUREMENTS /MAIN RESULTS 60 injuries occurred in boys and 4 occurred in girls . There were 26 boys with significant injuries and no girls with significant injuries . The significant game injury rates per 1000 player hours were 50.9 for boys combined , 57.9 for boys ' Peewee A , 42.7 for boys ' Bantam A , 64.8 for boys ' varsity high school , 44.8 for boys ' Junior Gold , and 0 for girls ' Peewee A and B. Cerebral concussion comprised 15 % of boys ' injuries . CONCLUSIONS The significant injury rate for boys ' tournament game play was 4 - 6 times higher than the season game injury rates in two previous season-long studies . In boys ' games , 65 % of " all " injuries and 77 % of " significant " injuries were related to collisions . The girls ' rules of play do not allow body checking , and there were no significant injuries in girls ' games . The boys had high rates of cerebral concussion injury at all age levels . Minimizing the frequency and intensity of collisions in the boys ' game may decrease the injury rates , especially in the tournament setting Background : In a previous prospect i ve study , the risk of concussion and all injury was more than threefold higher among Pee Wee ice hockey players ( ages 11–12 years ) in a league that allows  bodychecking than among those in a league that does not . We examined whether two years of bodychecking experience in Pee Wee influenced the risk of concussion and other injury among players in a Bantam league ( ages 13–14 ) compared with Bantam players introduced to bodychecking for the first time at age 13 . Methods : We conducted a prospect i ve cohort study involving hockey players aged 13–14 years in the top 30 % of divisions of play in their leagues . Sixty-eight teams from the province of Alberta ( n = 995 ) , whose players had two years of bodychecking experience in Pee Wee , and 62 teams from the province of Quebec ( n = 976 ) , whose players had no bodychecking experience in Pee Wee , participated . We estimated incidence rate ratios ( IRRs ) for injury and for concussion . Results : There were 272 injuries ( 51 concussions ) among the Bantam hockey players who had bodychecking experience in Pee Wee and 244 injuries ( 49 concussions ) among those without such experience . The adjusted IRRs for game-related injuries and concussion overall between players with bodychecking experience in Pee Wee and those without it were as follows : injury overall 0.85 ( 95 % confidence interval [ CI ] 0.63 to 1.16 ) ; concussion overall 0.84 ( 95 % CI 0.48 to 1.48 ) ; and injury result ing in more than seven days of time loss ( i.e. , time between injury and return to play ) 0.67 ( 95 % CI 0.46 to 0.99 ) . The unadjusted IRR for concussion result ing in more than 10 days of time loss was 0.60 ( 95 % CI 0.26 to 1.41 ) . Interpretation : The risk of injury result ing in more than seven days of time loss from play was reduced by 33 % among Bantam hockey players in a league where bodychecking was allowed two years earlier in Pee Wee compared with Bantam players introduced to bodychecking for the first time at age 13 . In light of the increased risk of concussion and other injury among Pee Wee players in a league where bodychecking is permitted , policy regarding the age at which hockey players are introduced to bodychecking requires further consideration OBJECTIVE To determine the rate , type , and severity of injuries to child hockey players as well as assessing coaches ' , parents ' , and players ' attitudes and knowledge of hockey . DESIGN A prospect i ve observation of a population 's injuries using injury-reporting forms and surveys . SETTING A community-organized hockey program in Minnesota . PARTICIPANTS One hundred fifty boys , aged 9 through 15 years , who played ice hockey during the 1990 - 1991 winter season . MEASUREMENTS AND MAIN RESULTS Injuries were reported by multiple observers , including coaches , managers , and trained independent observers at the time an injury occurred ; coaches , parents , and players were surveyed regarding hockey injuries , knowledge , and attitudes . One in three players experienced an injury during the season . The most common injuries were contusions . Six of 100 players experienced injuries severe enough to require cessation of physical activities for 8 to 25 days or longer . Weight differences of 53 kg and height differences of 55 cm were reported between Bantam-aged players ( 13 through 15 years ) , and body contact , including legal checks , accounted for 86 % of injuries during games . Illegal checks and violations were associated with 66 % of injuries during games , yet only four penalties ( 14 % ) were assessed . In addition , one in three games in which an injury result ed was described as hostile and 15 % of the injuries were considered intentional . CONCLUSIONS Eliminating violence and body checking for prepubertal boys while emphasizing rule enforcement and good sportsmanship are recommended OBJECTIVE : To test the feasibility of creating a valid and reliable checklist with the following features : appropriate for assessing both r and omised and non-r and omised studies ; provision of both an overall score for study quality and a profile of scores not only for the quality of reporting , internal validity ( bias and confounding ) and power , but also for external validity . DESIGN : A pilot version was first developed , based on epidemiological principles , review s , and existing checklists for r and omised studies . Face and content validity were assessed by three experienced review ers and reliability was determined using two raters assessing 10 r and omised and 10 non-r and omised studies . Using different raters , the checklist was revised and tested for internal consistency ( Kuder-Richardson 20 ) , test-retest and inter-rater reliability ( Spearman correlation coefficient and sign rank test ; kappa statistics ) , criterion validity , and respondent burden . MAIN RESULTS : The performance of the checklist improved considerably after revision of a pilot version . The Quality Index had high internal consistency ( KR-20 : 0.89 ) as did the subscales apart from external validity ( KR-20 : 0.54 ) . Test-retest ( r 0.88 ) and inter-rater ( r 0.75 ) reliability of the Quality Index were good . Reliability of the subscales varied from good ( bias ) to poor ( external validity ) . The Quality Index correlated highly with an existing , established instrument for assessing r and omised studies ( r 0.90 ) . There was little difference between its performance with non-r and omised and with r and omised studies . Raters took about 20 minutes to assess each paper ( range 10 to 45 minutes ) . CONCLUSIONS : This study has shown that it is feasible to develop a checklist that can be used to assess the method ological quality not only of r and omised controlled trials but also non-r and omised studies . It has also shown that it is possible to produce a checklist that provides a profile of the paper , alerting review ers to its particular method ological strengths and weaknesses . Further work is required to improve the checklist and the training of raters in the assessment of external validity CONTEXT Ice hockey has one of the highest sport participation and injury rates in youth in Canada .  Body checking is the predominant mechanism of injury in leagues in which it is permitted . OBJECTIVE To determine if risk of injury and concussion differ for Pee Wee ( ages 11 - 12 years ) ice hockey players in a league in which body checking is permitted ( Alberta , Canada ) vs a league in which body checking is not permitted ( Quebec , Canada ) . DESIGN , SETTING , AND PARTICIPANTS Prospect i ve cohort study conducted in Alberta and Quebec during the 2007 - 2008 Pee Wee ice hockey season . Participants ( N = 2154 ) were players from teams in the top 60 % of divisions of play . MAIN OUTCOME MEASURES Incidence rate ratios adjusted for cluster based on Poisson regression for game- and practice -related injury and concussion . RESULTS Seventy-four Pee Wee teams from Alberta ( n = 1108 players ) and 76 Pee Wee teams from Quebec ( n = 1046 players ) completed the study . In total , there were 241 injuries ( 78 concussions ) reported in Alberta ( 85 077 exposure-hours ) and 91 injuries ( 23 concussions ) reported in Quebec ( 82 099 exposure-hours ) . For game-related injuries , the Alberta vs Quebec incidence rate ratio was 3.26 ( 95 % confidence interval [ CI ] , 2.31 - 4.60 [ n = 209 and n = 70 for Alberta and Quebec , respectively ] ) for all injuries , 3.88 ( 95 % CI , 1.91 - 7.89 [ n = 73 and n = 20 ] ) for concussion , 3.30 ( 95 % CI , 1.77 - 6.17 [ n = 51 and n = 16 ] ) for severe injury ( time loss , > 7 days ) , and 3.61 ( 95 % CI , 1.16 - 11.23 [ n=14 and n=4 ] ) for severe concussion ( time loss , > 10 days ) . The estimated absolute risk reduction ( injuries per 1000 player-hours ) that would be achieved if body checking were not permitted in Alberta was 2.84 ( 95 % CI , 2.18 - 3.49 ) for all game-related injuries , 0.72 ( 95 % CI , 0.40 - 1.04 ) for severe injuries , 1.08 ( 95 % CI , 0.70 - 1.46 ) for concussion , and 0.20 ( 95 % CI , 0.04 - 0.37 ) for severe concussion . There was no difference between provinces for practice -related injuries . CONCLUSION Among 11- to 12-year-old ice hockey players , playing in a league in which body checking is permitted compared with playing in a league in which body checking is not permitted was associated with a 3-fold increased risk of all game-related injuries and the categories of concussion , severe injury , and severe concussion Aggressive behavior in professional ice hockey has seen a dramatic increase since 1975 , and many players and coaches consider such behavior an important strategy for winning ( Englehardt , 1995 ; Smith , 1979 ; Widmeyer & Birch , 1979 ) . A belief that aggression is necessary for successful performance can be found outside the ranks of professional hockey , as well . For example , Weinstein , Smith , and Wiesenthal ( 1995 ) pointed out that young Canadian ice hockey players are taught that engaging in illegal aggressive behavior is often vital for team success OBJECT The objective of this study was to measure the incidence of concussion ( scaled relative to number of athlete exposures ) and recurrent concussion within 2 teams of fourth-tier junior ice hockey players ( 16 - 21 years old ) during 1 regular season . METHODS A prospect i ve cohort study called the Hockey Concussion Education Project was conducted during 1 junior ice hockey regular season ( 2009 - 2010 ) involving 67 male fourth-tier ice hockey players ( mean age 18.2 ± 1.2 years , range 16 - 21 years ) from 2 teams . Prior to the start of the season , every player underwent baseline assessment s using the Sideline Concussion Assessment Tool 2 ( SCAT2 ) and the Immediate Post-Concussion Assessment and Cognitive Test ( ImPACT ) . The study protocol also required players who entered the study during the season to complete baseline SCAT2 and Im 
    Output:
    
INTERPRETATION Changes to m and atory rules were associated with reductions in penalties for aggressive acts and in injuries related to aggression among ice hockey players .
Effects of educational and cognitive behavioural interventions on injury rates are less clear .