***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 Given the decline in physical activity ( PA ) levels among youth population s it is vital to underst and the factors that are associated with PA in order to inform the development of new prevention programs . Many studies have examined individual characteristics associated with PA among youth yet few have studied the relationship between the school environment and PA despite knowing that there is variability in student PA levels across schools . Methods Using multi-level logistic regression analyses we explored the school- and student-level characteristics associated with PA using data from 2,379 grade 5 to 8 students attending 30 elementary schools in Ontario , Canada as part of the PLAY-Ontario study . Results Findings indicate that there was significant between-school r and om variation for being moderately and highly active ; school-level differences accounted for 4.8 % of the variability in the odds of being moderately active and 7.3 % of the variability in the odds of being highly active . Students were more likely to be moderately active if they attended a school that used PA as a reward and not as discipline , and students were more likely to be highly active if they attended a school with established community partnerships . Important student characteristics included screen time sedentary behaviour , participating in team sports , and having active friends . Conclusion Future research should evaluate if the optimal population level impact for school-based PA promotion programming might be achieved most economically if intervention selectively targeted the schools that are putting students at the greatest risk for inactivity Background Excessive weight gain among youth is an ongoing public health concern . Despite evidence linking both policies and the built environment to adolescent and adult overweight , the association between health policies or the built environment and overweight are often overlooked in research with children . The purpose of this study was to examine if school-based physical activity policies and the built environment surrounding a school are associated with  weight status among children . Methods Objective ly measured height and weight data were available for 2,331 grade 1 to 4 students ( aged 6 to 9 years ) attending 30 elementary schools in Ontario , Canada . Student-level data were collected using parent reports and the PLAY-On question naire administered to students by study nurses . School-level policy data were collected from school administrators using the Physical Activity Module of the Healthy School Planner tool , and built environment data were provided by the Enhanced Points of Interest data re source . Multi-level logistic regression models were used to examine the school- and student-level characteristics associated with the odds of a student being overweight or obese . Results There was significant between-school r and om variation in the odds of a student being overweight [ σ2μ0 = 0.274(0.106 ) , p < 0.001 ] , but not for being obese [ σ2μ0 = 0.115(0.089 ) ] . If a student attended a school that provided student access to a variety of facilities on and off school grounds during school hours or supported active transportation to and from school , he/she was less likely to overweight than a similar student attending a school without these policies . Characteristics of the built environment were not associated with overweight or obesity among this large cross-sectional sample of children . Conclusions This new evidence suggests that it may be wise to target obesity prevention efforts to schools that do not provide student access to recreation facilities during school hours or schools that do not support active transportation for students . Future research should evaluate if school-based overweight and obesity prevention programming might be improved if interventions selectively targeted the school characteristics that are putting students at the greatest risk OBJECTIVES : Comprehensive school health ( CSH ) is a multifaceted approach to health promotion . A key objective of CSH is to foster positive health behaviors outside of school . This study examined the 2-year change in physical activity during and after school among students participating in a CSH intervention in Edmonton , Alberta , Canada . METHODS : This was a quasi-experimental , pre – post trial with a parallel , nonequivalent control group . Intervention schools had to be located in socioeconomically disadvantaged neighborhoods . In the spring of 2009 and 2011 ,  pedometer recordings ( 7 full days ) and demographic data were collected from cross-sectional sample s of fifth grade students from 10 intervention schools and 20 comparison schools . A total of 1157 students participated in the study . Analyses were adjusted for potential confounders and the clustered design . RESULTS : Relative to 2009 , children in 2011 were more active on schools days ( 1172 steps per day ; P < .001 ) and on weekends ( 1450 steps per day ; P < .001 ) . However , the increase in mean steps between 2009 and 2011 was greater in CSH intervention schools than in comparison schools ( school days : 1221 steps per day ; P = .009 ; weekends : 2001 steps per day ; P = .005 ) . These increases remained significant after adjusting for gender and overweight status . CONCLUSIONS : These findings provide evidence of the effectiveness of CSH to affect children ’s  physical activity during and outside of school . Results of this study justify broader implementation of effective CSH interventions for physical activity promotion and obesity prevention in the long term This paper examines structured opportunities for student physical activity in Ontario elementary and secondary schools . R and om sample s of elementary and secondary schools were selected , and  telephone surveys of 353 elementary and 360 secondary school personnel were conducted in 1998 . The findings indicate that elementary schools offered physical education , on average , just under three days per week . The duration of physical education class and , in some cases , the duration of vigorous physical activity in class and the weekly amount of vigorous activity in class , were significantly higher at successive grade levels . The physical education enrollment rate in secondary schools was significantly lower at successive grade levels . Student participation in secondary school intramurals and interschool sports was 22.8 % and 28.7 % respectively . These findings suggest increasing the weekly frequency of physical education in elementary schools and increasing participation in physical education classes in secondary schools . Also , intramural opportunities and participation should be promoted Objective : To assess the impact of an active school model on  children ’s physical activity ( PA ) . Design : 16-month cluster r and omised controlled trial . Setting : 10 elementary schools in Greater Vancouver , BC . Participants : 515 children aged 9–11 years . Intervention : Action Schools ! BC ( AS ! BC ) is an active school model that provided schools with training and re sources to increase children ’s PA . Schools implemented AS ! BC with support from either external liaisons ( liaison schools , LS ; four schools ) or internal champions ( champion schools , CS ; three schools ) . Outcomes were compared with usual practice ( UP ) schools ( three schools ) . Main outcome measurements : PA was measured four times during the study using pedometers ( step count , steps/day ) . Results : Boys in the LS group took 1175 more steps per day , on average , than boys in the UP group ( 95 % CI : 97 to 2253 ) . Boys in the CS group also tended to have a higher step count than boys in the UP group ( + 804 steps/day ; 95 % CI : −341 to 1949 ) . There was no difference in girls ’ step counts across groups . Conclusions : The positive effect of the AS ! BC model on boys ’ PA is important in light of the current global trend of decreased PA Background There is evidence of school level variability in the physical activity of children and youth . Less is known about factors that may contribute to this variation . The purpose of this study was to examine if the school health environment ( Healthy Physical Environment , Instruction and Programs , Supportive Social Environment , and Community Partnerships ) is associated with objective ly measured time spent in light to vigorous physical activity among a sample of Toronto children . Methods The sample comprised 856 grade 5 and 6 students from 18 elementary schools in Toronto , Ontario .  Multilevel linear regression analyses were used to examine the impact of school physical activity policy on students ’ time spent in light-to-vigorous physical activity . Results Significant between-school r and om variation in objective ly measured time spent in light-to-vigorous physical activity was identified [ σ2μ0 = 0.067 ; p < 0.001 ] ; school-level differences accounted for 6.7 % of the variability in the time individual students spent in light-to-vigorous physical activity . Of the 22 school-level variables , students attending schools with support for active transportation to/from school and written policies/ practice s for physical activity , accumulated significantly more minutes of physical activity per school week than students who attended schools that did not . Conclusions School physical activity policy and support for active school travel is associated with objective ly measured time spent in light to vigorous physical activity . School physical activity policy might be a critical mechanism through which schools can impact the physical activity levels of their students PURPOSE The purpose of this study was twofold : 1 ) to evaluate the effectiveness of a school-based physical activity intervention , Action Schools ! BC ( AS ! BC ) , for maintaining academic performance in a multiethnic group of elementary children , and 2 ) to determine whether boys and girls ' academic performance changed similarly after participation in AS ! BC . METHODS This was a 16-month cluster r and omized controlled trial . Ten schools were r and omized to intervention ( INT ) or usual practice ( UP ) . One INT school administered the wrong final test , and one UP school grade d their own test , so both were excluded . Thus , eight schools ( six INT , two UP ) were included in the final analysis . Children ( 143 boys , 144 girls ) in grade s 4 and 5 were recruited for the study . We used the Canadian Achievement Test ( CAT-3 ) to evaluate academic performance ( TotScore ) . Weekly teacher activity logs determined amounts of physical activity delivered by teachers to students . Physical activity was determined with the Physical Activity Question naire for Children ( PAQ-C ) . Independent t-tests compared descriptive variables between groups and between boys and girls . We used a mixed linear model to evaluate differences in TotScore at follow-up between groups and between girls and boys . RESULTS Physical activity delivered by teachers to children in INT schools was increased by 47 min x wk(-1 ) ( 139 + /- 62 vs 92 + /- 45 , P < 0.001 ) . Participants attending UP schools had significantly higher baseline TotScores than those attending INT schools . Despite this , there was no significant difference in TotScore between groups at follow-up and between boys and girls at baseline and follow-up . CONCLUSION The AS ! BC model is an attractive and feasible intervention to increase physical activity for students while maintaining levels of academic performance PURPOSE Adolescents spend considerable time at school and thus it is important to underst and their opportunities for school-based physical activity . This study surveyed Ontario secondary schools to identify the range of structured opportunities and their engagement by students . METHODS A question naire was mailed to key informants in 600 r and omly selected secondary schools in Ontario , for which 474 respondents ( 79 % ) returned completed question naires . RESULTS  Curriculum-based physical education ( PE )  classes in grade nine were reported to be offered in all schools and these classes in grade s 10 , 11 and 12 were offered in almost all schools . Student enrollment in PE decreased from grade s 9 to 12 ( 97.9 % , 49.6 % , 43.3 % and 35.9 % , respectively ) . Respondents reported that funding , timetable , facilities and re sources made it somewhat difficult to implement the health and physical education curriculum in their schools . About two-thirds ( 65.5 % ) of the schools had an intramural program and 15.0 % of students participated in it , whereas 97.2 % of the schools had an inter-school sports program and 25.0 % of students participated in it . Supervision issues made it difficult to provide intramural programs and funding made it difficult to provide inter-school sports programs . CONCLUSIONS Although provision of physical activity opportunities in Ontario appears satisfactory , actual engagement by students is low . The results suggest that strategies to increase student participation in PE , intramural programs , and inter-school sports programs need further consideration Objective To examine associations between students ’ time spent in  moderate to vigorous physical activity ( MVPA )  and the school built environment while also considering features of the schools ’ social environment and student-level characteristics . Methods Using surveys and GIS measures , multilevel linear regression analysis was applied to examine the environment- and student-level characteristics associated with time spent in MVPA  among grade 9–12 students ( n = 22,117 ) attending 76 secondary schools in Ontario , Canada as part of the SHAPES-Ontario study . Results Statistically significant between-school r and om variation in student MVPA was identified [ $ $ \sigma^{2}_{\mu 0 } $ $ = 9,065.22 ( 250.64 ) ] ; school-level differences accounted for 3.0 % of the variability in student MVPA .  Students attending a school that offered daily physical education or provided an alternate room for physical activity spent more time in MVPA than students attending a school without these re sources . Moreover , as l and -use mix diversity and walkability of the school neighbourhood increased , students ’ time spent in MVPA decreased . Conclusion Developing a better underst and ing of the environment- and student-level characteristics associated with students ’ time spent in MVPA is critical for informing school-based physical activity intervention programmes and policies The ' active school ' model offers promise for promoting school-based physical activity ( PA ) ; however , few intervention trials have evaluated its effectiveness . Thus , our purpose was to : ( 1 ) describe Action Schools ! BC ( AS ! BC ) and its implementation ( fidelity and feasibility ) and ( 2 ) evaluate the impact of AS ! BC on school provision of PA . Ten elementary schools were r and omly assigned to one of the three conditions : Usual Practice  ( UP , three schools ) ,  Liaison  ( LS , four schools ) or Champion ( CS , three schools ) . Teachers in LS and CS schools received AS ! BC training and re sources but differed on the level of facilitation provided . UP schools continued with regular PA . Delivery of PA during the 11-month intervention was assessed with weekly Activity Logs and intervention fidelity and feasibility were assessed using Action Plans , workshop evaluations , teacher surveys and focus groups with administrators , teachers , parents and students . Physical activity delivered was significantly greater in LS ( + 67 
    Output:
    
Although the underlying objectives of the policies are similar , there are clear differences among them and in their various policy trajectories .
Limited data suggests implementation of DPA policies was moderate but inconsistent and that Canadian DPA policies have had little to no impact on  school-aged children ’s PA levels or BMI .
Conclusions This study detailed the history and current status of Canadian DPA policies , highlighting the conditional nature of policy adoption and diffusion , and describing policy and adopter characteristics and political context s that shaped policy trajectories .