childhood obesity remains one of the most serious threats to the public 's health , with 1 in 3 children and adolescents overweight or obese ( body mass index ( bmi )  85th percentile ) .
there is limited evidence for effective behavioral prevention interventions . to fill this gap , the institute of medicine , the strategic plan for nih obesity research , shaping america 's youth , and the white house task force on childhood obesity  
have called for community - engaged , family - centered approaches to pediatric obesity prevention .
these approaches are thought to have the greatest potential for sustained efforts and effects in our obesogenic environment .   in parallel , comparative effectiveness research
is being discussed within the national health reform debate as a mechanism for improving healthcare quality and decreasing healthcare spending .
clinical research typically examines the effectiveness of one prevention or treatment method at a time .
comparative effectiveness research compares multiple methods to determine the effectiveness of an intervention relative to alternatives .
identifying the most effective and efficient interventions has the potential to reduce unnecessary treatments , which should lower costs .  
it is estimated that 8.4 million children attend after - school programs ( asp ) , and an additional 18.5 million would do so if a program was available .
the purpose of this study was to evaluate the comparative effectiveness of a community - driven asp designed to combat physical inactivity versus a standard - of - care school - based asp available to working parents .
the community asp was derived directly from local input and sustained through the collaboration and sharing of resources by the parks department and the public school system ( davidson county , tn , usa ) .
this community - engaged effort has the potential to serve as a new model for youth obesity prevention because ( 1 ) it systematically addresses the top four barriers , identified by shaping america 's youth , that prevent children from being active ( lack of access to safe and appropriate places to be active , parental time constraints , cost of programs , and lack of parental motivation ) and ( 2 ) it engages multiple sectors of society to support program attendance and sustainability .  
systematic reviews suggest that it is possible to improve activity levels , physical fitness , body composition , and blood lipids in the after - school setting   and that limitations in study design , lack of statistical power , and problems with implementation have hindered the evaluation of most asps to date .   to assess the comparative effectiveness of this community - driven asp as a pediatric obesity prevention intervention , we compared it to the routine aftercare available to working parents in the community and asked two research questions : ( 1 ) are children in the alternative asp more physically active than children in the standard asp ? ( 2 )
this study was guided by principles of community - based participatory research ( cbpr ) .
cbpr is an important research approach that equitably involves community members who are affected by the issue being studied in all phases of the research process .
the community asp was developed by the parks department to address the community 's need for an affordable asp .
families provided input about their needs and preferences ( e.g. , transportation from school to the community center , flexibility in pick - up times , homework time , reduction of screen time , and increased physical activity ) .
the city 's public school system changed its policy around permissible bus stops allowing buses to deliver students to the community recreation center to support program attendance .
the leadership and staff of the parks department were involved in all aspects of this research project : grant acquisition , study design , implementation , interpretation of results , and dissemination .
the study design was an observational prospective cohort study and a natural experiment in nashville , tn , usa . the  naturally occurring  event , the parks department 's new asp , was the intervention , and children attending this community asp formed the intervention group ( n = 54 ) .
comparison participants ( n = 37 ) were recruited from an asp located in the same ( low income ) school district and operated by a national company that operates a high proportion of school - based asps in the city , making it de facto standard - of - care for the majority of the city 's school - aged children with working parents .
children were eligible for the study if the following was true : ( 1 ) age 5 and < 13 years ; ( 2 ) attended one of the glencliff [ neighborhood ] cluster of public elementary or middle schools ; ( 3 ) enrolled in the community or school - based asp .
parents of eligible children underwent a 15-minute oral consent process before providing written consent for their child .
children provided assent . the consent / assent process was conducted in the preferred language of english or spanish .
the study was approved by the vanderbilt university institutional review board ( # 090986 ) .  
the two asps followed similar formats , and operated from 36 pm every day public schools were open .
both asps included time for snack , homework , and play and did not focus on a single activity ( e.g. , tutoring , chess , and team sport ) .
the community asp was set in a community recreation center and involved staff - led games .
the school - based asp was set in a school cafeteria and involved opportunities for arts and crafts and playing on the playground .
the main differences between the two asps were ( 1 ) format of active play time ( adult - led versus unstructured ) and ( 2 ) location ( community recreation center versus public school ) .
all measures were collected at the asps at three time points over approximately 12 weeks ( february  may 2010 ) , with six weeks separating each wave of measurement .
the measurement period was selected based on the cochrane review that states that obesity prevention interventions should last at least 12 weeks for behavior change to be observed .  
physical activity was assessed using actigraph gt1 m accelerometers ( actigraph , pensacola , fl , usa ) only during asp programming time .
accelerometry is considered an objective measure of physical activity   and has been used with children [ 15 , 16 ] , including latino and african - american children , with high reliability : r = 0.93 .
the actigraph is a small monitor that is worn on an elastic waist belt and measures the intensity of physical activity associated with locomotion .
monitors were programmed to record in continuous 10-second epochs to capture the short , spurt - like activity characteristic of children . at each measurement period , the children wore monitors for five consecutive days , from the time they signed into the asp until they were picked up .
measurement start and stop times were recorded by study staff at each site ; these were used as precise wearing cut - off points , eliminating the need for wearing / nonwearing time analysis .
data were retained in analysis if the child wore the accelerometer a minimum of 3 days of the given measurement period [ 18 , 19 ] .  
freedson 's age - dependent cut points were used to determine time spent in sedentary , light , moderate , and vigorous activity .
trost 's validation study comparing various accelerometer cut points for predicting physical activity in children supports the application of freedson equations in field - based studies of school - aged children .
in particular , trost found that , for classification of mvpa ( moderate - vigorous physical activity ) , freedson cut points exhibited excellent classification accuracy .
the analyses described below were also conducted using pate 's cut points and resulted in similar findings ( not reported here ) .  
daily percentage of time spent in each level of physical activity ( i.e. , sedentary , light , moderate , and vigorous ) was determined by dividing the minutes spent in each activity level by the sum of minutes the actigraph was worn in a day ( i.e. , time in attendance at the asp ) .
thus , the continuous outcome measures were the proportion of time spent in lmvpa ( light - moderate - vigorous physical activity ) or mvpa ( moderate - vigorous physical activity ) out of total time in attendance , rather than the number of minutes the program was open , to allow for a meaningful comparison within individuals and across groups .
daily percentages were averaged across days to create individual participants ' physical activity ( pa ) scores at each measurement period . body weight was measured after voiding while children wore light clothing without shoes .
calibrated digital scales ( detecto , webb city , mo , usa , model#758c ) were accurate to the nearest 0.1  kg .
body height without shoes was measured to the nearest 0.1  cm with the scale 's stadiometer .
weight categories were defined by bmi percentile , according to centers for disease control growth charts : underweight : < 5th percentile ; healthy weight : 5th to < 85th percentile ; overweight : 85th to < 95th percentile ; obese : 95th percentile .  
body composition was measured by the rjl systems bia quantum ii ( rjl systems , clinton , mi , usa ) after voiding .
standard procedures for whole body bioelectrical impedance measurement were used , along with the vendor - provided child - specific regression equation to estimate percent fat mass from total body water .  
children were asked to complete a 1/2 mile run as fast as possible on a running track .
parents completed a survey asking about child 's date of birth ( used to calculate age ) , gender , race / ethnicity , and name of school . because children were not randomly assigned , preexisting differences between groups were potential confounders .
therefore , we compared children enrolled in the asps to test for differences on basic demographic and process variables , using bootstrap t - tests that controlled for the familywise false discovery rate .   to assess change in pa over time ,
a conditional linear latent growth model was used with random intercepts and slopes that were free to covary and time varying error variances .
this approach offers important advantages over older analysis of variance ( anova ) models , such as ( a ) better accuracy in assessing change over time , ( b ) graceful handling of missing values and unequal time intervals between waves and participants , and ( c ) repeated measurements that increase statistical power .
the key result is a group by time interaction , which shows whether groups differ in their slopes / rates of change in pa .
centering time zero at the first measurement let us answer two questions : ( 1 ) did the groups start out equally ? and ( 2 ) did their time slopes differ ?
the analysis assumed data were missing at random and used full information maximum likelihood to maximize sample size by including all participants with at least one wave of data .
using the ingredient method , we estimated the implementation costs , without estimating indirect costs or externalities associated with the programs , to indicate how much it would cost to replicate each asp . instead of accounting expenditures paid during the implementation , we valued resources using standard costs to society .
all personnel time ( including volunteer time ) was valued by using the median earning per hour of a comparable worker published by the bureau of labor statistics 2010 ; thus , differences in human capital endowment did not affect our estimates of implementation costs .
of the 91 children who attended the asps , baseline demographics were obtained from parents of 83 children .
the analytic sample included the 82 children with pa data from at least one time point ; one child in the school - based asp did not provide at least 3 days of pa data in any measurement period and was not included in the analyses .
of the 82 participants , 62 had data for all three time points , 16 had data for two time points , and 4 had data for only one time point .
the baseline sample was 65% female and 7.9 years of age ( sd = 1.7 ) on average ; 57% were healthy weight , 23% overweight , and 20% obese ; 40% were african - american , 40% white , and 20% latino . on average at baseline , children spent 77.4% ( sd 10.3% ) of the asp in lmvpa and 27.5% ( sd 14.3% ) in mvpa . at baseline , children in the two asps did not differ in gender , age , bmi , percent body fat , fitness ( table 2 ) , or physical activity level ( table 3 ) .
however , children in the community asp were less likely to be white than children in the school - based asp ( p = .027 , table 2 ) . at baseline , children spent approximately 30% of their asp time in mvpa ( sd = 15.6 ) .
the linear latent growth model implied that , on average , children in the community asp became more active over time ( average change between baseline - week 6 and week 6-week 12 ) , compared to the children in the school - based asp ( table 3 ) .
children in the school - based asp reduced their total physical activity ( lmvpa ) by an average of 3.4 percentage points over each measurement period ( p = .002 ) , for a total 6.8 percentage point decrease over the 12-week study period .
in contrast , children in the community asp increased their total physical activity ( lmvpa ) by an average of 3.0 percentage points over each measurement period ( p = .006 ) , for a total 6 percentage point increase over the 12-week study period ( figure 1 ) .
children in the school - based asp did not significantly change their mvpa on average ( p = .12 ) .
however , children in the community asp increased their mvpa by an average of 2.8 percentage points over each measurement period ( p = .006 ) , for a total 5.6 percentage point increase over the 12-week study period ( figure 2 ) .
taken together , the model - implied average difference between the two groups of children at week 12 was 15.4 percentage points in lmvpa ( p < .001 ) and 14.7 percentage points in mvpa ( p < .001 ) , favoring the activity - enhanced community asp .
however , as a more conservative indicator , the observed average difference between the two groups of children who had data at week 12 was 10.8 ( p = .001 ) percentage points in lmvpa and 13 percentage points in mvpa ( p < .001 ) .  
the community asp served 54 children ; the school - based asp served 37 children .
total implementation costs ( valued in 2010 dollars ) for the 12-week study period were $ 1,184 per child ( $ 19.25 daily per child ) for the community asp , compared to $ 1,087 per child ( $ 17.67 daily per child ) for the school - based asp ( 9% difference ; table 4 ) .
the facility cost represented 66% and 65% of the total implementation costs to run the community asp and school - based asp , respectively .
the main source of cost differential between programs was the child to staff ratio ( 6  :  1 at the community asp , 12  :  1 at the school - based asp ) . to run the asps for 12 weeks , the personnel cost was $ 380 per child for the community asp compared to $ 314 per child for the school - based asp ( 21% difference ) .   with more than 23 million parents of school - aged children employed full - time ,
this study demonstrated that , compared to a standard - of - care school - based asp , an asp set in a community recreation center with activities directed by recreation staff significantly increased total physical activity in a multiethnic sample of public school children by 6 percentage points over 12 weeks .
most ( 5.6% ) of this increase was in mvpa , which is the type of physical activity that has the greatest health benefits [ 3335 ] .
the incremental cost of implementing the activity - enhancing asp compared to the traditional asp was $ 1.59 per day per child .
the main source of cost differential between programs was their child to staff ratios .   assuming the improvement in activity was solely due to the intervention ; these findings suggest that children attending traditional school - based asps , already costing an average of $ 17.67 per day , would need an additional daily investment of $ 1.59 per child over 12 weeks to increase their lmvpa by 15.4 percentage points or their mvpa by a model - implied 14.7 percentage points .
the annual cost of childhood obesity - related health expenses in the us is $ 14.1 billion for outpatient care and $ 237.6 million for inpatient care which translates to about $ 5 in healthcare expenses per day per child , without including other relevant long - term costs related to school performance , labor market involvement , quality of life , welfare needs , and so forth . given this , providing structured pa programming by qualified staff in a community recreation center in the after - school hours could be a reasonable low - cost investment .  
asps have long played a critical role in supporting academic achievement , safety , discipline , and avoidance of risky behaviors .
they could now be leveraged as part of a broader approach to address physical inactivity .
community centers operated by local parks and recreation departments ( 20,000 nationally ) provide an ideal venue for structured pa programming for children   in large part because these centers , in conjunction with school transportation departments , can address community - based barriers   to increasing children 's activity levels . it is noteworthy that the parks staff initiated and led this program on their own .
their intimate knowledge of the community and the respect they commanded from both the children and adults in the community likely contributed to the program 's success .
we speculate that the combination of the built environment that supported activity , low child to staff ratio , and intentional activity leadership resulted in the increased pa levels .
the school - based asp could have let children play in the school 's gymnasium if there had been additional staff available to supervise .
thus , we speculate that importing adult - led activities with lower child to staff ratios into school - based asps might be a cost - effective approach to increasing activity in that setting as well
first , accelerometers do not adequately measure body movements of upper and lower extremities , but they are considered the gold standard for measuring pa under free - living conditions .
this should not have biased our results since the limitation of accelerometry was the same across groups .
second , our sample was small but having three waves of data increased statistical power and was sufficient for detecting a significant increase in pa under free - living conditions .
third , despite efforts to select a comparable comparison group and measure potential confounders , we can not rule out all systematic differences between the two groups .
we did rule out the most important possible confounds in the literature : body composition , fitness , age , and gender .
it is possible that the difference in racial composition of the groups could explain baseline variance   but is unlikely to explain change over time in activity levels .  
fourth , for the community asp , there were significant differences between the observed and model - implied averages at weeks 6 and 12 .
these discrepancies highlight the fact that the final specified model did not perfectly recreate the observed data .
this could have been partially due to missing data for this group at either time point .
the discrepancies could also have arisen because the community asp 's growth rate was not linear ; yet , a model with only three time points does not have the degrees of freedom to investigate more sophisticated growth parameter specifications ( e.g. , quadratic ) . nonetheless , applying latent growth models has provided further insight into how asps might impact children 's pa over time ( e.g. , what effect does asp type have on pa change over time ? what is the typical growth rate of pa for children over time ?
do some programs increase the growth rate of certain types of pa ( e.g. , light , moderate , or vigorous ) more than others ?
an asp set in a community recreation center and led by recreation staff incorporating structured physical activity opportunities was associated with significant increases to physical activity during asp time in a multiethnic sample of public school children in 12 weeks , compared to a standard school - based asp .
utilizing community recreation centers ' built environment and staff could be a promising low - cost proposition to improve health trajectories among school - aged children .
 
 background . 
 we conducted a comparative effectiveness analysis to evaluate the difference in the amount of physical activity children engaged in when enrolled in a physical activity - enhanced after - school program based in a community recreation center versus a standard school - based after - school program . 
 methods . 
 the study was a natural experiment with 54 elementary school children attending the community asp and 37 attending the school - based asp . 
 accelerometry was used to measure physical activity . 
 data were collected at baseline , 6 weeks , and 12 weeks , with 91% retention . results . at baseline , 
 43% of the multiethnic sample was overweight / obese , and the mean age was 7.9 years ( sd = 1.7 ) . 
 linear latent growth models suggested that the average difference between the two groups of children at week 12 was 14.7 percentage points in moderate - vigorous physical activity ( p < .001 ) . 
 cost analysis suggested that children attending traditional school - based asps  at an average cost of $ 17.67 per day  would need an additional daily investment of $ 1.59 per child for 12 weeks to increase their moderate - vigorous physical activity by a model - implied 14.7 percentage points . 
 conclusions . a low - cost 
 , alternative after - school program featuring adult - led physical activities in a community recreation center was associated with increased physical activity compared to standard - of - care school - based after - school program . 
1. Introduction 
2. Materials and Methods
3. Results and Discussion
4. Conclusion