Pediatric Weight Management

Child Nutrition and Environment


Scott MM, Cohen DA, Evenson KR, Elder J, Catellier D, Ashwood JS, Overton A. Weekend schoolyard accessibility, physical activity and obesity: The Trial of Activity in Adolescent Girls (TAAG) Study. Prev Med. 2007 (May); 44 (5): 398-403.

PubMed ID: 17292958
Study Design:
Cross-Sectional Study
D - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:

To examine the relationship between the accessibility of schools as recreational sites and physical activity and BMI in adolescent girls. This study examined:

  • Weekend (Saturday) accessibility of school grounds and availablilty of active amenities
  • Overall neighborhood recreational facilities and how schools contributed to the entire neighborhood
  • Presence of locked vs. unlocked schools according to neighborhoods
  • The association between school accessibility and weekend physical activity and BMI.
Inclusion Criteria:
  • Girls (sixth grade) with baseline TAAG measurements from spring 2003 and having usable data for weekend metabolic equivalent weighted moderate-to-vigorous physical activity (MW-MVPA)
  • Inclusion criteria for these girls in the TAAG study is not described in this research paper
  • Schools included in the analysis were those that were within a half-mile radius of the girls' homes (public K-12, private K-12 and college/university).
Exclusion Criteria:

Schools that were outside of the half-mile radius of each girl's home.

Description of Study Protocol:

This article examines data from the Trial for Adolescent Girls (TAAG), which is a multi-center randomized trial. The aim of TAAG is to test an intervention to reduce the usual decline in moderate to vigorous physical activity in middle-school girls.


Recruitment of TAAG participants is not described in this paper.


  • GIS was used to geocode girls' residences and map a half-mile radius around each girl's home. This defined neighborhood encompassed a distance that a middle-school aged girl might be expected to walk or bicycle. Schools (public K-12, private K-12 and colleges/universities) within this defined neighborhood were identified.
  • TAAG staff performed Saturday site visits to systematically inventory active amenities at schools and to determine whether or not school facilities were locked
  • Parks in the study area were mapped using existing digital data and hardcopy data that were digitized by the study team. Amenities within each mapped park were identified by a direct observation instrument.
  • Using 2000 U.S. Census block group data, several neighborhood measures were calculated within each half-mile radii, including population density, unemployment, adults with less than a high school education, households in poverty and median year of school construction
  • Physical activity was measured between January and June 2003, when girls wore an accelerometer for six days. MVPA was converted to METS using a regression equation. Total weekend (Saturday and Sunday) physical activity was chosen as the outcome to better estimate girls' typical activity.
  • BMI was calculated using height and weight measured by trained TAAG staff.

 Statistical Analysis

  • Chi square tests of proportions and ANOVA for differences among means was used to compared proportions of locked and unlocked schools (with and without active amenities) by site and school type
  • Neighborhood differences were characterized comparing those with locked schools vs. those with no locked schools. Chi square tests of proportions and T-tests for differences between means were used.
  • The relationships between weekend MV-MPA and BMI and the characteristics of the girls neighborhood were analyzed using a three-level hierarchical model. Clustering of girls within schools and schools within geographical sites was controlled. 
  • Covariates at girl-level, including race, SES, number of parks, number of accessible schools with active amenities, number of locked schools and dummy variable for presence of one or more schools within half-mile
  • School-level covariate: Percent of students in the sixth, seventh and eighth grade receiving free or reduced lunch
  • First-level residuals were not normally distributed, so long-transformed versions of dependent variables were used.  
Data Collection Summary:

Timing of Measurements

TAAG baseline data for MVPA and BMI was collected in the spring of 2003. TAAG staff performed school site visits on Saturdays between 9 a.m. and 5 p.m. in the spring of 2003.

Independent Variables

  • Locked status of schools (percent unlocked with active amenities, locked, unlocked with no active amenities and mean number of active amenities were determined by site and school type
  • Active amenities available (total number and percent of total were calculated for unlocked schools, parks and locked schools)
  • Differences between girls and neighborhoods by presence of locked school (girls with locked school vs. girls with at least one locked school were examined by race and site).

Dependent Variables

BMI and MVPA: Relationships with locked schools, unlocked schools with active amenities, no schools within half-mile, parks, SES, race and free lunch were examined.

Control Variables

  • Girl-level covariates: Race, SES, number of parks, number of accessible schools with active amenities, number of locked schools and dummy variable for presence of one or more schools within half-mile
  • School-level covariate: Percent of students in the sixth, seventh and eighth grade receiving free or reduced lunch.
Description of Actual Data Sample:
  • Initial N: BMI and MVPA data from 1,556 females was used. A total of 407 schools were identified within a half-mile radius of the girls' homes.
  • Age: Sixth-grade girls
  • Ethnicity:
Race (%) Girls with No Locked Schools Girls with at Least One Locked School
White 70.7 29.3
Black 44.7 55.3
Hispanic 48.0 52.0
Other 62.8 37.2
  • Other relevant demographics: Data used is from girls having usable weekend moderate-to-vigorous physical activity (MVPA) baseline measurements (spring 2003)
  • Location: Arizona, California, Louisiana, Maryland, Minnesota and South Carolina.


Summary of Results:

Key Findings

  • Description of schools and neighborhoods:
    • Over all six sites (N=407 schools), only 57% of schools were both unlocked and had active amenities; 34% were locked; 9% were unlocked with no active amenities; mean number of active amenities was 4.0 (3.0 SD)
    • There was variation in facility access and amenities between different states
    • School type: The percentage of locked public schools (35%) was similar to that for private schools (34%)
    • Public schools had more active amenities than private schools: 4.5 (3.1 SD) vs. 2.4 (1.8 SD), P<0.0001
    • A variety of active amenities were observed at schools, the most common being basketball courts (63%), playgrounds (60%), fields (50%) and blacktops (48%)
    • Over the six sites, there were a total of 670 public parks and unlocked schools with active amenities. Of this total, unlocked schools made up 35% (N=232) and contributed 83% of running tracks, 77% of blacktop space and 63% of handball courts. 
    • The authors calculated a percent increase in active amenities that would occur if locked schools (N=113) were made accessible. Opening the locked schools would result in a 17% increase in total active amenities, 43% increase in blacktop space, 20% in basketball courts, 18% in playgrounds and athletic fields by 16%.    
  • School accessibility, BMI and Weekend MW-MVPA:
    • Accessibility of schools and parks: 35% of girls had both a school and park within a half-mile; 25% had no school or park near their homes; 21% had only parks; 18% had only schools. Overall, 53% of girls lived near a school, but of these schools only 39% were both unlocked and had active amenities.
    • Differences between girls and neighborhoods were observed by presence of at least one locked school within the half-mile radius compared to those with no locked schools:
      • Girls with at least one locked school were less likely to be white, live in Minnesota, South Carolina or California
      • In neighborhoods with locked schools, schools were older (P=0.0144), population density was higher (P<0.0001), there was higher poverty (P<0.0001) and unemployment rates (P<0.0001), and fewer residents that completed high school (P<0.0001)
    • MW-MVPA:
      • Girls with no schools within a half-mile radius had 9.6% less MW-MVPA (P<0.10)
      • Neither the presence of locked schools nor unlocked schools was significantly associated with girls' MW-MVPA
      • Each additional park within the radius was associated with a 3% increase in weekend MV-MPA (P<0.10)
    • BMI:
      • Each additional locked school in a neighborhood was associated with a 3% increase (0.6 units) in BMI (P<0.05)
      • BMI was not significantly related to not having a school within a half-mile radius of a girl's home
      • BMI was not related to the number of schools with active amenities
    • Differences were observed in BMI and MW-MPA by race and SES.
Author Conclusion:
  • Adolescent girls may not see schools as a place for recreation as implied by the lack of relationship between MW-MVPA and school accessibility
  • The authors described school grounds as tremendous recreational resources that should be promoted by public health advocates as venues for physical activity
  • An association was found between BMI and locked schools. Thus, efforts to make schools more accessible are needed.
  • Qualitative studies are needed in the future to look at adolescents' perceptions of locked schools and examine the linkage between weekend physical activity and school accessibility.
Funding Source:
Government: NIH/NHLBI Grants
Reviewer Comments:
Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) N/A
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) N/A
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? ???
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? N/A
  2.2. Were criteria applied equally to all study groups? N/A
  2.3. Were health, demographics, and other characteristics of subjects described? N/A
  2.4. Were the subjects/patients a representative sample of the relevant population? N/A
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? Yes
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) Yes
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? N/A
  4.1. Were follow-up methods described and the same for all groups? N/A
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? N/A
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) No
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? No
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? N/A
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? N/A
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? N/A
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? N/A
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes