Background and Purpose
Building on interventions promoting active physical education (PE) and other strategies, school districts and states have initiated policies and programs to improve physical activity levels.  in March 2010, the Boston Public Health Commission received Communities Putting Prevention to Work (CPPW) funding.  in one initiative, the Boston Public Schools (BPS) implemented policies promoting an “Active School Day,” including increasing the quantity and quality of PE provided for students and integrating more moderate and vigorous physical activity (MVPA) throughout the school day. This study evaluates the potential effectiveness of these policy change strategies in six BPS schools.

Objectives
1) Collect accelerometer data from a student sample before and after “Active School Day” policy implementation in 3 intervention and 3 control schools; 2) Evaluate policy implementation within schools using a quasi-experimental design. Here we report preliminary estimates of changes in physical activity levels before and after implementation.

Methods
This quasi-experimental non-randomized matched control study compares changes in physical activity levels pre- and post-intervention among a diverse urban sample of fourth and fifth grade students using accelerometer and observational data. We collected accelerometer data among 480 students in 26 classrooms at 6 schools at baseline (March 2011) and follow up (June 2011).  The main outcome is accelerometer minutes of MVPA during the school day.  Teachers completed weekly logs recording types and timing of physical activity opportunities provided to students.  Accounting for clustering at the student and school levels, we calculated linear regressions to estimate changes in mean minutes of accelerometer MVPA levels among intervention and control students from baseline to follow up.  We also employed within-person fixed effects regression methods to estimate the impacts of PE and recess minutes on MVPA levels, and how these changed with intervention.

Results
We collected valid accelerometer data from 393 fourth and fifth grade students at both baseline and follow up (82% response rate).  Fifty-two percent of students were female, 53% in grade 5, and the majority were of black (59%) or Hispanic/Latino (31%) race/ethnicity.  Students provided on average 4.3 (SD 0.8) valid days at baseline and 4.0 (SD 1.0) days at follow up, for a total of 3,291 monitored person-days.  We collected 20 weekly physical activity logs from classroom teachers at baseline and 25 at follow up.  At baseline, teachers reported an average of 48 minutes per week of PE (42 intervention, 56 control) and 52 minutes per week of recess (65 intervention, 35 control) provided to students.  At follow up, reported weekly minutes of PE were similar (49 overall; 41 intervention, 58 control), while weekly recess minutes increased to 95 (104 intervention, 86 control).  Classroom movement breaks and other types of physical activity were also offered, though less frequently.  Overall, student activity levels during the school day increased overall from 18.4 (SD 9.6) minutes/day MVPA at baseline to 23.9 (SD 15.8) minutes/day MVPA at follow up.  Compared to students in control schools, students in intervention schools participated in fewer minutes/day MVPA at both baseline (17.4 intervention vs. 19.4 control) and follow up (23.4 intervention vs. 24.4 control).  Adjusting for monitored time, sex, grade, meter type worn, matched pairs, temperature and precipitation, results indicate that students in intervention schools increased MVPA levels from baseline to follow up by 4.2 minutes more than their control peers.  More detailed within-person fixed effects (repeated measures) analysis indicated that each minute of PE provided was associated with increases in MVPA (p<0.0001) for both intervention and control sites. At follow-up, but not at baseline, minutes of recess periods offered were associated with substantial increases in overall minutes/day MVPA in intervention sites compared to baseline (P<0.0001).

Conclusions
During school hours, fourth and fifth grade students in Boston engaged in higher MVPA levels in June compared to March.  Students attending schools that implemented initiatives to increase and improve PE and other physical activity opportunities during the school day showed higher increases in MVPA levels from March baseline to June follow up.  Providing PE was associated with higher MVPA levels, resulting in approximately 11 additional minutes of MVPA with provision of a 48-minute PE class, or 14 minutes MVPA for a 60-minute PE class. Physical activity levels associated with recess time, low at baseline due in part to high prevalence of indoor recess periods, increased among intervention schools following the implementation of active recess initiatives.  School-based physical activity promotion initiatives implemented at the district level may have the ability to increase student physical activity levels.

Support / Funding Source
Supported by Active Living Research (grant #68591).