Travel by walking before and after school and physical activity among adolescent girls.

OBJECTIVE To examine how "travel by walking" before and after school contributes to total physical activity of adolescent girls. DESIGN Cross-sectional sample. SETTING Thirty-six middle schools from Arizona, Maryland, Minnesota, Louisiana, California, and South Carolina participating in the Trial of Activity for Adolescent Girls (TAAG). PARTICIPANTS Seventeen hundred twenty-one sixth-grade girls consented to participate; adequate information was available for 1596 participants (93%). MAIN EXPOSURE Travel by walking before school, after school, and before and after school combined assessed from the 3-Day Physical Activity Recall. MAIN OUTCOME MEASURE Mean minutes of physical activity measured by accelerometry were estimated for total physical activity (light, moderate, vigorous), moderate to vigorous activity (MVPA), and MVPA of 3 metabolic equivalents. RESULTS Travel by walking was reported by 14% of participants before school and 18% after school. Girls who reported travel by walking before and after school (combined) had 13.7 more minutes (95% confidence interval, 1.2-26.3) of total physical activity and 4.7 more minutes (95% confidence interval, 2.2-7.2) of MVPA than girls who did not report this activity. Before-school and after-school walkers (but not both) accumulated 2.5 more minutes (95% confidence interval, 0.10-4.9) and 2.2 more minutes (95% confidence interval, 0.24-4.2) of MVPA on an average weekday, respectively, than nonwalkers. CONCLUSION Our results provide evidence that walking to and from school increases weekday minutes of total physical activity and MVPA for middle-school girls.