Physical activity during recess outdoors and indoors among urban public school students, St. Louis, Missouri, 2010-2011.

We measured the quantity and intensity of physical activity in 106 urban public school students during recess outdoors, recess indoors in the gym, and recess indoors in the classroom. Students in grades 2 through 5 wore accelerometer pedometers for an average of 6.2 (standard deviation [SD], 1.4) recess periods over 8 weeks; a subsample of 26 also wore heart rate monitors. We determined, on the basis of 655 recess observations, that outdoor recess enabled more total steps per recess period (P < .0001), more steps in moderate-to-vigorous physical activity (P < .0001), and higher heart rates than recess in the gym or classroom. To maximize physical activity quantity and intensity, school policies should promote outdoor recess.