Childhood obesity prevalence has reached an all-time high across the United States. Despite the link between limited physical activity (PA) and increased risk of obesity, current data suggest that few children are meeting PA guidelines. The school day has been targeted for PA interventions;​ however, with the exception of physical education (PE) and recess, there is little information on when children engage in PA during the school day. Furthermore, few studies have reported school-day PA at epoch lengths (i.e., one-second) that are representative of children’s sporadic movement patterns.

PURPOSE:​ The purpose of this study was to examine temporal characteristics and inter-child variability of PA accumulation across the elementary school day in an effort to better inform PA intervention approaches.

METHODS:​ Using a wristmounted GENEActiv accelerometer, we collected six days of accelerometry data from 133 children in first, third, and fifth grades who were participating in the Intervention of PhysicaL Activity in Youth (IPLAY) study. Acceleration data were collected at 75 Hz, filtered, and vector summed over a one-second interval. We then used calibration-derived intensity cutpoints to determine the amount of time spent in moderate-vigorous PA (MVPA). School-day MVPA was quantified during distinct CIs, which included the entire school day, class time, break time (i.e., AM recess, PM recess, and lunch/recess combined), and PE, to determine MVPA accumulation and inter-child variability in the time spent in MVPA.

RESULTS:​ Children spent a mean of 30.3% (122 min.) of the entire school day, 27.9% (95 min.) of class time, 42.6% (17 min.) of PE, and 49.3% (18 min.) of break time engaged in MVPA. The maximum percentage of time spent in MVPA across each custom interval was 43.2% (176 min.), 41.7% (152 min.), 69.3% (34 min.), and 72.5% (33 min.) of the entire school day, class time, PE, and break time, respectively. Break time and PE demonstrated the greatest inter-child variability between the minimum and maximum percentage of time spent in MVPA. During the entire school day and class time, first and third graders spent a significantly greater percentage of time in MVPA than did fifth graders. During break time, boys spent a significantly greater percentage of time in MVPA than did girls. Surprisingly, no main effect of weight status was found.

CONCLUSION:​ Our results suggest that elementary-aged children, regardless of weight status, are meeting/exceeding recommended amounts of school-day MVPA. Despite these findings, which may be due to the use of acceleration data summed over a very short one second interval, there is still room for increasing mean school-day MVPA, potentially by up to ~50 minutes per day