Understanding Physical Activity Patterns Across the School Day in Urban Pre-Kindergarten and Elementary Schoolchildren

Purpose

Physical activity in childhood is a key component for promoting lifelong health. Current guidelines for school-age children recommend at least 60 minutes of moderate-to-vigorous physical activity (MVPA) daily, with at least 30 minutes occurring during the school day in part because of its positive impact on academic performance.^1,2 The majority of daily physical activity often occurs during the school day; however, children from low-resourced schools often face a number of social and environmental barriers to meeting these recommendations. ³ Thus, understanding the patterns and amount of physical activity accrued across the school day, along with identification of opportunities for school-time physical activity engagement, provides important information for educators in helping children meet their physical activity goals. This study examined school-day patterns of physical activity and sedentary time among pre-K and elementary schoolchildren from lower-income urban elementary schools to identify opportunities for better integrating physical activity across the school day.

Methods

Four Washington, D.C. public schools (100% economically disadvantaged) participated in this study with data collection occurring among pre-K (4 years of age), 1st, 3rd, and 5th grade classrooms. Children were recruited via classroom presentations and parents were provided information regarding study procedures with the ability to “opt out” and children provided verbal assent. Study procedures, including waiver of parental consent, were approved by George Washington University Institutional Review Board, along with approval from the D.C. Public Schools Research Office.

Physical activity and sedentary time during school was objectively measured over 2 consecutive school days (∼8:55am-3pm) using Actigraph GT3X+ accelerometers (Pensacola, FL). Moderate-to vigorous physical activity was defined according to cut-points developed for elementary-aged children ⁴ and pre-school aged children. ⁵ Frequencies of sedentary bouts (>15-, >20-, and >30-mins in duration) and MVPA bouts (1-3-, 3-5-, and 5-10-min duration) also were calculated. Mixed effects regression models examined sex- and grade-specific differences in min/day of MVPA and sedentary time, while adjusting for average wear-time. Data were analyzed using SAS 9.4 and Stata 14 at an α-level of 0.05.

Results

Of the 704 eligible students, 629 children provided valid wear-time (48% female; 63% Black, 15% Hispanic/Latino, 18% White, and 4% other) and accrued an average school-time MVPA of 27.2 ± 12.6 min/day for the elementary-aged children, while pre-K children accrued 47.1 ± 17.9 min/day (Online Appendix 1). Only 34.7% of elementary-aged children and 25.3% of those in pre-K met the school-time public health recommendations for MVPA (≥30 and ≥ 60 minutes of MVPA in elementary and pre-K, respectively). Among elementary-aged children, boys accrued more MVPA than girls (30.8 ± 13.3 vs. 23.5 ± 10.7 min/day; p < 0.0001) with similar sex differences observed among pre-K children (51.3 ± 17.1 vs 41.9 ± 17.5 min/day; p < 0.001). The proportion of children meeting the school-time recommendation decreased significantly from 1st to 5th grade (49.4% vs. 17.6%, respectively; p < 0.0001), and was consistently lower among girls than boys. Most of the MVPA bouts were brief (1-3 minutes), with mean frequencies ranging from 10 ± 5.4 bouts/day in pre-K children to 4.8 ± 3.0 bouts/day in 5th graders. The average frequency of accruing MVPA bouts greater than 5 minutes in duration was negligible across all the grades (<1 bout).

Average school-time sedentary time was 222.2 ± 40.8 min/day for elementary-aged children and 285.0 ± 33.7 min/day for pre-K children, which is more than half of the 7-hour school day. Sedentary time increased with grade among elementary-aged children (207.9 ± 34.7 vs. 252.0 ± 36.1 min/day for those in 1st and 5th grade, respectively; p < 0.001), with girls accruing more sedentary time than boys (242.5 ± 48.2 vs. 233.8 ± 46.8 min/day, respectively; p < 0.0001). Over half (56.1%) of all students had at least one sedentary bout of 20 min or more in duration.

Averaged classroom physical activity patterns across a sample school day depict the highest prolonged activity peaks for pre-K, 1st, 3rd, and 5th grades corresponding to designated physical education (PE) and recess periods (Figure 1). On average, MVPA was not accrued outside of these 2 periods, aside from a short spike of midday activity (corresponding to lunch period). The majority of the school day for pre-K children was spent at or below the sedentary threshold.

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Figure 1.

Average physical activity intensity levels across one school day within a select classroom for each grade. Pre-kindergarten (n = 16), 1st grade (n = 16), 3rd grade (n = 17), 5th grade (n = 22). Vertical lines denote recess and physical education (PE) periods.

Discussion

Findings indicate school-time physical activity declines among schoolchildren as they progress from pre-K through elementary school, with notable disparities in MVPA by sex that start as early as pre-K. Previous studies using objective measures of physical activity among schoolchildren have demonstrated similar findings^3,6,7; however, to date, there are no published studies specifically examining these age- and sex differences in MVPA that extend from pre-K through elementary school. Less than 40% of children met school-day MVPA recommendations of 30 mins or more, and this appeared especially challenging for older children and for girls.

The health benefits of MVPA can be achieved regardless of how it is accumulated during the day. ⁸ Public health practitioners have been advocating for the inclusion of low-cost, easy to implement short MVPA movement breaks spaced throughout the school day for several years now,^1,2,8 as this strategy may help increase the level of MVPA achieved outside of PE and recess. Moreover, replacing sedentary time with short periods of standing desk work or light-intensity activity may help to alleviate the negative affective and cognitive health effects of prolonged sitting that are now observed in children. ² These interventions may be especially important for pre-K children, who were sedentary for over two-thirds of the school day, with noticeably more extended sedentary periods than their older counterparts.

We were able to examine physical activity patterns within a large, diverse sample of urban schoolchildren (pre-K though 5th grade) from low-income schools. Furthermore, we used device-based measurements of MVPA and sedentary time over 2 “typical” school days to determine whether children were meeting the minimum school-time recommendations for MVPA. We note that even though MVPA was objectively-measured, activity patterns observed across only 2 school days may not be representative of usual patterns and also may not account for weather-related or larger seasonal variations in movement patterns among young schoolchildren.

These findings highlight the challenge of meeting school-time physical activity recommendations among pre-K and elementary schoolchildren, particularly in low-resourced urban schools. The data indicate key areas for improvement with regard to school-time physical activity promotion outside of PE and recess. The age- and sex-based disparities in both MVPA and sedentary time in these schools suggest the need for low-cost, accessible, and targeted physical activity promotion strategies to help schoolchildren achieve public health targets.

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