Schoolyard Physical Activity on 6 Schools in Denmark – Using GPS, Accelerometry and GIS

Background Schools provide a unique setting for the promotion of physical activity (PA) in children through structured physical education, recesses, extracurricular sports and promotion of community activities. Because recesses may contribute up to 40% of moderate/vigorous activity, approaches that increase activity during recess are of interest. A number of recent studies have found associations between the characteristics of schoolyards and the level of PA of schoolchildren using the schoolyards. Based on these findings, it seems likely that making schoolyards more attractive will help to increase the total amount of PA among schoolchildren.

In order to test this hypothesis, an intervention study at selected schools in Denmark will commence in 2012. The ‘Activating Schoolyards Study’ will use combined qualitative and quantitative methods to study the effect of a series of schoolyard interventions. To prepare for this intervention study accelerometer and GPS data from 6 schools were used to get a better understanding of how children use schoolyards during recess and which schoolyard elements are associated with PA.

Objectives The overall objective of the Activating Schoolyards study is to determine the effects of schoolyard improvements on objectively measured physical activity levels and activity patterns among children (6-16yrs old).

The specific objective for the current explorative study is to describe activity patterns and identify hotspots for physical activity on 6 schoolyards varying in size and content, located in different types of neighborhoods.

Methods The data used in this explorative study stems from two separate data collections. Data from the first three schools was collected in the When Cities Move Children (WCMC) study in spring 2010. In this study 551 youth (10-16yrs old) enrolled at three public schools in relatively poor multi-ethnic neighborhoods in Copenhagen were asked to wear an accelerometer (ActiGraph GT3X) and a GPS (Qstarz BT-Q1000X) for 7 days (5 week days, 2 weekend days). To increase variation, both in participants and schoolyard characteristics, an additional 195 children (6-12 yrs old) at three other schools, in three different cities, were asked to wear an accelerometer (ActiGraph GT3X) and a GPS (Qstarz BT-Q1000X) for 5 week days in spring 2011. In both studies, GPS positions were recorded every 15 seconds and activity levels were recorded every 2 seconds.

Accelerometer data were compiled using the computer software Propero, recently developed by researchers at the University of Southern Denmark. Participants were included in further analysis if they had at least 3 week days of at least 8 hours wear time between 6am and midnight. Non-wear was defined as 60 or more minutes of consecutive zeros, allowing for two activity epochs in each block of non-wear. A recess period was considered valid if it had data for each epoch within the recess period, i.e. if it did not contain any non-wear. Recess periods varied in length between 15 and 50 minutes.

All GPS and accelerometer data were compiled and joined using an internet based computer program, the Physical Activity Location Measurement System (PALMS), developed by researchers at the Center for Wireless & Population Health Systems at the University of California, San Diego. The outputs PALMS produces consist of filtered and cleaned GPS points linked with PA data for those points. All PALMS outputs were imported into ArcGIS, a Geographic Information Software package.

All elements of each of the 6 schoolyards were mapped in detail using a high-precision GPS (Trimble GeoExplorer XT) combined with a handhold computer with ArcGIS Mobile software. For each participant, average activity counts per schoolyard element were calculated.

Results For our participants, artificial grass or rubber multi-courts, lawn areas, grass slopes and other more natural elements were associated with schoolyard physical activity. Playground equipment, climbing frames, slides, etc. were less popular for physical activity. Our results also show age, gender and time differences with different areas being popular for different age groups and at different times of the day.

Conclusions More natural elements, as well as lawn or court areas that can be used by groups, seem to be the most important elements for activity in schoolyards whereas playground equipment seems less important.