Teun Remmers

Summary | 207 The last four chapters focused on objective measurements of factors in the physical environment related to measurements of children's PA. The study presented in chapter 6 examined the influence of daily weather elements (e.g. rain, temperature) on children's PA patterns across the four seasons of one year, reflecting day-to-day variations over time within children. We analyzed data from an existing dataset of the Institute of PA and Nutritional Sciences in South-East Australia. Daily meteorological data was obtained from weather station registries that were closest to a child's residential location. Meteorological data was subsequently merged with daily accelerometer data. Results showed that temperature and day type (weekdays) were the strongest factors related of increased PA, followed by daily hours of solar radiation and humidity. In addition, temperature showed a strong curvilinear relationship, with optimum moderate-to- vigorous PA levels around 20-25 degrees Celsius. Apart from implications on providing infrastructure for appropriate PA on hotter days, this study also shows researchers how to retrospectively account for weather elements in future studies. Chapter 7 presents a study investigating the relationship between PA opportunities (i.e. playability) of school environments and objectively measured afterschool PA. Here we analyzed PA by existing accelerometer data obtained by the 'Active Living' study, in Zuid- Limburg, the Netherlands. Playability of school environments was measured by systematically auditing the number of quality of playgrounds (defined by an 800-m buffer area) of 21 primary schools. Time- and distance filters were applied to understand where and when these school environment influence children's PA. Although children from schools with higher playability-scores spent more light PA and moderate-to-vigorous PA directly afterschool until 6 PM, the strength of this association attenuated at time- segments later in the evening. In addition, we found that results were strongest for children that lived within 400-m of their primary school, and no longer significant for children that lived more than 800-m from their school. These results underline the empirical importance of the quality and quantity of playgrounds in school environments. In addition, these results support that relationships between attributes of the environment and PA can be elucidated by increasing specificity of time and place.