Teun Remmers

126 | Chapter 8 25), four studies solely investigated environmental features around the residential neighbourhood (16, 19, 24, 25). However, during the afterschool period, children may spend significant parts of their time outside their residential neighbourhood (26). Therefore, not only the residential environment, but also other environments such as children's school-environment and the daily transport route between home and their school, are of interest when investigating environmental determinants of afterschool PA. Consequently, features of children's so-called multi-place environments (e.g. including school, residence, and daily transport route as spatial anchor points) may be especially suited for investigating associations with PA during the afterschool time-period (27, 28). A methodology that can help us to increase our understanding of the relationships between features of children's multi-place environments and afterschool PA is Global Positioning Systems (GPS), especially when integrated with accelerometer data. In this way, PA behaviour and GPS-derived geographical location are collected at the same moment in time, which has the potential to assess the influence of contextual exposure by time and place on PA at an individual level (29, 30). Moreover, when integrated with extensive registries of the built environment such as Geographic Information Systems (GIS), researchers can measure underlying characteristics of the environment for each GPS observation. For example, results from earlier GPS-GIS studies suggest that greenspace environments are an important facilitator for PA (22, 31-35). To date, three studies have used accelerometers and GPS loggers to describe the afterschool period (15, 18, 22). GPS loggers can provide essential descriptive information regarding important additional afterschool contexts. For example, with GPS loggers it is possible to investigate the actual self-sustained afterschool leisure time PA, by excluding organized sports participation (based on GPS-derived presence at sports grounds). Likewise, afterschool time-segments may now be individually validated by the actual presence of a child on its school-parcel, rather than based on generic start time thresholds or reported school schedules. The present study's aim was to assess the relationship between features of children's multi-place environment and afterschool leisure time PA, cycling and walking, using more precise measurements of 1) context-specific afterschool leisure time PA and afterschool active transport in 10-12-year-old children, and 2) children's exposure assessment to objectively-measured multi-place environments using accelerometers, GPS loggers and GIS data. Methods Design and participants The present study analyzed data from the baseline measurement of the PHysical Activity in public Space Environments (PHASE-kids) study, which examined longitudinal relationships between the built-environment and children's PA patterns in the transitional phase from primary- to secondary schools. The PHASE-kids study was conducted in the municipality of 's-Hertogenbosch, which covers around 110 square kilometres, and has