| Chapter 1 General introduction | 7 |
| Chapter 2 Relationship between physical activity and the development of body mass index in children | 21 |
| Chapter 3 Moderators of the relationship between physical activity enjoyment and physical activity in children | 39 |
| Chapter 4 A longitudinal study of children’s outside play using family environment and perceived physical environment as predictors | 55 |
| Chapter 5 Moderators of the longitudinal relationship between the perceived physical environment and outside play in children: the KOALA birth cohort study | 73 |
| Chapter 6 Daily weather and children's physical activity patterns | 91 |
| Chapter 7 Playability of school-environments and after-school physical activity among 8–11 year-old children: specificity of time and place | 109 |
| Chapter 8 Critical hours and important environments: relationships between after-school physical activity and the built environment using GPS, GIS and accelerometers in 10-12-year-old children | 129 |
| Chapter 9 Unravelling the physical activity context: investigating context-specific physical activity patterns in transition from primary to secondary school using accelerometers, GPS, and GIS | 155 |
| Chapter 10 General Discussion | 181 |
| Summary | 209 |
| Samenvatting | 217 |
| Valorization addendum | 225 |
| Appendices | 231 |
| Dankwoord | 245 |
| Curriculum Vitae | 251 |
| Publication list | 255 |