Insights into individual and environmental correlates of physical activity among youth

Being sufficiently physically active and limiting sedentary behavior is associated with numerous health benefits for children and adolescents. Despite these health benefits, many children and adolescents do not reach the health recommendations of engaging daily in 60 minutes of moderate- to-vigorous-intensity physical activity and spend too much time being sedentary. Therefore, the promotion of physical activity and the prevention of spending too much time being sedentary among children and adolescents have become important public health aims. Especially the transition from primary to secondary school has been identified as a crucial time period for a decrease in physical activity. Before interventions can be developed, it is necessary to gain insight into the factors that influence these target behaviors. Ecological models state that besides individual characteristics, social and physical environmental factors may influence children’s and adolescents’ health behaviors. Therefore, the main aim of this thesis was to gain insights into individual and environmental correlates of physical activity among children (9 to 12 year) and adolescents (13 to 14 year) around the transition from primary to secondary school. Furthermore, the feasibility and effectiveness of two physical environmental interventions to increase physical activity and to decrease sedentary behavior among children was tested. The results of a systematic literature review, included in this thesis showed that associations between the physical neighborhood environment and children’s physical activity cannot be generalized across different continents. In Belgium, the association between the physical neighborhood environment and children’s physical activity also differed across different neighborhoods. Objective neighborhood walkability (characterized by street connectivity, land use mix diversity and residential density) was only associated with physical activity levels of children living in low-income neighborhoods. In high-income neighborhoods, walkability was unrelated to children’s physical activity. It can be assumed that intervening in the neighborhood environment in low-income neighborhoods may lead to higher physical activity levels among children. However, the associations between objective walkability and children’s physical activity were less consistent than previous findings among adults, which reported clear and direct positive associations between objective walkability and adults’ physical activity. In low-income neighborhoods, a higher walkability was related to more walking for transportation during leisure among children, similar as among adults. Besides, activity-friendly neighborhoods for children also require sufficient play spaces for safe active outdoor play. Furthermore, changing perceptions of physical environmental features in the neighborhood (e.g. accessibility, crime safety) towards more activityfriendly neighborhood perceptions may be related to higher physical activity levels in the neighborhood among children living in high- and low-income neighborhoods. Next to the importance of physical environmental characteristics to explain children’s physical activity, the results of this thesis also stress the importance of individual and social environmental factors to explain children’s changes in physical activity during the transition from primary to secondary school. Future interventions might be effective in increasing children’s physical activity levels during the transition from primary to secondary school, if they focus on increasing attitude, self-efficacy and parental support towards physical activity and decreasing children’s barriers towards physical activity next to changing the objective and perceived environment. Two small-scale physical environmental interventions (the organization of Play Streets in the neighborhood and the reduction of playground density by splitting up recesses in schools) were found to be feasible and effective in increasing children’s physical activity and decreasing children’s sedentary behavior. Although the effects of these interventions were rather small, they have the potential to influence large groups of children and they can be used in larger multicomponent interventions