Physical activity promotion in adolescents: Development and evaluation of interventions tailored to personal motivations and environmental opportunities

Improvement of physical activity (PA) levels is an important public health priority, that fits within the notion that the greatest gain in public health can be achieved by changes in lifestyle behaviors. Physical activity is associated with the risk for the ZonMw priority diseases, cardiovascular diseases, cancers, type 2 diabetes, overweight and obesity. These diseases are more prevalent in Rotterdam, compared to other Dutch regions. Rates of PA are low in Rotterdam, in adults as well as in adolescents, and vary between inhabitants of different socio-economic and ethnic backgrounds. An important main focus of the Municipal Public Health Service (MPHS) Rotterdam and surrounding areas is adolescent health and health promotion. The proposed study focuses on promoting PA in adolescents in the Rotterdam area. PA promotion interventions should target the most important determinants of PA behaviors. The role of the environment as a determinant of behavior is increasingly becoming recognized, especially in the domain of overweight/obesity research. Interventions to promote PA should, therefore, take the environment into account, in addition to individual determinants. Evidence based and effective interventions to promote PA in adolescents of different socio-economic and ethnic backgrounds, that take into account the specific characteristics of a large urban area such as Rotterdam do not exist. We propose to develop systematically planned computer-tailored PA interventions for adolescents, targeting important individual determinants of behavior, as well as actual and perceived environmental opportunities and barriers for PA. One version of the intervention will aim at improving motivation, and incorporate action initiation and maintenance strategies, and an extended version of the intervention will also include information about perceived and factual opportunities for PA that the physical environment has to offer, so that the intervention will target determinants in all important phases of the behavior change process. The interventions will be delivered in a school-based interactive Internet program. The interventions will be evaluated in a randomized trial design, for main effects and differential effects in groups of high and low socio-economic status and different ethnic backgrounds. Additionally, the influence of the physical environment on intervention effects will be examined.