The contribution of physical environmental factors to explain physical activity in European adolescents

Regular physical activity is associated with different well-known health benefits. Unfortunately, a large proportion of adolescents is not sufficiently active to achieve these health benefits. In addition, adolescence has been identified as one of the periods in life in which many health risk behaviors are developed and these behaviors may persist into adulthood. Therefore, the promotion of physical activity among adolescents has become a public health priority. Before effective interventions to promote physical activity can be developed, insight is needed in the multiple determinants of adolescents’ physical activity. The ecological models provide a framework to understand the factors that are expected to influence behavior. These models explicitly distinguish the role of the environment. Within the perspectives of the ecological models, the main objective of this doctoral thesis was to gain more insight in the association between physical environmental factors and adolescents’ levels of physical activity. This doctoral thesis focused mainly on the physical environmental characteristics of adolescents’ local neighborhood and in a lesser degree on the environmental characteristics of their school environment. The results of the studies included in this doctoral thesis, showed that neighborhood environmental characteristics are not as relevant for adolescents as they are for adults to explain their level of physical activity. Consequently, neighborhood environmental initiatives to increase physical activity in a large population group, will not achieve the desired effect among the overall Belgian adolescent population. These findings emphasize the need to use multidimensional interventions focusing on the environment as well as on psychosocial factors to increase the current physical activity levels of adolescents. Furthermore, it seems advisable to take into account the school environment since adolescents spend a large percentage of their day in school. In-depth analyses showed that the association between neighborhood walkability and adolescents’ physical activity is different between adolescents living in neighborhoods of high and low socio-economic status. In contrast to adolescents living in neighborhoods of high socio-economic status, adolescents living in neighborhoods of low socio-economic status often do not have the ability to deal with the financial outlay that certain activities require. Probably, adolescents living in neighborhoods of low socio-economic status are therefore more dependent of their neighborhood environment to be active than their peer group living in neighborhoods of high socio-economic status. Further, the results also showed that the association between neighborhood walkability and adolescents’ physical activity is different between adolescents with positive and less positive psychosocial characteristics. It seems that for adolescents living in neighborhoods characterized by low socio-economic status, who perceive many barriers or few benefits towards physical activity, in other words a group that is most difficult to reach through individual interventions, increasing the walkability of the neighborhood may be beneficial for their level of physical activity. These results provide support for the ecological models stating that factors can influence behavior directly but also indirectly through their interaction with other factors. When distinguishing the results based on the manner in which the neighborhood environment was assessed, the parental perception of neighborhood environmental characteristics was found to be more strongly related to adolescents’ level of physical activity than the perception of the adolescent him/herself or the objectively determined neighborhood environment. Initiatives to change parents’ perceptions of neighborhood environmental characteristics (e.g. the parental perception of the distance to school, the accessibility of neighborhood services, the availability of walking and cycling infrastructure and the degree of land use mix diversity) seem therefore promising to increase their child’s physical activity level and in particular their child’s level of active transport. Adults’ perception of the neighborhood environment may be changed by initiatives to enhance the environmental characteristics of the neighborhood and by information as well as education to target the awareness, knowledge and attitudes. Results of the study focusing on the association between school environmental characteristics and adolescents’ level of physical activity confirmed the promising role of the school environment to promote physical activity among adolescents. A positive health education policy at school, the endeavor to have active schoolyards and playgrounds and the promotion and facilitation of active commuting to school were found beneficial for adolescents’ physical activity. Schools can be recommended to design schoolyards and playgrounds appealing for physical activity, to make facilities (e.g. sports hall, outdoor sports fields) and sports equipment (e.g. play material, goals and nets) available for students, to promote active transport, to provide bicycle racks, to involve the students in the decision making process about sports and physical activity and to support teachers to have training on sports and physical activity. The school environment is obviously a setting that is promising to include in future interventions