In this paper, the relationship between adolescent sport participation and lifelong participation in physical activity (LLP) is scrutinized, in order to explain why people are active later in life. Literature treating the relationship between sport participation during adolescence was compared to literature into characteristics of Norwegian adolescent sport. Organized and competitive sport does not facilitate lifelong continuation in physical activity, due to its characteristics of sport: adolescents often drop out from sport, adolescents specializes in one sport instead of keeping or developing a broad repertoire for physical activity, and adolescents do not feel autonomous and free in a sport setting as it is adult controlled. Assisted by Bourdieu’s theory of field and habitus, the analysis indicates that habitus (including characteristics of social class) better explains LLP than does adolescent sport participation. It is proposed that habitus can be seen as the intermediate mechanism that explains both adolescent sport participation and LLP (instead of seeing the former explaining the latter).