Abstract The purpose of this paper was to discuss physical activity and sports participation in a life-course framework, long-term tracking, determinants, and correlates of physical activity from childhood to old age, and present possible causal links and pathways for the continuity of physical activity. It seems that intensive participation in general in physical activity and sports, as well as participation at school age, are important predictors of adulthood participation. Especially, inactivity rather than activity tends to track from youth to adulthood. Socioeconomic status, place of residence, and personal upward social mobility are related to participation. If physical activity is at a low level in early adulthood, it does not easily become a part of life later on, particularly among blue-collar workers, women, and people with initially poor perceived health. Furthermore, in old age, earlier physical activity seems to be the key determinant along with gender. Repeated social reinforcement in the form of support for autonomy, competence, and relatedness is important especially in transition periods and life events such as secondary schooling, change in employment, and change in family structure. In contrast, retirement presented itself as a good chance of starting new leisure time activities. A life-course approach provides understanding on long-ranging developmental trajectories. According to these results in particular, the polarization of exercise to the active and inactive portions of the population is accumulated over time, and gender and social background features require special attention.