In 1985, Professor Claude Bouchard provided a model showing the relationships between heredity, health-related fitness, physical activity, health, and multi-level factors. Health-related fitness includes morphological, muscular, motor, cardiorespiratory, and metabolic conditions. Health outcomes include wellness, morbidity, and mortality. Physical activity domains include leisure, occupation, transport, and home activities. Multi-level factors include lifestyle behaviors, personal attributes, physical environment, and the social environment. This presentation provides an overview of the model and highlights key research to support and extend the reach of Bouchardís model as a research paradigm for understanding the importance of physical activity on health and longevity.