Physical activity has an important role in growth and development and this role is not confined to the growing years, where lifelong PA is associated with reduced age related declines and healthy aging. PA during the growing years positively influences a range of systems and processes, including some aspects, for example motor skill and psychosocial aspects, that are beyond the scope of this chapter. A common theme in the research within this discipline is the lack of longitudinal studies to allow us to fully understand the complex relationships between PA and growth and development at various life stages, therefore as these studies are conducted our understanding regarding the role of PA will improve.