2 science – converged in an effort to understand and address the heart disease epidemic. In the United States, the percentage of all deaths caused by heart disease had risen from 8 to 10 percent in the early 1900s to slightly less than 40 percent by 1960.1 By the late 1980s, scientific evidence had clearly shown that regularly performed moderate-to-vigorous physical activity reduced the risk of heart disease.2 Evidence of other health benefits soon followed.3 This 2018 Physical Activity Guidelines Advisory Committee Scientific Report adds to the lengthening list of health benefits of regular physical activity. Less well recognized has been a third area of influence beyond exercise science and epidemiologic science. In 1974, the Canadian government published a report titled A New Perspective on the Health of Canadians. 4 More commonly referred to as “The Lalonde Report,” after the Canadian Minister of Health and Welfare, the report made a clear distinction between the clinical health care system and the arena of disease prevention and health promotion. Within disease prevention and health promotion, it called attention to the importance of “lifestyle,” including physical activity. The Canadian report was followed by the U.S. report, Healthy People: The Surgeon General’s Report on Health Promotion and Disease Prevention, which had a similar message.5 These documents called attention to the important impact of lifestyle behaviors on the risk of disease, an observation that is now well accepted. Also widely recognized is the fact that individual behaviors, including physical activity behaviors, are determined not solely by individual choice but by social and cultural factors as well as environmental impediments or opportunities. Thus, while exercise science and epidemiologic science remain central to the field of physical activity and public health, the field now includes an array of other scientific disciplines. Behavioral science, clinical science, recreation science, transportation science, city planning, political science, and other disciplines are now recognized to be essential for the proper study and practice of physical activity and public health. (i.e.,