The Guidelines for Exercise Training initially developed by the American College of Sports Medicine in 1978 and updated in 1990 have served as the foundation for most recommendations regarding physical activity program design for the general public. These guidelines have proven to be very useful by providing a specific regimen for enhancing aerobic capacity and body composition. As data supporting a causal link between increased activity or fitness and health status have evolved, questions have been raised about potential limitations of these guidelines for promoting physical activity to increase the health status of sedentary adults. The major issues have involved the necessity to achieve the values for each of the program parameters, especially the intensity, duration, and frequency of exercise, in order to improve health status. To address these issues, a paradigm shift from exercise training to promote physical fitness to physical activity to promote health has been introduced. This new paradigm is based on the results from numerous studies indicating that a generally active life style is associated with better health and performance and greater longevity and a certain set of assumptions, yet to be fully tested. The following article provides some background leading to the development of the ACSM guidelines and presents some of those issues we understand and some we do not regarding the characteristics of daily physical activity or exercise training that are likely to improve the physical health status of sedentary persons.