Data on the dose-response gradient for the relation of physical activity or physical fitness to health and function are reviewed, refuting the idea that physical activity programs are either exercise for health or for fitness and suggesting that the key factor is the total energy expenditure of the activity. (SM)

Examines recent evidence on the relations between physical activity, physical fitness, and health, noting the possible causal nature of the associations. The article evaluates the public health burden of sedentary lifestyles in the United States and provides suggestions for increasing participation in physical activity. (SM)