Epidemiology of physical activity, physical fitness and coronary heart disease.

Observational population-based studies have consistently shown an inverse dose-response gradient between physical activity or fitness and coronary heart disease. This relationship is more firmly established in men. Existing studies suggest that the physical activity gradient, and perhaps the fitness gradient, is produced by a combination of varying levels of both the intensity and the amount of habitual physical activity. It is not at present possible to definitively describe the dose-response association between the intensity of physical activity and the risk of coronary heart disease. An answer to this important question awaits further research.