Physical inactivity: An easily modifiable risk factor

The classic modifiable risk factors for the developmentof coronary heart disease (CHD), derived from theFramingham Heart Study and other long-term epide-miological studies, are increased blood pressure, elevated plasma cholesterol, and cigarette smoking. However, evi-dence has been accumulating for many years suggesting that physical inactivity or the lack of exercise is also a potent force in this field. The pioneering studies by Morris et al from England1,2 and Paffenbarger et al from the United States3,4 were the first to strongly suggest that increased physical activity, either at work or during leisure time, was a deterrent to the development of CHD. In 1953, Morris et al1 studied transportation workers in London, England, and found that sedentary bus drivers had a greater incidence of CHD than the more active conductors on double-decker buses. Later, this group showed that vigorous leisure time activity also de-creased the incidence of CHD.2 In 1970, Paffenbarger et al