Physical activity in work and leisure time in relation to cardiovascular diseases.

The epidemic increase of coronary heart disease (CHD) was contemporary with a decrease of human energy expenditure. The hypothesis emerged that physical activity would protect against CHD. This hypothesis has been put on a test in several epidemiological studies of various designs. Physical activity in occupation has shown varying associations with CHD. In the Seven Countries Study, sedentary men experienced a higher ten-year incidence of CHD than the more active groups in only three of the countries included. By using the results of the Finnish East-West Study, which was carried out as a five-year continuation of the Seven Countries Study, some methodological requirements for epidemiological studies, and their influence on the results, were examined. While marked differences in the incidence of and mortality from CHD have been observed between various occupations, they cannot be attributed solely to physical activity. Vigorous self-selected physical activity during leisure-time, on the other hand, has predicted a protection from CHD in some occupationally or culturally homogeneous groups. This protection has not been ascribable to the "classical" risk factors. The discrepant results on occupational versus leisure-time physical activity as protection against CHD are a challenge for further studies. The physical working capacity is not necessarily increased by high heart rates in industrial work. New methods of classifying the character of occupational work and of quantifying physical activity habits are available. Muscularity has shown positive correlations with the risk factors blood pressure and heart rate at rest. Potent psychological predictors of CHD have emerged from recent studies. Their associations with occupational work and leisure-time habits deserve to be mapped out.