What is the optimal type of physical activity to enhance health?

This review examines the potential of active daily living as a means of gaining the cardiovascular and health rewards previously sought through vigorous aerobic fitness programmes. Cross-sectional studies of occupational and leisure activity show encouraging associations between such activity and good health; in workers, the gross intensity of effort needed for health benefits has seemed to be 20 kJ/min. There has been less unanimity on the threshold intensity needed in leisure activities, but various recent "position statements" have decreased the recommendation to 50% of an individual's maximal oxygen intake, sustained for one hour three to five times per week. Life-style activities such as walking seem likely to reach this intensity in older individuals, but are unlikely to do so in young adults. A growing number of controlled longitudinal studies of walking programmes have demonstrated gains in aerobic fitness, modest reductions in blood pressure, improvements in lipid profile, increased bone density, and enhanced mood state, with less consistent reductions of body fat. However, gains have been greatest in the elderly, sedentary, and obese populations. The main component of active living, fast walking, seems likely to enhance health in such populations, but it is unlikely to be effective in young adults who are in good initial health.