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Physical activity and health: current issues and research needs.

A substantial body of evidence now demonstrates the burden of ill-health attributable to sedentary living. This is most compelling for coronary heart disease (CHD) and, combined with the high prevalence of inactivity, 1 provides the rationale for Professor Morris’s claim that exercise is ‘today’s best buy in public health’. 2 Besides a reduced risk of CHD, evidence is secure for many other health gains from physical activity; these include a reduced risk of stroke, 3,4 type II diabetes, 5,6 colon cancer, 7,8 and hip fracture. 9,10 There is evidence enough to justify the further development of public health policies to promote physical activity. The difficulty is with the specifics of what to promote and prescribe. This paper is concerned with future contributions by research to an evidence-based rationale for exercise recommendations— both to the public at large and to individuals. It is clear that physically active people have a lower disease risk than sedentary individuals but the components of activity which determine particular health gains are poorly understood. Thus the ‘doseresponse’ relationships for physical activity are the subject of current research interest. Intuitively, these will not be the same for different health outcomes and this is one reason why further study of the associated mechanisms is important. Understanding the underlying mechanisms will clarify the relative importance of intensity, frequency, duration and mode of exercise for specified health gains. It will also help us to distinguish the effects of exercise per se from those of co-existing behaviours and to identify stages of life during which levels of particular types of activity are critical for given health outcomes. This paper presents a personal view of research needs.