Introduction

It is a fundamental biological principle that man is adaptable. Regular physical activity provokes adaptations, many of which are beneficial, but the amount and intensity of exercise needed to confer benefit remains uncertain. The purpose of this chapter is to examine the potential of modest amounts of physical activity to promote health by 1) maintaining or increasing functional capacity, 2) influencing energy balance, 3) decreasing the likelihood of some diseases and 4) contributing to the management of patients with existing disease.

Functional capacity

The single most important aspect of functional capacity is, arguably, the maximal oxygen uptake (VO2max). This important quantity imposes a limit on the intensity of whole body dynamic exercise which can be sustained. Other aspects such as muscle strength and mobility become increasingly important in old age as the decline in capacities means that thresholds which limit daily activities are approached.

Classic studies in Scandinavia at the end of the 1960s showed that endurance training increases, and enforced inactivity decreases, VO2max (Saltin et al., 1968). The relative improvement with training depends on two factors: 1) the initial physical activity level, the more sedentary the individual the greater the scope for improvement, and 2) heredity. Exceptionally, training has been reported to increase VO2max by as much as 44% (Hickson, Bomze & Holloszy, 1977) but increases in the range 10–20% are more usual.