Lack of exercise is a major public health problem in the United Kingdom, contributing to the incidence of chronic illness. Adults are recommended to engage in at least 30 minutes of moderate or vigorous activity daily and children at least an hour. However, surveys have shown a trend towards declining fitness, on the basis of which it has been predicted that more than half the population will be clinically obese by 2050.

Health experts have proposed urgent action to remedy this situation, and the government now aims to get far more of the inactive population walking or gardening regularly or, preferably, taking up more vigorous physical activity, such as sports, aerobics, or cycling (especially as a means of travel). Although most people are aware of the benefits—a lessened risk of coronary heart disease, obesity, diabetes, hypertension, and some cancers—routine physical activity features in few people’s everyday lives. Only a small proportion of adults are motivated to undertake it throughout the year, and the school curriculum allocates insufficient time for it. …