ABSTRACT
Whereas improvements in housing, sanitation, hygiene and medicine have largely eliminated infectious diseases in industrialized societies the incidence of coronary heart disease, obesity and cancer have increased. That exercise might also be important for good mental health, an idea originating in Greek philosophy, was ignored until recently by psychologists. In psychology, exercise was first investigated as a treatment of depression, a possible cheap alternative to drugs or psychotherapy that was without side effects. Stephens looked at physical activity and psychological functioning in a large-scale survey of the general population. Such a non-experimental approach can only identify associations but has the advantage of being free from some of the problems of experimental studies. Goldwater and Collis randomly assigned college students either to a cardiovascular conditioning group or to a control group that was designed to give the appearances of a physical training programme while minimizing the cardiovascular benefits.
