In the case of long term exercise programmes, improvements in the mental health of ‘normal’ individuals are either modest in magnitude or do not occur, whereas the changes for those with elevated anxiety or depression are more pronounced. Evidence from studies involving clinical samples indicates that the psychological benefits associated with exercise are comparable to gains found with standard forms of psychotherapy. Hence, for healthy individuals the principal psychological benefit of exercise may be that of prevention, whereas in those suffering from mild to moderate emotional illness exercise may function as a means of treatment