least one significant way. To explain, whereas the latter field is concerned mainly with
the study of physical activity, exercise behaviour and/or physical fitness as dependent
variables (typically indicated by measures such as VO 2 max), health psychology has
traditionally explored these processes as independent variables (Rejeski and Thompson,
1993).
Exploring the benefits and hazards of physical activityThe idea that physical exercise confers a number of health benefits on people dates back
at least as far as BC fourth or fifth centuries (Buckworth and Dishman, 2002). Thus the
Greek physicians Herodicus (c. 480 BC), Hippocrates (c. 460–377 BC) and Galen (c.
199–129 BC) advocated the importance of exercise in treating various forms of illness.
This “gymnastic medicine” approach continues to the present day—but with one
important difference. Specifically, contemporary physicians do not just recommend
exercise as a form of treatment for illness but as a preventive measure in an effort to
counteract the health risks posed by people’s increasingly sedentary lifestyles. By the
way, a person is usually deemed as being “sedentary” if s/he engages in little or no
physical activity. The health risks associated with such a lifestyle include coronary artery
disease, colon cancer, depression, hypertension, osteoporosis and strokes (President’s
Council on Physical Fitness and Sport, 2002). Indeed, so worried are many health
scientists about these problems that the insidious effects of an inactive lifestyle have been
called “the silent enemy” or “sedentary death syndrome” (ibid.). The prevalence of this
problem can be gauged from certain epidemiological trends. For example, Caspersen and
Merritt (1995) discovered that less than 10 per cent of a sample of almost 35,000 adults
in the US exercised enough to obtain significant fitness benefits from their efforts. More
generally, the problem of physical inactivity has been reported to be more common
among women than men, among older than younger adults and among less affluent than
more affluent people in most developed countries (United States Department of Health
and Human Services, 1996). As a consequence of such data, a picture is emerging of a
lifestyle in the twenty-first century whereby people have to plan to exercise simply
because they no longer expend enough physical energy to achieve health benefits through
manual work or even as result of walking or cycling to work on a daily basis. But as we
shall see later in this chapter, planning or having an intention to exercise is no guarantee
of actually doing it. In addition, another problem that we shall encounter concerns the
fact that exercise prescription should not be undertaken naïvely. To explain, Sime (2002)
warned that, for this practice to be effective, the physician in question must set realistic
goals and provide regular supervision or guidance to the patient. Otherwise, this patient
may not achieve his or her exercise targets and hence end up feeling more depressed and
guilty than beforehand.
Before reviewing the research literature on the effects of regular physical activity, it is
important to point out that there have been far more studies on the positive effects (i.e.,
the benefits) of exercise on physical and psychological processes than on its negative
consequences—a trend which I hope to rectify in this chapter. Let us now summarise the
principal research findings on the benefits of exercise for both physical and mental health
Does a healthy body always lead to a healthy mind? Exploring exercise psychology 219