Physical Activity and Cardiovascular Health

Abstract

In 1953, Morris et al1,2 published the findings from a study showing that bus conductors in London, who spent their working hours walking the length of the buses as well as climbing up and down the stairs of the English double-decker buses to collect fares, experienced half the coronary heart disease (CHD) mortality rates of their driver counterparts, who spent their day sitting behind the wheel. Investigators hypothesized that it was the physical activity of work that protected the conductors from developing CHD, at the same time realizing that other factors may also play a role because the conductors were smaller in size, as evidenced by their smaller uniform sizes. Thus was born the field of “physical activity epidemiology”: formal epidemiological investigations into the associations of physical activity with many health outcomes.4 Since the initial observations of Morris et al, many other studies have been conducted, yielding similar results: Active people have lower rates of CHD and cardiovascular disease (CVD) than inactive ones.5–7 These findings have been supported by plausible biological mechanisms, which are detailed in other articles in this review series. The collective body of evidence led the American Heart Association in 1992 to recognize physical inactivity as a risk factor for CHD and CVD8 and led the Surgeon General in 1996 to conclude that “regular physical activity or cardiorespiratory fitness decreases the risk of CVD … and CHD.”9 The basis for these conclusions was derived primarily from studies in men and in white populations; for example, in a 1990 meta-analysis of physical activity in the prevention of CHD10 that included 33 studies, women were subjects in 5 studies, and racial/ethnic minorities were the focus of 2 studies. In 2008, the federal government issued its first-ever physical activity guidelines for Americans11 based …