Physical Activity in Capsule
Exercise has been equated with health since antiquity and Hippocrates. Regular and peak muscular activity during hunter-gatherer evolution is thought to have provided a metabolic legacy requiring exercise for the health of modern humans. Since Ramazzini (and Charles Dickens) in the early Industrial Age, sedentary occupations have been found unhealthy.
Formal epidemiological study of physical activity and chronic disease risk got underway with Jeremy Morris’s idea that change in activity levels was consonant with wartime and post-war trends in coronary deaths. He first tested this hypothesis by comparison of active and less active civil occupations in the UK, and his work was soon followed by Ralph Paffenbarger’s studies of California longshoremen and college alumni and Henry Taylor’s comparison of U.S. rail clerks and switchmen.
Questionnaires on habitual activity used for years in epidemiological studies have left, nevertheless, residual questions about the health and preventive role of the frequency, intensity, and duration of exercise.
Robert Bruce, Marcel Kornitzer, Henry Taylor, and Steven Blair advanced the concept and methodology of physical fitness as a relevant and reliable measure and predictor of cardiovascular risk. Blair extended this understanding with epidemiological studies of work capacity in prediction of CVD risk in women as well as risk of death from cancer and all causes.
Pilot trials by Henry Taylor and Richard Remington, and by John Naughton, demonstrated the infeasibility of carrying out trials of the independent role of physical activity in the primary prevention of CVD. This was concluded in part because the adoption of regular exercise had a major and favorable impact on other behaviors and biomarkers of CVD risk, but also because activity trials were costly in injuries and money. Statistical summaries of clinical trials reviewed by Arthur Leon suggest, however, that the exercise component of cardiac rehabilitation programs probably contributes to the secondary prevention of CVD.
Observational studies and small-scale experiments established clearly the favorable influence of exercise on blood lipoprotein patterns, hemostasis, blood pressure levels, obesity, smoking habit, mental health, and health attitudes. These effects on CVD risk characteristics provided sufficient evidence for medical and public health recommendations of exercise programs and to encourage environmental engineering of greater physical activity into the lifestyle of industrial societies. (Henry Blackburn)