ABSTRACT
The first systematic investigation on the effect of regular physical exercise as a protective factor against coronary artery disease was published more than 60 years ago (1). It showed a negative correlation between the amount of physical work performed and the incidence of myocardial infarction in London bus drivers. Since then this finding has been confirmed by a great number of studies conducted on thousands of patients. More than 3000 healthy, nondiabetic volunteers participated in the U.S. railroad study, which established a linear, inverse relation between the amount of energy spent during leisure time physical activity and the risk to develop coronary artery disease (2). The lowest risk was calculated for the most active persons who consumed more than 3000 kcal/week, which requires roughly 6 hours of training at medium intensity. The optimal level of intensity has been a matter of considerable controversy and contradictory recommendations. In the U.S. railroad study 100 kcal/week spent in the form of intensive exercise weighed as much as 1000 kcal/week of moderate exercise with regard to its protective effect, i.e., intensive physical exercise was 10 times more effective than moderate exercise, whereas walking was associated with beneficial effects in other trials (3, 4).
