The heart and physical exercise.

Cardiac hypertrophy and extreme bradycardia occur in the highly trained endurance athlete, but not in those with lesser degrees of training. Several longevity studies in athletes fail to show any beneficial effects of athletic training confined to the college years. The invaluable British studies relating physical activity of various occupations to coronary disease show that while exercise does not prevent coronary atherosclerosis, it may reduce the incidence of large and fatal infarctions and of complete coronary obstructions. Various American studies have not confirmed this beneficial effect of exercise. To be of any value in the prevention of coronary disease, exercise must be continued on into middle age. The sedentary life characteristic of western civilization is probably not a major factor in the high incidence of coronary disease.