To evaluate possible differences in the cardiac effects of different types of running training, 22 competing male runners-10 sprinters and 12 endurance runners-were studied with a physical examination, electrocardiography, chest X-ray film and echocardiography. Thirteen sedentary men served as control subjects. There were no differences between the athletic groups in physical findings. However, left ventricular hypertrophy in the electrocardiogram was more apparent in the endurance runners (P <0.05), whose relative heart size on chest X-ray examination was also greater than in the sprinters (P < 0.02). On echocardiography the left ventricular end-diastolic volume was equally greater than normal in both groups of athletes (P < 0.005), but in the endurance runners the percent change of the minor axis diameter in systole was greater than in the sprinters or control subjects (P < 0.02). Values for left ventricular wall thickness and mass were greater than normal in both groups of athletes but were higher in the endurance runners than in the sprinters (P < 0.001). The left atrial diameter was apparently greater in the endurance runners than in the sprinters or control subjects (P < 0.001), whereas that of the sprinters did not differ from normal. Thus, intensive sprinter training seems to dilate the left ventricle but causes less increase in wall thickness and mass than training for endurance running and no change in left ventricular function or left atrial size. Endurance running causes left ventricular dilatation equal to that of sprinter training, greater wall hypertrophy and improved systolic emptying of the left ventricle, and it also dilates the left atrium perhaps because of decreased left ventricular compliance. © 1979.
