Aim of this study was to evaluate left ventricular function during exercise, in 10 male elite runners and in 10 sedentary males. End-diastolic(EDV) and end-systolic volume (ESV), left ventricular ejection fraction (EF), early peak transmitral flow velocity (peak E), time-velocity integral of mitral inflow (m-TVI); mitral cross sectional area (m-CSA); mitral stroke volume (SV), and cardiac output (CO) were measured by echo-Doppler. We simultaneously analyzed: ˙VO2max by spirometric method, mean arterial blood pressure (MAP) by sphygmomanometer, and heart rate (HR) by ECG. The parameters were measured under basal conditions (level 1), at 50% of maximal aerobic capacity (level 2), at peak of exercise (level 3) and during recovery. Ejection fraction in athletes increased significantly at peak of exercise through Frank-Starling mechanism. Stroke volume and cardiac output increased significantly in athletes at peak of exercise. Left ventricular diastolic function was superior in athletes versus controls: in fact, higher peak E in athletes enhanced early diastolic ventricular filling. Therefore, the athletes showed complex cardiovascular adjustments induced by training, which allowed an higher peak working power, a greater cardiac output, and˙VO2max when compared with an untrained control population.