Few studies have examined the effect of prolonged exercise training on left ventricular diastolic function in previously sedentary subjects. We performed M-mode, 2-D, and Doppler echocardiography on 16 previously sedentary men before and after 1 yr of exercise training. Six men served as controls. Exercise subjects participated in four 1-h supervised sessions weekly at 60-80% of their measured maximal heart rate. Maximal oxygen uptake, maximal exercise cardiac output, and resting left ventricular systolic and diastolic function were determined before and after training. Maximal oxygen uptake and peak cardiac output increased 27.3% and 8.5% in the trainers (P < 0.001 for both) and 1.3% and 1.0% in the controls. Left ventricular diastolic and systolic dimensions changed slightly in both groups. Maximal early inflow velocity decreased in both trainers (-9.9 +/- 14.0 cm.s-1, mean +/- SD, P < or = 0.01) and controls (-7.2 +/- 10.2 cm.s-1). Maximal atrial inflow velocity decreased (-7.8 +/- 10.9 cm.s-1, P < or = 0.01) only in the trainers possibly because of a reduction in resting heart rate (-6 +/- 11 beats.m-1, P < or = 0.05). Acceleration and deceleration times were unchanged in both groups. These results demonstrate that substantial increases in exercise performance and exercise cardiac output can occur without detectable changes in resting cardiac dimensions or left ventricular systolic and diastolic function.