Left ventricular (LV) performance increases during acute exercise, but the mechanisms for this increase are not known. To determine the feasibility of studying echocardiographic indexes of performance and its determinants (preload, afterload, and contractility) during exercise, and to examine changes in these indexes, we tested 24 normal male subjects (aged 21 +/- 5 years) by echocardiography--at rest; at 25%, 50%, 75%, and 100% maximal oxygen consumption; and immediately, 3 minutes, and 5 minutes after cycle ergometry. The LV performance (shortening fraction), preload (LV end-diastolic dimension), afterload (wall stress), contractility, heart rate, and peak systolic blood pressure were measured. Data could be obtained during 98% of the exercise studies. The LV performance, heart rate, blood pressure, and contractility increased significantly with increasing exercise, reaching peak levels at maximal exercise, and decreased toward resting levels in the post-exercise period. The LV afterload and preload decreased significantly with increasing exercise intensity, reaching nadir levels at maximal exercise, and increased toward resting levels in the post-exercise period. We conclude that echocardiographic measurement of LV performance and its determinants is feasible during exercise. Performance of the LV increases with increasing exercise intensity because of an associated increase in contractility and decrease in afterload. These data will serve as a basis for comparison with those from other patient populations.