Objective: To evaluate the accuracy of two-dimensional and three-dimensional (3d) color Doppler echocardiography in cardiac stroke volume quantification.

Increases Cardiac Output, stronger heart contractions pump more blood, increased stroke volume, thickens left ventricle wall (more muscular), decreases hearts' oxygen requirements.

Endurance training results in an increase in oxygen consumption and delivery. Stroke volume and cardiac output increase. Peripheral vascular resistance decreases.