Preload (Frank-Starling Relationship) Definition of preload:Amount of stretch imposed on the left ventricular muscle when the left ventricular chamber fills with blood during diastole Preload is defined as the amount of ventricular filling during diastole. Increasing Preload (ventricular muscle stretch)increases (a)the amount of pressure the ventricle can produce,and (b)the velocity of shortening during systole. Preload