EDV is often referred as “preload” and it influences stroke volume in the following way. Two physiologists, Frank and starling, demonstrated that the strength of ventricular contraction increased with an enlargement of EDV (i.e., stretch of the ventricles). This relationship has become known as the Frank-Starling law of the heart. The increase in EDV results in a lengthening of cardiac fibers, which improves the force of contraction in a manner similar to that seen in skeletal muscle (discussed in Chap. 8). The mechanism to explain the influence of fiber length on cardiac contractility is that an increase in the length of cardiac fiber increases the number of myosin cross bridge interactions with actin, resulting in increased force production. A rise in cardiac contractility result in an increase in the amount of blood pumped per boat; the relationship between EDV volume and stroke volume is illustrated in Fig. 9.15