The Frank-Starling law of the heart states that:

The Frank-Starling law of the heart describes the relationship between the length of cardiac muscle fibers and the force of contraction. This principle states that the greater the initial stretch of the cardiac muscle fibers (which is influenced by the volume of blood filling the heart, or preload), the greater the force of contraction during systole. This mechanism is crucial for maintaining an efficient pumping function, as it allows the heart to adjust its output based on the volume of blood returning to it.

When the heart is filled with more blood during diastole, the fibers are stretched, leading to a more forceful contraction when the heart beats. This relationship helps to ensure that the volume of blood ejected from the heart matches the volume returning to it, promoting a balanced flow through the circulatory system.

In contrast, assertions regarding arterial pressure's effect on contraction strength, the heart's pumping rate during exercise, and conditions resulting from low stroke volume do not specifically align with the core tenet established by the Frank-Starling mechanism. The law primarily emphasizes preload and fiber length, making the connection inherent to cardiac performance.