What happens to stroke volume as a result of increased end-diastolic volume (EDV) according to the Frank-Starling mechanism?

The Frank-Starling mechanism describes how the heart's stroke volume is influenced by the volume of blood filling the heart's chambers, specifically the end-diastolic volume (EDV). According to this principle, as EDV increases, the myocardium (heart muscle) is stretched. This stretching leads to a more optimal alignment of the muscle fibers, which enhances their contractile force during systole (the contraction phase of the heartbeat).

When there is an increased volume of blood in the ventricles at the end of diastole, it causes a greater preload, which is the initial stretching of the cardiac muscle before contraction. This increased preload allows the heart to pump more vigorously, leading to an increase in stroke volume—the amount of blood ejected from the heart with each beat. Thus, as EDV rises, the stroke volume correspondingly increases, which is a fundamental aspect of how the heart responds to varying levels of blood return during the cardiac cycle.

This mechanism is critical for maintaining adequate cardiac output, especially during physical activity when the demand for oxygenated blood increases. Therefore, understanding this relationship helps exercise physiologists predict how the heart will adapt to different levels of exercise and overall cardiovascular function.