What is the main contributor to increased cardiac output during aerobic exercise?

During aerobic exercise, the primary contributor to increased cardiac output is heart rate. Cardiac output is defined as the product of stroke volume (the amount of blood pumped by the heart per beat) and heart rate (the number of beats per minute). While both stroke volume and heart rate play important roles in determining cardiac output, during periods of intense aerobic exercise, heart rate typically rises significantly.

When an individual engages in aerobic activities, such as running or cycling, muscular demand for oxygen increases. To meet this demand, the body responds by increasing the heart rate, which, in turn, elevates cardiac output to help deliver more oxygenated blood to the working muscles. This increase in heart rate is essential because stroke volume, although it also increases during exercise, has a limit based on the capacity of the heart to fill and pump effectively. Thus, the rise in heart rate becomes the more prominent factor in enhancing cardiac output as exercise intensity rises.

In contrast, blood volume and peripheral resistance have secondary roles in influencing cardiac output during exercise. Blood volume contributes to stroke volume and overall circulatory efficiency but does not increase to the same extent during a single bout of exercise in comparison to heart rate. Peripheral resistance typically decreases during exercise due to vasodilation in the working