What is Cardiac Output?
Cardiac output (CO) is the amount of blood your heart pumps each minute. It's calculated as:
* Cardiac Output (CO) = Stroke Volume (SV) x Heart Rate (HR)
* Stroke Volume (SV): The amount of blood pumped out of the heart with each beat.
* Heart Rate (HR): The number of times your heart beats per minute.
How Aerobic Exercise Increases Cardiac Output
Aerobic exercise increases both stroke volume and heart rate, thus increasing cardiac output:
1. Increased Heart Rate (HR): During aerobic exercise, your muscles need more oxygen. To meet this demand, your heart beats faster (increasing HR) to deliver more oxygen-rich blood.
2. Increased Stroke Volume (SV):
* Increased Venous Return: Exercise increases blood flow back to the heart (venous return). This is due to muscle contractions squeezing veins and the action of breathing. More blood filling the heart leads to a greater stretch of the heart muscle.
* Frank-Starling Mechanism: The heart contracts more forcefully when stretched, ejecting more blood (increased SV).
* Increased Contractility: Regular aerobic exercise strengthens the heart muscle, making it more efficient at contracting and pumping blood.
* Reduced Afterload: During exercise, blood vessels in working muscles dilate, reducing resistance (afterload) that the heart has to pump against.
Long-Term Adaptations
Regular aerobic exercise leads to beneficial long-term adaptations in the cardiovascular system:
* Increased Heart Size: The heart muscle gets stronger and slightly larger (cardiac hypertrophy). This is a healthy adaptation to the demands of endurance exercise.
* Increased Blood Volume: The body increases its blood volume, leading to a higher stroke volume.
* Lower Resting Heart Rate: Over time, the heart becomes more efficient. A trained individual can pump the same amount of blood with fewer beats.
* Improved Blood Vessel Function: Blood vessels become more elastic and efficient at delivering blood to working muscles.
In summary: Aerobic exercise increases cardiac output by increasing both heart rate and stroke volume. Regular exercise leads to beneficial long-term adaptations that improve cardiovascular health and fitness.