What Is Cardiac Output

If we were to measure the amount of blood pumped out of our heart during one heartbeat, whether it be from the left or right ventricle, we would know our stroke volume. Then, if we multiply the stroke volume by our heart rate (heartbeats per minute) we would know the cardiac output:

cardiac output = stroke volume (milliliters) x heart rate (beats/min).

Cardiac output is the volume of blood pumped out of the heart, either to the lungs or toward body tissue, in 1 minute. It should not matter which of the two destinations we consider, as they occur simultaneously and will have a similar stroke volume of about 5 to 6 liters (or quarts) per minute.

During exercise both heart rate and stroke volume increase, which consequently increases cardiac output. For some of us, cardiac output may increase as much as five to six times during heavy exercise. This allows for more oxygen-rich blood to be delivered to working skeletal muscle.

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