During acute aerobic exercise, what happens to cardiac output?

During acute aerobic exercise, what happens to cardiac output?

• A. It increases
• B. It decreases
• C. It remains constant
• D. It becomes irregular

Answer: (A)

When you start aerobic exercise, your muscles demand more oxygen and need to remove more CO2 and other wastes. To meet that demand, the heart pumps more blood each minute. This happens because heart rate rises quickly due to sympathetic drive and contractility increases, and venous return also improves from the muscle and respiratory pumps, boosting how much blood the heart can pump with each beat (stroke volume). The combination pushes cardiac output—the product of heart rate and stroke volume—well above rest. Resting cardiac output is about 5 L/min, and during vigorous activity it commonly reaches roughly 15–25 L/min, with individual values depending on fitness. Stroke volume tends to rise early in exercise and may level off at higher intensities, but the overall cardiac output still increases because heart rate continues to climb.

When you start aerobic exercise, your muscles demand more oxygen and need to remove more CO2 and other wastes. To meet that demand, the heart pumps more blood each minute. This happens because heart rate rises quickly due to sympathetic drive and contractility increases, and venous return also improves from the muscle and respiratory pumps, boosting how much blood the heart can pump with each beat (stroke volume). The combination pushes cardiac output—the product of heart rate and stroke volume—well above rest. Resting cardiac output is about 5 L/min, and during vigorous activity it commonly reaches roughly 15–25 L/min, with individual values depending on fitness. Stroke volume tends to rise early in exercise and may level off at higher intensities, but the overall cardiac output still increases because heart rate continues to climb.