How is cardiac reserve calculated?

How is cardiac reserve calculated?

• A. CO during exercise minus CO during rest.
• B. CO during rest minus CO during exercise.
• C. Stroke volume at rest times heart rate.
• D. Heart rate during exercise minus heart rate at rest.

Answer: (A)

Cardiac reserve shows how much the heart can increase blood flow above resting needs. It is the difference between the maximum cardiac output achieved during exercise and the resting cardiac output. Since cardiac output equals stroke volume times heart rate, the reserve specifically reflects the extra amount of blood the heart can pump beyond resting output, not just resting values or changes in heart rate alone. Therefore, the best way to express this reserve is maximal cardiac output during exercise minus resting cardiac output. The other formulations don’t capture this concept: resting CO is not the reserve, heart-rate differences alone don’t account for how much blood is pumped per minute, and subtracting in the opposite order would yield a negative or mismatched quantity.

Cardiac reserve shows how much the heart can increase blood flow above resting needs. It is the difference between the maximum cardiac output achieved during exercise and the resting cardiac output. Since cardiac output equals stroke volume times heart rate, the reserve specifically reflects the extra amount of blood the heart can pump beyond resting output, not just resting values or changes in heart rate alone. Therefore, the best way to express this reserve is maximal cardiac output during exercise minus resting cardiac output. The other formulations don’t capture this concept: resting CO is not the reserve, heart-rate differences alone don’t account for how much blood is pumped per minute, and subtracting in the opposite order would yield a negative or mismatched quantity.