If stroke volume remains 0.07 L and heart rate increases from 60 bpm to 120 bpm during exercise, what is the approximate change in cardiac output?

If stroke volume remains 0.07 L and heart rate increases from 60 bpm to 120 bpm during exercise, what is the approximate change in cardiac output?

• A. 4.2 to 7.0 L/min
• B. 4.2 to 8.4 L/min
• C. 6.0 to 9.0 L/min
• D. 3.5 to 6.0 L/min

Answer: (B)

Cardiac output is the product of stroke volume and heart rate. With the stroke volume fixed at 0.07 L, resting CO is 0.07 × 60 = 4.2 L/min. At 120 bpm, CO becomes 0.07 × 120 = 8.4 L/min. So CO increases by about 4.2 L/min, moving from roughly 4.2 to 8.4 L/min during exercise. The option that lists a range from 4.2 to 8.4 L/min matches this calculation, making it the best choice.

Cardiac output is the product of stroke volume and heart rate. With the stroke volume fixed at 0.07 L, resting CO is 0.07 × 60 = 4.2 L/min. At 120 bpm, CO becomes 0.07 × 120 = 8.4 L/min. So CO increases by about 4.2 L/min, moving from roughly 4.2 to 8.4 L/min during exercise. The option that lists a range from 4.2 to 8.4 L/min matches this calculation, making it the best choice.