How does cardiac output change during exercise?

• A. It decreases to maintain efficiency
• B. It remains constant regardless of intensity
• C. It increases to 20-30L/min
• D. It stabilizes at 10L/min

Answer: (C)

During exercise, cardiac output significantly increases to meet the higher metabolic demands of the body. This rise in cardiac output is typically achieved through an increase in both heart rate and stroke volume. During intense physical activity, it can increase to levels around 20-30 liters per minute, depending on the individual's fitness level, the intensity of the exercise, and other physiological factors. This increased blood flow ensures that more oxygen is delivered to active muscles while facilitating the removal of carbon dioxide and other metabolic wastes.

The other potential choices reflect misunderstandings about the body's cardiovascular response to exercise. For instance, the idea that cardiac output decreases is inaccurate, as the body actually requires more oxygen and nutrients during physical activity. A constant cardiac output regardless of intensity does not align with the physiological changes that occur; the body's demand for blood flow increases with exercise intensity. Lastly, stabilizing at a specific level like 10 L/min does not capture the dynamic nature of cardiac output during varying intensities of exercise. Thus, the correct response illustrates the adaptive mechanism of the heart during physical strain.