During exercise, the cardiovascular system must supply muscles with large amounts of oxygen and fuel and get rid of a lot of wastes. How do the cardiovascular systems of athletes respond to prolonged exercise? Researchers have also observed that athletes and non-athletes have the same mean resting cardiac output, even though athletes have a far lower resting heart rate. How is this possible?

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1. 1. During prolonged exercise, the cardiovascular system of athletes responds by increasing the heart rate and stroke volume. This is to ensure that more blood, and therefore more oxygen and nutrients, are delivered to the working muscles. The blood vessels in the muscles dilate to allow for increased blood flow, while those in non-essential systems constrict. The body also increases its breathing rate to get rid of carbon dioxide, a waste product of respiration, more quickly.
2. 2. The cardiovascular system also adapts to prolonged exercise in the long term. Regular exercise leads to an increase in the size of the heart, particularly the left ventricle. This allows the heart to pump more blood with each beat, increasing the stroke volume. The number of red blood cells and capillaries also increase, improving the body's ability to transport and use oxygen.
3. 3. Despite having a lower resting heart rate, athletes can have the same mean resting cardiac output as non-athletes. This is because cardiac output is the product of heart rate and stroke volume. So, even though athletes have a lower heart rate, they have a larger stroke volume due to the increased size of their heart. This means they can pump the same amount of blood, or even more, with fewer beats.
4. 4. This is beneficial as a lower heart rate can reduce the strain on the heart. The heart of an athlete is more efficient, needing fewer beats to pump the same amount of blood. This is one of the reasons why regular exercise is good for cardiovascular health.
5. 5. In conclusion, the cardiovascular system of athletes adapts to prolonged exercise by increasing its capacity to deliver oxygen and nutrients to the muscles and remove waste products. Despite a lower resting heart rate, athletes can maintain the same cardiac output as non-athletes due to an increased stroke volume.