Fabian and Jill write in their report that the heart beats faster after exercising. This makes the blood flow faster than when at rest.
Because the red blood cells carry oxygen so when you excercise you need oxygen
to increase your athletic capabilities, because when excerscising you use more energy so the heart pumps faster
blood carries oxygen and in order for your organs to work, they need oxygen. you move your muscles a lot which causes the blood to flow faster in order to get more oxygen
Because during exercise organs need to work harder, so they need more respiration than usual, respiration requires oxygen which is transported by the blood, thus the heart has to pump more blood