You also need to keep your body fit. you can do this by exercising and staying active. One form of exercising is aerobic exercising. Aerobic activity requires your body to use a lot of oxygen. Running or playing soccer makes your breathe harder, which means you are talking in more oxygen. Aerobic exercise increases your heart rats as well. Because they use oxygen, most aerobic activities can be done for extended periods of time. When your body is using a lot of oxygen, your muscles are able to work foe extended periods because they can use the oxygen to get energy. Aerobic exercise is good for strengthening your heart and lungs.