[excerpt] Most of you have heard the word "aerobics". Though often used when talking about fitness, it is often misunderstood. The word "aerobic" means "with oxygen" - and oxygen is the key to your body's energy. Here is how it works:
Energy comes into the body in the form of food. The body then stores this energy in a chemical form until it is needed. Much of the energy is stored in your body's fat cells.
ENERGY REQUIRES OXYGEN
However, just because this energy source is present in the body doesn't mean it can be used automatically. This is because oxygen is needed to release the energy. The more energy your body uses, the more oxygen it needs. During vigorous activity such as running or rowing, your body may need 15 to 20 times more oxygen than at rest.
This is what aerobic fitness is all about - improving the body's ability to process and deliver oxygen. The more fit you are, the more oxygen your body can take in and process.
HEART, LUNGS AND BLOOD VESSELS AT WORK Read the entire article. "
