How does Aerobic Respiration work during exercise?

Aerobic respiration is simply breathing. When you exercise, your breathing rate increases to compensate for the increased need of oxygen that is required by your muscles. When you exhale, you expel carbon dioxide, the by-product of used oxygen.

After two minutes of exercise, the body works to supply muscles with oxygen. In the presence of oxygen, glucose is completely broken down into carbon dioxide and water. This process is called aerobic respiration.

Glucose comes from three different places:

• the glycogen supplies that remain in muscles
• theliver's glycogen which is broken into glucose, carried to working muscle through the bloodstream
• glucose absorbed from food in the intestine, carried to working muscle through the bloodstream

Fatty acids from fat reserves in muscle and other parts of the body are also used by Aerobic respiration to produce ATP. (Adenosine triphosphate, or ATP, is the way your body uses biochemicals to store and use energy.) In extreme cases (such as starvation), proteins are broken down into amino acids and used to make ATP. Aerobic respiration first uses carbohydrates, then fats and finally proteins, when necessary. Aerobic respiration uses more chemical reactions to produce ATP than either the Phosphagen System or the Glycogen-Lactic Acid System.

The slowest rate of the three systems is aerobic respiration, but it continues to supply ATP for several hours or longer if the fuel supply lasts.

Energy is also produced by the Phosphagen System and the Glycogen-Lactic Acid System.