ATP (Adenosine Tri-Phosphate)
ATP is the chemical currency used to supply the energy needed for muscle contraction.
When this high energy phosphate is broken down, it releases a tremendous amount of energy to the cell, initiating muscle contraction.
Of all the high energy compounds in the body, only ATP can be used directly to supply the energy needed for the mechanical work of exercise.
Activities that rely on immediate energy sources and do not require oxygen for ATP production are known as anaerobic activities - high intensity explosive exercises. There is ATP already present in the muscle cell at rest, but remember its concentration is very low and will not last long.
Carbohydrate is the only macronutrient that can be broken down both aerobically and anaerobically to supply ATP.
The anaerobic pathway involves the breakdown of glucose in glycolysis, and results in the production of two ATPs, and two lactic acids or lactates. Again, this is anaerobic, as no oxygen is required for this pathway.
The major aerobic sources for ATP production during exercise come from the oxidation of carbohydrates and fats. Notice that one, oxygen is required. And two, the oxidation of glucose yields 30 ATP as opposed to only 2 ATP if we break down glucose anaerobically.
Thus, for the very same glucose molecule, we get 15 times more ATP via the aerobic versus the anaerobic pathway. This is extremely important as we'll see in subsequent videos as there is a limited amount of carbohydrates stored in the body. So if we were able to use our glucose aerobically, we will not only get more bang for the back but we will also spare our precious carbohydrate stores.