As discussed previously, there is only one currency for mechanical work. This is produced in the mitochondria which is the powerhouse of the cell. Because ATP cannot be supplied by the blood stream it must be re-synthesized in the cell.
Creatine phosphate is the a substance that exists in limited quantities within the cells.
This substance is hydrolyzed to form Creatine, energy, and phosphate. The energy that is liberated from this action is not mechanical energy. Energy transferred in the form of phosphate bonds is termed phosphorylation. Energy from phosphorylation is ultimately generated by the oxidation of carbohydrates, fats, and protein. This form of energy does not require the presence of oxygen so it is termed anaerobic.