Now, the major supply of fuel is not fatty acids but it's glycogen. So the polymer version of sugar where we break down glycogen into glucose and then the glucose goes into the process of glycolysis, then into the crept cycle and onto the electron transport chain. So these also contain many mitochondria and many capillaries. Now it also used a type of molecule known as creatine phosphate. Creatine phosphate itself is not actually used directly as an energy source. We use creatine phosphate to pass down the phosphate group onto ADP to form our ATP.