Creatine is a combination of three non-essential amino acids. These are methionine, arginine and glycine. Creatine is used to produce adenosine triphosphate. The short word for Adenosine triphosphate is ATP. ATP is the energy of the human body. Creatine is already in the body as a natural substance and in some food (for example beef). The body changes creatine to phosphocreatine. It is then stored as energy in the muscles. The energy systems of the body are: aerobic, lactate and phosphocreatine. Most of the creatine is used in the lactate system and the phosphocreatine system because these two systems need more energy the aerobic system. They also take a part of the energy from the production or the absorption of creatine.