Creatine is found naturally in the body. It is an essential component of one of the body’s three energy systems called the ATP-PC system. The ATP-PC system provides ATP at the beginning of all activity to initiate movement including muscle contraction during exercise. This system is able to provide a large quantity of ATP very quickly, but can only be maintained for a very short time. It is the main energy source for high intensity short duration activities like sprinting and weight lifting.

Creatine supplementation could benefit those with lower than average Total Cr stores who engage in activities of high intensity and short duration especially if it involves repeated bouts. Some sports in which Creatine supplementation can be beneficial are: body building, power lifting, football, basketball, baseball, soccer, hockey and some track and field events. However, the associated increase in body mass with Cr supplementation maybe counterproductive in some sporting events.

Through this energy system creatine allows ATP to be re-synthesized after it has been chemically split apart and converted to ADP to produce energy. The re-synthesized ATP is then available for continued energy production for muscle contraction.

Creatine is found in two forms in skeletal muscle, free creatine and phosphocreatine. Phosphocreatine is creatine that, as its name implies, has a phosphate molecule attached to it. At rest about 60% is bound to phosphate producing phosphocreatine(PCr). ATP (Adenosine tri phosphate) losses its phosphate and becomes ADP to produce energy. Phosphocreatine will donate its phosphate to ADP to re-synthesize ATP for continued energy production. The PCr that donated the phosphate is now free creatine. This process will continue as long as PCr is available.

About 95% of the total body stores of creatine are found in skeletal muscle