 Creatine monohydrate is a popular nutritional supplement with athletes involved in sports involving strength and power. When creatine is orally ingested it combines with inorganic phosphate to form phorylcreatine PCr in skeletal muscle . Adenosine Triphosphate ATP is the immediate source of energy in muscle - during exercise ATP is broken down to Adenosine Diphosphate ADP and inorganic phosphate. Duration of high-intensity exercise is limited to a few seconds based on limited ATP stores in muscle. PCr acts to re-phosphorylate ADP to form ATP so that muscle contraction can continue at high intensities. After creatine monohydrate is ingested, high-intensity exercise capacity is increased because of the increased PCr stores in muscle. 