Creatine Health Dictionary

A nitrogenous substance, methyl-guanidineacetic acid. The adult human body contains about 120 grams – 98 per cent of which is in the muscles. Much of the creatine in muscles is combined with phosphoric acid as phosphocreatine, which plays an important part in the chemistry of muscular contraction.

n. a product of protein metabolism found in muscle. Its phosphate, creatine phosphate (phosphocreatine, phosphagen), acts as a store of high-energy phosphate in muscle and serves to maintain adequate amounts of *ATP (the source of energy for muscular contraction).