Creatine: a dietary supplement and ergogenic aid.

Creatine is an amino acid that plays a vital role as creatine phosphate (phosphocreatine) in regenerating adenosine triphosphate in skeletal muscle to energize muscle contraction. Oral administration increases muscle stores. During the past decade, with notable popularity this past year, creatine has assumed prominence as an ergogenic aid for professional and elite athletes. Safety issues of long-term use, however, have not been addressed satisfactorily.