noun. A nitrogenous organic acid, C₄H₉N₃O₂, that is found in the muscle tissue of vertebrates mainly in the form of phosphocreatine and supplies energy for muscle contraction.

noun. A neutral crystallizable organic substance (C₄H₉N₃O₂) obtained from muscular tissue. See extract under creatinine. Also spelled creatin, kreatin.

noun. An amino acid 2-(carbamimidoyl-methyl- amino)acetic acid which naturally occurs in vertebrates and helps to supply energy to muscle and nerve cells

noun. an amino acid that does not occur in proteins but is found in the muscle tissue of vertebrates both in the free form and as phosphocreatine; supplies energy for muscle contraction

"Players showed high levels of an enzyme called creatine kinase, which is a sign of vigorous exercise."

amino acid  aminoalkanoic acid  

asparagine  beta-carotene  carnitine  choline  creatin