Purity Assured by HPLC. Creapure®. Gluten Free. Creatine is synthesized in the liver and stored in the major muscles including cardiac skeletal tissues. Once inside the muscle cells creatine is phosphorylated to form creatine phosphate (CP) which as a high energy substrate for the universal energy molecule adenosine triphosphate (ATP) assists in the contraction of the myofibrils (muscle fibers). Creatine Phosphate is utilized to maintain higher levels of ATP during exercise. Creatine Phosphate maximizes physical performance and reduces exercise fatigue by absorbing hydrogen ions released by muscles in the form of lactic acid. Intense anaerobic exercise such as weight lifting and sprinting depletes ATP and greatly increases the demand for creatine.