Creatine is synthesized in the liver from the amino acids arginine and glycine and stored in the major muscles, including cardiac and skeletal tissues. Once inside the muscle, creatine is phosphorylated to form Creatine Phosphate (CP), which, as a high energy substrate for ATP, assists in the contraction of the myofibrils (muscle fibers). Creatine Phosphate is utilized to maintain higher levels of ATP (energy molecules) 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.