In the body, creatine is synthesized from the amino acids glycine, arginine and methionine. Taking supplemental doses of creatine monohydrate can increase muscle creatine and phosphocreatine (PCr) concentrations. These increases can lead to improvements in muscle energy production and recuperation. Muscle PCr is used as a high-energy substrate (fuel) required for immediate bursts of energy during high intensity and anaerobic exercise. Bodybuilders and athletes often notice remarkable increases in muscle cell size and strength, with decreases in the onset of fatigue with faster recovery. Best results are achieved when taken with fluids or foods containing glucose or dextrose. Results may be diminished if taken with foods and beverages containing caffeine.