Creatine Creatine is a naturally occurring metabolite produced by the human body that has a powerful role in energy metabolism as a muscle fuel. The immediate energy source for skeletal muscle contraction is from a molecule called adenosine triphosphate (ATP). During a brief period of high intensity exercise, i.e. weight training, the ATP demand in the working muscles increases significantly to several hundred times higher verses when at rest. High intensity exercise can totally deplete phosphocreatine stores within 10 seconds. The depleted stores of ATP and CP must be steadily replenished in order for muscular contractions to continue at peak levels of frequency and intensity. Oral supplementation of creatine has been shown to increase the free creatine pool; maximize ATP production and resynthesis; increase anaerobic power output; increase CP (creatine phosphate) reserves and increase intracellular volume, increasing muscle size.