As a performance enhancer for power and strength athletes, creatine plays an important role in the transfer of energy. In muscle, it fuels the process of contraction by combining with ADP (adenosine-di-phosphate) to form ATP (adenosine-tri-phosphate), the body's ultimate energy source. It does this by converting to phosphocreatine which supplies the extra phosphate ion to bond with ADP. It has been proven to enhance strength safely and effectively by supplying short energy bursts during activities involving fast-twitch muscle fibers (which require a greater short-term available supply of ATP) such as sprinting and weightlifting. Depletion of phosphocreatine without replenishment can result in muscular fatigue and fading muscle power.