Creatine is stored in the heart, brain, retina, and skeletal muscles, where it is critical for high-intensity muscle contractions. By enhancing ATP turnover, creatine functions as an energy reservoir during repetitive activities that require short bursts of explosive energy. Creatine delays fatigue in repeated bouts of all-out strength work or sprinting, and allows the body to sustain a high power output. According to the American College of Sports Medicine, creatine supplementation can improve performance in repetitive anaerobic exercises. There is no conclusive evidence that it helps in swimming, running, or a single sprint event.
Creatine also causes muscle cells to retain water, and bloated cells produce bulkier muscles.
Muscle mass is not increased, but water weight is. Endurance athletes will generally not benefit from creatine use, and the extra pounds of water weight may actually slow them down. Creatine also increases the risk of dehydration, not a good thing for a runner or soccer player. A common misconception is that creatine, on its own, will increase strength . Taking excessive amounts of creatine can be hazardous.