To perform optimally, muscles need a lot of energy. The body provides this energy, in situations like high-intensity exercise, in the form of ATP or adenosine triphosphate. Since the body stores only a limited supply of ATP, which lasts for only a few seconds of intense exercise, ATP must then be continuously produced to supply enough energy for the muscles to function. A burst of energy is produced by the breakdown of ATP, when one phosphate group is released, creating metabolic energy. The body then uses creatine phosphate to quickly replenish ATP.
The more energy muscles store, the better they can perform in events that require intense, immediate action, such as weightlifting, sprinting, jumping, football, hockey and soccer. Since creatine is stored in the muscle as creatine phosphate, intake of supplemental creatine can increase the production of energy that enables muscles to perform at higher intensity. While the body produces its own supply of creatine, it is not sufficient to supply the muscle with the added energy necessary for intense performance.
The benefits of creatine supplementation for endurance athletes have been actively researched. This research has established that creatine can, in fact, extend endurance at a relatively high dose of 20 grams per day. Creatine increases muscle mass and muscle girth if taken along with a sustained exercise regimen. Initially, it may also increase weight due to gain in the muscle mass. This increase may slow down some athletes, especially swimmers. This “slowing down” may be due to the highly aerobic nature of the exercise, and should be reversible after sustained exercise.