Creatine supplementation in endurance sports

Creatine (Cr) is a compound that is synthesized endogenously in the kidneys, liver, and pancreas by the transamidination and subsequent transmethylation of three constituent amino acids: glycine, agrinine, and methionine (1). As a result of its amino acid origin, Cr can also be manufactured and consumed as a nutritional supplement. Consequently, Cr is currently regarded as a true ergogenic aid, owing to many well-controlled clinical trials that have demonstrated increases in muscle strength, power output, and muscle mass in response to exogenous Cr consumption (1-6). In fact, aside from the potential ergogenic benefits of caffeine, Cr is the most widely marketed nutritional supplement in the world.