Creatine

Creatine is a combination of amino acids that are stored in the skeletal muscles. These muscles can use one of its derivatives-creatine phosphate-to sustain a muscle contraction when the usual fuel-a substance called ATP (adenosine triphosphate)-has been exhausted. In simplified terms, here’s an example of how it works: when you lift a heavy weight, the muscles of your arms contract, or shorten, to provide the needed strength and resistance. The energy for this contraction is derived by converting ATP to ADP (adenosine diphospate). When the muscles’ reserves of ATP are exhausted, creatine comes to the rescue by giving over its phosphate molecule to make more ADP. High reserves of creatine phosphate allow the muscles to work longer and harder.