Approximately 60-70% of the total creatine in muscle is stored in the form of the highenergy molecule phosphocreatine. The remaining 30-40% is present in the form of free creatine. Besides adenosine triphosphate, phosphocreatine is the most important source for energy in the body. All of the body’s cells can use only adenosine triphosphate (ATP) as an energy-releasing substance. Since the ATP reserves in the body are limited, ATP has to be continuously resynthesized. ATP is produced from the energy sources fat and carbohydrates over a fairly long time frame.