Creatine is one of the most well-tested and popular supplements. What is it? Creatine is a molecule produced in the bodies of vertebrates from amino acids. It is therefore a naturally occurring substance in humans, and also a lot of the meat and fish that we eat. Vegetarians or people who eat less meat/fish may have lower amounts of creatine.
There are three different energy systems used by your body to produce movement. Creatine is a key player in one of them: the adenosine triphosphate/creatine phosphate (ATP-CP) system. At a chemical level, it stores high-energy phosphate groups in the form of phosphocreatine, facilitating the recycling of adenosine triphosphate (ATP), the body’s “energy molecule”.
Around 95% of it is stored in the muscle tissues, with the other 5% being found in your brain, kidneys and liver. Creatine is needed for muscles to generate energy during heavy or intense exercise.
For sudden and intense activities — like sprinting, jumping and very heavy lifting — your ATP-CP system kicks into play. It is the fastest energy system to respond, but its speed in activation is almost matched in its duration. You can only naturally store a small amount of ATP in your muscles, enough for about 6-10 seconds of max effort.