Where does phosphocreatine come from?
Well, like almost everything else in your system it comes from your food. Creatine or derivatives (phosphocreatine, esterfied or other chemically modified versions) are absorbed into your system and transported to the cells, where they become phosphorylated by ATP. So basically, when at rest you will naturally restore cellular ATP and PCr stores. PCr will be present in most tissues, especially muscular and neural. Although [almost] everyone has creatine naturally present in them, supplementation can be (and in the world of sports frequently is) used to help increase performance.
