Creatine increases phosphocreatine stores, regenerating ATP for high-intensity efforts. Decades of evidence for strength, power, and lean mass gains. Newer evidence shows cognitive benefit, especially in vegetarians and the sleep-deprived.
Dose: 5g daily. No need to load.
Caveats: Very safe. Slight water retention initially. Buy monohydrate (Creapure is the gold-standard brand). Fancier forms aren't better.