Some athletes, footballers and sports people from lots of other fields take many different types of drug. They do it to make their performance better.
They hope that the drug will give them an edge over all the other people they are competing against.
But it is very risky, as this is cheating and they don't want to get caught.
Taking drugs can also be very bad for a sportsperson's health. Often they are experimental drugs and the long-term effects of taking them are not yet known.