Usually they are physical outliers, you don't get into the NBA without being an incredibly gifted athlete.

It's certainly possible, as one of the biggest driving factors behind muscle growth is testosterone levels, which can vary widely from person to person.

It's interesting when you look at routines of some of the best college athletes specifically in football, a lot of them seem really odd. But when you talk to the trainers you find out that a lot of them have the kind of genetics that it doesn't matter what you do, they'll grow regardless.

Irregardless, I don't think there's a ton of proof either way. The NBA isn't going to come out and say that their players are on PEDs, but the extremely lax nature of testing in both the NBA and NFL suggest that their widely used in the industry.