The Internet? 90% of the hot chicks, with muscles or without, are fake.
Unless you're paying for their webcam ...
You'll find plenty of female athletes in college but many of them bat for the other team.
Fakes are easy to spot, and not many people think to make a fake muscle girl profile - so, i disagree completely with your percentage - i think it's actually rather low, but of course it exists. It's more like 90% real, i would say.