Very likely small amounts, yes. It's Holywood, folks.
As I say, just a tiny amount to "help" tighten everything up and aid in attaining what they wanna see onscreen.
P.S. Captain America is a shitty superhero. He doesn't earn a damn thing, but rather "cheats" himself to awesomeness via drugs. Unlike even top bodybuilders, this tosser doesn't even have any gym training in his resume.