To be swollen; to be fucking jacked. Gaining so much mass that girls offer ass. The definition of having guns for buns. Flex for sex? You don't even need to flex to get sex. Remember, Muscles, never steamers.
Dude have you seen that kid AAJ? Kids a fucking Muscle Hamster.
The term was originally used in reference to being "all-in" on Tampa Bay Buccaneers running back Doug Martin, who is known as the muscle hamster. However, the term sounds much more like putting on a condom.
"You don't know where that chick has been. Better hang your hat on the muscle hamster."