|1.||get the muscle|
To be the recipient of sexual intercourse. The "muscle" refers to the penis.
The phrase "could get the muscle" by itself is synonymous with "is fuckable"; however, "get the muscle twice" is often used to indicate high attractiveness or physical beauty in a woman.
I guess after a couple more beers, she could get the muscle. But her friend with the fat ass; she could get the muscle twice.