From the movie Choke (2008) In the beginning the lead character is describing a group of sex addicts saying:
They may not look like much to you, but they were all-stars on the circuit.
Toward the end of the movie, the lead character has flashback about how he's became a sex addict. He remembered a woman in a plane's lavatory he accidentally saw naked and she made him to have sex with her saying
There are no accidents on the circuit, honey.
I've read all vocabularies, but didn't find any definition that could explain what circiut they were talking about
I only can guess that it has something to do with sex addicts slang or something