How many affairs begin at the gym?

I go to a local gym and it seems like it is the Spot for beautiful married people to pick up like minded married person of the opposite ( or same for that matter) for discreet fun. Just wondering if this is common in many gyms or do I just live in a abnormally promiscuous area. I mean I am guilty of watching the girls work out in my case and thinking out things I should not be.