Whatever it makes you think of. Like when I say bean I think of one you eat. So then if someone else thought the same thing, they would post the word: Kidney (like a kidney bean)
And then the next person would post a word that Kidney made them think of.
I guess around exercise junkies it means buff through hard work. haha like you get swollen at the gym. One of the guys I worked with wanted to be super swoll, and would always talk about how breakfast was his favourite meal.