Why Olympic athletes are into cupping

They were hard to miss — the dark, purply circles dotting Michael Phelps' back and shoulders and running all the way down his leg. Perfectly circular, they look like some kind of rash.

In Phelps’ case, they’re completely intentional. “I’ve done cupping for a while before meets,” says Phelps. “But I haven’t had a bruise like this for a while. I asked for a little help yesterday because I was a little sore and I was training hard.