Michael Phelps and a host of gymnasts are walking around covered in bruises from a treatment for sore and injured muscles that uses suction to reverse-massage muscle tissue in need of care.

The technical term for the treatment is cupping: a sports medicine fad with ancient roots. A cup is applied, and suction pulls the skin away from the body.

"The suction typically lasts for only a few minutes, but it's enough time to cause the capillaries just beneath the surface to rupture, creating the circular, eye-catching bruises that have been so visible on Mr. Phelps as well as members of the United States men's gymnastics team."

- New York Times

The New York Times reports that, as with many health fads, some people swear by it while science has iffy proof of benefits. Maybe athletes are recovering faster. Maybe it's a placebo effect.

But it's certainly a head turner for spectators and other athletes alike, and any psychological advantage you get can be worth it.