Michael Phelps won his 19th Olympic gold medal on Sunday night, when the United States soared to victory in the 4x100 relay. However, Phelps' appearance -- namely, the giant red circles all over his back and shoulder -- might have left you scratching your head. Turns out they're not as strange as they look.
In addition to Phelps, several Team USA athletes have appeared at the Rio games sporting the somewhat unsightly spots -- all thanks to an ancient Chinese healing technique that's apparently become incredibly popular among some of the Olympians.
As explained in a report by The New York Times, the practice is called cupping, and just as its name suggests, it involves placing circular cups on the skin and using heat (or an air pump) to create enough suction to pull the skin away from muscles below. And while the process lasts for only a few minutes, it creates enough suction to leave those deep purple bruises that look more like the results of a fist fight than an Olympic event. And yes, it's the same thing that happens when you give/receive a hickey.