A new medical treatment that has its origins in Islamic and Middle Eastern traditions is trending at the Rio Olympics used by star-athletes like Michael Phelps.

Cupping, or known as ‘hijama’ in Arabic, involves applying glass or plastic cups to an area of discomfort on the body and either applying heat or suction to create a vacuum. The suction pulls the skin away from the muscle and draws oxygenated blood to the area. The suction also is what causes the bruising, like giant hickey without the fun that comes with it.Phelps, who won his 19th career gold medal so far, was seen with a huge bruising on his right shoulder on the morning of his meet, prompting many to ask whether he was applying the ancient Middle Eastern medical treatment.Researchers have traced cupping’s origins back to China and Greece somewhere around 1500 B.C., and Team USA gymnast Alex Naddour was among other Olympians who have been seen with the purple marks in Rio.

It roots in Islam is reported several times in quotes by the Prophet Mohammed who said: “Indeed the best of remedies you have is hijama (cupping)…”

And it’s not just for star athletes. Health spas often offer the service for a few hundred dollars and the cups can be purchased online for as little as $15 and applied at home.

Some in the medical community believe it’s nothing but hocus pocus, the latest form of snake oil that tricks patients into paying for it again and again. Others insist that it aids recovery, relaxes muscles and helps an athlete maximize performance.

Phelps certainly believes in it. In the end, that may be all that matters.

“I’ve done it before meets at pretty much every meet I go to,” he said.