Circular Bruising on Michael Phelps at 2016 Olympics Down to Cupping Therapy

When Michael Phelps took to the swimming pool to claim a 19th career Olympic gold medal on Sunday, he did so with some bizarre bruising on his back and shoulders.

And while the American great was busy doing the business in the pool, the world of social media was left wondering how he got the markings. The answer, it appears, lies in an ancient form of therapy.

According to Daniel Tran of Yahoo, Phelps is among a handful of U.S. athletes who use cupping therapy, which is believed to improve blood flow and heal muscle soreness.

NBC New York also highlighted that U.S. gymnasts had the marks on their skin, with the visible bruising a side effect of the treatment, which sees heated glass attached to a pump pushed onto the skin.

The lengths some people go to for a potential, legal edge.

[h/t Yahoo]