Anyone who watched the 2016 Summer Olympics couldn't help but notice the circular bruises on some of the athletes. It's called cupping, and it's a traditional Chinese medicine (TCM) treatment. It involves glass vessels placed on the skin. These cups then draw suction, which is how the bruising appears. It's supposed to treat deep scar tissue, knots in muscles and inflammation, but no one knows exactly how it works. In ancient times, some practitioners would also include bloodletting in the treatment, which is not that common anymore. "Wet cupping" is where bleeding is induced, but it's not known how many practitioners still offer that.
Glass cups are placed on the skin and suction is created either by heating and cooling the air in the cups, or with an air hose. Olympic swimmer Michael Phelps is a fan of the treatment as are many elite athletes, but there's some controversy over it as well since no one seems to know exactly how it works or if it could be causing more problems than it treats. While it's considered alternative medicine, there are many who swear by it for treating pain, inflammation and deep tissue injury.