Michael Phelps is red, white, and black and blue all over this Olympics thanks to a scientifically questionable technique known as cupping. Phelps and other athletes are turning to cupping therapy in hopes of healing their sore muscles. It’s a procedure based in ancient medicine in which cups are placed on top of the skin. The cups create a vacuum, pulling up the skin in an effort to stimulate blood flow to the area. It leaves behind the hallmark round bruises, often deep red or purple, that several swimmers and gymnasts are sporting in Rio.
