If you watched Michael Phelps in the men's 4-by-100 relay at the Olympics last night, you probably noticed that the 31-year-old swimmer looked like he'd been pelted by balls from an angry pitching machine.

Those circular bruises on his shoulders came from cupping, a type of alternative medicine where cups are placed on the skin to create suction. The suction is said to increase blood flow to stimulate healing—similar to a massage—and many Olympians swear by it.

The British Cupping Society claims the therapy can be used to treat blood disorders, rheumatic diseases, fertility issues, skin problems, high blood pressure, migraines, anxiety, depression, and allergies.

But like most forms of alternative medicine, few scientific studies exist testing its effectiveness. So while Michael Phelps and other Olympians are onboard, the scientific jury is still out. 

READ THIS NEXT: Katy Perry's New Music Video Is Making Us Ridiculously Excited for the Olympics
 

Take on too much in the New Year?

We'll make crushing your goals a whole lot easier by sending you a healthyish idea you can do every day.
Sign up to get healthy ideas
via Facebook Messenger
 
CLOSE

Sign up for a daily healthyish text message

Status Available in the U.S. and Canada only. Clicking "SIGN UP" means you would like to receive text messages from Greatist. Msg & Data rate many apply. Text STOP to cancel or HELP for help.