Michael Phelps' circular bruises are due to 'cupping therapy'

For those of you who have been tuning into the Rio Olympics and watched swimmer Michael Phelps' race in the men's freestyle relay finals on Sunday, you probably noticed the circular bruises that dotted his back.

But before you jump to conclusions thinking that Phelps got into a wrestling match with a giant octopus, relax. Those bruises are the result of a traditional Chinese medicinal therapy called "fire cupping."

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The practice involves creating local suctions on a person's skin with heated glass globes. For thousands of years, the Chinese believe that cupping helps to mobilise blood flow to promote muscle healing.

The downside to cupping is the bruising, which usually worsens on the second or third day post-therapy.

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According to AP, Phelps is no cupping noob. His moving ad for Under Armour to announce his return to competitive swimming in March even features a scene of him undergoing fire cupping therapy.

Phelps has in the past posted cupping photos onto this Instagram:

View this post on Instagram

And it looks like Phelps is not the only U.S. athlete who's using cupping therapy to stay in form. Gymnast Alex Naddour recently posted a picture of himself on Instagram and on his back and arms were the same telltale bruises.

View this post on Instagram

Although athletes and celebrities swear by cupping therapy, the practice has had its fair share of critics dismissing it as a "fad" and "gibberish."

In February, a 26-year-old Singaporean woman died after she suffered a seizure during a tuina session. Tuina is a Chinese acupressure massage treatment that is often used in conjunction with cupping therapy.