REVEALED - Why some Olympic athletes have those little red marks on them

Michael Phelps had the red marks on his right shoulder last night

Watched much of the Olympics recently? You may have noticed that several athletes - particularly the American ones - have small red circle marks on their body.

The marks as the result of a process known as 'cupping', an ancient form of acupuncture popularised by celebrities such as Gwyneth Paltrow and Jennifer Aniston, where hot cups are placed on the skin to create a vacuum. The suction is said to improve blood flow, and that's what creates those little marks.

It's not the first time cupping marks have been seen at the Olympics - the technique was previously used by Chinese swimmer Wang Qun at the 2008 Olympics in Beijing. And while those marks look sore, the process is apparently painless.

Chinese swimmer Wang Qun is seen with marks after cupping treatment during a training session at the National Aquatics Center a few days before the start of the Beijing 2008 Olympic Games on August, 04 2008. There are 32 swimming gold medals up for grabs at the Olympics, making it the second most prolific sport behind track and field. AFP PHOTO / DDP / MICHAEL KAPPELER (Photo credit should read MICHAEL KAPPELER/AFP/Getty Images)

Despite the celebrity and athlete endorsements, there are questions as to how well cupping works. UCL pharmacology professor David Colquhoun says the techique "doesn't make sense at all" medically.

"Putting a suction cup on the body may cause the skin to constrict and there could be some increased blood flow, but the idea that this could treat any medical condition is laughable," he said

"It’s utterly implausible and just another ingenious way of relieving the rich and gullible of their money."

CHONGQING, CHINA - JULY 8: (CHINA OUT) A patient undergoes cupping treatment at a Chinese medicine clinic on July 8, 2008 in Chongqing Municipality, China. Cupping is an alternative form of pain therapy that has been part of Chinese medicine for over 2,500 years. (Photo by China Photos/Getty Images)

However a 2012 study in the journal PLOS OneE found that cupping could potentially be effective for some medical conditions such as acne and facial paralysis. Whether it works for athletes remains to be seen...