Rio Olympics 2016: What are those mysterious black marks on Michael Phelps’ back as he wins record 19th Olympic gold medal?
EAGLE-EYED viewers will have noticed the strange purple dots on Michael Phelps’ body when he claimed his record 19th Olympic gold on Sunday night.
The most decorated Olympian ever hit the pool in Rio to help the USA win the men’s 4x100m freestyle relay.
The 31-year-old swam a sensational second leg to see off rivals France and Australia as the United States quartet clocked a winning time of three mins 9.92 secs.
But the main talking point became, what on Earth are those little circles on the superstar’s back?
Phelps had a number of mysterious disc-shaped marks across his shoulders and legs.
And he is not alone, as various US athletes – including gymnasts and fellow swimmers – have been spotted sporting similar strange patterns in the two days of competition in Brazil so far.
Is the US camp suffering from an outbreak of extreme chicken pox? Or maybe even widespread tattoo removal?
We can reveal the marks are the end product of a healing technique called cupping.
Cupping is an ancient Chinese medicinal practice that involves placing heated glass cups on your skin.
The technique relies on suction to pull the skin back and loosen muscles and tendons, unlike a massage where they would be pressed.
Suction can be created using heat or mechanical devices such as electronic pumps.
For athletes, the idea is that the practice helps in recovery – which becomes even more important during an eight-day stretch when you might swim a dozen races.
It is not even supposed to be painful, with patients feeling a 'pinch' followed by hours of pain relief.
The only down side is the bruises, which can last for up to two or three weeks.
Doctors are divided on how effective cupping can be for athletes' performance - with some claiming it may provide nothing more than a placebo effect.
But if it's good enough for the Flying Fish, it's good enough for us.