It’s the hottest issue at the Rio Olympics – okay, apart from the length of the British TV presenter’s skirt, the Chicago newspaper describing a bronze medal-winning athlete as the wife of a Bears footballer, and China’s made-in-China flags having the wrong emblem on them.
Yes, it’s those big red spots on the back of US swimmer Michael Phelps and some of his team-mates.
The answer: cupping.
Practitioners of the technique — or sometimes the athletes — put specialised cups on the skin. Then they use either heat or an air pump to create suction, pulling the skin slightly up and away from the underlying muscles.
Cupping is thought to draw blood to the affected area, reducing soreness and speeding healing of overworked muscles. Athletes say it keeps them injury-free and speeds recovery.
Phelps featured cupping in a recent video for a sponsor. He also posted an Instagram photo showing himself stretched on a table as Olympic team-mate Allison Schmitt placed several pressure cups along the back of his thighs.
Keenan Robinson, Phelps’ personal trainer, says: “Because this particular recovery modality shows blemishes on his skin, he walks around and looks like a Dalmatian or a really bad tattoo sleeve.”
Robinson says it’s both pyschological – “Michael has been doing this to feel good for a long time, about two years” – and phsyiological. “I’m not just going to throw a stick of butter on him. I’m going to make sure I have an educated approach to it.”
The technique is allegedly based on an ancient Chinese – and possibly Egyptian, certainly Islamic – therapy.
There are two variations. Dry-cupping involves holding a cup against the skin and using a hot liquid or suction to reduce pressure; wet-cupping or hijama involves cutting inch-deep and wide cuts in the skin to remove “bad bloods”. The blood and its “toxic chemicals” flow into the cup.
There is limited scientific evidence on cupping therapies. A 2008 study of 70 patients with chronic headaches or migraines, published in The American Journal of Chinese Medicine, found that severity decreased 66 per cent following wet-cupping.
A 2011 study in the Focus on Alternative and Complementary Therapies journal said two out of three reviews into wet- and dry-cupping found “some evidence” that it worked in treating pain.
Forget the science: it’s hard to argue with the results. Phelps has 19 gold medals, more than any other athlete in history. And Sonny Bill Williams shared a photo of him undergoing cupping with the caption “Detox time” after last year’s Rugby World Cup win.