RIO DE JANEIRO — Olympics trivia: What has 19 gold medals and a bunch of purple circles?
If you watched a certain swimmer’s Rio Games debut on Sunday night, when he propelled the United States 4×100-meter relay team to a gold medal, you know the answer: Michael Phelps.
While it may look like Phelps and several other Olympians with those skin marks have been in a bar fight, the telltale dots actually are signs of “cupping,” an ancient Chinese healing practice that is experiencing an Olympic moment.
“Because this particular recovery modality shows blemishes on his skin, he walks around and looks like a Dalmatian or a really bad tattoo sleeve,” said Keenan Robinson, Phelps’s personal trainer. “It’s just another recovery modality. There’s nothing really particularly special about it.”
Practitioners of the healing technique — or sometimes the athletes themselves — place specialized cups on the skin. Then they use either heat or an air pump to create suction between the cup and the skin, pulling the skin slightly up and away from the underlying muscles.
The suction typically lasts for only a few minutes, but it’s enough time to cause the capillaries just beneath the surface to rupture, creating the circular, eye-catching bruises that have been so visible on Phelps as well as members of the United States men’s gymnastics team. If the bruising effect looks oddly familiar, it’s because it’s the same thing that happens when someone sucks on your neck and leaves a hickey.
“I’ve done it before meets, pretty much every meet I go to,” Phelps said on Monday. “So I asked for a little cupping yesterday because I was sore and the trainer hit me pretty hard and left a couple of bruises.”
Physiologically, cupping is thought to draw blood to the affected area, reducing soreness and speeding healing of overworked muscles. Athletes who use it swear by it, saying it keeps them injury free and speeds recovery. Phelps, whose shoulders were dotted with the purple marks as he powered the relay team, featured a cupping treatment in a recent video for a sponsor. He also posted an Instagram photo showing himself stretched on a table as his Olympic swimming teammate Allison Schmitt placed several pressurized cups along the back of his thighs. “Thanks for my cupping today!” he wrote.
“There is a psychological component where Michael has been doing this to feel good for a long time, about two years,” Mr. Robinson said. “Anything you can do to get the body to feel good — you have to use an educational assessment on it. You have to make sure that what you’re doing is causing a physiological intent to recover.
“I’m not just going to throw a stick of butter on him,” Robinson said, adding, “I’m going to make sure I have an educated approach to it.”
While there’s no question that many athletes, coaches and trainers believe in the treatment, there’s not much science to determine whether cupping offers a real physiological benefit or whether the athletes simply are enjoying a placebo effect.
One 2012 study of 61 people with chronic neck pain compared cupping to a technique called progressive muscle relaxation, or P.M.R., during which a patient deliberately tenses his muscles and then focuses on relaxing them. Half the patients used cupping while the other half used P.M.R. Both patient groups reported similar reductions in pain after 12 weeks of treatment. Notably, the patients who had used cupping scored higher on measurements of well-being and felt less pain when pressure was applied to the area. Even so, the researchers noted that more study is needed to determine the potential benefits of cupping.
Another experiment involving 40 patients who suffered from knee arthritis found that people who underwent cupping reported less pain after four months compared to arthritis sufferers in a control group who were not treated. But the cupped group knew they were being treated — it’s not easy to blind people about whether a suction cup is being attached to their leg or not — and so the benefits might have been due primarily to a placebo effect.
Still, a placebo effect can be beneficial, and for athletes at the Olympic level any legal edge, however tenuous, may be worth a few eye-catching bruises.
“A placebo effect is present in all treatments, and I am sure that it is substantial in the case of cupping as well,” said Leonid Kalichman, a senior lecturer at Ben-Gurion University of the Negev in Israel, who recently co-authored a commentary reviewing cupping research in theJournal of Bodywork and Movement Therapies. “A patient can feel the treatment and has marks after it, and this can contribute to a placebo effect.”
Even so, Dr. Kalichman said he believes the treatment has a real physiological effect as well. It may be that cupping, by causing local inflammation, triggers the immune system to produce cytokines, small proteins that enhance communication between cells and help to modulate the immune response.
A few years ago the Denver Broncos player DeMarcus Ware posted a photo on Instagram showing his back covered with 19 clear cups as a therapist held a flame used to heat the cup before placing it on the skin. Celebrities including Jennifer Aniston and Gwyneth Paltrow have also been photographed with cupping marks on their skin.
Last year, Swimming World magazine noted that some college programs had begun using cupping therapy as well as the former Olympian Natalie Coughlin, who has posted a number of photos of herself undergoing the treatment.
“We know that science says it isn’t detrimental,” Mr. Robinson said. “We know that science says it does in some cases help out. So we’re at least going to expose the athletes to it years out so they can at least get a routine into it.”
Todd Schmitz, who coaches the Olympic swimmer Missy Franklin, said Franklin started using cupping when she joined the swim team at Cal-Berkeley. “I would say cupping is very much along the lines of ice baths,” Schmitz said. “Some people will tell you that ice baths have no purpose whatsoever. It’s one of those things if you think it helps you, you leave it in your repertoire.”
The American gymnast Alexander Naddour was sporting the purple dots during the men’s qualifying rounds on Saturday in Rio. He told USA Today that he bought a do-it-yourself cupping kit from Amazon. “That’s been the secret that I have had through this year that keeps me healthy,” Naddour told USA Today. “It’s been better than any money I’ve spent on anything else.”
Kevin Rindal, the chiropractor for the United States swim teams, is one of only four chiropractors Phelps trusts to work on him. Rindal said that the device they use can be found on Amazon for $30. He acknowledged that some practitioners might not use it effectively.
“I had a patient come in and he had a headache and he had a huge cup on his forehead because he thought he could cup his forehead,” Rindal said. “So people do some ridiculous stuff.”