RIO DE JANEIRO -- They are the purple circles that set social media on fire Sunday night, the circular bruises on Michael Phelps' right shoulder that left television viewers around the world wondering if the most decorated Olympian of all-time had contracted some rare skin disease, been attacked by an octopus, or perhaps was part-Dalmatian.
The answer, of course, was none of the above. The bruises were the result of a form of cupping therapy Phelps had endured Sunday morning to treat some shoulder discomfort that set in after waiting in line for 40 minutes at the Olympic Village wearing a backpack. A day later, the mysterious circles became an international inquisition. Following Phelps' prelim swim in the 200 butterfly on Monday, the first question a reporter asked a perplexed Phelps was about cupping.
"I've done this for a while," he said. "I asked for a little cupping yesterday and [trainer Keenan Robinson] hit me pretty hard with one and it left a couple bruises."
Robinson, USA Swimming's director of high performance, was equally entertained Monday, suggesting that all the attention over the $30 cups was missing the bigger picture of all that goes into preparing Phelps and other athletes to compete at their highest levels.
"It's like asking a chef about his garnish when you're missing the main meal," Robinson said. "You've got this beautiful steak and vegetable medley -- that's what you're paying $75 for. Not the garnish. But this recovery modality shows the blemishes when he walks around, so people ask."
The practice of Chinese cupping has been around for more than 2,000 years. But Robinson and USA Swimming chiropractor Kevin Rindal said that the form of therapy used on Phelps is somewhat different. It's essentially the opposite of a massage, using the suction from perfectly circular cups to manipulate and help separate the various layers of fascia and muscle beneath the skin. The end result is decreased discomfort and an increase in range of motion.
"Think of us as an Indy Car pit crew," Rindal said, "looking at the structure and alignment of the vehicle to see if there is any kind of drag or anything. And if you think of how close these racers are, a little bit of restriction adds up in each stroke and can prevent a full reach. It's basically the fine-tuning of the tissue."
Robinson, Phelps' longtime trainer, said he has been using the therapy on Phelps since the fall of 2014. He brought the idea to the swimmer as a way to help the then-29-year-old recover from his two-a-day training sessions.
"Mike is probably the best at telling you what's voodoo and what's actually working," Robinson said. "He was like, 'OK Keen-dog, what are you bringing me this time?' But then he'll do it and instantaneously he'll tell you it's hokey-pokey business or if it's kind of effective."
Phelps took to the treatment and, according to Robinson, has used it about twice a week since. Sometimes it can leave dark red bruises, other times there is no mark at all. The visibility of the bruising or lack thereof has no impact on whether or not the sometimes painful therapy has been effective. Since Phelps began using the treatment several other athletes have followed suit, including Dana Vollmer, who has already won two medals in Rio 17 months after giving birth.
"I know it looks weird but it really helps with blood flow, helps pull swelling out of different areas," she said. "It works great for a lot of us."
Added U.S. teammate Cody Miller: "It's superficial bruising. It's not real bruising. Your muscle tissue isn't torn up in there. It's pulling blood into a certain area where tension has built. It's great. My fiancee does it to me in training."
Robinson said that the training staff is constantly evaluating all the U.S. swimmers and the tension, stress and range of motion in their joints. Everything from massages to stretching to ice baths to the Graston technique, a form of therapy that uses instruments to massage the skin, can be used to treat inflammation or increase range of motion.
"We don't want people banged up," he said. "We don't want broken products here at the Games."
Not everyone agrees the cupping treatment even works. As is often the case with any type of alternative therapy, it takes just a few minutes online to find a detractor who doesn't believe there is a correlation between the treatment and athletic success. Robinson suggests the naysayers are wrong.
"I'm not just going to throw a stick of butter on him and say, 'Well, I read that Usain Bolt or whoever is doing this,'" Robinson said. "I'm going to have an educated approach to it. You can stand on either side of the spectrum that it doesn't work. But we know the science says it is not detrimental and in some cases can really help out."
In other words, it's the latest in a long line of high-performance therapy fads that include everything from electrotherapy and cryotherapy (ice baths) to Kinesio tape and acupuncture needles. But this one has now been endorsed by the most decorated Olympian of all-time, after one of the most impressive races of his career.
"It's going to blow-up now," Robinson said. "Actually, it just did."