Michael Phelps woke up on the morning of the first race of his fifth Olympic Games with some soreness in his right shoulder.
At age 31, the swimming superstar could not afford to have anything slow him down. So he went to a Team USA trainer for some cupping therapy, a treatment he has been receiving for years to help relax his muscles and ease soreness.
"The trainer hit me pretty hard with one and left a couple of bruises," Phelps said.
With large purple circles dotting his shoulder and back, Phelps delivered a performance that put him back on the podium and thrust cupping therapy into the spotlight.
The practice dates back centuries and has enjoyed a bit of a renaissance over the past decade after athletes like Phelps and NFL star DeMarcus Ware and actresses Gwyneth Paltrow and Jennifer Aniston started promoting its benefits.
The treatment involves applying glass or plastic cups to the area of discomfort and either applying heat or suction to create a vacuum. The suction pulls the skin away from the muscle and draws oxygenated blood to the area. The suction also is what causes the bruising.
Researchers have traced cupping's origins to China and Greece somewhere around 1500 B.C., and Team USA gymnast Alex Naddour was among other Olympians who have been seen with the purple marks in Rio. And it's not just for star athletes. Health spas often offer the service for a few hundred dollars, and the cups can be purchased online for as little as $15 and applied at home.
Cupping is offered at more than a half-dozen business in the Baltimore area, including Baltimore Shiatsu Acupuncture Center in Baltimore, all four locations of Ojas Wellness Center, and Well-Being Massage Studio in Columbia.
The owners of Woodberry Wellness in Baltimore were excited to see Phelps' body covered by the telltale signs of cupping treatments when he won Saturday. They immediately took to Instagram, posting that they could provide the public with the same treatment Phelps received.
As a result, they've received more than 20 phone calls, which has led to seven appointments for the therapy.
"It's exciting to see people who haven't been aware of this complementary medicine gain awareness through the public display of Michael Phelps' cupping," said Tiffany Houchins, co-owner of Woodberry Wellness.
Houchins' company offers cupping as part of a package that includes an evaluation, cupping and acupuncture for $130 for a 90-minute to two-hour session.
Hourlong follow-up sessions are $75. And most of the time the session is covered by health insurance.
Patients generally get relief after the first session, according to Houchins.
"They say it feels good. A lot of people say they feel tender the first day. By the second day, I get a phone call saying they feel amazing," she said. "They feel much less stiff. They feel looser. They feel much more flexible."
Some in the medical community believe it's nothing but hocus pocus, the latest form of snake oil that tricks patients into paying for it again and again. Others insist that it aids recovery, relaxes muscles and helps an athlete maximize performance.
Phelps certainly believes in it. In the end, that might be all that matters.
"I've done it before meets at pretty much every meet I go to," he said.
Steve Hamilton, a massage therapist for the Denver Broncos, has used the technique for years in working with players. He said the biggest benefits include increased circulation, decreased muscle tension, decreased inflammation, increased range of motion and improved blood flow.
"Its effectiveness is because it's all part of the body's natural healing process," Hamilton said. "But cupping helps the body recover faster by keeping the process moving forward. It's awesome because it's all natural."
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But there is a scarcity of accredited studies to prove cupping's efficacy, which has led to a fair amount of skepticism. Many doctors have called it nonsense, and others believe it is no more effective than a placebo.
Russian state TV, after watching more than 100 of its athletes become embroiled in a doping investigation that excluded them from the Rio Games, took a dig at Phelps when it branded cupping "as-yet legal doping" in a lengthy feature on the treatment.
Hamilton said cupping is "no such thing."
"It helps enhance the body's natural neurological and circulatory function, thus allowing the body to be pushed and perform at a higher competitive level," he said.
Phelps even included the process, which can be painful, in a commercial he did for Under Armour on the rigorous training he puts his body through to get ready to compete. When he is competing in an event where victory is measured in fractions of a second, any little edge could make the difference.
"If he feels like he feels better," Hamilton said, "that's never a bad thing."
The Associated Press and Baltimore Sun reporter John-John Williams IV contributed to this article.