The odd-looking marks are from an ancient Chinese massage therapy technique called myofascial decompression, or cupping.
“It can be used on anyone, really, from Olympic athletes to a 59-year-old desk worker with back pain and stiffness,” says Michael Mancuso, a physical therapist in New York City who specializes in the technique, which is thought to increase blood circulation.
A “suction cup-like tool” is used to apply negative pressure to a person’s underlying sore tissue, explains Mancuso. The patient then moves into a position that stretches out that spot. The cups stay in place for about five to 10 minutes.
“It can be used as a massage technique, it can stretch the tissue out, it can bring local inflammation to an area for healing, or even break up scar tissue after surgery,” Mancuso says. “What you’ve been seeing with the Olympic athletes is probably used to either warm up the muscles before an event, or to release tension afterwards.”
While a person may experience temporary pain, “most patients feel immediate relief, and feel looser with increased ranges of motion.”
The red marks they’re left with – like those on Phelps’ back Sunday night as he swam with his teammates to victory in the 4×100 meter freestyle relay – result from blood rising to the skin’s surface, and can last for seven to 10 days, according to Mancuso.
While cupping is having a moment at the Olympics, thanks to not only Phelps but also gymnast Alex Naddour, Hollywood’s Paltrow and Aniston have been fans for years, famously hitting the red carpet with spots across their backs.
According to Mancuso, the treatment is gaining new fans across the country.
“I use cupping on about 50 to 75 percent of my patients, and I’ve been seeing it used more and more each year,” he says. “The people who popularized this technique in the U.S. are on the West coast, so it’s slowly making its way to the East coast.”