Michael Phelps Photo: CFP

After photos of China's Olympic team using mosquito nets to ward off the Zika virus went viral online, one of the country's homegrown specialities is now being pushed into the spotlight.

Bahuoguan or cupping therapy, a treatment used in Traditional Chinese Medicine (TCM), seems to have become a favorite of US athletes at the Rio Olympic Games. Some have even praised it as the best therapy they've ever had.

The dark red circles on athletes' bodies left by the treatment have been pretty easy to spot at the games.

Champion swimmer Michael Phelps showed off very visible marks scattered on his back and shoulders while competing in the men's 4x100 freestyle relay. His use of the treatment can also be seen in some of his promotional videos.

Phelps isn't the only one. Only a few days ago, US gymnast Alex Naddour posted a photo on his Instagram account which revealed one of the distinct circular marks on his left shoulder. Former US Olympic swimmer Natalie Coughlin also posted a picture on Instagram which showed three cupping glasses stuck on her body just below her neck.

Screenshots of Alex Naddour's Instagram feeds Photo: GT

Screenshots of Natalie Coughlin's Instagram feeds Photo: GT

"That's been the secret that I have had through this year that keeps me healthy. It's been better than any money I've spent on anything else," Naddour told USA Today.

He explained that he uses the therapy to ease the "soreness and pounding" that comes from gymnastics practice.

Cupping therapy uses suction created by using heat or mechanical pumps to cause cups to stick to the surface of one's body. It has long been used in China alongside another TCM remedy acupuncture.

"Although it is secondary type of therapy, cupping is more popular than acupuncture and other types of TCM," Tian Lifang, director of the Acupuncture and Massage Department at Beijing Hospital, told the Global Times.

According to Tian, cupping is usually used to help treat mild sicknesses such as colds or fevers, some skin diseases such as eczema and muscle injuries.

"Cupping does two things that benefit people's muscles. It increases local blood circulation and helps ease muscle tension caused by sports-related injuries," Tian said.

Cupping isn't just popular among US athletes. Hollywood star Gwyneth Paltrow was also caught on camera sporting the distinctive cupping marks on her back while attending a press conference.

"Cupping therapy can help with fatigue," Tian explained.

"That's why my colleagues always joke that in the US it's a favorite among truckers."