In the pool yesterday, Michael Phelps would help the U-S win the 4x100 metre relay. The swimmer would make headlines not just for grabbing his record 19th gold medal, but also for some marks on his body.

Those purple bruises on his torso, are from an ancient Chinese practice known as cupping -- and he and several Americans are doing it to try and improve circulation to muscles.

One specialist in the practice in America has suddenly seen an increase in business and explains why she believes the athletes are using it.

"An athlete can benefit from cupping because it moves blood stagnation in the muscle layer," said Erika Weber, licensed acupuncturist.

"When there's blood stagnation, it causes range of motion issues, inflammation, so this helps bring it to the surface of the skin, so free flow of blood can move through the muscles and help move muscles more freely."

"So I have a neck and a back injury that can cause very, very tight muscles. It's a chronic condition, so with that, I find a lot of knots around my shoulder blades and I would say definitely the cupping helps to heal that process," said Colette Magnam, cupping patient.