Cupping has left its mark at the pool at Rio, but the signature circular bruises have also been spotted in the jockeys' room at Sydney racetracks.

Used to treat muscle pain, the Chinese therapy involves placing cup-like devices on the body to draw blood to the surface of the skin using suction, leaving large bruises.

It's popular among athletes, including Sydney-based jockey Jason Collett.

"I probably get it done once every two weeks, sometimes once a week if I'm really tight," Collett said.

"It's meant to loosen up the muscles, create more blood flow through them, help them repair quicker. I find it works."

Collett has been having regular treatment at the Traditional Chinese Medicine Clinic in Rhodes for about six months.

"One day I went home and found out about the benefits of it and thought Id give it a crack," he said.

"I generally like getting it done on a Friday. I should probably get it done on a Monday or Tuesday so then I'm ready for the start of the week's racing."

While medical opinion is divided on cupping, it had the desired effect for Collett who rode a winner at Canterbury on Wednesday just a few hours after American Michael Phelps, the most famous exponent of the treatment, won his 21st Olympic swimming gold medal.