Phelps is touting the benefit of cupping _ but does it work?

(Photo: The Associated Press)RIO DE JANEIRO (AP) — Michael Phelps woke up on the morning of the first race of his fifth Olympic Games with some soreness in his right shoulder.

At 31 years old, the swimming superstar could not afford to have anything slowing him down. So he went to a Team USA athletic 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 for the ages to lead the 4x100-meter freestyle relay team to victory, giving him his 19th career gold…