The torch in the 400 metres may have just been passed in Eugene, Oregon, as Sanya Richards-Ross pulled up at the Olympic trials.

Richards-Ross pulled up halfway through her heat in the USA Olympic trials as her right hamstring would not let her finish.

Courtney Okolo, who recently won the NCAA Division I title at Eugene, took out the heat in 50.78 seconds.

The 31-year-old Richards-Ross was hoping to compete in her fourth Olympic Games. Instead, she will retire just a bit earlier than she wanted to.

"I thank God I was able to come out here today," Richards-Ross told NBC.

"But when I tried to go into fourth gear, my hamstring just locked up on me."

Richards-Ross was part of gold-winning USA Olympic 4x400m teams in 2004, 2008 and 2012, as well as winning the individual gold in the event in London in 2012.

"I don't take for granted that I got to stand on top of the podium and I'll hold those memories forever," she said.

"I'm excited for the next chapter of my life."