Shaunae Miller (BAH) of Bahamas throws herself across the finish line to win the gold medal ahead of Allyson Felix (USA) of USA and Shericka Jackson (JAM) of Jamaica in the women's 400m final during the 2016 Rio Olympics in Brazil, Aug 15, 2016. [Photo/Agencies]

Felix, who finished in 49.51, was also on the floor after failing to claim her fifth Olympic gold medal, let alone the 200-400 double she had originally planned for the Rio Games.

"Disappointment," said the 30-year-old, struggling to hold back her tears. "It's been a tough one and I really hoped it would come together tonight.

"I just gave it all I had, I don't think I had anything left to give. I feel emotionally and physically drained at this moment. I really wanted it, it's painful."

Felix was denied the chance to defend her 200m title, and bid for an unprecedented double, after failing to finish in the top three at the U.S trials while suffering the effects of an ankle injury she suffered in a gym accident earlier this year.

The Californian's silver medal was, though, her seventh in four Games, the most of any American female track and field athlete at the Olympics.