Olympic 200 metres gold medallist Allyson Felix has chosen to run the 400 metres at next month's world championships, her coach told Reuters on Wednesday.
"We wanted to do both (the 200m and 400m) but the schedule will not allow it, so it's the 400," Bob Kersee said in a telephone interview from Oregon.
"It's more of a challenge for us," Kersee added when asked why the longer race.
Had the 29-year-old American attempted both races, as she did at the 2011 worlds, she would have had to run the semi-finals of the 200m an hour before the 400m final on Aug. 27. The 200m final is the next day.
Felix will also compete in both the 4x100 and 4x400 metres relays in Beijing, Kersee said.
The year's fastest at 200 metres, Felix could have run either the 200m or 400m or both in the world championships. She had a bye into the 200m as the 2014 Diamond League winner and won the 400m at June's U.S. world championships trials.
"Excited to step it up and challenge myself next month," Felix said on her Instagram account along with a picture of her training and the words "Getting some 400 work in to get ready for worlds."
Felix currently ranks as the year's fourth fastest at 400m, but the two faster Americans on the list, Francena McCorory and Sanya Richards-Ross failed to make the U.S. team.
Injured at the 2013 worlds, Felix had placed second in the 400m and third in the 200m at the 2011 world championships. She also ran on winning U.S. 4x100m and 4x400m relay teams.
Asked if Felix would consider doing both sprints at the 2016 Rio Olympics, Kersee said: "Yes.
"That would be the crowning point of her career."
But like Beijing, the challenge would be difficult, and most likely would require a schedule change.
Felix would be required to run the first round of the 200m 75 minutes before the 400m final under the current schedule.
Kersee would like a more favourable opportunity.
The precedent is there, he said, noting both American Michael Johnson and France's Marie-Jose Perec won 200-400m doubles at the 1996 Olympics.
Not to change Rio's timetable, "would be to deny an athlete realistically capable of winning four gold medals," Kersee said.
Image: Allyson Felix competes in the Womens 400 Meter during day two of the 2015 USA Outdoor Track & Field Championships
Photograph: Andy Lyons/Getty Images