Team GB's Shana Cox has failed to qualify for the final of the women's 400m.
The American-born runner got off to a good start, which left her in contention with 200m of the race run.
However, she appeared to tighten up on the final bend and ended up finishing seventh with a time of 52.58 seconds.
Botswana's Amantle Montsho won the race, with America's Francena McCorory taking second spot.
