Athing Mu stumbles, falls in 800 meters and will not have chance to defend her Olympic title

Athing Mu got tangled up in the middle of the track and started falling. One hand hit the ground, then the other. As she rolled onto her back, her bright pink shoes started pointing toward the sky.

With that, one of America's most promising runners saw her hopes of back-to-back Olympic titles in the 800 meters go down the drain, while sports fans got a refresher on just how unforgiving these U.S. track trials really are.

The 22-year-old from became the first big-name casualty of the trials Monday, victimized by a bunched-up pack in the backstretch of the first