She was under American record pace at the half way mark .
NCAA Champion Kelsi Worrell clocked a 56.84 to move up to fourth in the world rankings this year , a four tenth improvement from her previously tenth 57.27 .
Kelsi Worrell was under American record pace at the half way mark .
NCAA Champion Kelsi Worrell clocked a 56.84 to move up to fourth in the world rankings this year , a four tenth improvement from her previously tenth 57.27 .