The 17-year-old broke her own world junior record in the 1000m.
His Oregon Project teammate, Matthew Centrowitz, has withdrawn from the race.
The 17-year-old Cain took nearly a second off the previous mark.
The American silver at the World XC Champs is a the top of the list.
American runners had a good showing last week in Moscow!
Bernard Lagat, Ryan Hill, and Galen Rupp all run qualifying times.
The American record-holder says it was her farewell to high-level marathons.
One study suggests that runners who rely on less muscle activation actually go faster.
Galen Rupp and Mary Cain are two distance stars to check out.
Men's, women's 800m winners triumph in quick fashion on the final day of the USA Outdoor Track & Field Championships.