Rachel Alexandra returned to work at Churchill Downs, as did Mine That Bird -- winner of the Kentucky Derby and runner-up to the filly at the Preakness.
After becoming the first filly to win the Preakness in 85 years, Rachel Alexandra galloped Wednesday and was scheduled to do so again Thursday.
A decision has yet to be made whether she will run in the Belmont Stakes, the third leg of the Triple Crown.
Mine That Bird, meanwhile, galloped 1 1/2 miles in a second workout since returning to Churchill Downs.
"The horse is just doing super; he's on his game," trainer Chip Woolley said. "We're really surprised that he's as fresh as he is after two good, hard races."
Mine That Bird will take part in the 1 1/2-mile race at Belmont Park in Elmont, N.Y., although it is not yet known who the horse's jockey will be.
Calvin Borel, who rode Mine That Bird to the Kentucky Derby win, switched to Rachel Alexandra for the Preakness. Mike Smith, who rode Mine That Bird in the Preakness, will be unavailable for the Belmont.
If Rachel Alexandra does not run at the Belmont, Borel could switch back to Mine That Bird. If Borel wins all three Triple Crown races aboard two different horses, it would be a first in thoroughbred racing history.