
It takes an exceptional horse to be able to run the short distance of the Preakness and the longer distance of the Belmont. Most horses are either sprinters (the Preakness winners) or stayers (the Belmont), few are both. Look up the footage of Secretariat's win of the Belmont sometime if you want to see something incredible. After he died, they did an autopsy and discovered that his heart was almost twice the size of the average thoroughbred's heart.