Well, the thing is, Shaqque, they aren't allowed to break pace from their trot, so however fast they can trot is how fast they are allowed to go. Standardbreds (the type of horse used in harness racing) aren't as broad as, say, a quarter horse, but they are very strong nevertheless. The sulkies are made to be very light and drivers are typically small, broad-shouldered men, so they aren't really pulling as much weight as you might think.