Gaits
Standardbred racing is contested on two gaits, the trot and the pace. Trotters move with a diagonal gait; the left front and right rear legs move in unison, as to the right front and left rear. It requires much skill by the trainer to get a trotter to move perfectly at high speeds, even though the trotting gait is a natural one in the animal world. But horseman and fans agree that there are few things more beautiful than a trotting horse in full stride.
Pacers, on the other hand, move the legs on one side of their body in tandem: left front and rear, and right front and rear. This action shows why pacers are often called "sidewheelers." Pacers, which account for about 80 percent of the performers in harness racing, are aided in maintaining their gait by plastic loops called hobbles, which keep their legs moving in synchronization. Due to the sureness of their action, pacers are usually several seconds faster than trotters.
Actually, a third gait often manifests itself in harness racing running. But a horse who runs, or goes "off-stride" in the parlance of the sport, must return to his natural gait or face disqualification