Harness racing is the practise of racing standardbred horses - horses bred specifically to suit this sport - pulling the jockey, or driver, in a light two-wheeled cart known as the 'sulky'. Harness racing is especially popular in the United States and the United Kingdom.
There are two main forms of harness racing: Trotting and Pacing. The difference between the two types of harness racing is the gait the horses adopt for the race.
A pacing horse, or Pacer, uses a lateral stride; meaning the right front and right hind leg move forward in unison as the left front and left hind leg are moved back. This form of movement makes the horse rock from side to side, which means that riding on the horses back as it is done in a standard thoroughbred race would be intensely uncomfortable. For a harness race however, pacing is an ideal gait to use, as it prevents the horse from getting tangled in the racing harness and does not affect the balance of the sulky.
A trotting horse, or Trotter, uses a diagonal stride; meaning the left front and right hind leg are moved forward when the right front and left hind leg move back. There are several variations of the classic trot; ranging from the two-beat 'square trot', with diagonal pairs of hoofs hitting the track simultaneously, to a four-beat 'ambling trot', with each hoof connecting with the track at a different moment. Other variations of trotting, such as the 'collected trot', are often used in dressage riding performances.
In harness racing, there are two techniques employed to start a race: the standing start and the moving start.
In a standing start the horse and sulky remain stationary behind a line of tape stretched across width of the track until the race begins. This technique is used in handicap harness races, as the standardbred horses are handicapped with distance rather than height. Individual starting lines are marked with separate lengths of tape for each horse, ensuring that the horses with the higher handicap ratings have a longer distance to travel.
A moving start sees the horses trotting or pacing at a relaxed speed behind a vehicle mounted with collapsible gates covering the width of the track. To signal the start of the race the vehicle speeds away, collapsing and folding away the gate as it gains distance from the horses and sulkies. The vehicle requires two operators; the driver and a starter, who sits on the vehicles rear facing the horses, determining whether a false start or any other irregularities have occurred.
The United States, United Kingdom, Australia, Canada and New Zealand host harness races for trotters and pacers alike; while harness races on the European continent are limited to trotters only. In the US pacing is the far more popular mode of harness racing, with pacer events accounting for an estimated 90% of harness race meetings.