Harness racing use a standing start. The sulky (informally known as a "bike") is a light, two-wheeled cart equipped with bicycle wheels. The driver (not a "jockey", as in thoroughbred racing) carries a light whip chiefly used to signal the horse by tapping and to make noise by striking the sulky shaft. There are strict rules as to how and how much the whip may be used; in some jurisdictions (like Norway), whips are forbidden. For exercising or training, the drivers use what is known as a "jog cart," which is a sulky that is heavier and bulkier than a racing unit.
Horses in the Middle Ages their hindquarters. Harnessed in such a manner, horse teams could pull no more than 500 kg. The breastplate-style harness that had flat straps across the neck and chest of the animal, while useful for pulling light vehicles, was of little use for heavy work. These straps pressed against the horse's sterno-cephalicus muscle and trachea, which restricted breathing and reduced the pulling power of the horse. Two horses harnessed with a breastcollar harness were limited to pulling a combined total of about . In contrast, the horse collar rested on horses' shoulders and did not impede breathing. It allowed a horse