The sport of horse racing has morphed over the centuries into a vast, multimillion-dollar public-entertainment industry that requires complex electronic monitoring equipment and enormous sums to run. But its basic concept has not changed: a contest of speed and stamina between two horses over long distances. While spectators show off their fancy outfits and sip mint juleps, the horses race for their lives. Pushed beyond their limits, they are subjected to a cocktail of legal and illegal drugs designed to mask injuries and boost performance. Injuries are common; many horses bleed from their lungs, a condition known as exercise-induced pulmonary hemorrhage.

In the earliest days of horse racing, most races were closed events in which only a few well-bred horses were eligible to compete. But as the demand for public horse races increased, rules were developed to open up racing to larger numbers of horses. Eligibility was based on age, sex, birthplace, and previous performance. Horses were divided into categories such as colts, geldings, and fillies.

Handicap races were also introduced to level the playing field and allow weaker horses to win. In these races, horses are assigned a specific amount of weight to carry, which is adjusted for the type and class of race. This weight adjustment is based on a mathematical formula that takes into account the speed and class of the other horses in the race as well as the horse’s own past performances.

During the early days of the sport, horses were typically trained to run a specific distance such as six or twelve furlongs. The onset of modern training techniques in the 1930s has resulted in horses being trained to run longer distances and be able to finish strong at the end of their races. The modern thoroughbred is a larger animal, capable of covering ten or twelve furlongs in a race, and has more stamina than its predecessors.

While the majority of horse races take place on dirt tracks, there are a number that are held on grass or turf. The surface of a racetrack is a major factor in the running and jumping of horses, as well as the overall quality of the races. A muddy track will force a horse to slow down, and it will likely lose ground to its competitors. A dry track, on the other hand, will enable a horse to accelerate quickly and gain ground.

A jockey will use a whip to urge a horse to run faster and more vigorously. Whipping a horse can be dangerous if the rider is inexperienced or careless, and it is important for the safety of the riders and the animals to learn proper technique. When a jockey only uses his or her hands, it is called riding in hand and the horse is not whipped. A hand rider is more apt to have good control over the horse and will not be so quick to use the whip. Having good riding skills is a vital part of becoming a winning jockey.