A horse race is a contest of speed and stamina between two or more horses. The horse with the fastest time wins the race. It is one of the oldest sports, and its basic concept has changed little over the centuries. A modern thoroughbred race can involve enormous fields of runners, sophisticated electronic monitoring equipment, and enormous sums of money, but the essence of the event remains unchanged: a contest of speed and endurance between two or more horses, with the winner being the one that crosses the finish line first.

The sport has also adapted to meet the changing needs of spectators, from a popular diversion of the leisure classes to an entertainment industry that caters to a wide variety of people and income levels. Its popularity has waned in recent decades, however, as concerns about animal welfare and the use of performance-enhancing drugs have grown.

Races have evolved from a primitive contest of speed and stamina between two horses to what is now a sophisticated spectacle involving large fields of runners, sophisticated electronic monitoring equipment, enormous sums of money, and intense competition among owners and trainers. The horse racing business has become a multibillion-dollar enterprise.

The sport’s popularity has waned in recent years, though, as concerns about animal welfare and the use and abuse of performance-enhancing drugs have grown. The brief season of premier 3-year-old thoroughbred races that begins on Saturday in Louisville this year is perhaps all that remains of the former glitz and excitement of horse racing, which was once the greatest of all spectator sports.

Many of today’s racing horses are bred to run only a few races before retiring, and they are different animals from the rugged Seabiscuit or the hardy Secretariat. Their leg bones are slender matchsticks, and their muscles are not nearly as dense or as powerful. Their bodies have been sculpted into an image of sleekness, and they are as likely to lose their balance on a sharp turn or at the far end of a straightaway as to win on those same turns or straightaways.

In the era before modern drug-testing, racing officials couldn’t keep up with the proliferation of new medications designed to mask injuries and enhance performance. Painkillers, anti-inflammatories, growth hormones, and blood doping were all commonplace. The penalties for breaking rules were lenient, and a trainer who was punished for a positive test in one jurisdiction could simply move to another.

The term dark horse refers to a horse who is not yet well known to the public or to racing’s betting pools. It can also refer to a horse who is unlikely to win, whether or not it has won any races, or to an outsider in a political race. A dark horse is usually a long shot to win the race, which makes it an attractive bet for those who want to place a wager on a big upset. A bet to win is a wager that a horse will come in first, while a bet to place means the horse will finish either first or second, and a bet to show places the horse in third or better.