Horse races have evolved into a spectacle of huge fields, sophisticated electronic monitoring equipment, and immense sums of money, but they are still basically contests of speed and stamina between two horses. One wins, the other loses, and that has been the basic concept of the sport since its inception 2,000 years ago.

Horses have a natural aptitude to run, but they also need extensive training to develop their physical and mental abilities to be able to compete in the most demanding race conditions. Despite these efforts, injuries, breakdowns and fatal accidents continue to be a major problem in thoroughbred racing. The deaths of Eight Belles and Medina Spirit, both champions in their respective classes and just three years old when they died, sparked a national reckoning of the sport’s ethics and integrity.

A new video filmed by PETA and published in The Atlantic shows some of what animal activists have long complained about at the highest levels of American horse racing. It features the trainers Steve Asmussen and Scott Blasi, and it provides glimpses of the exploitation of world-class horses at Churchill Downs and Saratoga.

This is only the latest in a series of exposés by PETA, which has been probing the dark side of racing for more than 20 years. Its investigations have uncovered abusive training practices, drug use and the shipment of horses to foreign slaughterhouses, among other problems. Growing awareness has helped to improve some of these problems, but PETA is determined to keep the pressure on.

There is a sense of desperation in the crowds at big racing events, as well as in the bowels of the grandstand. Away from the private suites and the high-end betting parlors, many of the fans are working-class men who periodically gather to stare at banks of TVs that broadcast races from all over the world, even Peru and Argentina. They talk in a language of their own, and the curses that rise with the stretch runs have a universal rhythm and ring of imprecations.

Despite their popularity with the public, races are often held for horses that are too old to have reached their peak ability. The classic age for racing is three, but escalating breeding fees and sales prices have led to a decline in races that take place with horses older than that.

A horse’s pedigree is an essential component of its eligibility to race. A horse must have a sire and dam who are purebred members of its breed in order to race. A horse with a winning pedigree will have an advantage over its competitors in any race.