The first American Triple Crown winner in 37 years, American Pharoah, silenced critics who said modern racehorses weren't up for the challenge, and now, new research says horses are getting even faster—at least in Britain.
A study published in Biology Letters shows Thoroughbred racehorses in Britain have grown speedier, especially sprint horses, which run short races of about 0.7 mile (1.2 kilometers), or 6 furlongs.
From 1997 to 2012, sprint horses improved their race times by over a second, or about seven horse lengths. Over middle and long distances—up to 20 furlongs, or 2.4 miles (4 kilometers)—racehorses only improved their speed slightly.
The study runs counter to previous research that suggested racehorse speeds had peaked, and the animals weren't getting any faster, says study co-author Patrick Sharman, an evolutionary biologist at the U.K.'s University of Exeter. The new study is more comprehensive than prior efforts, and takes into account every race run on British turf since 1850, when people started consistently timing races. (Read "People of the Horse" in National Geographic magazine.)
"I never really believed they reached a limit to how fast they can get," says Sharman.
Now that he knows how much faster horses have become, Sharman’s next question is "why?"
It's possible horses are evolving into genetically quicker beasts, which Sharman can determine by looking at pedigrees of horses going back generations.
It could also be diet or training, or maybe the jockeys have an influence.
A 2009 Science study found the modern riding style, where jockeys crouch over their horses, reduces energy demand and lets the horses run faster. Before 1900, British jockeys sat upright in long stirrups. The switch to short stirrups improved race times by up to 7 percent, according to the study. (Related: "Jockey Postures Make Things Easier for Horses and Speed up Races.")
A co-author on the 2009 jockey research, Alan Wilson, agrees that jockey style could influence why horses are getting faster, though he says many factors could be at play, including breeding.
Whatever the exact cause or causes, it could keep speeding up horses. "There is no hard physical limit to how fast [horses can get], though there will be a gradual process of diminishing returns," adds Wilson, head of the Structure and Motion Laboratory at London's Royal Veterinary College.
"But that could be a long way off."