It doesn't look like Thoroughbred racehorses will be breaking records anytime soon ... or perhaps ever again.
According to Mark Denny, PhD, of California's Stanford University, a plateau in racing speed was reached back in 1949, 1971, and 1973 for the Kentucky Derby, Preakness Stakes, and Belmont Stakes, respectively.
Denny analyzed the records for the U.S. Triple Crown races from 1896-2008 for the Kentucky Derby, 1925-2008 for the Preakness Stakes, and from 1926-2008 for the Belmont Stakes (when the current race distances were set).
In addition to noting that horses are not running any faster than they were decades ago, his assessment also revealed that the predicted maximum running speed is only 0.52-1.05% faster than the current race records.
"These results suggest that definite speed limits do indeed exist for horses and that their current speeds are very close to these predicted limits," said Denny.
Despite the fact that horses have been bred for speed and the population from which to select fast racehorses has increased over the past 50 years, race speeds have not increased in the past 40-60 years.
"Horses appear to have reached their limit," noted Denny.
While Denny's analysis may be construed as disappointing by some, Denny attests that his findings should not, "diminish the awe with which we view the performance of horses."
The study, "Limits to running speed in dogs, horses and humans," was published in the Journal of Experimental Biology in December 2008.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.