Researchers say more work is required to determine whether the increased speeds are due to breeding techniques or changes in training and riding.
Patrick Sharman, a PhD student at Exeter University and race enthusiast, decided to take a closer look. He found that previous studies were not comprehensive. They only analysed the winning time of a small number of races. These studies included middle distance (8 to 12 furlongs) and long distance (14 to 20 furlongs) races, but excluded sprints (5 to 7 furlongs). Mr Sharman analysed the times from every single so-called elite race involving the very fastest horses between 1850 and 2012, and also included all race meetings since 1997. He found that there had been little improvement in speeds between 1910 and 1975. But since then there has been a steady improvement in sprint races. The average winning time for a six-furlong race over the past 15 years has been cut by more than a second - which is a huge amount by sprint standards!
''A modern-day horse would beat a horse from the early 90s by seven horse lengths''
The improvement could be explained by a change in riding techniques since the 1970s - with jockeys adopting Lester Piggott's style of riding with shortened stirrups or improved training methods. But Mr Sharman wonders why there has been no improvement in the longer distances.
"My hunch is that we are seeing a genetic change, with breeders focusing on speed rather than endurance," he told BBC News. "I don't believe that over the longer distances horses have reached their limit."