Human athletes can increase the size of their hearts through proper conditioning.
Now, new scientific research shows that superior racehorses, both Thoroughbreds and Standardbreds, also have hearts substantially larger than average horses. Unlike humans, the size of equine hearts is an inherited trait. Large racehorse hearts are passed from generation to generation through the mare, or as geneticists call it, the X chromosome. The challenge facing breeders and buyers is learning how to capitalize on this important new research. Marianna Haun was part of the U.S. team that conducted this ground-breaking research.