cannot be paid back.

Food and Drug Administration, Baltimore, Md. (3,090 square feet)National Oceanic Atmospheric Administration, Barre, Vt. (287 square feet)

Mine Safety Health Administration, Birmingham, Ala. (20,554 square feet)Animal and Plant Health Inspection Service, Bismarck, N.D. (28,954 square feet)Natural Resources Conservation Service, Blythe, Calif. (980 square feet)

Corps of Engineers, Civil, Bountiful, Utah (2,961 square feet)United States Fish and Wildlife Service, Bozeman, Mont. (7,853 square feet)

Environmental Protection Agency, Castle Rock, Colo. (10,800 square feet)

Federal Communications Commission, Cerritos, Calif. (3,680 square feet)“Adrenaline when exercising causes the spleen to release extra red blood cells into circulation,” veterinarian Hilary Clayton said. “What horses are doing is essentially ‘blood doping’ themselves.”

Meanwhile, horses’ brains allow them to process sensory information and react quickly. That’s despite having frontal lobes, parts of the brain used for thought and planning that are proportionally smaller than those in humans.“Brainwise, they’re designed with a real desire to play and run independent of any fear,” said Dr. Scott Bailey, a veterinarian at Claiborne Farm in Paris, Kentucky, a thoroughbred breeding farm where Secretariat is buried. Horses are also able to focus intently, which “is really important for an athlete.”

Bone structure and musculature also help. The ligaments and tendons in their hind legs act like springs, Farmer said, helping propel them forward. Like other large prey animals, he added, they have “long, thin legs that are meant to run.”The adaptations that make horses faster also predispose them to injury, Reed said. Their skinny legs absorb the impact of each stride, she said, and over time the repetitive stress of racing and training can lead to deformation of tendons and ligaments.