By contributor

Explainer: The science of horse racing

  • Secretariat Turcotte
    Associated Press

    Secretariat was the first horse to win the Triple Crown in 25 years when he crossed the finish line at the Belmont Stakes in 1973 with a lead of 31 lengths. His time of 2 minutes and 24 seconds remains an unbroken course record. The chestnut colt also set a still-standing record at the Kentucky Derby, the first leg of the crown. A timer malfunction at the Preakness Stakes put his speed on that track in question. His unofficial time of 1:53 2/5 has been tied twice, but never beaten.

    "That horse was a phenomenon," says Kenneth McKeever, associate director of the Equine Science Center at Rutgers University in New Jersey. Now the phenomenon has been immortalized in "Secretariat," Disney's feel-good movie about the racehorse and his dynamic owner, Penny Chenery Tweedy.

    Click the "Next" label to learn more from McKeever about the science behind thoroughbred racing.

    — By John Roach, contributor

  • Horses are natural blood dopers

    Image: 136th Running of the Kentucky Derby
    Andy Lyons  /  Getty Images

    Some people say horses are natural blood dopers. That's because they store a tremendous amount of red blood cells in their massive spleen — an organ that measures as much as 4 feet long, 8 inches wide and 4 inches thick.

    "The extra amount of red blood cells that are sort of sequestered in the spleen can be infused into the central circulation at the outset of exercise, and that gives them an ability to transport a tremendous amount of oxygen within the blood," McKeever says.

    When at rest, about 35 percent of the total blood volume in humans and horses is made up of red blood cells. Humans maintain that proportion even during exercise. The extra blood in the spleen allows horses to increase their red blood cells numbers to more than 65 percent.

  • Horses outdo humans in aerobic capacity

    Spectators throw water at US Lance Armst
    Franck Fife  /  AFP - Getty Images

    The oxygen that racehorses breathe is used exceptionally efficiently. The maximum volume of oxygen that an athlete can use is called VO2 max. It's an indicator of aerobic capacity, measured in milliliters per kilogram of body weight per minute.

    Elite human athletes such as Tour de France seven-time champion Lance Armstrong have reported VO2 maxes in the upper 80s. Elite thoroughbred racehorses are in the 150 to 160 range. "That's huge," McKeever says.

    "Not only do they have a tremendous aerobic capacity, but they have an ability to hang on at the end of the race and tolerate relying on those intermediate sprint fibers that are in there helping with that kick at the end of the race," McKeever adds.

  • Lungs operate like a bellows

    Adam Coglianese / AP

    Inhaling all the oxygen isn't as simple as breathing deeply, even for a horse. Unlike humans, a galloping horse's breathing is coupled with its stride so that it operates like a giant bellows. Horses can inhale only when their front hooves are striding outward. They exhale when all four legs come together.

    "The horse's lung in general is not large enough to do what it should be doing, so one of the things that limits the ability to take enough oxygen is that coupling of stride and respiration," McKeever says.

    As a result, horses never get the “second wind” that humans get when they expel excess carbon dioxide and begin to take in more oxygen. Instead, the oxygen levels in their blood decrease and carbon dioxide levels increase.

  • A great body ... and a good head, too

    Calvin Borel, Rachel Alexandra
    Julie Jacobson  /  AP

    Take all of the physiological advantages of racehorses, and the difference between the winner and also-rans comes down to how well the bones and muscles are put together — called conformation — and what's in the horse's head.

    "If everything falls into place and you've got a horse that has got the tools as far as the physiology, is sound orthopedically, and upstairs is feeling good and wants to win, has that drive, then you look at conformation … It's a combination of all those things," says McKeever. "That's why when it comes to pointy-headed scientists like myself trying to predict performance, I stay away."

  • Can speed be spotted in the genes?

    Image: 136th Running of the Kentucky Derby
    Andy Lyons  /  Getty Images

    If thoroughbred owners are unsure whether their foal is best suited for sprints, mid-distance races or endurance events, they can fork over 1,000 euros (about $1,400 at current exchange rates) for a genetic test that claims to remove guesswork from the decision. Scientists at the University of College Dublin identified the so-called speed gene by comparing the genetic code of 148 horses with their results on the racetrack. They found variants of the gene, which encodes for muscle development, that match up with the horse's optimum racing distance.

  • Why crouching makes horses run faster

    Image: Jockeys
    Equine Action Images

    Not all of a horse's speed comes from within: When jockeys shortened their stirrups and began crouching uncomfortably as they leaned over their horses' necks in the last decade of the 19th century, racetrack times improved by 5 to 7 percent.

    More than 100 years later, scientists figured out why the change in posture translated to the gain in speed: The crouch essentially allows the jockeys' legs to act as giant shock absorbers. No longer did horses have to lift up the jockeys’ full weight with every stride.

    More from and NBC Sports:

    Review: 'Secretariat' mixes mush and thrills
    Sorry, screenwriters: Most animals just want to eat us
    Jockeys figure out the science of speed
    Horse science: What makes a winner?
    Horse racing coverage on NBC Sports


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