Image: Jockeys
Equine Action Images
Jockeys use the posture associated with the modern riding style as they cross the finish line at Royal Ascot 2009.
updated 7/16/2009 7:54:01 PM ET 2009-07-16T23:54:01

Over a century after a Yankee Doodle jockey revolutionized how racehorses are ridden, scientists are figuring out why a jockey’s posture speeds up the horse.

Nope, it’s not wind resistance. That tough balancing crouch saves the horse some energy.

First, the fun history: Racing fans may have heard of Tod Sloan, an 1890s U.S. jockey widely credited with sparking the trend of shortening stirrups and leaning over the horse’s neck — and along the way taking England by storm and inspiring an early George M. Cohan musical with a song called “Yankee Doodle Boy.” The days of tall-in-the-saddle racing ended quickly as other riders adopted the crouch.

Fast forward to 2009 and a University of London research team famed for studying how horses and other animals move.

In more than 100 years of recorded race times, the biggest improvement in speed — a 5 percent to 7 percent change in the U.S. and Britain — came around the turn of the 20th century when jockeys changed their posture, the Royal Veterinary College team reports Friday in the journal Science.

To find out why, researchers stuck a GPS unit in some jockeys’ helmets and inertia sensors on the riders and five speedy racehorses, and hit the track to measure training races.

They discovered the jockeys’ crouch lets them isolate their bodies from the horse’s movement — the horse is moving up and down a lot more than its rider. When the horse’s feet hit the ground, its motion temporarily slows until accelerating again with push-off. Through incredible effort that makes the jockey’s legs act like a spring, his or her mass stays at a more constant speed. It’s basic physics.

“The jockey adds weight but not inertia to the horse,” explained research fellow Andrew Spence, a study co-author. The jockeys “say things like, ’You need to go with the flow of the horse.’ ... The neat part of the study is we’ve shown how that happens mechanically.”

And that information, he said, could help in the quest to build better robots that can handle a bumpy environment.

It fits with other research: University of Pennsylvania scientists a few years ago discovered that a backpack made to bob up and down less as the wearer walks is far easier to carry, because it reduces the extra force when the pack comes down.

“The horse expends a lot of energy in the fact that the body slows and they have to speed it up again,” said Dr. Susan Stover of the University of California, Davis, who studies the biomechanics of racehorse injuries. “The argument these people put forward is very compelling.”

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