July 17, 2009

Science Behind Jockey’s Posture Revealed

Scientists are now discovering why a jockey's posture during a horse race speeds up the horse.

The Royal Veterinary College team reported Friday in the journal Science that after 100 years of recorded race times, the biggest improvement in speed came around the turn of the 20th century when jockeys changed their posture.  The change was a 5 to 7 percent difference in the U.S. and Britain.

The researchers stuck a GPS unit in some jockeys' helmets and inertia sensors on the riders and five speedy racehorses while taking measurements during training races.

The team discovered that the jockeys' crouch lets them isolate their bodies from the horse's movement because the horse is moving up and down a lot more than its rider.  Once the horse's feet hit the ground, its motion temporarily slows until accelerating again with push-off.  The jockey's legs then act like a spring, with his or her mass staying at a more constant speed.

"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."

He said that information could help in the quest to build better robots that are able to handle a bumpy environment.

A few years ago, University of Pennsylvania scientists 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 came 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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