horse anatomy

How thoroughbred horses convert air into blazing speed

In honour of today’s run for the roses, Wired magazine talks about horses and their spleens and how important they are to their blazing speed.

“There are sprinters and there are distance runners, but the thoroughbreds charging down the track this month at the Kentucky Derby (sometimes called the fastest two minutes in sport) need to be both. The race stretches a grueling mile and a quarter, so those horses have to be machines that convert air into speed.

1// Slow-Twitch muscle uses oxygen more efficiently, which aids endurance. Thorough­breds have nearly twice as many slow­ twitch fibers as sprinty quarter horses, so they can clock speeds up to 40 mph even on the home stretch.

2// The spleen can squirt out 12 bonus liters of blood, jack­ing up cardiac output. The extra red blood cells provide a Lance Armstrong–style boost to the horse’s blood oxygen levels.

3// Big hearts mean fast racers, because the organ can pump more blood (and thus 02) to the muscles. A gene on the X chromosome gives some thoroughbreds a heart that’s nearly twice normal size.”

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