Cheetahs can run 60 miles per hour, at top speed. By comparison, greyhounds can only run about half as fast, despite having roughly the same size, weight, shape and running motion as cheetahs. Why are those cats so fast, and why are those dogs so slow?

A group of scientists, probably after losing too much money at the dog track, decided to find out. Their experiment was a failure, but it actually taught us a great deal.

Alan Wilson, Penny Hudson, and Sandra Corr, all from the Royal Veterinary College decided to risk a great deal of scientific equipment, finding out why those damn dogs are so slow. They wheedled the resources to get some force plates, which are delicate and expensive pieces of equipment. They then buried these pieces of equipment in the ground of a cheetah enclosure, possibly in front of the frowning faces of the people they'd got them from. They also installed high speed cameras, and got both greyhounds and cheetahs to race around the enclosures after scraps of meat, hoping to find out the secret of the cheetahs' speed.

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It did not work. Not because the experiment was wrong, but because the cheetahs, captive for generations and not in need of great speed to hunt down their meals, didn't run as fast as the greyhounds did. At their peak, they did a little over a meter per second less than the greyhounds. Surprisingly, it still provided answers.

Greyhounds, trained to go at their peak, managed about 3.5 strides per second at any speed. At ten miles per hour, they took small strides, and as they increased their speed, their strides kept coming at the same rate, but got longer. The cheetahs, however, managed to increase their stride rate as they went faster. At a slow run of nine meters per second, they did about 2.4 strides per second, while at their fastest of 17 meters per second, they managed 3.2 strides. Researchers think that at their top speed, they can manage a stride rate of four strides per second, and can do it with a longer stride than greyhounds.

So it seems that cheetahs get their ability to increase speed and reach such high speeds because of a built-in gear shift. And it also appears that researchers will have to stick with greyhounds at the track — even if they do lose a bundle.