What Is the Fastest Dog in the World?

The greyhound is often known as the 45-mph-couch-potato. Kate Grishakova/Shutterstock

Different dog breeds have distinct reputations. Some are known for their brilliance or athleticism, while others are revered for their dashing good looks or amiable personalities.

When it comes to pure speed, however, the lean and agile greyhound earns the honors. Often dubbed the "45-mph couch potato," the greyhound is a part-time speedster, only going full throttle for short bursts. The rest of the time, this graceful pup is quite happy to lounge around.

The greyhound is the perfect example of "form follows function," the American Kennel Club points out.

From the narrow, aerodynamic skull to the shock-absorbing pads of the feet, Greyhounds are perfectly constructed for high-speed pursuit. The lean beauty of the Greyhound "inverted S" shape, created by the deep chest curving gently into a tightly tucked waist, has been an object of fascination for artists, poets, and kings for as long as human beings have called themselves civilized. Greyhounds are the template from which other coursing hounds have been struck.

At maximum acceleration a greyhound can reach 45 mph (72 kilometers/hour) within its first six strides from a standing start, dog author and professor of psychology Stanley Coren, Ph.D. says in Psychology Today. The cheetah is the only other land animal with that degree of acceleration. (And what impressive numbers it boasts: This beautiful creature regularly reaches speeds of 60 mph and beyond, but its real talent lies in going from rest to 60 mph in roughly 3 seconds.)

As Coren points out, greyhounds are the fastest member of a group of hunting dogs called sight hounds, since their job is to spot prey by sight and then run it down. Sight hounds include whippets, salukis and Afghan hounds, and they all have the huge chest, over-sized heart and narrow waist that lets them bend their body so that each stride carries them more than a full body length.

Although greyhounds are known for sprinting, if they feel like going the distance, they can settle into a nice 35-mph pace and keep at it for as long as seven miles, according to Cohen.

That is, if they haven't already gone home and curled up on the sofa.

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