The greyhound is the fastest dog breed and, perhaps, the second fastest land animal behind the cheetah. Greyhounds reach speeds as high as 45 miles per hour in an open run and achieve maximum velocity in six strides over 100 feet.
Greyhounds have a thin, aerodynamic and tall build with an anatomy that lends itself to rapid acceleration and high speeds. Their hearts are large, and their muscles, although lean, produce a strong power-to-weight ratio. A greyhound's spine, like a cheetah's, is extremely flexible and allows it to cross great distances with each stride. Because of their speed, greyhounds were used as hunting dogs throughout recorded history. In the 20th century, greyhound races began to take place and, as of 2014, remain common.