The Greyhound is a very old European breed of dog, a sighthound which has been historically bred for coursing game and latterly Greyhound racing. Since the rise in large scale adoption of retired racing Greyhounds, particularly in North America from the end of the 20th century, it has seen a resurgence in popularity as a family pet.It is a gentle and intelligent breed whose combination of long, powerful legs, deep chest, flexible spine and slim build allows it to reach average race speeds in excess of 64 kilometres per hour (40 mph). The Greyhound can reach a full speed of 70 kilometres per hour (43 mph) within 30 metres or six strides from the boxes, traveling at almost 20 metres per second for the first 250 metres of a race. There are few mammals that can accelerate faster over a short distance, such as the cheetah, which can reach speeds of 109 kilometres per hour (68 mph) over 3-4 strides from a standing start, and pronghorn with an alleged top speed of 93 kilometres per hour (58 mph)