What are the kinds of adaptions that make an animal fast?

There are various adaptations animals' bodies can have for speed. The cheetah is a good example, since its entire body is designed for this purpose - it is the fastest-running animal on Earth. It is a slim, stream-lined animal with long, slender legs - this means its weight is kept to a minimum, and the stride is lengthened as much as possible, especially as it has a digitigrade stance (meaning it walks on its toes, rather than walking on the flat of the feet, like we humans do). The head is small and rounded, to cut more easily through the air and reduce drag. The nostrils are large, helping to breathe in a greater amount of oxygen quickly. The lungs and heart are large, in order to process that oxygen fast and rapidly distribute it to the muscles. The spine is very flexible, which further increases the length of stride the cheetah can take - its hind legs actually reach in front of the forelegs with each bound. The tail is long and flattened, and acts like a rudder, helping the animal change direction quickly at high speed. The pads of the paws have ridges on the skin, and the claws are only semi-retractile (unlike those of other cats, which are fully retractile) - both of these are adaptations which help the cheetah grip the ground (think of the treads and spikes on running shoes). All these things combine to give the cheetah a top speed of over 60 miles per hour - each bound at full speed covers around 7 metres, and the paws are actually off the ground more often than in contact with it. A cheetah running at top speed is almost flying. This is the result of millions of years of evolution - there is no way a human could ever hope to match it. Our bodies are just not designed that way. Fortunately, we have a big brain instead, which has let us invent cars!