What makes cheetah the fastest land mammal? Why aren't other animals, such as horses, as fast? While we haven't yet figured out why, we have some idea about how—cheetahs, as it turns out, make use of a galloping gait at their fastest speeds, involving two different types of 'flight': one with the forelimbs and hind limbs beneath their body following a forelimb liftoff, called gathered flight, while another with the forelimbs and hind limbs stretched out after a hind limb liftoff, called extended flight. Of these, the extended flight is what enables cheetahs to accelerate to high speeds, and it depends on ground reaction forces satisfying specific conditions; in the case of horses, the extended flight is absent.