Usain Bolt might be the fastest man on Earth, but a cheetah can run 100 metres (328 feet) over three and a half seconds quicker. A cheetah called Sarah from Cincinnati Zoo, Ohio, holds the record at just 5.95 seconds. Cheetahs are faster than humans because they are smaller, which means they require less force to accelerate, and they have four legs which gives them more points of contact with the ground to push themselves forwards. But the reason that cheetahs are faster than any other four-legged animal is their incredibly flexible spine. As they run, it folds up to the point where the back legs actually overtake the front legs. This gives them an effective stride of about seven metres (23 feet) – the same as a racehorse!