For starters, cheetahs have an incredibly long stride length of 25 feet, a little over 4 times longer than the average stride of an elite miler and just over 3 times longer than the enormous 8 foot stride of 100m world record holder Usain Bolt. Just as Bolt dominates international competition by traveling farther on each stride than the competition, cheetahs can easily reach 70 mph by taking giant bounding strides. The cardiovascular system of the worlds fastest cat is a marvel in itself, with a much larger than average heart pumping more blood per beat than many other animals can manage. However to supply oxygen to this heart is a unique respiratory reflex. Like most four legged animals, cheetahs are forced to breath one breath for every full stride which while makes for large air intake, severely restricts endurance. What makes cheetahs unique is the fact that their abdominal cavities are tied to their diaphragms. When they push off with their hind legs the body tips up away from the ground a little and the organs slide back in the abdominal cavity, drawing the diaphragm back and forcing inhalation. When the front paws hit ground the body tips forward and the organs slide forward, expelling air from the lungs. The motion of the internal organs along with expansion and contraction of the abdominal cavity allow for cheetahs to take in the enormous amount of oxygen they need to sustain speeds of 70 to 75 mph. For a nice video of this check out:
stay posted for the reasoning why cheetahs can't run far and humans can't run fast.