The reason why the relatively diminutive domestic cat can run as fast as the fastest human i.e. almost 30 mph (45 km/h) is because they have four legs. They can gallop, and they can use their trunk muscles to help propel them forwards. Humans use their legs primarily, which limits their top speed.
Researchers from the University of Cologne and Stuttgart developed a computer model to work out an animal’s maximum speed based upon body structure. The model incorporates factors such as: muscle inertia, air resistance, propulsive leg force, body shape, leg length, number of legs and spine rigidity. They all affect the speed at which an animal can run.
Dr. Weihmann, the lead scientist in the study, said that the “shape of an organism must change as a function of body size in order to achieve a high running speed”. The model helps determine how “specific shapes affect the maximum speed that can be achieved.”
Comment: achieving a maximum speed is a compromise, however. I would argue that using the trunk less to propel the animal forward provides the animal with greater endurance. Therefore, they run slower but for longer distances at a consistently reasonable high-speed. The Mongolian wild ass is the animal which can run fastest over the longest distance. Although the cheetah can run at 60-70 mph top speed, they can only do it for about 400 meters as they overheat with the huge amount of muscular work. The domestic cat can run at a maximum of about 30 mph but it would be for a relatively short distance. Domestic cats are not long-distance runners as humans can be.
Bigger animals require more powerful muscles but they don’t help according to Dr. Weihmann, as larger muscles take more time to contract at top speed. He says that there is a weight limit above which the top speed starts to decrease. This limit is around 50 kg (110 lbs). This is somewhere near the average weight of cheetahs and pronghorns both of which are the fastest sprinters in the world.
The researchers decided that humans have almost reached their top theoretical speed. You can make running shoes more effective which is happening (although Nike’s Vaporfly ZoomX running shoes are set to be banned) or humans can evolve longer legs (won’t happen!) or have more elastic tendons, all of which would help humans run faster.
Comment: the cat has a floating shoulder bone. The forelimbs are connected to the rest of the body by muscle. The cat has a vestigial clavicle which floats. This allows for greater flexibility which in turn allows the cat to have an increased stride length and, in my view, allows the muscles of the trunk to work more effectively in propelling the cat forwards.
The study is published in the Journal of Theoretical Biology. It is titled: Rules of nature’s Formula Run: Muscle mechanics during late stance is the key to explaining maximum running speed.
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