Cheetahs are the fastest mammal on earth. In short, a cheetah’s muscles need to rapidly contract and relax. Cheetahs are 4 feet in length from head to tail (tail alone is 2 feet long) and weigh about 100 pounds. Cheetahs unique musculature system allows them to run up to 70mph as their stride is equivalent to a race horse (23 feet or nearly 6 times their length). Cheetahs have super- fasttwitch muscle fibers (IIX) that are nearly 70 % makeup of their skeletal muscle mass. There as are really 3 types of skeletal muscle fibers: Type I slow twitch fibers, Type II fast twitch fibers and super- fast twitch fibers type IIX. By comparison, a human may have on average nearly 50 % slow and 50% fast twitch muscle fibers with only 2% super- fast twitch fibers. The fastest human sprinters may have up to 25% super -fast twitch fibers and as above the Cheetah has nearly 70% super- fast twitch fibers. So ,what is the difference?
Type I or slow twitch fibers are small in size, red color, slow and small contraction capability that has a higher density of mitochondria utilizing oxygen with diverse substrates of energy (fatty acids, glycogen or glucose). The advantage to this muscle type is that it is resistant to fatigue.
Type II or fast twitch fibers are medium in size, red color and have more power (contraction) and at a faster rate of speed (mile runner, swimmer or shorter distance cyclists).
Type IIX super-fast twitch fibers are larger, more dense muscles that are white in color as the oxygen capacity is low (less mitochondria), quicker contractions and more power that utilizes glycogen as fuel source under anaerobic conditions that may last 15 to 30 seconds as the disadvantage is that the muscles get tired or fatigue easily. Cheetah’s muscles are built for power and acceleration, but endurance is the rate limiting step.