Every time a 100 meter record falls, there is speculation on how fast a human can go. After all - Banister only had a four minute mile.
This article is interesting as it mentions a cheetah's time - about 6 seconds for 100 meters (and this is an average cheetah). But the person interviewed notes cheetahs have the same muscles, tendons and bone structure as a human...
Yeah- and they have four legs, and only weigh about 70 pounds .. small differences.
A big of googling finds this:
Williams TM, Dobson GP, Mathieu-Costello O, Morsbach D, Worley MB, Phillips JA.
Department of Biology, University of California, Santa Cruz 95064, USA. firstname.lastname@example.org
To establish a skeletal muscle profile for elite sprinters, we obtained muscle biopsy samples from the vastus lateralis, gastrocnemius and soleus of African cheetahs (Acinonyx jubatus). Muscle ultrastructure was characterized by the fiber type composition and mitochondrial volume density of each sample. Maximum enzyme activity, myoglobin content and mixed fiber metabolite content were used to assess the major biochemical pathways. The results demonstrate a preponderance of fast-twitch fibers in the locomotor muscles of cheetahs; 83% of the total number of fibers examined in the vastus lateralis and nearly 61% of the gastrocnemius were comprised of fast-twitch fibers. The total mitochondrial volume density of the limb muscles ranged from 2.0 to 3.9% for two wild cheetahs. Enzyme activities reflected the sprinting capability of the cheetah. Maximum activities for pyruvate kinase and lactate dehydrogenase in the vastus lateralis were 1519.00 +/- 203.60 and 1929.25 +/- 482.35 mumol min-1.g wet wt-1, respectively, and indicated a high capacity for glycolysis. This study demonstrates that the locomotor muscles of cheetahs are poised for anaerobically based exercise. Fiber type composition, mitochondrial content and glycolytic enzyme capacities in the locomotor muscles of these sprinting cats are at the extreme range of values for other sprinters bred or trained for this activity including greyhounds, thoroughbred horses and elite human athletes.
Sort of amazing -- so 83% of the quadriceps and 61% of the calf muscles of the cheetah are fast-twitch muscle. This is at the very high end of olympic sprinters. The glycogen breakdown of a cheetah is twice that of a human. Several other important differences are noted. Cheetahs and humans are very different animals, with one being much better suited to sprinting than the other. One wonders what an olympic class cheetah would be like. Of course cheetahs would be lousy marathon runners.
So it is likely that humans will never be at 6 seconds and extremely likely that the current record is not far from its limit.