Cheetahs vs. Humans: Sprinting limits

How fast can humans run? 100m in six seconds? "A cheetah can...!" The limits to human performance (and logic)

Last Saturday, the world crowned its newest "fastest man", when Usain Bolt of Jamaica dethroned Asafa Powell as the world record holder for the 100m event. We gave a very brief run-down of that performance the day after, but now that the dust is settling, there are some more meaty discussion topics arising out of the performance. And since we've been discussing Cheetahs quite extensively in the last few months, I thought we could pick up on a similar discussion, though this one doesn't involve the high-tech carbon fibre kind, but rather the African Cheetah, the quintessential sprinting "athlete"!

The usual response to world records - the limit to performance...

Whenever a world record is broken, the one question that ALWAYS comes up is "How much faster can humans run?" It happened last year, after Haile Gebrselassie broke the world record in the marathon, and suddenly people were talking of a sub-2 hour performance. Never mind the fact that he took "only" 29 seconds off the old time, running 2:04:26, which means that it will take another 8 or 9 similar performances to get to that 2-hour barrier. No, people said it was "imminent", 2 hours was waiting to be broken.

The same is happening now in the 100m event. And it's not just the media getting in on the act. This morning, an article came across my inbox which talks about the limits to human sprinting, and draws on what I must say is perhaps one of the most bizarre comparisons yet made in exercise science - essentially, it suggests that humans have large room for improvement, because an African cheetah (yes, the four-legged variety) is able to run 100m in six seconds...! Read on.

Cheetahs show that humans have room for improvement?

The article, which you can read here, describes the limits to human performance and discusses just how low the 100m time can still fall before athletes hit a limit. It makes use of a scientific expert opinion from Peter Weyand, of Rice University, to answer that question.

At one point in the article, the journalist makes the statement:

I feel pretty safe in assuming no man will ever run 100 meters in 6 seconds, but Dr. Peter Weyand won't join me in that generally baseless assumption.

Now, I'm not sure where the "six seconds" comes from, but later on in the article, it's revealed that this is the time a cheetah would run over 100m. So then, the journalist asks Weyand the following questions (Weyand's words in italics):

• Just how fast can man run?

Weyand's response:

"That's always the question of interest," said Weyand..."By definition, that's unknowable. It's intrinsically speculative, and there is no way around that."

• Next question from the journalist: What are man's limits?Are you really telling me that a man, who is not on steroids or some other performance-enhancing substance besides protein bars, might one day run the 100 in less than 6 seconds?

"A cheetah can," Weyand said.

• Your point?

"Well, cheetahs have the same muscles, tendons and bone structure as humans," Weyand said.

Given this "scientific fact", it would seem that Usain Bolt has a lot to answer for: Despite the fact that he has the "same muscles, tendons and bone structure" as an African cheetah, he's 50% slower over 100m than they are! His maxium speed is a pedestrian 50 km/hour, compared to a sweet 100 km/hour for the Cheetah. Back to the drawing board for Bolt, Gay and Powell then...?

I'd love to give the benefit of the doubt here, and say that maybe the journalist has taken quotes out of context, or that the true meaning was lost in translation. But it would seem that Weyand is suggesting that because a Cheetah can run 100m in six seconds, then humans (being so "similar" to cheetahs, of course!) have the potential to improve that "slow" time of 9.72 seconds by quite a margin...?

Not quite down to six, for Weyand doesn't go that far, though he certainly doesn't discount the possibility, which is itself interesting (or ludicrous, depending on your point of view). The comparison he makes between humans and Cheetahs (we have the same muscles, tendons and bone structure) is perhaps the most...shall we say, debatable. There is of course the small matter that humans run upright, on two legs, not four, along with all the associated biomechanical differences this creates (but let's leave that "trifle" difference aside for now). (As an aside, you'll note in the "Comments" section of this post below, that Peter Weyand was one of the scientists in the Houston study on Pistorius, giving him the distinction of delivering opinions on both types of "Cheetahs" in a matter of weeks)

A study of the African cheetah

About ten years ago, a study was actually published on that very question - a scientific investigation of the African cheetah. The study looked only at muscle fibre type and enzyme activity in the muscles of a cheetah, and essentially, it found the following:

• 83% of the vastus lateralis (the quadriceps muscle, basically) and 61% of the calf muscles of the cheetah consisted of Fast-Twitch muscle fibre. That is on the very high end of human ranges, with the very highest levels in humans around 70%.
• The enzyme activity of certain key enzymes in what is called the "glycolytic" pathways is substantially HIGHER in cheetahs than in humans. For example, the activity of one enzyme, LDH, is NINE times HIGHER than that of humans.
• Cheetahs have a rate of glycogen breakdown that is more than double that of humans
• A likelihood that phosphocreatine (PCr) was a primary energy source for sprinting and remarkably capable of providing energy for at least the first 15 seconds of sprinting. In humans, PCr is relatively limited and unable to sustain muscle contraction for any significant period.

In conclusion, the Cheetah has similar muscle composition, but vastly different enzyme activities. And we haven't even touched on the tendon and bone structures, which are also massively different. For example, fully grown male cheetahs weigh only 35 to 40 kg! Top sprinters are more than twice as heavy, which means the claim regarding bone structure is also likely to be off the mark. The implications of this mass difference on acceleration are obvious. And then, of course, there's that small matter of biomechanics (two vs four hardly seems comparable), but then that's so obvious no one would dare make the comparison, surely?

In that case, how much faster can humans run?

So let's just say that six seconds is just a little ambitious, regardless of whether Cheetahs, or any other animal can run that fast. And while Weyand is correct when he says that the answer to this question is "intrinsically unknowable", I do believe that it's possible to say with pretty high certainty what it WILL NOT reach, and six seconds definitely falls into that category.

Earlier this year, science that I do believe is credible was published, investigating the progression of world records, and it concluded that world records have already reached 99% of their limit, and that by 2027, half the world records will not improve by more than 0.05%. According to this research (which you can read here), we're pretty close to the limit NOW, and the idea that we have room for improvement in the magnitude of seconds in a 100m race represents what at best might be described as "over-ambitious". I know which science I believe.

I'm not suggesting, incidentally, that we've reached a cul-de-sac - I made the point once before that scientists can get themselves into trouble when they start predicting performance based on mathematical equations. Remember when it was once predicted that women would soon outperform men over the marathon, simply because women were improving very rapidly?

The real limit - 9.5 seconds is more likely the ceiling

But really, the idea of even a sub-9.5 second 100m performance is too big to conceptualise logically now. Consider that in 1968, the world 100m record was 9.95 seconds. It took 40 years to knock down by 0.23 seconds. Even if the world record continues to fall at that same rate (which it won't), then it will "only" take us until 2048 for it to hit 9.50 seconds! Remember too that the record has gone through the "drug-era" (and may still be in it!), where performance gains are amplified by what was pretty unrestricted use of some pretty potent drugs. If those drugs have made such a small impression on the performance, then what will it take to get it down to 9 seconds?

So as far as a sub-9 second time goes (forget 6), there's about as much chance of that happening as people inventing a tablet that gives you or I the chance of being around long enough to see it --- in the year 2190 perhaps! Unless of course, the right athlete hooks up with the right technology...then make it 2019...

Or maybe they just need to learn to run on all-four legs, taking advantage of the inherent similarity between us and natures best sprinter - then the scientific comparison between humans and cheetahs can really be put to the test...!

Ross