Are we growing super humans?
Provocative new research from Duke University shows that the fastest people on the planet, whether they are running on a track or swimming through the water, are getting bigger.
The fastest runners today on average have grown 6.4 inches since 1912 and they have shaved nearly a full second off the 100-meter dash. The same pattern was found in a wide range of competitive events where speed is the most critical factor.
So are we growing super humans? Apparently so, according to Adrian Bejan, professor of mechanical engineering at Duke, who says animals, including humans, are simply following a law of physics that dominates everything from how a river flows to how fast a human can run.
The secret, he says, lies in the economy of scale, and bigger means more efficient use of energy, especially when it comes to moving a mass at considerable speed, even if the mass is an Olympic sprinter.
Are Humans Getting Faster?
OK, we all know people are getting bigger, chiefly because of better nutrition. But are we also getting faster?
Thirteen years ago Bejan developed what he calls constructal theory, a new concept in physics that he believes determines the design of everything in nature.
The theory was initially applied to fluid dynamics, or how any material moves through its environment. But in a paper published in the Journal of Experimental Biology, Bejan moved his theory into a controversial new arena. It also applies to biological systems, and just about everything else in the universe, he said in a telephone interview.
"Anything that moves, or anything that flows, must evolve so that it flows more and more easily," Bejan said, and that means that competitive sports -- where speed is everything -- will continue to be dominated by the giants who tower over the rest of us.
Anyone who reads that sentence is going to think of an exception to the rule, the little guy, or gal, who wins in the end, but Bejan said that doesn't invalidate his theory because the theory applies to that great mass of humans moving through history, not to individuals.
Records Show Current Athletes Bigger Than Past Athletes
However, the statistics released by his office show that even if the theory applies to the collective mass, it is manifested in world records that are shattered nearly every year.
One of Bejan's students, Jordan Charles, lead author of the paper, compiled the records and physical characteristics of champions in a number of events, but in the interest of brevity only the men's 100-meter dash and the men's 100-meter freestyle swimming events were included in the study.
Beginning with the fabled Hawaiian swimmer, Duke Kahanamoku in 1912, Charles listed the time it took for each competitor to complete the race, and break the world record, along with the height, weight and slenderness of every winner through 2008. The duke, at 6 feet 1 inch tall, set the record at 61.6 seconds.
In most years thereafter, the record was broken by a man who was a little taller, a little heftier, and a little slimmer. The biggest guy was Matt Biondi, 6 feet six inches, who broke the record in 1985, 1986 and 1988, when the time was sliced to 48.4 seconds.
A new record of 47.05 seconds was set again in 2008 by Eamon Sullivan, who was only 1 inch taller than the duke. That may not seem like much of a difference, but Bejan said the overall record is clear -- as the athletes grew bigger, the records continued to fall.
Not Just Top Athletes Are Bigger
"The constructal law is not about the individual," Bejan said. "It is about the parade of many individuals."
But is it all simply because the athletes are bigger? Any coach would argue that many factors contribute to victory in sports, including overall fitness, personal preparation, concentration, and that elusive force, the will to win.
"I couldn't agree more," Bejan said, referring to individual champions. But he's looking at the long parade, not just this season's winner.
"There are millions of would-be sprinters all over the globe who have been trained to be faster and faster," he added. "You see a small sample of the peaks of this population (on the winners stand.) And it is showing an evolution that we believe is an evolution of the entire mass movement of speed sports."
'Getting Faster Means Getting Bigger'
Bejan said his theory explains why that happens. All of nature, including humans, is governed by the conservation of energy. While it may seem counterintuitive, getting faster means getting bigger, he added.
All nature wants to "find a smoother path, to flow more easily, to find a path with less resistance," he said.
"The animal design never gets there, but it tries," he said. "It tries to be the least imperfect that it can be."
Locomotion, for animals, involves two main forces, he added.
"The animal has to get itself off the ground, meaning it has to be a weight lifter in order to move," Bejan said.
"And to move forward it must move against the friction of the surrounding air, the mud on the ground, or the water in the lake.
"So the first step in this process is weight lifting, and then we step forward," so there are two forces acting against the animal's motion: gravity and friction, he said. "It turns out that these two forces depend on the speed at which this body, this animal, is proceeding forward. Speed is the unknown, and it has a great effect on these two forces."
That can be demonstrated by holding your hand outside the window of a moving car, he said. If the palm is facing forward, the horizontal drag increases as the speed of the car rises. But if the hand is tilted so the passing air pushes it upward, speed becomes an asset, offsetting both friction and gravity.
"The sum of the two forces can be tolerated if the speed of the forward travel is just right," he added. And incidentally, the bigger the hand, the greater the lift, so size really does matter.
The theory runs into a little trouble when it is applied to the specific, not the general. Seven-time Tour de France champion Lance Armstrong is an amazing human specimen by any standard, but he isn't all that big.
But, the effect of the size of the animal is less obvious when he is riding a bike, Bejan said. That's because bike and rider act as one, and "whatever height and weight that the biker brings is a smaller increment if you add the bicycle."
OK, but what about Michael Phelps, who stole all that goal at the Olympics. His 6-foot 4-inch frame is significant, but what about his feet? He wears a size 14 shoe. That's like having built-in flippers. That's hard to work into any equation.