Homo Ambulus

Homo Ambulus
by Kenneth E. Ely

We call ourselves Homo sapiens sapiens, the hominid that knows that he knows. We could call ourselves with equal validity – maybe with even greater validity – Homo ambulus, the hominid that walks. I am uncertain in my Latin here, but I doubt I’m much off the mark when I assert that, throughout our long history, man has done a great deal more walking than knowing. We were walking when our skulls held smaller brains and we knew a great deal less. We are still walking (those of us not riding in cars) and using only 20% of our larger present brain capacity. It would appear that walking has always been favored over knowing for Homo. But laying aside speculation where cognizance is concerned, our anatomy certainly enables us to walk better than to do just about anything else. Our legs are as long as our torsos and endowed with plenty of muscle for carrying around not only the torso but other loads, as well. Our ability to shift our center of gravity to accommodate a load and still walk effectively gives us a migratory advantage over all other hominids. Walk we did and do, carrying our babies and our stuff, all over the habitable world.

Man has two gaits, walking and running. Both break down into subcategories but the great watershed is ballistics. In running, humans go ballistic – that is, both feet leave the ground and the runner is airborne. In walking, one foot is always on the ground.  A second difference between walking and running is how the gravitational center of the body moves in each. In walking, as the legs diverge, the body’s center drops slightly. The center is then vaulted upward and reaches maximal height as it passes forward over the supporting leg as the legs approximate; it begins to descend as the legs diverge again. This is a double pendulum dynamic. The first pendulum occurs as the leg leaves the ground and swings forward. The second, an inverted pendulum, occurs when the heel strikes the ground and the torso is carried forward over the heel. Running contrasts this in that the arc of the torso’s forward trajectory actually sags at its midpoint because the torso is ballistic: there is no leg on the ground to force it upward. Its trajectory begins to fall.

Energy is handled differently during walking and running. In walking, the body’s forward kinetic energy converts to potential energy as the center of mass is forced upward over the posted leg and reconverts to kinetic energy as it descends again. The energy to move the torso forward, and hence upward, is produced in the muscles. Sixty percent of the muscles’ energy expenditure can be recovered because of pendulum dynamics and ground resistance. Walking, for Homo ambulus, is very economical. Running, however, is a different energy dynamic. At the end of the torso’s ballistic phase, when it comes in for a landing, energy is absorbed in the muscles and tendons of the extended leg as it bends when it strikes the ground. This converts kinetic energy into potential energy, which is reconverted to kinetic when the leg unbends. Just to make the concept muddier, the energy absorbed by the muscles and tendons is termed ‘elastic energy.’ Common experience tells us that it is not as energy efficient as walking.

People who walk or run barefoot do so differently than people who wear shoes. Only heels that are covered by shoes can endure being slammed repeatedly onto the earth. Without the synthetic padding of shoes, walkers and runners must shift their gaits to make contact with the ground forward of the point of the heel, rolling onto the outside of the mid-foot sooner in the stance phase of the gait to ameliorate the shock of contact. In reality, even people with shoes should do this to avoid excess jarring forces on the ankle, knee, hip, and low back. Certain venture capitalists have developed a shoe that looks like a bare foot to capture the best of both worlds:  it is a barefoot shoe. It may be just the ticket. At any rate, the luxury of shoes has contributed to lazy walking and running which has accelerated our orthopedic degradation.

When I was a boy, my father told me that a man in good condition and used to walking and running could out-travel a horse. That assertion is probably put forth in every country that has horses. In Wales, in the tiny town of Llantwrtyd Wells, a publican overheard two of his customers arguing on that topic and decided to promote his business and the town by holding a yearly ‘marathon’ of 22 miles, over every sort of ground, pitting men against horses. The first race was held in 1980. They’re still doing it. Since 1986, only two humans have won. Lately, there’s been some controversy over subtracted time. The horses are given a delayed start, which is not subtracted from their overall times, and they’re made to stop halfway for a vet inspection, which is subtracted. I can understand the rationale for the vet inspection; I don’t see why the humans should be given a head start. With or without the head start, though, the event busts the myth that men can out-travel horses.

So, Homo ambulus is not the champion walker of the world? Well, I didn’t say he was. I said he walks better than he does anything else. A horse’s walk is analogous to a human crawling on all fours. A horse’s trot is more like our walk and a man has to jog to keep up with a trot. And when a man moves into his last gear, his run, the horse still has an in-between: his canter. The horse doesn’t go ballistic until he runs, which leaves the man in the dust. The horse ends up covering more ground in an equal amount of time but he’s not as efficient as a man: Homo ambulus can keep it up for longer, if he’s mostly walking. And Homo ambulus can carry things. Oh, sure, a horse can, too; but he has to have Homo ambulus put the load up for him.

Copyright © February 2011 Kenneth E. Ely