Three Feet!
In the course of each stride, your foot must flex to absorb the impact against the ground and become stiff to push off for the next step. When your foot hits the ground, it pronates, that is, it rolls inward toward the arch. In this position, your foot can flex. As you lift your foot, it supinates, or rolls outward, away from the arch. This rotation causes the bones in your foot to lock together, making a rigid lever for pushing off.
Some feet are so extremely flexible or rigid that they skip the whole cycle of supinating and pronating, creating both advantages and disadvantages in sports. They may perpetually pronate, due to very loose ligaments or intrinsic flatness, or hardly pronate at all because of taut sinews. In either case, by dispensing with the whole pronating-resupinating ballet, they save valuable time that ordinarily goes into collapsing and rotating. In long-distance running, those savings can add up to a respectable lead, as much as ten minutes in a marathon or a couple of seconds in a 440, according to Blake. He stresses, however, that it takes unusual foot strength, and often special shoes and padding, to avoid injuring such feet.

Take speed skating for instance. Speed skaters must struggle against an intuitive desire to push downward and backward to accelerate--a motion made second--nature by walking and running. But gliding across the ice at speeds in excess of seven meters per second makes it impossible to push back faster than you're going forward. Any attempt to do so lowers the tip of the blade and causes a drag rather than a push off. Speed skaters must instead learn to keep their blades level and to thrust perpendicular to the way they want to go.

In ballet, toe shoes make the seemingly impossible possible, but the success of ballet careers really depends, dance experts say, on starting exercises early enough so that the foot skeleton itself changes. Researchers have found that as many as eighty percent of adult ballet dancers have enlarged bones in their lower legs and feet.

In swimming, the foot's arched contours make it hydrodynamic; its motion through the water generates lift forces in the manner of a moving airplane wing or hydrofoil blade. But unless you wear flippers, those kicking forces are puny.

Experiments have shown that in a competitive crawl stroke, for instance, the kick adds little to the propulsion created by the arms. Indeed, according to a university swim coach, marathon swimmers shut down their kick and drag their feet." Otherwise. the big leg muscles burn up too much fuel for too little effect. Mermaid myths seem to acknowledge this inadequacy by dispensing with feet altogether.

Ironically, fossil evidence suggests that our feet may have evolved from fins. We play sports on hand-me-downs: ancient skeletal designs found in sea creatures and modified for life in the trees.

Yet we can't grasp tree branches well with our feet anymore, either. In evolutionary terms, our recent adaptation to motion on land changed those hand-like feet so that the big toe aligned with the other toes and lengthened beyond them.

Have you checked your big-toe length yet? Are you in step with evolution? Most of us aren't; we miss out on that sporting edge. But we all gain, perhaps, from that long and varied ancestry, the remarkable versatility of our feet that makes them well suited for almost any kind of sport.

"Remarkable Feets" originally appeared in the Sports Issue of Exploring Magazine in 1991.  

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