Such power, such grace

ORTHOPEDIC surgeons and podiatrists who study it, operate on it and care for it are as enamored of the often sweaty, sometimes stinky, foot as are cardiologists of the heart, or neurologists of the brain. "It's ingenious," says Edward Glaser, a Tennessee podiatrist who switched professions from mechanical engineering to podiatry because of his admiration for the foot's function. "As a machine, it's an engineering marvel."

The foot is built to walk on everything natural -- grassy knoll, pine needle forest floor, volcanic rock -- uphill and down. It is constantly balancing, changing direction and absorbing a pounding equal to 3.5 times the body's weight, only to spring back in time for the next step.

With its 26 bones and 33 joints, the foot is a biomechanical masterpiece. "There's something wonderful about it," says Dr. Nancy Kadel, professor of orthopedics and sports medicine at the University of Washington. "It's a flexible shock absorber, then it's a rigid platform that propels you forward. It adapts to sand when you walk on the beach. Then you climb onto rocks to look at the tide pools, and it drapes over the rocks."

But as close as it is to perfection for locomotion, two modern environmental necessities stand in the way of allowing it to maintain its full nature-given glory: hard surfaces and the shoe. For a walker, and more so for a runner, a steady diet of concrete asks a lot of that magnificently springy arch. By forcing it flatter, it shifts balance unnaturally, the effects being felt all the way through the foot, ankle, leg, hips and back. Add a pair of shoes for the toes to bump against, the heel to blister against, and you've got the potential to adversely affect almost every bone, muscle and ligament in the body.

It took millions of years for the foot to assume its present shape, a shape it's held for millions more years. The rest of the body has adapted, finding its center of gravity over the spaced left, right footprints of walking, the straighter, in-line footprints of running. But the foot and its attached body parts have had mere thousands of years to adjust to a steady diet of cobblestone, wood surfaces and sandals -- not to mention the relatively recent introduction of concrete, asphalt, loafers and stilettos.

To see what's happened in the evolution of the foot over several million years, try the old trick used to teach kids their left from their right hand. Stick the thumbs out as the back of the hand faces you. The one that forms the "L" is the left hand.