Only one out of four runners has a normal gait. The rest of us have ankles that wobble either in or out with every step. Add this biomechanical flaw to a pounding force equal to two to four times your body weight, then multiply it by the four thousand strides in an average three-mile jaunt. For anyone who hasn’t divined the exact right choice of space-age shoe, this equation eventually spits out an injury.
“The problem,” says Mark Reeves, a podiatrist at Virginia Mason Medical Center, “may well be that we underuse our feet so much that they aren’t ready when we actually ask them to do some work.” The next thing you know, your bones and tendons are taking the blows that would otherwise have been softened by the foot’s natural shock-absorbing mechanism. The good news is that, thanks to the geeks with Ph.D.’s in biomechanics, up to half of all running injuries can be avoided if you choose an appropriately designed shoe.
After the outside of your heel strikes the ground, your foot rolls forward into its weight-bearing position. At the same time, your heel rocks inward and your arch elongates, safely absorbing much of the shock of your stride. In the well-adapted, this fancy footwork stops when the back of the heel is straight up and down.
The sad news is that for half of us, the rocking motion goes past this midpoint–we “overpronate.” The forty muscles and tendons of the foot strain to hold it steady. Another 25 percent of us–the “supinators“–have heels that roll in too little, absorbing less shock, and the joints take a hit with every step. Overpronation, together with overtraining, causes the bulk of running injuries.
If most of us have these problems, how do we find the right shoe? First of all, not every brand of shoe suits every type of foot. Nikes, for example, tend to be narrow; New Balance shoes come in varying widths and can be particularly good for wide feet. Supinators need a shoe with plenty of cushioning, something available in all the major brands.
But if you overpronate, shopping is trickier. You need stability, or “motion control.” According to the foot does, overpronators should look for a strong heel counter–the stiff back of the shoe that holds the heel perpendicular to the ground–and a rigid midsole, which are best for holding the foot in place and controlling its motion.
And what if you’re one of those oddballs who have normal feet? Find the cushiest shoe you can and enjoy the ride.