Try this test: Take off your shoe, and put it on a tabletop. Chances are the toe tip on your shoes will bend slightly upward, so that it doesn’t touch the table’s surface. This is known as “toe spring,” and it’s a design feature built into nearly every shoe. Of course, your bare toes don’t curl upward; in fact, they’re built to grip the earth and help you balance. The purpose of toe spring, then, is to create a subtle rocker effect that allows your foot to roll into the next step. This is necessary because the shoe, by its nature, won’t allow your foot to work in the way it wants to. Normally your foot would roll very flexibly through each step, from the heel through the outside of your foot, then through the arch, before your toes give you a powerful propulsive push forward into the next step. But shoes aren’t designed to be very flexible. Sure, you can take a typical shoe in your hands and bend it in the middle, but that bend doesn’t fall where your foot wants to bend; in fact, if you bent your foot in that same place, your foot would snap in half. So to compensate for this lack of flexibility, shoes are built with toe springs to help rock you forward. You only need this help, of course, because you’re wearing shoes.
Here’s another example: If you wear high heels for a long time, your tendons shorten—and then it’s only comfortable for you to wear high heels. One saleswoman I spoke to at a running-shoe store described how, each summer, the store is flooded with young women complaining of a painful tingling in the soles of their feet—what she calls “flip-flop-itis,” which is the result of women’s suddenly switching from heeled winter boots to summer flip-flops. This is the shoe paradox: We’ve come to believe that shoes, not bare feet, are natural and comfortable, when in fact wearing shoes simply creates the need for wearing shoes.
Okay, but what about a good pair of athletic shoes? After all, they swaddle your foot in padding to protect you from the unforgiving concrete. But that padding? That’s no good for you either. Consider a paper titled “Athletic Footwear: Unsafe Due to Perceptual Illusions,” published in a 1991 issue of Medicine and Science in Sports and Exercise. “Wearers of expensive running shoes that are promoted as having additional features that protect (e.g., more cushioning, ‘pronation correction’) are injured significantly more frequently than runners wearing inexpensive shoes (costing less than $40).” According to another study, people in expensive cushioned running shoes were twice as likely to suffer an injury—31.9 injuries per 1,000 kilometers, as compared with 14.3—than were people who went running in hard-soled shoes.
(from New York Magazine)