Training – It’s Time to Replace Your Running Shoes When. . .

Perhaps the first piece of advice that I give runners on a an almost daily basis is to replace their shoes. Sometimes I get the feeling that they think this is a cop out, like a doctor replying to something that hurts by saying, “well don’t do that then.” But here’s the thing, when someone advises you to replace your shoes, they’re not just buying time while they go get the latest copy of Runner’s World to diagnose your problem. There are often real signs and symptoms that your shoes have gone bust.

Today I’d like to present to you a couple of photos to help illustrate this a little better. What I’ve done here is taken two of the same model of shoe (albeit in a different color) and photographed them together. The two shoes are a brand new pair and a pair that I’d been running on for a few months. What I’m hoping that you’ll see in these photos is how the shoe has changed in both its shape and cushioning properties. You should be able to see this just be looking at the two shoes.

This shoe is called the Nike Streak XC Racing Flat. This is a very light-weight shoe, so it shows the changes in the shape of the shoe over time perhaps better than you might see in a bulkier shoe with more structure. The first thing that you’ll notice is that the new shoe (black and blue) is essentially flat across the sole whereas the older shoe is now curved. This happens as the cushion begins to break down from the repeated twisting and curving of the foot as the toes push off the ground. You can see that the curvature involves the entire shape of the shoe, including the heel support structure behind the Achilles Tendon (the back of the older shoe is now tilted in a much more forward position).

Now look at the squishy foam material under the heel. You’ll notice that there are compression lines running cross-ways through the material. This compression of the cushioning material comes from the repeated force of the heel slamming on the ground. The cushion is meant to take up that force and over time the foam is being squashed flat. You can see that the cushion here has been squashed down all along the back-half of the shoe. This means that the spongy cushion of the shoe (what little there is in this shoe) has lost its ability to spring back after impact — meaning that the shoe has lost the ability to protect the heel from those impacts.

Even looking at the front of the shoe you can see how the compression extends up through the mid-foot toward the end of the cushion. It should be said that this shoe is made for fast, forefoot runners, so the front of the shoe has almost no cushion even on the new shoe. But the older shoe is curved upward and compressed under the mid-foot.

Now back to the original advice to “replace your shoes.” After a few months running in the same pair of shoes, you can see why the shoe is starting to lose its protective properties. Imagine the difference between running on this old shoe versus the brand new pair shown. The foot is going to have much more structure and cushion under it in the newer pair. Or to put it another way, the shoe will perform as designed, rather than in whatever way it will after all of the stress and pounding that’s been put on it.

I’ve often used the analogy that old shoes are like a “flat tire” on a car. I think these images are a good way to see what that means. Next time you start feeling bumped and bruised in the middle of your season, just look down and maybe it’s time to replace those shoes.

Coach Joe English, Portland Oregon, USA
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