So when do you replace your running sneakers? This is a question that we get a lot. What happens is, you have the mid-sole, and the you have the out-sole of a sneaker, and it's EVA film which you have in the mid-sole. It's kind of like your kitchen sponge. After a while you'll notice when you start to squeeze your kitchen sponge, it doesn't quite go back to its original shape. It's the same thing with the mid-sole. It's like that kitchen sponge. After a while, with that pounding, it doesn't quite go back to its original shape.
So if you take a look at your sneaker, you might notice that you'll see wrinkles along the mid-sole. And what that is, just like that kitchen sponge, when you start to squeeze it, it's not going back to its original shape. It's starting to lose its cushion. And it's starting to not absorb the shock that your body's creating when you hit the ground.
Also, if you look at the bottom of your sneaker, the mid-sole, this white portion on this shoe, will start to push through to this outer sole, this yellow portion that you see. It'll almost start to become flush with the out-sole. And again, that means that it's no longer that cushiony EVA foam that you originally had with the new shoe. And those area really good indications on when you should get a new sneaker.
Now, why should you get a new sneaker? The reason is because it's no longer functioning the way the sneaker is supposed to. It's no longer absorbing that shock that you're creating when you hit the ground. And that shock is being absorbed through your knees, through you hips, and again, it's creating that domino effect of shock through your body.
Running shoes tend to last about 350 to 400 miles. That's your average trainer. If you're going to get a lighter racer sneaker or a light trainer, those generally last maybe a little less, maybe about 250 to 200 miles. But if you ever have any questions, just take your shoes to your local running store, and they'll be able to help you out.