If you're exercising in shoes that have passed their prime, it's OK to let them go up to shoe heaven. You can harm your feet, and possibly other areas of your body, if you continue to wear shoes that no longer offer the support they once did.
A Shoe's Life Span
As a general rule, most running and walking shoes last up to 500 miles. How and where you use your shoes could alter that number. For example, pavement wears down shoes faster than a track, a trail or gravel. Also keep in mind that shoes with an EVA midsole tend to wear down faster than shoes with a polyurethane midsole.
How to Tell
Here are three guides for determining when you need new shoes.
Do the Press Test
To determine if the midsoles of your shoes are compressed and are no longer providing cushioning, do the press test. Using your thumb, push on the outsole upward into the midsole. With new shoes, it should be easy to see the midsole compress into lines or wrinkles. As the shoe wears down, the midsole compresses less with the same amount of pressure. When the midsole shows heavy compression lines and the press test reveals a minimal amount of compression, there is little or no cushioning left.
Examine How Your Shoes Look
Don't worry about how dirty they are. That's a good thing. It means you've been using them. What you should be concerned with is general wear and tear. Take a look at your shoes. Are the heels stretched out? Are places on the outsoles worn down? Can you see how the shoes have molded to your foot? These are all signs of excessive wear.
Pay Attention To How They Feel
Your body will know when there is little or no cushioning left in your shoes. If you notice any aches or pains in your feet, legs, knees, hips or back after you've worn your shoes, it's a good sign that you need a new pair. Other signs include friction or blisters in unexpected places, which means your shoes have stretched and your feet are moving around too much.
Make Your Shoes Last Longer
Here are some tips for increasing your shoes' life span.
Rotate Two Pairs of Shoes
It's a good idea to have two or three pairs of walking or running shoes that you can alternate using. You'll find they'll last much longer in the long run—or walk, as the case may be.
Take Them Off Properly
If you take off your shoes properly—by unlacing them and removing them with your hand instead of kicking your shoe off with the other foot—they'll last much longer.
Use Them Just for Exercise
Wearing your exercise shoes around the house or around town will wear them down more quickly. Save your running or walking shoes for exercise.