Is it time for new running shoes?

Worn out Running Shoes

Last updated on July 21st, 2022 at 08:44 pm

There is one question our customers ask most in store:

“how do I know when it is time to replace my running shoes?”

Whilst the definite answer to this question is elusive and depends on many factors, one thing is for certain; running in battered, worn-out shoes is a leading cause of running injuries and can be just as bad for you as running in shoes that don’t fit your foot profile.

“This all seems designed to make me spend more money!”

No, it’s really not! Running shoes are a consumable product, just like batteries in a remote control or printer paper. However, they are generally more expensive than many consumables and many people treat them as a long term product. The truth is they are actually designed to “run out”, if you can pardon the pun. They degrade due to the inherently sacrificial design of their cushioning units and midsole. This isn’t the big conspiracy that many people might think! It’s simple mechanics and material science. Any material that is subject to continual stress, will eventually breakdown; just like if you are subject to continual stress you’ll breakdown!

Shoe breakdown graph
Cushioning degrades slowly and then at a point drops off rapidly


Why replace my running shoes?

The midsole of your running shoe at a microscopic level, is effectively like bubble wrap. Every step you take, a few “bubbles” burst and eventually you end up with a flat lifeless midsole which, from a distance, still looks the same but certainly won’t feel or perform the same. While it’s obvious that the cushioning disappears once the shoes are worn out, what many people don’t realise is that the support and structure of the shoes also break down. The resulting breakdown means your feet, knees, legs and hips all go through motions that aren’t the same as when you were fitted out for the shoes originally. In short, this is when you start getting injuries.

Is there any risk if I wait too long to replace my shoes?


Once the midsole breaks down, your feet (and therefore your legs, knees and hips) will go through motions that they wouldn’t have done when the shoes were new. If you had the shoes fitted so they matched your biomechanics, the chances are they no longer match your biomechanics. Combine this with a lack of impact protection from the breakdown of the cushioning and it soon becomes clear how running in the old shoes will start to cause problems, such as:

  • Excess wear on your joints can cause pain in the short term, however, the long term effect of this is hard to measure and many doctors agree that excess wear can trigger arthritis.
  • Certain muscles have to work harder than they need to, therefore, risking muscle pain/inflammation as well as possible tendonitis.
  • Other supporting structures such as bone and facia to become subject to increased stress, therefore, risking conditions such as stress fractures and plantar fasciitis.

Your shoes will deteriorate quite slowly, therefore, noticing their decay can be difficult.

So when should I replace my running shoes?

Horn Heel

This is the magic question and one that cannot be answered precisely with a blanket statement for every runner. But, we will try our best to give you some expert advice. If you answer “Yes” to two or more of the statements below, it’s time to get some new shoes:

  • You have aches, pains or injuries that you didn’t have when the shoes were new.
  • You have run over 800 miles (1300 km) in your shoes since they were new.
  • The rubber on the underside (the outsole) has worn down to within a millimetre of the midsole (the soft middle foam) in at least one point in either shoe (see picture above).
  • There are visible wrinkles in the midsole foam, particularly on the medial (arch side) of the shoe.
  • The shoe now bends in the middle, when it never used to.
  • If you put your fingers inside the forefoot of the shoe and press down hard on a flat firm surface then there is very little or no give.
  • You have holes in the sole of the shoe or the shoes have developed their own personality and have started to crawl on their own!

Don’t believe us, Jordan at New Balance would tell you exactly the same thing!

And while we’re really not advocating an unnecessary new purchase, if you are looking for a change, look no further than our fantastic range of Running Shoes.

Finally – the best approach to this situation, if you want to completely avoid any risk of replacing your shoes too late, is to buy a second pair when you have done about 300 miles in your first pair. Slowly start to use the new ones on shorter runs to break them in; this can actually preserve the life of the old pair and result in more useful mileage overall. As both pairs get more time to recover and this, believe it or not, helps them to recover some of the microscopic air bubbles that are trapped in the midsole.

For more science lessons, and expert advice, check out our other blog articles, stuffed with insightful fitness posts.

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Ryan Tooes
Ryan has worked in the sports industry since 1999 and has a wealth of experience across most subjects. Ryan holds a BSc in microbiology and has studied sports physiology in great detail in his own time. His main areas of specialisation are: footwear construction, footwear technology, strength & conditioning and anatomy & physiology. He splits his 13 hours a week exercise between, Kickboxing, MMA, Crossfit, Rock Climbing and Running.