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How often should you replace your running shoes?
How often should you replace your running shoes?  - blog post image
How often do you replace your running shoes? More importantly, how do you know when to change them? Do you follow the guideline of 300-500 miles? Are old running shoes giving you injuries? 

Running footware is often a highlighted factor when addressing a running related injury and worn out or inappropriate shoes are frequently reported to be the cause (Rethnman & Makwana, 2011). 

Most runners will follow what is known as a "mileage rule", which basically gives a 300-500 mile guideline as to when you should be changing your worn out running shoes. We are told that this is because the shoe has deteriorated after this time and is no longer sufficient to maintain the forces impacting our joints whilst running.  However, if you're a seasoned runner, you might start to question this statement. Is this just a marketing scheme by running shoe companies to get you to buy more shoes? Or is there scientific evidence that would suggest that this is the optimal amount of force/time for shoe materials? Perhaps there is a running shoe manufacturer manual that has been tested to prove this? All questions which we have done our best to find the answers to...


Here is what we found in the research: 

A study by Rethnman and Makwana in 2011 used a prospective study to investigate if old running shoes are detrimental to your feet. They measured the plantar pressures of  old and new running shoes to compare the difference of forces, which essentially is the main role of a shoe. Surprisingly, they found that plantar pressures were consistently higher in the new shoes versus the participants old used shoes. They concluded that this was likely due to the stiff material in a new shoe and could actually create a higher risk of injury if running shoes were change too often. So far, still no evidence to back up 500 miles and this paper was in favour of older shoes! 


In 2009, Christopher McDougall (author of 'Born to Run') wrote an article in the Daily Mail titled "the painful truth about trainers: are running shoes a waste of money?". This lengthy 8 page article describes how running barefoot or extreme minimalist shoes are what humans are designed to do. Hard to argue with that, we aren't born with shoes on. But, we also aren't born with phones in our hands either and we seem to be getting on pretty well in the world with that technology! Interestingly, in this same article (last paragraph) he recommends running shoes should be replaced between 500-1000 miles and seek advise from a running shoe specialist. You would think, that if he is already suggested don't wear shoes in the first place, what would it matter then if your shoe was a worn down? 

Runners World also frequently quotes changing shoes every 300-500 miles. An article published in 2008 by Ken Becker on "Running Shoe FAQ" states that " 300-500 miles is the range of when to retire old running shoes". However, he also explains in this article how a shoe wears down is dependent on each individual and that going by FEEL is really important. Still no evidence yet on why 500 miles...

Mizuno, Asics and likely other running shoe companies all seem to follow similar guidelines of somewhere in between 300, 400, 500 miles to replace a running shoe. Expert advice published on a Mizuno blog by Bob Wischnia (2008) gives knowledgeable considerations and information about different variables that need to be considered such as ; surfaces, size of foot, weight, biomechanics, how fast you run, weather conditions run in. He also says don't run over 500 miles in a running shoe....no reason why. 

A team of engineers at the University of Wisconsin in 2004 attempted to create a device that would notify runners when their running shoe had worn down beyond the point where they were functioning properly ( Pauls et al, 2004). The idea was that it would measure the change in elasticity of the shoe material over time. They stated that "the average running shoe lasts 300-500 miles...and beyond this a person is 50-75% higher risk of injury". So far we haven't' seen a product on the market that does this though. 

Do worn out shoes actually cause or contribute to running related injuries? Taunton et al (2012) seems to think it does but also related other variable factors such as foot type and biomechanics. 


500 still seems to be the number, but no mention as to why?

You may be starting to get a general picture of the evidence and suggestions here. Nearly all running shoe companies suggest changing your shoes every 500 miles -  But, they also state how individual this factor is and how biomechanics, body weight, type of terrain, weather conditions, and other factors also will have an impact. Therefore, if we are considering a running related injury and factors involved, these 'other' variables relating to when to replace your shoes are probably also risk factors of what has caused your injury in the first place.

It's very easy to blame a shoe for a problem, because that is a quick fix. Changing shoe takes almost no time or effort at all. Changing your biomechanics or your weight or terrain that you run on - these are much harder to change. 

As far as we can tell, 500 miles is simply a nice moderate mileage that someone has convinced everyone is the rule for when to change your shoes. New runners may even choose to follow this rule, because it is simply a "quick-fix" solution. It may or may not work, but at least it is an attempt to do something about a problem. For those more experienced, you may be slightly more in tune with how a shoe feels and can judge when to change based on those factors. If you feel like your shoes are wearing down, buy a new pair and interchange them every so often to give you a better idea. Other things to look out for are holes in the material, a feeling of increased stiffness from the shoe, lack of response from the cushioning, and significantly increased wear patterns on the bottom. 

If you are injured and blaming your shoe, you of course could try and change it, but you should also considering trying to address the other factors that are likely having a much bigger impact. Your biomechanics, for example can be easily assessed by a 3D gait analysis to diagnose your joint movement patterns and how to improve them. By reducing your risk factors, you're likelihood of getting to the bottom of your injury faster is going to be much more successful. 

 

 

References:

Rethnam, U., & Makwana, N. 2011, "Are old running shoes detrimental to your feet? A pedobarographic study", Biomed Central Research Notes, Vol. 4, p.307. 

Mizuno. 2013 " Running shoe durability. How many miles can you expect and how to extend the life of your running shoes", by Bob Wischnia. 

Taunton, J., Ryan, M., Clement, D., McKenzie, D., Lloyd-Smith, D & Zumbo, B. 2002 " A retrospective case-control analysis of 2002 running injuries", British Journal of Sports Medicine. Vol. 36, pp. 905-101. 

The Daily Mail. 2009, "The Painful truth about trainers: are your running shoes a waste of money?" by Christopher McDougall. 

Pauls, S., Schwatrz, B., &Kochsiek, B. 2004, A device to determine when the soles of running shoes are past their useful life, Biomedical Engineering Design 301, University of Wisconsin Madison 

Runners World. 2008, "Running shoe FAQ" by Ken Becker, Runners World Online. 

 

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