by Any runner will tell you that there’s nothing better than putting on a brand new pair of shoes. But how regularly should runners spend hundreds of dollars on their next pair?
Conventional wisdom tells us that the average lifespan of a running shoe is about 300 to 500 miles. But where does this advice come from and is it based on science?
Some evidence comes from impact testing with machines designed to simulate the shoe making repeated contact with the ground while running. Other evidence comes from monitoring runners who have used shoes for long periods of time in the real world.
This research often focuses on shoe materials and structure. But we think more compelling features for the runner are shoe comfort, performance benefit and injury risk.
Rather than looking for a “one-size-fits-all” answer to how much mileage your shoes should limit, it’s also better to consider individual signs based on your shoe type and its purpose.
The three signs you should look out for
Runners tend to replace their shoes for three main reasons:
- they believe their performance is negatively affected
- their shoes cause some physical discomfort that could cause (or has already caused) injury.
- the shoes no longer fit as comfortably or “feel” as good as they used to.
What does the evidence say about these factors?
Performance
Some properties of the shoe material contribute to better running efficiency. Deterioration of these materials through mileage can hinder peak performance on race day.
This is most evident in shoes with carbon fiber plates used by modern elite runners to achieve fast road race times. The design features thought to drive this are the combination of highly flexible and resilient midsole foam and a rigid embedded carbon fiber plate, which supports energy storage and return.
Runners will typically ‘save’ these shoes for race day and replace them after fewer miles, compared to conventional running shoes.
The available research supports the performance benefits of these shoes. However, it is not known how long the benefits last compared to kilometers of wear.
To our knowledge, there is only one study on running performance and shoe wear, but unfortunately it did not involve shoes with carbon fiber plates. A 2020 University of Connecticut master’s thesis examined eight college-level runners who used Nike Pegasus shoes for more than 400 miles (643 kilometers).
A large reduction in running consumption was reported at 240 km, and this was statistically significant at 320 km. No reduction was observed at 160 km.
So if you’re looking for personal best times, the evidence above suggests that peak performance shoes should be replaced somewhere between 100 and 150 miles (although this isn’t directly based on research on shoes with carbon fiber plates).
It appears that minimizing training miles in your favorite racing shoes – by keeping them ‘fresh’ – can contribute to peak performance on race day, compared to racing in an old pair of shoes.
Injury or discomfort
The link between shoe wear and injury is unclear and based on minimal and often conflicting evidence.
One study found that runners who alternate their running shoes have a lower risk of injury than runners who run only in the same pair of shoes over a 22-week period. Runners who changed shoes during the study period would have suffered less wear and tear on each shoe.
This provides some support for the idea that racking up too many miles in your shoes can increase your risk of injury. Unfortunately, the exact age of running shoes was not reported in this study.
However, based on reported running characteristics, users of a single pair of shoes covered an average of 200 miles (320 km) in their shoes (after adjusting for a small portion of the number of people who had to replace shoes during the study).
This was compared to multi-shoe pair users who used an average of 3.6 pairs of shoes, walked more miles in total, but averaged only 200 km per pair of shoes.
Comfort
Comfort and fit are the two most important factors for runners when selecting running shoes. The evidence linking improved shoe comfort to fewer injuries or better running economy is mixed, but reducing the damage caused by ill-fitting and uncomfortable shoes is clearly a priority for runners.
Most runners land on their heel. The repeated compression of the midsole causes the material to harden, possibly after just 100 miles, according to a 2017 study. However, there was virtually no change in the amount of cushioning runners experienced under their heel after 100 miles. Even after using the shoes for 400 miles, they noticed little difference – about 3%.
While this may initially seem like runners are not very good at judging when shoes are losing their cushioning, it also tells us that changes in the perceived cushioning of shoes are very gradual and may not be important to runners until they reach a certain threshold.
This amount will vary from person to person and shoe to shoe, but research shows that runners only find this meaningful when the perceived cushioning reaches a change of about 10%.
We need to be careful when applying these findings to the latest running shoes that use newer materials.
But you can use it as a rule of thumb: as soon as you notice a decrease in comfort, it’s time to buy a new pair.
When should you choose new shoes?
Ultimately, there’s no one-size-fits-all answer to the question of when to buy new running shoes. It may also be that you are not keeping track of how many kilometers your favorite pair has driven.
Overall, we believe the most practical advice is to keep your racing shoes “fresh” (less than 150 miles), rotating a few other pairs during regular training and replacing them if you notice it comfort noticeably decreases.
John Arnold, Senior Lecturer in Sport and Exercise Biomechanics, University of South Australia and Joel Fuller, Senior Lecturer, Department of Health Sciences, Macquarie University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
