Patients and friends are constantly asking me when they should replace their running shoes or are telling me they replace their running shoes every 300-500 miles. This guideline of 300-500 miles is based on a study (Shock absorption characteristics of running shoes.) published in 1985 and, to my knowledge has never been reproduced or even updated.  This study also makes no mention of injury rates as a result of wearing shoes beyond 300-500 miles.  What about the cushion?  We know the from this study by Bates et al. that foot control seems to improve as cushioning is lost and foot control accounts for at least half of running shoe related injuries.

Shoes have actually improved considerably in regards to the materials used in both the midsole (cushion) and the sole (tread) which can make them last well beyond 500 miles.  So the question is: 1.) do they need to be changed that often,  and 2.) when or why.

The simple answer is whenever the shoe causes the runner to change their gait or run differently. This could be from severe tread pattern wear or midsole collapse which can cause the shoe to become “wobbly” causing the runners gait to change.

The following article which was published by Reebok at https://www.reebok.com/en-US/Blog/2017-08/When-to-Replace-Running-Shoes-According-to-the-Experts/ continues to advise changing shoes every 300-500 miles but sites no literature to support this.

Whether you’re a toe or heel striker, or have high arches or flat feet, runners go to great lengths to assure their shoes allow them to run at their best.
When you’ve broken in your trusty shoes to perfection, it can be hard to retire them. But replacing them on a regular basis is crucial to maintaining your performance and health.

To find out when you should replace your running shoes, use the chart above based on your mileage per week.

Most experts agree you should replace your shoes every 300 to 500 miles. Obvious signs of wear and tear should be a first warning that it might be time to upgrade to new shoes.

“Since each runner is unique this is often a personal preference, and signs of age like the rubber tread wearing down should be a cue that it might be time to replace your running shoes,” says Keith Stern, the head of Reebok’s research and analysis team.

In addition to the mileage, there are other factors to consider when determining when to buy new running shoes. If you run on softer surfaces, like grass or a trail, rather than a hard surface like the road, they will last longer.

Another simple way to extend the life of your running shoes is to only use them for running. They will last longer than if you’re also running errands or doing other activities in them.

Aside from normal wear and tear, the main factor leading to the need to replace shoes is the foam of the sole, which wears down over time.

“The normal forces from running cause the foam in the shoe to compress and bounce back with each step you take,” says Stern.

“Over time, the foam compresses more than it can rebound as the foam structure gradually breaks down due to the repeated stress. Your shoes might feel less soft or responsive when this happens.”

In addition to the repeated pounding of running, the decline of the cushioning system is affected by other factors like running environment and gait.

Reebok’s award-winning Floatride running shoe has a unique foam cushioning that is specifically designed to be responsive and long-lasting.

“Running conditions such as terrain and even temperature can affect the life of your cushioning, and so will the way you run,” says Stern. “How heavy your steps are, what part of your foot you land on, and how much your shoe rubs against the ground will all affect the life of the cushioning.”

The Floatride cushioning system is unique in both the manufacturing process and chemical structure, differentiating it from traditional foam that most shoes use.

That means you can run longer and farther before the cushioning system wears out and you need to replace your Floatrides.