Your running shoes are like your car’s tires. They provide traction and support while getting you where you want to go. Just like tires, your running shoes should be replaced after a certain number of miles. But what about shoes that you haven’t worn yet?
Some runners buy multiple pairs of their favorite shoes or stock up when they’re on sale. But even if you’re not wearing them, your running shoes will eventually begin to break down while sitting inside your closet.
We sat down with Kyle Stump, co-owner of Fleet Feet Delray Beach, and Jason Richter, coach of Fleet Feet Delray Beach’s training programs, to find out more about the shelf life of running shoes and how it affects you. Here’s what we learned:
To answer the question, it’s important to understand how running shoes are made.
Most shoes are made with a rubber outsole, which grips pavement and adds durability, and a foam midsole to absorb shock and provide a springy feel. Sadly, neither component lasts forever; both will eventually break down, even on unworn shoes. If the soles feel noticeably less cushioned than when you first bought them, it’s time to get a fresh pair.
“Once shoes have been sitting around for a while, the impact absorption rate will go down, because the rubber and foam age,” says Stump. “The foam can also start to splinter on the inside.”
The decreased shock absorption may also cause injuries to some runners, Richter says.
“Instead of the shoe absorbing the impact, the legs and body are now taking on a greater amount of force than they were when the shoes were new,” he says. Experiencing new aches and pains without any increase in training volume is another clue that your shoes have worn down.
The rubber and foam aren’t the only materials that begin to deteriorate. The upper can malfunction as well. That’s because the upper piece is usually all one stitch and is typically attached to the midsole with glue.
“It’s usually the glue that degrades first, even just sitting on a shelf,” says Stump. Noticing loose threading on the upper, specifically around the edges, is another clue that your shoes have aged.
While shoes won’t start to deteriorate immediately after buying them, you should begin using them six to 12 months after your purchase. According to Stump, this is when they start to break down little by little.
“It may not mean they’re completely unusable,” he says. “It just means that if you were to compare them with a new pair of the same exact shoe, they won’t feel as cushioned.”
Not only will the shoes begin to feel stiffer, but they won’t last as long as a fresh pair. Most manufacturers recommend using their shoes for about 400-500 miles. Stump says you’ll sometimes only be able to get 200-300 miles out of older unworn shoes without increasing your risk of injury.
“You can maybe still get 400 to 500 miles on an older pair of shoes, but your injury risk will definitely go up because the materials are already breaking down,” he says. “But they might not even last that long because the outsole is going to wear out faster.”
Knowing how to make your running shoes last longer when you’re using them can extend the time between buying pairs. If you have shoes that you’re not ready to wear, though, it’s best to keep them indoors in a climate-controlled environment.
“Heat and humidity really hurt the shoes because the glue can start breaking down faster and the foam will become softer and worn down,” says Stump. “If they’re stored in cold weather, the foam will become stiff, making it unable to decompress and absorb shock the way it should.”
A good rule of thumb is to keep your running shoes indoors, whether they’re new or old.
If you are going to buy an older model of shoes on sale, Stump recommends doing so within two to three months from when the newer model is released.
“If it’s one of the last colors made by the manufacturer, they’re likely from the last batch and haven’t been sitting around for too long,” he says. “Any longer than that, you won’t know how long they’ve been sitting around.”
Your local running store can likely tell you how long they’ve had a pair of shoes in stock, but there’s no telling how long the manufacturer has had them.
Even though we all love a great discount, it may not be cost effective to buy sale shoes if they’ve been sitting around in a warehouse for six months. They probably won’t last you the full 400 to 500 miles that a new shoe will.
By Caroline Bell. Caroline has been running competitively since high school. When she’s not writing for the Fleet Feet journal or training for her next race, you can find her looking at cat pictures on Instagram. She lives in Florida with her cat, Jade.