There’s no getting around it: Running shoes are not inexpensive. Fortunately, a good pair of shoes—hopefully a Mizuno—is the only piece of equipment we absolutely need. So almost all of us are concerned with getting the most miles out of our shoes.

By now, most of us have heard the advice that you should replace your shoes every 400-500 miles or so. That’s a decent enough approximation of when it’s time to buy a new pair of shoes, but we all probably know runners who get way more than 500 miles out of a single pair of shoes, while others get fewer.

What gives?

Clearly, running shoe durability (or lack of same) is a major issue, particularly when shoes cost well north of $100 these days. That’s a big investment and so it’s completely understandable why runners have two primary questions when they buy new shoes: How many miles will my shoes last and how do I tell when the shoes are worn out?

Both are pertinent questions, but, unfortunately there isn’t a simple answer to either which applies to every runner and every different model of running shoe. Nevertheless, we’ll tackle a few of the questions about the durability of your Mizuno shoes and hopefully, provide some insight how you can extend the life of your shoes.

Shoe Life: How Long Do Running Shoes Last?

That’s the number one question all runners have. There are just so many variable that go into determining the life of a running shoe—surface you run on, your size and weight, running speed, style and form,  weather conditions—that it’s virtually impossible to give a precise number of how many miles each runner should get out of a certain shoe. Adding to the confusion, running shoes are made from different materials and constructed differently, therefore mileage expectations are also quite different.

There’s no question though that some runners—particularly bigger runners–are much harder on their shoes and get fewer miles than others. Some runners will only get 250-300 miles out of the same model of shoe than someone else who may double that.

Another factor in determining shoe life is the fact that not all running shoes are created equally. For example, a Mizuno shoe, designed for daily use, such as the Wave Inspire, Wave Creation or the Wave Prophecy are much more durable than say a light, racing shoe such as the Wave Hitogami. (Racing shoes, lightweight trainers and minimalist shoes are the least durable types of running shoe.)

Clearly, if getting the most miles out of your shoes is a priority, your shoe of choice should be a conventional training shoe such as the Wave Inspire or Wave Rider. Worn under normal conditions, a high-quality trainer such as the Rider or Inspire should get anywhere from 300-500 miles. That’s still a pretty wide range, but, as we have said, some runners get more miles and some get considerably fewer.

Bigger, heavier runners are at a disadvantage when it comes to shoe durability. Generally, the bigger you are, the fewer miles you’ll get out of your shoes. That only makes sense. A 6-4, 250-pound guy will generate much more force at each foot strike than a 100-pound woman does and therefore, get fewer miles out of the same shoe. That’s why a bigger runner usually does better in a heavier shoe which provides more cushioning and outsole durability.

Also, heavy heel strikers who may drag or shuffle their heels create plenty of friction with the ground every time they strike the ground. Because of that type of stride, their shoes won’t last as long as someone who is a midfoot or forefoot striker.

How do you tell when your shoes are worn out?

First, the ability of all running shoes to cushion the ride is reduced by use. As you run for weeks and months in a particular shoe and accumulate a couple of hundreds of miles, the shoe will show wear and tear. In that respect, running shoes aren’t any different than your car tires as the limiting factor is number of miles.

Running shoe wear shows up first on the outsole (the black material on the bottom of the shoe) before the midsole (the light colored cushioning element), but the midsole usually wears out first.  Again, the rate at which your shoes wear out differs from, runner to runner. For example, outsoles wear down on pavement faster than on dirt trails, grass fields or treadmills because roads and sidewalks are harder and much more abrasive than a softer surface. So there will be less wear and tear on shoes if you stick to dirt trails or the treadmill, but the impact forces (your weight when it hits the ground) are about the same so the cushioning will still eventually wear.

The most important component of any running shoes is its midsole. This is where most of the cushioning takes place. Almost all midsoles are made of lightweight foam. Mizuno’s proprietary midsole foam is called U4ic or U4icX—both of which are a light, cushy and durable material.

But the midsole cushioning material gets compressed with each step on every run. Although the midsole foam springs back within a couple of hours after a run, daily running compresses this foam. This is called compression set.

A running shoe with 200 miles of use will feel differently than a brand new shoe because the midsole gets compressed from dozens and dozens of runs. After extended use, this compression creates visible lines or wrinkles in the midsole that are easily observed from the side of the shoe. This is normal wear. But as the midsole gets more and more compressed, the number of compression lines increase and come closer together. When this occurs, the midsole has lost most of its ability to cushion.

To determine if the midsole is worn out, flip the shoe over and press a thumb on the outsole and upward to the midsole. It should be relatively easy to see the midsole compress into the compression lines. But as the midsole breaks down with wear, the midsole will compress less into these compression lines with the same amount of pressure. When the midsole shows distinctive compression lines, it appears brittle which is indicative that the midsole is shot to the point where there’s not much cushioning left. Time to buy another pair.

Two other ways to determine shoe life are even simpler. All of a sudden, a normal run results in post run aches or soreness that ordinarily wouldn’t be present. Also, when a shoe feels much firmer than it did a month ago, is a sure sign that the shoe is losing its ability to cushion.

Experienced runners usually have an approximate idea of the number of miles they get out of their shoes and are keenly aware of any change in cushioning when they approach that max mileage. It’s always a good idea to monitor your mileage on a pair of shoes (so you can approximate when they begin to break down). Some runners either note in their training log when they first begin wearing a new pair or write on the tongue or the midsole of the shoe the date they start wearing the shoes. By calculating the number of miles you run per week (or month), you will have a good idea of how much accumulated mileage you have on a particular pair of shoes and once you approach the 350-500 mile threshold, can monitor the amount of shoe life left.

For a casual, fitness runner who wears Mizuno shoes at the gym and for treadmill running (perhaps 20 miles per week), six months is about when shoes need to be replaced. The length of time is not a true indicator of running shoe life—mileage is—but even after six months, a casual runner will have accumulated 4-500 miles.

Although no guarantees on mileage can be made, 500 miles is still about the max for most conventional running shoes (again, racing and minimalist shoes get fewer miles). True, some runners are known to double that mileage range, but once the midsole foam has lost its ability to cushion, the shoe will no longer provide the protection you need to run safely.

If that’s the case, it’s time for a new pair. It makes much more sense to a buy a new pair of shoes a bit early than a little too late. Trying to squeeze another 100 miles out of a worn-out pair, is an invitation to injury.

How to extend the life of your shoes

We all know that running shoes are not inexpensive. A great pair of Mizuno shoes costs anywhere from $90-$220. Most runners need at least two pair to get through a year, but high-mileage runners training for a marathon may need as many as five pair.

But there are a few things you can do to prolong the life of your running shoes:

• Dry your shoes out completely after every run. Remove the insoles and allow the shoes to dry outside in direct sunlight or near a heat source.
•  If you scuffle or scrape the heels along the ground, try and pick up your feet and land either squarely on the heel or closer to midfoot.
• Choose shoes with firmer midsoles. They will last longer than shoes with softer cushioning.
• Only wear running shoes for running or walking. The quickest way to trash your running shoes is to wear them for basketball, tennis, ultimate frisbee, volleyball, soccer or other lateral-motion sports.
• Shoe rotation. If you run more than once a day or do a second workout in the gym, you’ll need an additional pair of shoes. But, if you run once a day, it isn’t necessary to rotate two pair of shoes by “resting” one pair. There’s nothing wrong with doing so, but it won’t extend the life of either shoe as the limiting factor is usage (i.e., mileage).
• Store shoes properly. Don’t leave them in a hot or cold car for days on end. Also don’t store shoes in an unheated garage or porch during the winter.

What to do with old shoes

Just because a shoe is worn out from hundreds of miles of running, doesn’t mean you should toss it in the garbage. Worn out shoes can still be used for outdoor activities such as mowing the lawn, gardening and playing soccer with the kids. Or even better: Many running stores offer a discount (often 10 percent) when you buy new shoes if you return your old shoes. Those old shoes are then recycled or the ones in reasonable condition are provided to the less advantaged by the store.

Mizuno shoes are renowned for durability. The midsole and outsole materials are light, but resilient. Although Mizuno’s Wave technology which is part of every Mizuno running shoe, is not designed primarily for durability, it does add life to the midsole.