Saying Goodbye to Old Friends

© Dawson DeLay for GoFamz Saying Goodbye to Old Friends

Knowing when to replace your running shoes isn't an exact science and may require more thought and consideration than simply using miles run as a guide. Here are some things to consider before purchasing a new pair of shoes.

Time to move on

My old friends and I have a great relationship. They've been good to me and I to them. We've run marathons together in the Midwest and even a 5K in China. We've trained together on cold, slush-covered asphalt in the city and among the red rock arches of sunny Moab, Utah. We've had some great times together. But lately the've been failing me, and I'm beginning to wonder if it is time to say goodbye. Time to move on... to a new pair of running shoes.

Knowing when to replace your running shoes isn't an exact science and may require more thought and consideration than simply using miles run as a guide. Here are some things to consider when purchasing a new pair of shoes.

EVA, midsoles, and cushioning

The most visible signs of wear on running shoes are on the fabric upper and the hard, rubber-like outsole where the shoe strikes the ground. However, wear that most affects running mechanics is in the midsole, the white EVA foam in the sole that cushions impact. Most running shoes employ EVA foam, although there are some exceptions.

As your shoes accumulate more miles, the midsoles become thinner and stiffer, and cushioning deteriorates. One study concluded that the cushioning ability of EVA decreases sharply after just 50 miles, then continues to decrease at a slower rate until leveling off at 500 miles. After 500 miles cushioning decreased by a total of only 20% from the initial amount of cushion.

What type of runner are you?

As such, many industry professionals recommend replacing running shoes after 300 to 500 miles of use. However, one of the greatest determining factors is the type of runner you are. If you are a lighter, more efficient runner with a neutral forefoot and are a forefoot or midfoot strike runner, your shoes may last longer. If you are heavier, pound the pavement with force, or do not have neutral foot mechanics, your shoes will wear unevenly and won't last as long.

5 tips from the pros

Here are some great tips to help you make an informed decision:

Fit First - Visit a quality running store that can do a detailed analysis of your foot and running mechanics. This will help you choose a shoe that is appropriate for your foot type. Ill-fitting shoes can cause a host of problems.

Pay attention to your body - A relatively recent study found that as shoe cushioning capability decreased, runner's legs adapted to the thinner, stiffer shoes. This adaptation resulted in very little change in running mechanics (no change in hip and knee angle) and no change in impact force. In other words, the subject's bodies adapted to the gradual wear in their shoes allowing them to maintain an even stride throughout a range of shoe conditions.

This adaptation isn't necessarily a bad thing. In fact, adaptation is what makes you stronger, builds endurance, and can help prevent injury. And based on this study, adaptation can possibly allow you to wear shoes longer.

However, as 2X Boston Marathon finisher and Head Coach at PRS FIT, Jeff Kline, says,"One of the first signs that your shoe is breaking down is feeling the impact in your ankles and knees. This generally means the EVA midsole has reached its limit." Other little annoyances such as sore arches, blisters, and shin pains will begin to manifest themselves. If you are starting to experience these symptoms regularly on normal runs, it could be an indication that your shoes need replacing.

Also, if you rely on orthotics and/or a stability shoe with dual density foam to correct for non-neutral foot anatomy, midsole deterioration is a more serious issue and will likely cause pain and possibly injury. In this case, shoes should be replaced sooner.

Pay attention to your shoes - Coach Jeff Kline says, "When you start to notice wrinkles in the EVA midsole this is a sign that the shoe is breaking down and the EVA is starting to reach it's maximum shoe life." Other pros say that when the sole starts to feel hard and "dead," it is time to replace your shoes.

Use time or distance as a guideAccording to Coach Kline, "In general most midsoles should last in the neighborhood of 500 miles, dependent on the type of surface you run and your individual impact force."

Mario Fraioli, senior editor at Competitor, recommends that as you approach 300 miles on a pair of shoes, go ahead and break in a new pair by rotating the two pairs for a few weeks.

Accomplished triathlete and head coach at Blue Iron Coaching, Mari Fridenmaker, says, "If I am running on a regular basis (ex. 2 - 3 times per week/10 - 20 miles per week), I will replace my shoes at least every six months."

Alternate pairs of shoes - Some industry professionals recommend "resting" your shoes by alternating two different pairs. The idea is that this allows the EVA to recover or decompress, thereby extending shoe life. However, at least one study does not support this idea. Regardless, alternating shoes may have the advantage of varying the stress on your feet, promoting adaptation and therefore preventing overuse injuries.

My old friends and I will part ways soon. We had some great times, but I look forward to a shiny new pair of kicks and the many miles we'll share together.

Brian DeLay

Brian DeLay is an airline pilot living in the Midwest with his wife and three children. As an avid runner and cyclist he has completed numerous half-marathons, marathons, and cycling "century" rides, and serves as the race director for the Run for the Ridge 5K. His favorite activities are those he shares with his family. Visit Brian on Google+

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