Core Knowledge for Injury Prevention
Knowing when to replace running shoes is an essential part of a healthy running program. Running in old shoes increases your risk for a multitude of injuries, including shin splints, stress fractures, plantar fasciitis, runner’s knee, IT band syndrome, Achilles tendonitis, and much more. This is caused by the shoe losing its stability and shock absorbing properties, increasing the stress load on the lower body. Use the following guide to know when the need for a new pair of running shoes is coming around the corner.
The life expectancy of a pair of running shoes is 300 – 500 miles. In terms of time, you’d really have to figure out what your weekly mileage is. If you run, let’s say 20 miles per week, the life expectancy of your running shoes is three to six months. At exactly what mileage point you’re supposed to replace your running shoes depends on many factors. Things such as your particular body weight, your style of running, the surfaces your run on, the climate you run in, and shoe brand, can all affect the durability of your running shoes.
Heavier runners simply wear shoes out quicker because the amount of force they hit the ground with is greater than a lighter runner’s. Likewise, some runners, no matter what their body weight, strike the ground harder. Just imagine a runner who has an efficient stride and seems like she is gracefully gliding across the ground. Now imagine a runner who trots and bounds on her feet when she runs. The latter runner will have to replace her running shoes more often. If you are running mostly on pavement, you will wear your shoes out quicker than if you are running on dirt, grass, treadmills, tracks, or even the asphalt. Extremely cold temperatures can stiffen up a shoe and make them crack at the midsole. On the other hand, extremely hot temperatures can make a shoe mushy. Moisture from streams, beaches, lakes, rivers, rain and even sweat could seep into the midsole foam and make the shoe too soft if you don’t let them dry out. By the way, don’t try your shoes out in the sun or dryer. This will accelerate the wear. Instead, dry them with a fan in a dark place at room temperature. Some brands are more durable and some simply are not. Brooks, for example, is generally a very durable brand. The midsole foam materials in Brooks actually outlast the rest of the shoe most times. On the other end of the spectrum, Saucony is notorious for its lower durability. Sorry, I love Sauconys when they’re brand new but they simply don’t last as long as some other brands.
The best way to gauge the wear on your shoe is to track your mileage. I keep a little 3 x 5 card to log the miles for each pair of shoes that I have. Every time I come in after a run I update my mileage with a pencil. I personally replace my running shoes after they have reached 350 miles.
It’s harder to know when to replace running shoes just by looking at them because in many cases they can look almost new but still can be worn out. There are a few small details that may tell you whether or not it’s time to replace your running shoes. First, take a look at the midsole. This is the foam cushioning, which is usually white, that fits between your foot and the hard black tread on the bottom. If there are any creases or cracks at the ball-joint or heel areas, then you may want to get a new pair. If the shoe is too easy to twist sideways, it is definitely time to put it to rest. Next, place your shoes on a table and look at them from behind. If the shoes are leaning to one side excessively, this may be a sign that they are too worn. Lastly, check for discoloration of in the midsole. A worn out shoe will have a midsole that is turning yellowish, brownish, or grayish.
I generally recommend ignoring the tread at the bottom of the shoe. This is the same stuff that is used in car tires so it is very durable, so durable that it will start wearing long after the midsole foam (which is the most important part) has worn out. The only area that I would maybe consider is the outer edge of the heel area, as this is the first and greatest point of impact. But even the wear at this area can be misleading because manufacturers will pack on extra carbon rubber there.
You can many times know just by feel when a shoe is beginning to lose its ability to stabilize the foot and cushion impact. Check and see if you feel any pain or tightness during and after your runs. Pain or tightness at the bottom of the feet, or at the ankles, shins, knees, hips, and lower back are all good signs that you are wearing in worn out shoes. You definitely want to replace your running shoes if on your runs you feel very strong jolts going through your legs when you hit the ground. A good way to gauge by feel is going to a store that carries the same or similar shoe as yours. Try on an old and new pair simultaneously. If your current shoes are too worn you will notice that they will have less cush, spring, and structure than new shoes. I highly recommend that you log your miles and note when you notice the first signs of aches, pains, or tightness. Do this a couple times for each pair of shoes that you go through so you can get a good average so that you can stick with.
One last thing, if you have a pair of running shoes that you’ve simply never wore and kept in the box for a year or two, I don’t recommend you run in them. This is because the materials of a shoe will still start to decompose after about a year even if it is just sitting there without use. You can often tell if a running shoe is not usable by looking at the midsoles color. If it has turned yellowish, brownish, or grayish, throw them out.