Running shoes can wear down in a variety of ways, and it is important that you evaluate this in the pair of shoes you are using, as it can give you clues regarding an injury you’ve developed or that you may be at risk for developing. Also, telling signs that it is time to replace the shoes you have can be determined by the wear patterns. Finally, certain wear patterns can warn you that you should strongly consider a different model of shoe to replace your current model. Wear patterns can be seen on the outsole, the midsole, the insole, and the upper of the shoe, all of which are important to inspect. In part 1, I will discuss what to inspect for. In part 2, I will explain the relevance of specific findings and what action should be taken.
Before your first run in a new pair of shoes, you should inspect them for pre-existing problems that could lead to abnormal wear patterns such as asymmetry in the length and width of the right shoe as compared to the left shoe, asymmetry in the location of stitching and trim on the upper of the shoe, and any potential material damage. Also, you should place both shoes on a flat surface and make sure that neither of the shoes tilt inward (valgus) or outward (varus); in other words, you want an imaginary vertical line bisecting the back of the heel counter of the shoe to be perpendicular to the ground surface. I have seen brand new shoes fail all of these tests.
Once you start using a pair of shoes, they should be dedicated strictly to running, as that way, you can be sure that the wear patterns you are creating are purely from running and not influenced by any other activities you may be doing in them, such as walking, driving, cycling, etc.
At least once a week, or every 50 miles of run wear, whichever comes first, you should inspect the shoes for unusual wear patterns. The following should be looked at: Whether one or both shoes has begun to tilt into valgus or varus (see above), whether there are new “creases” in the midsole material in any location, whether the outsole has worn down substantially, and if so, in what location(s), whether the insole has become indented significantly in any particular location(s) (you must pull the insole out of the shoe to inspect for this), and whether the upper has any areas that have distorted in shape or worn down: key areas to look at for this are around the toes and inside the heel region. In the next part of this blog, I will discuss specific inspection findings that should be “red flags”, how to interpret them, and what actions you should consider taking.