Unlike a comfortable pair of jeans that can be worn for years with increasing comfort, athletic shoes will wear and require frequent replacement. The notion of using an athletic shoe for years that is “broken in” is a recipe for injury disaster. The midsole portion of the shoe is typically constructed from two types of foam including ethyl vinyl acetate (EVA) as well as polyurethane. These foam materials have a limited life span based on many factors including the firmness of the foam, amount of shoe usage as well as foot landing patterns during walking or running. An important function of these materials is to provide injury preventing cushioning as well as a stable platform for foot support during activity. The upper fabric portion of the shoe and even the hard outsole rubber materials may look great but if the midsole has worn excessively injury risk will increase.
How often should I replace my shoes is an important question to ask but one that is difficult to answer. Consider a few things: the foam in athletic shoes needs time to rest and recover so alternate your shoes daily for running and only use your athletic shoes for the sport that it is intended. As a general rule, whether you are running or walking for exercise, replace your shoes every 300-500 running miles or six months of active daily use.