Is it time for new running shoes for the upcoming Chicago Marathon? Experienced runners know their running shoes have to be replaced regularly, but the question is: how often? According to the American Academy of Orthopedic Surgeons, the EVA in running shoes starts to show structural damage as early as 120 miles, and by the time a runner completes 500 miles in the same pair of shoes, around 45% of the initial shock absorption has been lost. But the weight of a runner affects the deterioration rate as well. A man’s size 10 shoe for example, might be worn by a 130 pound high school athlete, or 220 pound middle aged adult. It makes sense that the heavier athlete is going to wear down the sole and other structures long before the lighter one. To do this, divide 75,000 by your weight, and that number represents the upper limit in miles for a pair of running shoes. For example, if you weigh 185lbs, 75,000 divided by 185 equals 405 miles for that pair of shoes. If you have any questions, please call Dr. Bennett at 312 266-7404.