Wearing worn out shoes to exercise can increase your risk of hip, knee, ankle and foot injuries. How often should you replace them? It is recommended that you replace exercise shoes between 350-500 miles depending on your activity, style, body weight, and the surface you exercise on. A shoe can lose its support and mid-sole cushioning even if the outside looks fine. In addition to tracking your mileage, pay attention to how you feel. New aches or pains in your bones and joints or shin splints might be signs that it’s time to get new shoes.
Source: Ace Fitness