HOW TO KNOW WHEN YOU NEED NEW RUNNING SHOES

The general rule is that running shoes should be replaced after 300 to 400 miles of use. A good way to keep track is to keep a running log. After every run, the number of miles completed should be noted. Otherwise, runners can roughly calculate the distance they've completed by estimating how many miles they run per week or month. 

However, the amount of wear imparted by a mile of running can vary significantly from runner to runner. This means that while the distance rule is useful, even this rubric isn't perfect. For example, the shoes of smaller, less heavy runners will last longer. Conversely, someone who mostly runs on rough, hard terrain will have to get new shoes sooner. 

Running shoes that need to be replaced will generally show certain signs of wear and tear. The first part of a shoe to break down is usually the midsole (the shock-absorbing layer between the inner and outer soles).

While the midsole is hidden from view, damage to this area can be indicated by shoes becoming lopsided. Worn soles will often lean to one side. The midsole can also be tested by trying to twist the shoe. If the shoe moves easily, the midsole is probably cooked. Another sign of excessive wear is if the treads of a pair of shoes become worn down to a smooth, flat surface. The appearance of holes in the exterior fabric indicates wear as well.

The presence of pain and minor, niggling injuries is another good sign that it's time for new running shoes. As shoe cushioning and support is slowly lost, the impact delivered to the joints with each stride steadily increases. Sore arches, shin pain, and achy, balky knees are some of the common results. The knees are especially likely to suffer from bad footwear. Generally, if a runner notices they are slowly experiencing more and more aches and muscle fatigue, they likely need to buy new shoes.