Shoe manufacturers usually indicate how long you should use a shoe before getting it replaced. An even more authoritative body, the American College of Sports Medicine (ACSM) advises that you need to replace your running shoes after 350 miles. Shoes that have passed their useful life (also called dead shoes) will usually have lost their tread and are plain uncomfortable. Dead shoes are the leading cause of shin splints (pains in the shin bone) and it is important to replace your shoe at the right time. Getting the size wrong when buying – Your running shoes are different from your office shoes and this factor should be taken into consideration when you go to the shop. A running shoe that fits perfectly when you buy it will prove too small when you run in it. Ideally, your running shoes should be at least ½ size larger than your normal shoe. It always helps to try the shoes on at the store. Should you go buying in the morning, remember that your feet swell as the day progresses and you must make an allowance for this before buying or simply make your purchase in the afternoon.