Every runner should have at least two pairs of their main running shoes that they are actively wearing at the same time, and they should cycle different running shoes between workouts. Because your kilometres are distributed across many pairs of shoes, your shoes will last longer. Also, it's important to rotate your shoe wardrobe so that no pair wears out prematurely. The number of shoes you need depends on how often you run a race and how far you plan to run each time. If you run multiple races per year, then you should be able to get by with just one pair of each type of shoe - marathon, half-marathon, and shorter distances. However, if you plan to cover considerable distances in each race, then you'll need more than one pair of each type of shoe. In addition, runners should have a backup pair of shoes in case their primary pair gets damaged or becomes too tight around the heel. These could be used as replacements or as training shoes until the others can be fixed or bought new. It is recommended to buy brand-new shoes every time you run a race. This will help you avoid any possible problems with the sizing or fit. Of course, this is not always possible so used shoes can be substituted but only after they've been worn for several runs outside of competition season to allow for some leeway in the size.