The function of a running shoe is to protect the foot from the stresses of running, while permitting the athlete to reach his or her full potential. Many sports now use a sport specific shoe due to the force and motion of the sport. An example of this can be demonstrated by comparing the sport of running to tennis. Tennis requires much side-to-side motion and the shoe must provide lateral stability. Shoes appropriate for racquet sports have minimal heel elevation. If the heel were elevated the lateral stability would be decreased and this would increase the chance of an ankle sprain. Running usually occurs in a straight line. Lateral stability is not as important. Running shoes usually have a slight heel elevation to help decrease the stress to the Achilles tendon. Running shoes also have a larger toe box, more shock absorption and improved foot control than a tennis shoe. Many walking shoes have characteristics more similar to tennis shoes. Since walking and running both occur in a straight line one would be better off walking in a pair of running shoes.

Shoe Wearing and Buying
A shoe's midsole only lasts so long. It degrades from use and the resultant life of a running shoe is 350 to 550 miles. This means that if you are running 20 miles a week, you should consider changing by the 20th to 25th week. The shoe can still be used for casual walking.

Sole wear does not necessarily reflect the loss of shock absorption by a shoe. Even with a new looking shoe, adequate shock absorption may be lacking. Use the 350-550 mile guideline instead of guessing how worn your shoe should look.

Buy your shoes at the end of the day, when your feet are somewhat larger from the day's walking.

Make sure there is about a finger's width at the front of the shoe. This will help prevent irritation of the toe.

If you have had good experience with a particular brand and model of a shoe, try to stay with it.

Don't dream of running a marathon in new shoes. Your shoe should have at least 100 miles on it to be broken in well enough to run a marathon.

Carefully lace your shoes before running. Too tight may make the top of your foot sore or squeeze your metatarsals too tightly. Too loose a shoe may allow your foot to move excessively and be less stable, resulting in more than normal foot pronation.

Shoe Wear
Shoe wear is often taken to hold much meaning. While the wear pattern on the bottom of your shoe may be helpful - it is usually not of great benefit. It is most beneficial to examine a bare foot in standing, prone, and supine positions and watch you walk.