The Last Shall Be First: Shoe Construction

Running shoes vary greatly from one to another, but all good ones have these basics of construction in common (refer to the following figures):

• Outsole, the bottom of the shoe that hits the ground
• Midsole, the soft, cushioned part directly above the outsole
• Insole, the usually removable part on which your feet rest
• Upper, the top part of the shoe that holds the laces
• Heel counter, the sturdy back part of the shoe

How these parts of a shoe are built and shaped is what makes one shoe good for you and another one not.
In addition to the midsole, most modern shoes also provide cushioning through technologies that the various running-shoe companies have devised in their labs. The best known is Nike’s Aircushioning. (It’s so well known, in fact, that if you ask runners what shoe they wear, they’ll often say, “Nike Air,” rather than accurately name the model.) Other examples are Asics’s Gel, Brooks’s HydroFlow, and Etonic’s StableAir. Although the running-shoe companies would vehemently deny it, most of these cushioning technologies are roughly equivalent for most runners. They all do a good job of increasing the amount of shock that the shoe absorbs and therefore decreasing the amount of shock your legs absorb. Some shoes have these cushioning technologies only in the heel, some have them only in the forefoot, and some have them throughout the shoe. The other major construction part of a shoe is its last. Running geeks love to bandy about this term because it can be used in two ways, so it can confuse outsiders. For the purposes of this book, the last is how the shoe’s upper is attached to its midsole. There are three basic types of last:

• Board lasting, in which the upper material is glued to a shoe-length board (usually made of paper fiber), and then attached to the midsole
• Slip lasting, in which, as in a moccasin, the upper material is stitched directly to the midsole
• Combination lasting, in which the upper material in the forefoot is attached directly to the midsole, as in slip lasting, while the upper material in the rear of the foot is attached to a board, as in board lasting.

You can tell which kind of last a shoe has by removing the insole. Once it’s out, you’ll see either a solid piece of material (a board-lasted shoe), a piece of material that runs to the arch area (a combination-lasted shoe), or stitches (a sliplasted shoe). The best last for your shoe depends on how you run.
The term last can also refer to the shape of the shoe. To avoid confusion, this book uses the term shape. There are three types of shoe shapes:

• Straight, in which the shoe is built straight along the arch
• Semi-straight, in which the shoe is built so that the forefoot points slightly toward the heel
• Curved, in which the shoe is built so that the arch area appears partly carved out A shoe’s shape is best determined by looking at it along the outsole.

As with a shoe’s last, which shape your shoe should have depends on how you run. A final piece of construction lingo you may run across while shoe shopping is dual-density midsole. In many shoes, you’ll see that the inside of the midsole will be darker than the rest. (It’s usually gray.) If you push on this area, you’ll notice that it’s harder than the rest of the midsole. That darker, firmer area is a medial post, designed to add stability to the shoe. Shoes that have a medial post have a dual-density midsole, which means that part of the midsole is denser than the rest.