Parts of A Shoe

The parts of a shoe

The last
All shoes are built on a last. This is the heart of a shoe. It is a piece of plastic, metal, or wood, and its contour determines the shape and size of the shoe. The etymology of the word is "laest", the Old English word for footprint. There are three basic shapes: straight, semi-curved; and curved; but all three shapes vary from company to company as each company has its own lasts. Semi-curved is by far the most popular and most runners do well in a semi-curve-lasted shoe.

A straight-lasted shoe features a straight-shaped sole with little indentation at the arch. A straight last is appropriate for the overpronator with a flexible, flat arch. It helps to control inward rotation. Shoes with a straight last offer the most medial support, and "motion control" shoes tend to be built with a straighter last than stability shoes. A stability shoe is more likely to have a semi-curved last. Most racing shoes are built on a curved last.

The downsides of straight-lasted shoes is a lack of flexibility; they weight quite a bit; and they're less able to deliver a performance run. This isn't a speedwork shoe, or a tempo run shoe. Curved or semi-curve-lasted shoes are what you want for tempo runs, fartlek, speedwork. But, they break down quicker if you're an overpronator, and your orthotic, if you use one, will "help" break down the medial side of a curve-lasted shoe.

The term "last" can be confusing, because it can also refer to how the upper is attached to the midsole. You'll hear three terms used: slip-lasted; board-lasted; and combination-lasted. A slip-lasted shoe is made by sewing the upper into a shape that resembles a moccasin. This construct is then glued directly to the midsole without any board in between. These are flexible shoes with lots of cushioning and, on balance, little motion control.

Board lasted shoes have a sturdy insole fiberboard running the entire length of the foot bed. This type of construction provides the greatest stability. But shoes of this construction are rare nowadays because of weight, and lack of flexibility.

A combination-lasted shoe is stitched in the forefoot and glued in the rearfoot to that fiberboard. While slip-lasting is the most common construction, Asics is one brand that combination-lasts many of its shoes.

Some runners believe a combination-lasted shoe is the most stable and most supportive for orthotics, because the fiberboard mates nicely with the orthotic's heel. To determine which type of lasting the shoe has, remove the insole (also called the sock liner). If there's stitching in the rearfoot, it's slip-lasted. If you see that fiberboard on top of any of the stitching, it's combination-lasted.
Outsole
This is the outer sole of a shoe—the bottom of the shoe. It's the layer of the shoe that contacts the ground.

Carbon Rubber, a common outsole material, is rubber with a carbon additive to increase durability. It is denser and heavier than blown rubber, and often used in high impact areas.

Blown rubber, a common outsole material, is rubber mixed in some fashion with air. Blown rubber yields a relatively light, cushier outsole, but suffers in durability compared to carbon rubber. Blown rubber is a process most triathletes rely upon: it's what their wetsuits are made of (though wetsuit rubber is much lighter and softer than what is used in the outsoles of running shoes). It's not inconceivable that your wetsuit, your shoe's midsole and EVA outsole, your swim goggle's liner, and your cycling shoe winter booties, are all made of material from the same factory.

Many outsoles use a combination of blown rubber in the midfoot and forefoot—for a lighter shoe with a cushier ride—with carbon rubber in the rearfoot for added durability.

Midsole
This is the area of the shoe between the upper and outsole. It's primarily responsible for the shoe's cushioning. Most midsoles are made of foams: either EVA (ethylene vinyl acetate) or polyurethane. EVA is lighter and more flexible than polyurethane, but it also breaks downmore quickly. Many midsoles also have additional cushioning elements such as air and gel.

Just as there are proprietary types of blown rubber used by different triathlon wetsuit manufacturers, there are proprietary types of EVA in the marketplace, such as Nike's Phylon and Brooks' Substance 257. Whether in wetsuits or in running shoes, some proprietary designations are more market- than substance-specific, and some really are substantive and provide specific efficacy. Adidas adiPRENE, Brooks HydroFlow, New Balance AbZORB, are additional examples of proprietary EVA.

Medial posting
"Medial" in this context refers to the inner side (the arch side) of a shoe. Lateral is the corresponding term referring to the outside edge of a shoe. Shoes rarely need much extraordinary support on their lateral sides, because most runners pronate, that is to say, their feet roll to the inside. Arch supports, and orthotics, are examples of products designed to buttress and support the foot on the medial side.

EVA is the most common midsole compound used in running shoes. This shock-absorbing foam is soft, light, and flexible. It can be made in variable densities: the more dense the EVA, the harder the ride, but the more supportive for over-pronators. For this reason, many footwear makers employ two densities of EVA, with the firmer density on the medial side of the midsole. This dual-density EVA combines a smooth, supportive ride with a barrier to compression on the shoe's medial side. This technique is called a medial post.

Other parts of the shoe
The "upper is the leather or mesh material that encloses the foot.

"Flex grooves" are midsole and outsole notches to allow the shoe to bend and flex properly with the natural motion of the foot improving forefoot flexibility at toe-off.

The "heel counter" is a device—often a piece of leather, or a plastic cup—forming the back of a shoe. Its job is to reinforce the heel and prevent excessive heel motion. The heel should fit snugly without being too tight. If it's too wide, the heel will slip in and out of the shoe and cause blisters. Women, in particular, often have narrower heels than men and require a narrow heel counter, common in some brands such as Saucony.

The "sock liner" is the removable insert added to cushion and protect your foot from the shoe's midsole. Orthotics, when used, replace sock liners.

The "toebox" is the area of the shoe that encases your toes.