The Anatomy of a Running Shoe

These days buying a running shoe has never been more challenging. Many companies only talk up all the different technologies that they put into their shoe (through hours of research and design) instead of keeping it simple. Then you go to your trusted running review videos to see what they have to say about the latest shoe and sometimes they simplify it but often just regurgitate whatever it says in the description on the websites. And finally when you’re ready to pull the trigger on a new shoe at your local running store, the expert once again hits you with all the technical terms. So I’m here, for you, to just dissect a running shoe. And in a series of follow-up articles talk to you about the technical stuff in a simplified way.

All shoes can be broken down into three main categories: The Upper, The Midsole, The Outsole. Sometimes individuals and companies will group the Midsole and Outsole into one category and create a different category known as “The Last.” So what we will do here, is create four categories.

The Upper Unit: The primary purpose of the upper unit is to secure your foot in the sneaker.

The Upper – typically made up of several different types of fabrics. Some several different fabrics that are used are: engineered mesh, a knit material, or leather. The upper is designed to be supportive and strong yet flexible and breathable. Many sneaker brands have transitioned to an engineered mesh upper, as it is lighter and more breathable.

• Engineered Mesh (4 block pictures below)
• Knit (2 block pictures below) – A trend that started back in 2007-2008, every company came out with some rendition of a knit upper
  • Nike – Flyknit and Atomknit
  • Adidas- Primeknit
  • Brooks – Stealthfit
  • New Balance – Hypofit
  • Leather
• For trail shoes and “winterized” shoes – some uppers can be integrated with GORE-TEX or given a water-repellant layer.

Overlay – They can generally be added into the upper material of a sneaker. They can often provide increased stability and support of the upper. Often times they may be made up of a different material to provide reflective attributes to the sneaker.

Tongue – Generally a separate piece of material that is designed to protect the top of the foot from the lacing system. The tongue can also be padded or not padded as well. The extra padding is designed to take continued pressure off the top of the foot. Finally, there has been a newer designed in tongues that split the tongue so that it does not irritate the muscle tendon.

• There are several different types of tongues.
  • The tongue is part of the upper knit.
  • A gusset tongue is when the lateral parts of the tongue are attached to the upper knit. Generally seen in trail shoes, they are designed to protect from debris falling into the sneaker.
  • A burrito tongue is when one of the lateral parts of the tongue is attached to the upper knit.

Heel Tab/Heel Counter/Heel Collar – an inflexible plastic or reinforced part of the upper that has several different functions. The first is to lock down the heel to prevent sliding out of the back of the shoe. The heel collar is a pad that is designed to prevent irritation of the Achilles’ Tendon. Sometimes the heel collar gets a reinforced pad and sometimes it is not.

Toe Box – Located in the “front” or the “forefoot” of the shoe. Used to house the toes, the height and width of the toe box is important. The toe box should allow for room for your toes to move up and down, wiggle, and splay. Especially important as you spend more time on your feet, your feet will swell, so you do need sufficient space in the toe box to account for that. If the toe box is too tight around the foot, it can lead to irritation, blistering, and damaging of the toenails. The fit of the toe box is going to be influenced by the upper material.

• Toe Box Height – important to preventing pressure on top of the toes and irritation to the toe nails. Can also become an issue for runners, athletes, and individuals that have “hyperflexion” at their distal toe joints or “hammer toes.”
• Toe Box Width – important to prevent squeezing of the toes laterally and blistering of the toes. Shoe companies do make a number of their models in a “wide” version.

Vamp and Quarter – both portions of the upper that connect to one another on the outside portions of the upper

• Vamp – an extension of the toe box that connects to the quarter.
• Quarter – an extension of the heel that connects to the vamp.

Eyelet and Laces – holes built into the upper to allow for the laces to pass through. The eyelets and laces allow to create a secure upper fit. There are many different ways to lace up. Different lacing styles and techniques are designed to take pressure off different portions of the upper foot. The eyelets final eyelet, closest to the heel, can allow for a firm lockdown of the heel but if laced too high, it can cause irritation of the front of the ankle.

The Sole Unit

Midsole – The core of any sneaker and one of the most, if not the most, influential factor when you buy a running shoe. It provides cushion and energy return. In a follow-up article, I will talk about the midsoles. The most common midsoles used:

• Ethylene Vinyl Acetate (EVA)
• Polyurethane (PU)
• Thermoplastic Polyurethane (TPU)
• Pebax

Outsole – the bottom of the shoe. It is usually reinforced with a rubber bottom. Some companies also have an air-injected rubber. A rubber outsole is generally more durable (Adidas used the rubber in continental tires) compared to an air-injected rubber which is more flexible and cushioned. The outsole design is also influenced by the function and type of shoe. The outsole can be more rugged and have an aggressive lug pattern for grip or can have a less aggressive lug pattern and flexed for a smoother ride.

Heel Stack Height – usually measured in millimeters, it refers to the height of the midsole and outsole in the posterior/back part of your shoe, closest to the rearfoot. In other words, the amount of “shoe” between your heel and the ground. The general rule, the greater the stack height the greater the cushion underneath the foot.

Forefoot Stack Height – usually measured in millimeters, it refers to the height of the midsole and the outsole in the anterior/front part of your shoe, closest to the forefoot. In other words the amount of “shoe” between your forefoot and the ground. The general rule, the greater the stack height the greater the cushion underneath the foot.

Heel-to-Toe Drop – It refers to the difference in height (measured in millimeters) from the heel stack height to the forefoot stack height. Many companies generally will have a range of running shoes that will have a significant heel-to-toe drop (>12mm) to a zero drop (no difference between the heel and toe). There will be future articles on the potential implications of heel-to-toe drop.

Medial Post – generally found in shoes that are designed for “mild pronators to over pronators.” The medial post is found on the medial side or “inside” portion of the shoe built into the midsole. It generally is a more dense piece of foam designed to lessen the amount of “pronation” that occurs at the foot with each step.

Shank/Footbridge – located between the heel and forefoot on the bottom of the shoe, generally a supportive piece of plastic (or some other stiffened piece of material). The purpose of this piece is to stiffen the shoe and to prevent a twisting/torsion motion of the shoe at the arch. It does not prevent the forefoot from bending, flexing, and twisting

Last/Lasting Shapes: It is any given manufacture’s three-dimensional mold that create the most common shapes of a running shoe. The type of last used as the foundation of the shoe influences the midsole, the function, and the overall purpose of the shoe.

• Straight – the foundation of a stability and motion control shoe. A “motion control” shoe is used for the most overpronated or “flat feet” of athletes and individuals. (Far Right)
• Semicurved – the most common used for many of the shoes seen on the market today, regardless if the shoe is highly cushioned or on the minimal end. It is the hybrid between a straight and curved shoe. (Middle)
• Curved – the foundation of a racing flat or cross-country/track spike. It does not provide the support that a semi-curved or straight lasted shoe provides but allows for design of a lightweight runner. (Far Left)

Last/Lasting Attachments: The last influences the function of the shoe but also influences the attachment of the upper and the midsole.

• Slip-lasted – A slip-lasted shoe makes for a lighter shoe. It is directly stitched or glued to the last.
• Board-lasted – A board-lasted shoe is part of the foundation of a stability shoe. The upper is stitched or glued to the board that sits on top of the midsole.
• Combination-lasted – A combination-lasted shoe is used to keep the forefoot flexible and the rear foot stable. The board-lasted portion is used in the heel and the slip-lated portion is used in the forefoot.

I hope you took something away from this article and learned a little bit of something before buying your next pair of shoes. In follow-up articles we will talk about different foams used in midsoles, different types of running shoes, and stability-type of shoes. Talk to you next week!