In the 1928 Summer Olympics, the running spike was born. Now, it’s commonly believed athletes need specialized shoes to perform their best. Almost 100 years later, the running shoe is still undergoing constant revision. What started as a relatively simple concept has turned into an athletic arms race, with companies like Under Armour funding teams of scientists and elite runners to create the best shoes possible.
Doug Smiley, the senior product line manager for Under Armour’s high-performance run team, explained that running shoe design is a balancing act between serving your needs as an athlete and honoring the biomechanics of running. Running shoe technology has changed drastically in the previous decades, ranging from large, cushiony shoes to a bare-bones minimalist design.
Currently, companies like Under Armour are finding the sweet spot between cushion and stability. Modern shoes are designed to support your foot, cushion impact and propel you forward. To understand how running shoes can help you, it’s important to understand how they’re designed.
BOTTOM AND TREADS
The bottom of the shoe, which is made of protective rubber and tread, gives you traction and protection. Thick rubber materials are used in areas that have high impact, according to Smiley. However, thicker rubber is heavy and has to be used sparingly to keep the shoe light.
The heel and toe have the most durable rubber, because that’s where the highest impact forces go. The mid- and forefoot areas of the shoe have thinner rubber. Those areas are designed to give you more cushion and rebound.
Tread patterns are different depending on the area of the shoe. The tread on the heel is segmented to allow the shoe to flex upon impact. In the midfoot, the tread pattern is more linear and moves forward toward the toe to help guide your foot. Under the toes, the tread is smoother because big bumps of tread would be uncomfortable to run on.
The midsole is above the outsole. It’s made of softer materials, which have evolved over the years. A February 2017 research paper published in Peer Journals explains that the midsole is the most-researched part of the shoe. Much of this research is focused on how hard or soft to make the foam in the midsole to find the correct balance between force absorption and stability.
A softer midsole gives your foot more cushion, because it allows your foot to sink into the shoe upon impact. However, it gives your foot and ankle less stability. According to the research paper, the hardness of the midsole influences the way your ankle moves. A softer midsole can throw off your ankle, making it unsteady.
Polyurethane midsoles were used in the 1970s–80s until a new technology, ethylene-vinyl acetate (EVA), emerged. It’s a porous material, similar to rubber. EVA is used in shoes because it’s flexible, durable and temperature-resistant. Materials like polyurethane get harder when it’s cold and softer in the heat, but EVA won’t change significantly.
Under Armour is taking things one step further, says Smiley, mixing rubber with EVA to improve stability in certain areas of the midsole. Rather than changing the density of the entire midsole, they add thickness to specific areas that require more stability. While everyone has slightly different mechanics when they run, there’s a basic pattern the average person follows.
MIDSOLE ACCOMMODATES BASIC RUNNING
Runners who strike the heel first tend to land on the outside of the heel. As the foot rolls forward, weight shifts in toward the arch of the foot. Then, when they push forward off the front of the foot, their weight shifts toward the pinky toe. That’s the basic pattern most runners follow, and shoes are designed to guide them along that path.
Normally, when your foot strikes the ground, your foot squashes the midsole. This helps absorb the shock of the impact, but it gives you less of a spring forward. The effect is similar to running on sand, where your foot strikes the ground, but it’s difficult to push off. Under Armour fixed that by encasing the midsole of its HOVR line of shoes in an energy web. It’s a thin, stretch-resistant web that wraps around the foam of the midsole.
An August 2015 study published in the Journal of Sports Sciences found running shoes with energy-returning technology, like the energy web, improved performance more than normal shoes. It’s a small innovation that literally adds a spring to your step.
Running shoe companies market the terms “pronation” and “supination.” Pronation of the foot happens when your foot rolls in and the arch flattens. Shoes made to correct this are often labeled as “control” or “stability” as opposed to “neutral.” They’re made with something called a medial post, which is a hard section of foam underneath the middle of your foot. It gives the arch of your foot support when you land to prevent it from rolling in excessively.
This sounds great in theory, but an article from the American Academy of Podiatric Sports Medicine states that there’s no concrete scientific evidence that buying shoes in one category can help your running performance or prevent injuries.
The shank of the shoe is a piece of hard material that can also act as a medial post. It’s placed in the middle of the shoe to add stability. While it can act as an arch support, the main responsibility of the shank is to make sure the shoe bends at the forefoot instead of the midfoot. If you pick up your running shoe and try to bend it in half, it will only bend near the toe because of the shank.
The main shape of the shoe comes from something called a last. Each brand and line of running shoes has a specific molding that’s used to give it shape. Some are wider in the front of the foot, some are narrow and some are curved. That’s why it’s important to try different types of running shoes to see what fits best with your foot.
The upper is the top half of the shoe. That’s the part that connects to the midsole and envelops your foot. It includes the tongue, heel counter, heel collar and even the sockliner. Light and breathable materials are used on top to keep your feet cool and lower the overall weight of the shoe.
The heel collar and heel counter keep your foot from slipping out of the shoe as you run. Inside the soft material that hugs the back of the heel is a hard heel counter. This hard material is made to hug your heel, pressing it down into the shoe. Usually only one heel counter is used inside the shoe, according to Smiley, but another heel counter can be placed on the outside of the shoe for extra grip. However, that adds weight to the shoe, and is often avoided.
The heel collar is the thick material under your ankles that gives you lateral support. Running shoes have a linear design, which means they’re made to go forward and backward. They’re not like cleats or tennis shoes that have more lateral stability, because runners don’t move side-to-side. That’s why running shoes don’t come up too high around the ankle.
When it comes to preventing injuries, your running shoes aren’t the biggest factor. A September 2019 study published in the Journal of Science in Sport and Exercise found adding cushioning to the midsole wasn’t as effective in lowering impact forces on the heel as shortening stride length. That means runners who want less pounding on their heels should focus on shortening their stride before changing shoes.
A separate study published in August 2015 in The American Journal of Sports Medicine found stride length was correlated to injuries, but foot strike was not. The researchers found subjects had the same risk for injury whether they landed on their heel, mid-foot or toes during running. The only thing that lowered injury risk was a shorter stride length.
While shoe technology is advancing at a rapid pace, keep in mind that your running technique, training plan and nutrition are key to performance. Your shoes are the icing on the cake.