How Are Running Shoes Made? From Design To Finished Shoe

A modern running shoe might look relatively simple. There is a fabric upper around your foot, a thick layer of cushioning underneath and rubber where the shoe meets the ground. Take one apart, however, and you discover a surprisingly sophisticated piece of engineering made from numerous materials and components.

Depending on the model, a running shoe can combine engineered mesh or knitted fabrics, reinforcing materials, several types of foam, rubber compounds and plastic components. Performance shoes may add a carbon fibre, nylon or other stiffening plate within the midsole. All of those elements have to work together while keeping the shoe comfortable, durable and, particularly in racing shoes, as light as possible.

The process of making a running shoe therefore begins long before anything reaches the production line. Designers first decide what they want the shoe to do, engineers develop its shape and materials, prototypes are produced and tested, and only then can the various components be manufactured and assembled into the finished shoe. So how are running shoes made, and what actually goes into creating the pair on your feet?

It Starts With The Purpose Of The Shoe

Before designing a running shoe, a manufacturer needs to decide what sort of running it is intended for. An everyday road shoe has different requirements from a lightweight racing shoe, while a trail shoe needs greater traction and protection for running over loose and uneven surfaces.

Designers establish objectives covering characteristics such as cushioning, stability, flexibility, weight, durability, grip and fit. These decisions influence almost every stage that follows. A highly cushioned daily trainer might use a substantial amount of foam and more outsole rubber for durability, while a racing shoe could prioritise lightweight, responsive foam and incorporate a stiffening plate.

The geometry of the shoe is also developed. Designers determine features including stack height, heel-to-toe drop, the shape of the midsole and the amount of space available around different parts of the foot. Computer aided design can be used to develop and refine these ideas before physical prototypes are produced.

The Last Helps Determine The Shape And Fit

One of the most important pieces of equipment used to make a shoe never appears in the finished product. It is called a last.

A shoe last is a three-dimensional form shaped broadly like a foot. It helps determine the internal dimensions and shape of the finished shoe, including characteristics such as heel width, midfoot volume and the space available around the toes.

Manufacturers can develop different lasts for different types of shoes and fits. This is one reason two running shoes carrying the same numerical size can fit very differently. The number printed on the box is only part of the story because the underlying shape of the shoe can vary between brands and even between models from the same manufacturer.

The last becomes particularly important later in production when the completed upper is placed over it, giving the shoe its intended three-dimensional form before the sole is attached.

How The Running Shoe Upper Is Made

The upper is the part of a running shoe that surrounds the top and sides of your foot. It needs to hold the foot securely while remaining comfortable, flexible and sufficiently breathable for running.

Many modern shoes use engineered mesh. Rather than using material with identical properties everywhere, an engineered upper can provide more ventilation or flexibility in some areas and greater structure in others. Reinforcing elements may also be added around high-stress areas such as the eyelets, heel, toe or sides of the shoe.

Knitted construction provides another option. Different structures can be incorporated into a knitted upper so that support and flexibility are placed where they are required without necessarily adding numerous separate pieces of material. This can also reduce some of the cutting waste associated with conventional cut-and-sew manufacturing.

Other parts are incorporated as required, including the tongue, eyelets, laces, heel counter, collar and internal padding. The amount of material varies considerably according to the shoe's purpose. A comfortable daily trainer might have substantial heel and tongue padding, while a racing shoe often uses a much more stripped-back upper to save weight.

The Upper Is Turned Into A Three Dimensional Shoe

Once its individual pieces have been assembled, the upper still needs to acquire the shape of a shoe.

Many modern athletic shoes use a form of Strobel construction. The lower edges of the upper are stitched to a flexible fabric underneath the foot, creating something resembling a fabric shell. If you remove the removable sockliner from some running shoes, you can sometimes see this construction underneath.

The assembled upper is then placed over the shoe last. This is the lasting stage, which establishes the final shape and dimensions of the upper before it is joined to the sole.

This order is important. The upper is not normally attached to the finished sole and then placed on the last. Lasting prepares and shapes the upper so that it can subsequently be aligned and securely bonded to the sole unit.

Making The Midsole

The midsole sits between the foot and the outsole and is responsible for much of the cushioning and ride you experience when running. It has also become one of the most technologically competitive parts of modern running shoe design.

EVA, or ethylene-vinyl acetate, has been widely used in running shoe cushioning for decades and remains important today. Manufacturers can alter its formulation and processing to produce different levels of softness, weight and resilience.

Modern shoes can also use TPU and PEBA-based materials, as well as blends and proprietary formulations. PEBA is particularly associated with some high performance running shoes because suitable formulations can produce lightweight foams with high resilience.

Simply knowing the name of the polymer does not tell you exactly how a shoe will feel. The formulation, density, cell structure, geometry and manufacturing process all influence the characteristics of the finished midsole.

How Midsole Foam Gets Its Shape

Midsole materials have to be turned into the precisely shaped cushioning units underneath a running shoe. Manufacturers use several processes depending on the material and the characteristics they want to achieve.

Compression moulding is one established method. Prepared foam material is placed into a mould and shaped using heat and pressure. Injection-based processes provide another approach, while some midsoles are produced from expanded beads that are fused together.

The mould determines much more than the external appearance of the shoe. Modern midsoles can incorporate curved sidewalls, cut-outs, channels and rocker shapes that influence weight, stability, flexibility and the way the shoe transitions from landing to toe-off.

Manufacturing methods continue to evolve alongside the materials themselves, which is one reason two shoes described as using similar types of foam can behave very differently on the road.

What Is Supercritical Or Nitrogen Infused Foam?

Some running shoes are marketed as having nitrogen infused or supercritical foam. These descriptions relate to processes used to create the cellular structure within certain midsole materials.

In a supercritical foaming process, a gas such as nitrogen can be used under controlled temperature and pressure conditions to help create cells within the material. Manufacturers can manipulate the resulting structure to pursue characteristics such as lower weight, greater softness or increased resilience.

Brooks, for example, describes using nitrogen in a supercritical foaming process for its DNA LOFT v3 cushioning. Other manufacturers use their own materials, gases and processes, so the phrase nitrogen-infused should not be treated as a universal recipe for one particular type of foam.

It also does not automatically mean one shoe will perform better than another. The polymer, foam structure, midsole geometry and overall design still determine how the finished shoe behaves.

How Plates Are Added To Some Running Shoes

Not every running shoe contains a plate, but plates have become particularly familiar through the development of modern racing shoes.

Depending on the design, a plate or other stiffening element can be positioned within the midsole so that it works with the surrounding foam and shoe geometry. Carbon fibre is commonly associated with high-performance racing shoes because it can provide substantial stiffness at a relatively low weight.

Other shoes use nylon, thermoplastic materials or alternative structures to modify stiffness without necessarily creating the same characteristics as a carbon fibre racing shoe.

The plate is only one part of the system. Its shape, position and stiffness interact with the foam and the geometry of the shoe. Simply adding a carbon plate to a running shoe does not automatically make it faster.

How The Outsole Is Made

The outsole is the part of the shoe that comes into direct contact with the ground. Its main jobs are to provide traction and protect the softer midsole from excessive abrasion.

Rubber compounds are widely used because they can offer substantially greater wear resistance than exposed cushioning foam. The rubber is formed into the required shapes and tread patterns before being attached to the bottom of the midsole.

Road shoes usually have relatively shallow tread because they are primarily intended for tarmac and other hard surfaces. Trail shoes typically have deeper lugs designed to grip loose, soft or uneven terrain.

Manufacturers do not always cover the entire underside of a running shoe with rubber. Strategically placing it in high-wear or high-grip areas can reduce weight and allow other parts of the midsole to remain exposed.

Bringing The Sole Unit Together

Depending on the shoe, the sole may consist of several separate components. Different layers or densities of midsole foam can be combined, a plate may sit between or within those layers, and individual pieces of outsole rubber can be attached underneath.

These components need to be positioned accurately because relatively small changes can alter the finished shoe. In a plated racing shoe, for example, the relationship between the plate and the surrounding foam is an intentional part of the design. Once the sole unit and lasted upper are ready, they can finally be brought together.

Attaching The Upper To The Sole

For many modern running shoes, the lasted upper and sole unit are joined using specialised adhesive systems. The surfaces may first need to be cleaned, roughened or otherwise prepared, and primers or adhesives can be applied to create a reliable bond.

The upper and sole are carefully aligned and brought together. Pressure is then used to establish the bond, while heat or other activation processes may be involved depending on the materials and adhesive system being used.

The strength of this bond matters enormously. Every running step repeatedly bends and loads the shoe, so the connection between upper and sole has to survive a large number of flexing and impact cycles.

Only after sole attachment and the appropriate production checks is the last removed from inside the shoe.

Read about looking after your running shoes here.

Finishing The Running Shoe

With the last removed, the shoe begins to look like the product that will eventually appear in a running shop.

The removable sockliner can be inserted and the laces fitted or adjusted. Finishing work may include cleaning away marks or excess adhesive, trimming materials and checking the alignment and appearance of the different components.

Branding and decorative details may have been incorporated at earlier stages rather than simply being added at the end, depending on the construction of the particular shoe. The completed shoe can then move through final inspection and quality-control procedures.

How Running Shoes Are Tested

Testing takes place throughout shoe development and manufacturing rather than only after the first production pair has been completed.

During development, prototypes can be subjected to mechanical testing for characteristics such as flexibility, cushioning, abrasion and material durability. Manufacturers also use wear testing, putting prototypes onto runners to discover problems that may not be obvious from a computer model or laboratory test.

A shoe might feel uncomfortable around the heel, create pressure over the toes or allow too much movement through the upper. Designers can use this feedback to alter materials, dimensions or construction before production begins.

Quality control testing continues during manufacturing. The bond between the upper and sole is one example. Footwear testing organisation SATRA has specific procedures for assessing sole adhesion in completed footwear, demonstrating how important that apparently simple glued joint is to the durability of a finished shoe.

How Running Shoe Manufacturing Is Changing

Running shoe manufacturing continues to develop as companies look for ways to improve performance while reducing material use, waste and environmental impact.

Engineered knitted uppers can place material more precisely and reduce some of the waste associated with cutting individual upper components from larger sheets. Recycled polyester, recycled rubber and other recycled materials are also now incorporated into some running shoes.

Manufacturers are experimenting with different production methods too, including automated knitting, advanced moulding and increasingly automated handling and assembly processes. Producing a running shoe is nevertheless difficult to automate completely because flexible materials have to be positioned, stitched, shaped and bonded with considerable precision.

End of life recycling remains another challenge. Running shoes deliberately combine materials with very different properties and bond them together strongly enough to withstand hundreds of miles of use. Those same characteristics can make the components difficult to separate afterwards.

Read about sustainable running shoe brands here.

Why Construction Changes How A Running Shoe Feels

Understanding how running shoes are made helps explain why choosing a shoe involves much more than looking at how much foam is underneath it.

The last influences the basic shape and fit. The upper determines how the shoe holds your foot. Midsole material and geometry contribute to cushioning, responsiveness and stability, while plates and other structures can alter stiffness. The outsole affects grip and durability, and the way all these components are assembled influences the finished shoe.

Change one element and the character of the shoe can change with it. Two running shoes with similar stack heights and weights can consequently feel completely different once you start running.

There is also no single construction that makes the best running shoe for everyone. A lightweight PEBA based racing shoe with a carbon fibre plate may make sense for someone chasing a personal best, while an everyday runner may place greater value on comfort, durability and stability.

From An Idea To The Road

A modern running shoe is much more complicated than a piece of fabric glued onto some foam. It is the end result of design, materials science, prototyping, manufacturing and testing, with each component performing a particular job.

The upper is designed and assembled before being shaped around a last. Midsole materials are formulated and moulded into carefully designed geometries, outsole rubber is produced for traction and durability, and some shoes add plates or other structures within the cushioning system. The lasted upper and sole are then prepared, aligned and bonded before the last is removed and the shoe is finished and inspected.

The next time you lace up your running shoes, take a closer look. The mesh around your toes, the sculpted foam beneath your foot and the carefully positioned rubber underneath are not there by accident. They are the visible results of a manufacturing process that turns a collection of very different materials into a shoe capable of carrying you through hundreds of miles of running.

Read about the running shoe brands here.