When you walk into a running store, it’s not uncommon to see dozens, if not hundreds, of options for running shoes.
These different choices can vary considerably in terms of appearance and functionality, with differing amounts of arch support, room in the toe box, height differential between the front and back of the shoe, grip on the bottom of the shoe, and so on.
One feature that has been subject to debate over the past several decades is the amount of cushioning necessary for running shoes.
Because a runner’s lower extremities are subjected to forces several times greater than their body weight with each stride, it would seem logical that more cushioning would be beneficial when selecting a running shoe. A deeper look into this topic, however, tells a different story.
Early Days of Running Shoes
It is essential to first look at the evolution of running shoes. During the early 1970s (after nearly a decade of trying to produce a shoe specifically designed for runners), Nike co-founder, Bill Bowerman, used his wife’s Belgian waffle iron to create a sole for running shoes that were not only able to grip the ground but was also lightweight.
As a hall of fame track and field coach at the University of Oregon, Bowerman was keen on making running shoes as light and flexible as he could to improve his athletes’ performance, which included numerous All-Americans, national champions, and Olympians.
These early prototypes resembled the minimalist shoes that are popular today.
The Rise of Midsole Support
Over the next several decades, shoe manufacturers began experimenting with different materials and incorporating them into the design. Running shoes, particularly the midsole of the shoe, started to become thicker and more cushioned.
What emerged were three different types of running shoes (Cushion, Stability, and Motion Control), which were recommended to runners based on the specific characteristics of their feet.
- Cushion running shoes, with less midsole material and a curved design, were designed for runners with high arches and more rigid feet.
- Stability running shoes, with a little more midsole material and a straighter design, were designed for runners with a more neutral foot type.
- Motion Control running shoes, with even more midsole material and a very straight design, were designed for runners with low arches and a more flexible foot.
According to this thought process, flexible feet were paired with stiffer straighter shoes and rigid feet were paired with more flexible shoes. While there are differing amounts of midsole material in each of these three types of shoes, they all have considerably more cushioning than the early running shoes designed by Bill Bowerman and Nike.
The Minimalist Movement
After the book “Born to Run: A Hidden Tribe, Superathletes, and the Greatest Race the World Has Never Seen” was published in 2009, the mindset shifted again.
The book was a huge advocate for barefoot running and made the case that humans are naturally well-adapted, both physiologically and biomechanically, to run long distances. This bestselling book helped launch the ‘minimalist movement,’ whereby shoes were designed to mimic bare feet.
As a result, manufacturers began designing flexible, lightweight shoes with far less midsole material.
Over the last half-century, the running shoe pendulum has swung from lightweight shoes with minimal cushioning, shoes with more material, and back to lightweight minimalist shoes. As it pertains to the amount of cushioning in running shoes, where should the pendulum settle?
First, let’s take a look at the midsole of the shoe, which, in addition to creating rigidity of the shoe, provides cushioning for the runner. Midsoles are usually made of a lightweight foam called Ethylene Vinyl Acetate (EVA), which helps the shoe handle the forces imposed on it from both the ground and the runner.
There are different types of midsoles, for example, dual-density midsoles, which means that the foam on the outer side of the shoe is softer than the inner portion. The desired function of dual-density midsoles is a motion control, primarily the control of pronation.
For the purposes of this article, however, we will focus on the role that midsoles play in terms of cushioning.
When considering the forces that running imposes on the body, it would be reasonable to assume that more midsole cushioning was a good thing. A closer look into this notion is warranted.
Let’s begin with the function of proprioception. A simple definition of proprioception is the perception of the position and movement of the body.
According to the article entitled Proprioception from the journal Physical Medicine and Rehabilitation Clinics of North America, it is extremely important in preventing and rehabilitating athletic injuries. Even subtle alterations in proprioception have been implicated in various lower extremity conditions involving the foot, ankle, knee, and hip.
It is imperative, therefore, to know what effect midsole cushioning has on proprioception.
In his book Anatomy for Runners: Unlocking Your Athletic Potential for Health, Speed, and Injury Prevention, world-renowned physical therapist and running expert Jay Dicharry compared midsoles to marshmallows. If you take this ‘marshmallow-like EVA foam and stick it between your foot and the ground, it will change your body’s proprioceptive ability.
From both a performance and injury prevention perspective, your brain needs to know exactly where your foot is when you run. If you have too much soft material in your shoe, you won’t get the necessary proprioceptive input to optimally perceive the foot’s position and movement.
This is especially important in running, where the contact time between the foot and the ground is extremely short, often under 0.25 seconds.
With that being said, it is vital for you to be able to quickly sense where your foot is relative to the ground. Even though they were incorporated into running shoes for shock absorption purposes, cushioned midsoles have changed the relationship between our feet and the ground and our brain’s ability to detect both.
Since they work against us in terms of proprioception, it would be good to know if overly cushioned shoes actually help us attenuate ground reaction forces.
The study entitled “Running in highly cushioned shoes increases leg stiffness and amplifies impact loading” looked into this topic. The researchers compared a conventional running shoe with less cushioning, the Brooks Ghost 6, to a maximalist shoe with more cushioning, the Hoka Conquest, in order to determine which shoe produced higher impact forces in runners.
The runners in each shoe group had similar characteristics in terms of step length, contact time, and cadence.
They found that the highly cushioned maximalist shoe actually increased, rather than dampened, impact loading compared to the less cushioned conventional shoe. This was demonstrated at two different training speeds, 10 km/hour and 14.5 km/hour.
In addition, when running in cushioned shoes with thick midsoles, runners may develop a false sense of security and subconsciously choose a gait pattern that results in an increased loading rate. For example, when your foot contacts the ground close to your body, it produces a much lower loading rate compared to contacting farther out in front of the body.
Contacting too far out in front is termed overstriding and is much easier to do in shoes with more cushioning. Running in less cushioned footwear forces the runner to land with their foot closer to their body and land more softly, two components that can significantly decrease impact forces.
Weight of the Shoe
The weight of the shoe is also very important. Even though it is not directly related to the amount of cushioning, shoes with thicker midsoles tend to be heavier than shoes with less midsole material. This is vital when it comes to running economy, which is defined as the aerobic demands of running in terms of energy utilization.
According to the article entitled Factors Affecting Running Economy in Trained Distance Runners, there is a strong association between running economy and distance running performance. It has also been shown that for every 100 grams of weight that you remove from the foot, in this case, the shoe, you save about 1% in economy.
This can translate into large changes in energy expenditure, especially when running long distances. Therefore, the weight of the shoe is also something to consider when purchasing a pair of running shoes with more cushioning.
Why Do We Buy Cushy Running Shoes?
If shoes with more cushioning have been shown to impair proprioception, create higher impact forces on the body, and increase the amount of weight a runner carries around, why do so many people choose running shoes with cushy midsoles?
One answer is that many people make running shoe purchases based on look and ‘first feel’. They see a shoe that they like, and it feels good when they try it on and walk a couple of steps.
Most people like the feel of shoes that are soft and cushy, and although it feels good in the store, this doesn’t translate to how well the shoe functions when running on the road or trail, or track. Another reason is that we see cushioned shoes advertised on television and in other media as a solution to the back, hip, or knee pain we may experience when running.
Benefits of Cushioning
Even though I have listed reasons why cushioned footwear can be detrimental, some degree of cushioning can be beneficial. This article wouldn’t be complete if I didn’t outline some pros of cushioning.
While heavier shoes with a lot of cushioning can increase running economy, some cushioning can actually help decrease the energy expenditure associated with running.
This is because running barefoot or in very minimalist shoes can cause the runner to use more muscular effort to stabilize their feet. A little EVA cushioning can help reduce the need for the lower extremity muscles to stabilize the foot without greatly increasing the weight of the shoe, thereby decreasing running economy.
In addition, some midsole cushioning is necessary to prevent injury of certain foot structures caused by repeated trauma. Of particular vulnerability are the fat pads located under the forefoot and heel, which function as major shock absorbers for the foot.
It has been shown that running in shoes with some degree of cushioning can result in significantly less fat pad deformation, helping to preserve the lifespan of these crucial tissues.
While it seems intuitive that overly cushioned shoes would be better for your body, thicker midsoles have never been proven to reduce injury rates. As demonstrated throughout this article, the contrary may be more likely to occur.
While the optimal amount of cushioning varies between individuals based on their running experience, foot morphology, body weight, and overall preference, there is a good starting point.
In his book Injury-Free Running: How to Build Strength, Improve Form, and Treat/Prevent Injuries, running expert Dr. Thomas Michaud states that that “10 millimeters of midsole cushioning provide the ideal amount of energy return with less weight and only a minimal reduction in proprioception.”
From here, runners can modify their choice based on comfort, performance, and experience. This is good to know because although the softer, cushier shoe will almost always feel better in the store, it may end up causing you problems when the rubber, or more correctly, the EVA foam, meets the road.