Shock Absorption in Running (It’s Not Your Shoes — It’s the Biomechanics)

Nearly every search result about shock absorption in running focuses on what shoes you wear. 

If you’ve ever looked it up yourself, you know what we’re talking about. Athletic shoe companies have pumped us full of effective marketing strategies convincing us that cushioned shoes are the answer to all our shock absorption needs in running.

And as consumers, being given an answer as straightforward as a new pair of high-tech shoes seems too good to be true, right? (But also highly convenient.)

But alas, our biomechanics don’t quite work that way — when the answer seems too good to be true, that’s usually because it is.

No matter how many shoe designs exist, it’s virtually impossible for them to cater to every single runners’ needs. And even in the scenario where that were true, adding some extra cushion under your feet is far from a complete solution for effectively controlling your impact forces while running.

Let’s review why that’s the case, and what you can actually do about it.

Why is Shock Absorption Important for Runners?

Shock absorption is the process by which an object — in this case, your muscles — absorbs the brunt of the impact forces you sustain during movement. It’s an absolutely vital aspect to proper running form to ensure that your joints and other passive structures (like your bones or tendons) are protected from undue stress.

Mitigating these impact forces while running goes well beyond the impact that occurs when your foot hits the ground.

With every step you take while running, you’re virtually landing a small, single-leg jump, subjecting your body to about 2.5 to 5 times its weight upon every landing. Plus, your body has to tolerate this increased weight bearing from the point of initial contact through the stance phase of your gait (i.e., from the moment your foot touches the ground until your knee is at peak bend while underneath your body):

This combination of increased weight and velocity means that your body is subjected to much larger impacts at a highly repetitive rate. So, while having additional cushioning in your shoes may help reduce some of these forces, they can only do so much when the forces actually originate elsewhere.

Why Running Shoes Aren’t the Long-Term Solution

Let’s think of this in the context of mountain biking: imagine you’re riding a mountain bike, equipped with hydraulic shocks and properly “cushioned” tires.

Both are important aspects to effective shock absorption, but if you start to feel harder impacts as you continue to ride, you’d want to check the hydraulics first, because those mechanics play a larger role in controlling shock and impact forces compared to the tires.

This same concept applies to your running! Your “hydraulics” are your running form and biomechanics, and your tires are the shoes you wear. While they’re both important, the former has a much more significant impact on actually addressing shock absorption at its core, as opposed to simply trying to dampen impact forces upon landing.

On top of all that, let’s not forget that runners have to switch out their shoes pretty regularly, roughly every 300-500 miles. 

With this knowledge comes the general logic that your shoes get worn down the longer you run in them. Some research has even identified the general rate of deterioration for your wear patterns, specific to how quickly the cushioning can break down under the repetitive pounding of constant running.

One study utilized a mechanical loading machine to simulate running, that way they could assess the rate at which the sole got worn down. After just 50 miles of running, they found that the cushioning deteriorated by 25%; by 150 miles, it decreased to 33%, and finally down to 45% once it hit that final 500 mile mark.

So, even in the perfect world where enough shoe cushioning could control impact forces, their effectiveness would quickly wear down with just a few weeks (or days) of training.

While this eliminates the convenience of simply buying some new footwear for an easy fix, it does shed light on what runners actually need to focus on: their biomechanics, specifically during initial contact and peak knee flexion.

Proper Biomechanics for Shock Absorption

Let’s dissect that mountain bike analogy a little further. Your body is the bike, and your biomechanics contribute to the hydraulic mechanism that helps absorb shock.

Within your “hydraulic system,” your biomechanics are controlled by muscle contraction and joint angles. This creates a response similar to spring mechanics, where your tissues compress and store energy while under load, then release it during propulsion or push-off.

In order to absorb as much shock as possible, your body has to maintain sufficient flexion in the three main joints of your legs: the hips, knees, and ankles. This is what prompts your large muscle groups to contract upon landing, leading to that “compression” that stores the energy gained from impact forces.

But why just tell you when we can show you? Take a look at these two images for reference:

Image A

Image B

In image A, we have a runner with poor shock absorption upon initial contact. As you can observe, they’re landing in a position where their spine is upright, the ankle is flexed excessively, and the knee is straight. Altogether, their leg is almost completely straight upon landing each step, eliminating any chance for compression or storing energy.

As a result, the incoming impact forces will end up affecting passive tissues, like your bones, ligaments, or tendons. (That’s where many runners sustain injuries like stress fractures or tendonitis.)

Conversely, the runner in image B demonstrates sufficient flexion and the hip and knee. These joint angles are much more optimal for promoting muscle contraction, that way your active tissues can take on the forces and channel it back into your push off as you move into the propulsion phase of your gait.

If you’re feeling a little in the dark about what “ideal joint angles” actually means, fear not — we’re here to break it down, joint by joint.

What Are the Best Joint Angles for Shock Absorption?

Alright: let’s get into the nitty gritty details, from the top down.

(If you’re more inclined to visual or audio learning, you can follow along with Kevin in the video below! He’s here to help us break down each joint angle one at a time.)

The best range for your hip joint lands somewhere between 25-35 degrees of extension. This range typically indicates that the runner has sufficient hip hinge, which better recruits their gluteal muscles for improved power generation.

In this screencap, the runner presents with 36 degrees of hip flexion. (This is an excellent example of how you don’t have to achieve joint angles down to the exact degree, as long as your body is recruiting the proper physiological processes to keep your passive systems safe from excessive impact.)

For your knee joints, it’s important to strike the right balance, roughly around 40-45 degrees for the most activation in your quadriceps muscles. The runner in this video is right at that sweet spot, presenting with 41 degrees of knee flexion.

Ensuring proper quad activation and contraction is necessary, as the muscle directly attaches to your knee cap. Without sufficient functionality, your knee is at much higher risk of sustaining injury as a result of misdirected impact forces.

Last but not least are the ankle joints. Your ankles function best around the 20-degree mark, as this is the point in its range of motion that promotes the best amount of muscle contraction (specifically in the calves). When your calf muscles are turned on and working properly, you’re less likely to experience stress and impact-related injury in the passive systems of your lower legs.

(Keep in mind: retaining these joint angles doesn’t guarantee your absolute best running form. These data points are ideal in terms of shock absorption and muscle use, but it’s important to ensure that your form — in its entirety — is symmetrical, and that the rest of your body isn’t compensating elsewhere just to hit the right numbers.)

Focus on the Biomechanics!

The bottom line is this: there’s isn’t any harm to buying yourself a good pair of high-tech sneakers… as long as they aren’t your only source of shock absorption. (After all, great shoes can’t compensate for poor mechanics.)

Addressing impact forces starts with your biomechanics, first and foremost. Train your “hydraulic system” with strong, active muscles, sufficient joint angles, and ample control over both sides. The more deliberate practice you get with it, the better you can adapt your body’s response to shock absorption as your form and efficiency improves.

And then, maybe, you can splurge on some fancy footwear!

Originally published May 12, 2016; updated on December 15, 2021

By Dr. Kevin Vandi DPT OCS CSCS

Dr. Vandi is the founder of Competitive EDGE Physical Therapy — with his background in physical therapy, orthopedics, and biomechanics, he is a highly educated, compassionate specialist. Using state-of-the-art motion analysis technology and data-driven methodologies, Kevin has assisted a wide range of clients, from post-surgery patients to youth and professional athletes. When he isn’t busy working or reading research, he spends his time with his wife Chrissy and their five wonderful children, often enjoying the outdoors and staying committed to an active lifestyle.

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