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IMPACT: Why We Need It

By Stuart Wakefield RKin

It’s safe to say, the word impact gets a bad rap. How many times have you heard “running is bad for my knees” or “I have arthritis so I can only perform low impact activities”?

Of course, there’s a time and a place for lower impact activities, such as following a surgical procedure. But have you ever thought of impact as a gift?

The first step in this process of efficient movement is our ability to feel and sense the ground

This is the gift of FREE energy. Our body has the incredible ability to take in approximately 1.5x our body weight in impact forces with every step that we take. We can then double that free energy and release approximately 2.5x our body weight as we push off the ground. We call this the catapult effect. This is ultimately what allows humans to conserve energy and travel long distances by foot.

What’s the catch you ask?

Well, you have to FEEL the impact. You have to FEEL the ground.

The skin on the bottom of our feet contain mechanoceptors. These fast adapting type 1 and 2 receptors can sense low and high frequency vibrations. 70% of these receptors on the bottom of the foot are sensitive to vibration, which is how our body senses impact. This alone tells us that vibration/impact is an essential stimulus for human movement!

The aforementioned catapult effect is a process driven by your fascia. This incredible tissue has many different properties, one of which is elasticity. This creates a bow and arrow like effect. As soon as our foot hits the ground, the bow starts to stretch and as your leg goes through the stance phase of gait, the bow gets stretched further and further until push-off, where it’s released to sling shot our leg forward. When we lose this elasticity (too much sitting/lack of movement/injuries), our muscles have to kick in to assist in propelling us through the gait cycle. This is a very energy expensive and an inefficient way to move.

The first step in this process of efficient movement is our ability to feel and sense the ground. Research out of the University of Calgary (Nigg et al, 2017) shows that in order for us to store energy in fascia, muscles in the foot and lower leg need to contract isometrically, matching the frequency of vibration from the ground we’re walking on. In order to match the frequency, we need to accurately sense the frequency. This is a process that we call pre-activation. After a few steps on the surface that we’re walking on, our brain senses the frequency of the ground and the amount of compartment pressure needed to drive these forces into our fascia for elastic and efficient movement. Enter the modern shoe. Almost every single type of shoe you can purchase today has layers of cushion, negatively affecting our ability to accurately sense the ground. Some of the same research out of the University of Calgary shows that cushion in shoes INCREASES impact forces. This confirms the importance of accurately sensing the ground, which is the first step in this process of movement efficiency and injury prevention.

So could impact have a negative effect? Of course. Is there a time and place for shoes? Absolutely.

But when you’re considering or educating patients on the effects of impact, ask yourself:

“Can I feel the impact via my foot?” “Am I controlling the impact?”

Just like we can strengthen our muscles and bones, we can also upregulate this aspect of our nervous system. One major step you can take to improve this system is by spending more time barefoot! By just simply walking barefoot around your house or out on the grass in your backyard, you’re keeping these fast adapting mechanoceptors stimulated and this pre-activation pathway active.

Along with being barefoot, there are exercises like short foot. Several studies have shown short foot to have a sensory-motor benefit post ankle sprain or through improvement in dynamic balance. (Lee et al, 2019, Kim et al, 2016)

Lastly, we can also upregulate these sensory pathways via tools like Naboso textured insoles. This texture matches the same science as braille and is sensed through our slow adapting type 1 mechanoreceptors that are critical for movement accuracy.

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