The GPS in Your Feet
In my last post, I talked about the Ascending Influence—how the geometry of a shoe can dictate the health of areas such as your neck, back, and hips. Take a read here if you haven’t read it already. After it went out, I had a client ask me a deceptively simple question relating to a term I’d used a few times within the post but which I hadn’t really offered a detailed description:
“What do you actually mean by ‘grounding’? Is this some kind of woo-woo earthing thing?”
It’s a fair question, and something I shouldn’t have overestimated readers would grasp onto intuitively without explanation. In the health and fitness world, “grounding” will often get merged into the idea of standing barefoot in the grass to “align your electrons.”While I’m all for going out and touching grass, in the context of biomechanics—and specifically in relation to the Hruska Clinic’s Shoe List—grounding is a neurological phenomenon. It’s about your brain’s GPS.
The Conversation You Don’t Know You’re Having
If your feet are in contact with the floor, right now your brain is asking them a frantic question: “Where are we in space?”
To answer that, our bodies use a high-speed data motorway called a Sensorimotor Loop.
The Input: We have receptors in our feet that feel the floor beneath us (Ascending Pathway).
The Processing: That information travels up the spine, through the midbrain, and reaches the Parietal Cortex—the part of the brain that creates the ‘3D Map’ of your body.
The Output: Once the brain knows where it is in space, the Motor Cortex sends a command back down the body (Descending Pathway) telling your muscles how to move in response.
This is obviously a vastly simplified version of the process; however, if the input from your feet is clear, the responding movement is fluid. If the input is blurry or unclear, the brain gets “anxious” without a clear answer to our initial question: “Where are we in space?”
An anxious brain expresses itself through an increase in defensive behaviour in the form of muscle tension (think of the body’s response to stress: fight, flight, or freeze).
Three Shoes, Three Different “Signals”
To understand how your shoes impact this conversation between the floor and your brain, let’s look at three different running trainers that offer very different “signals.”
1. The Nike Alphafly:
Nike’s Alphafly series is an engineering marvel designed for one thing: speed. However, from a “grounding” perspective, it’s a sensory deprivation tank. When you’re standing on 40mm of essentially “super foam,” the signal traveling up to your brain is going to be incredibly muffled.
It is like trying to read braille with a pair of oven gloves on. Because your brain can’t find the solid ground beneath it, it’s going to refuse to allow muscles to relax and tone down unnecessary tension. You’re going to go fast, for sure. But know that your nervous system is working overdrive to keep you upright. This is a shoe built for a single purpose in mind.
(Watch the documentary Kipchoge: The Last Milestone for detail on how they built the Alphafly for his sub-1:59 Marathon attempt)
2. The Vibram 5-Fingers:
On the opposing end of the spectrum is the ultra-minimalist shoe—essentially a sock with a thin layer of rubber underneath. Here we can consider “grounding” at its rawest and most unfiltered. Every stone and crack in the pavement is going to send a signal up to the brain.
For some individuals, this level of sensation is great! But for many runners—especially those already dealing with the “kinks” in their 50-story building—this is the equivalent of trying to have a conversation inside the Millennium Stadium, roof on, with Wales 24-23 up against the All Blacks with 30 seconds on the clock. The signal is so loud and chaotic that the brain enters a “protective” state, stiffening the calves, tipping the pelvis forward, and increasing tension in the lower back to shield itself from impact.
3. The Brooks Adrenaline GTS 24:
This is the Hruska Clinic-approved shoe that isn’t trying to hide the ground from you, nor is it letting you become overwhelmed with signals. By having a stiff heel counter, arch sensation, and a specific flex-point, we can consider these an ideal balance of signal-to-noise. They tell your brain exactly where your heel is and exactly where the big toe is pushing off. When the brain gets this clear “grounded” signal, it inhibits (relaxes) unnecessary tension. You’re no longer having to fight for stability because the shoe is helping the brain map stability.
The Foot as a Tripod
So how does a shoe actually provide this “signal”? It comes down to the reference of the foot itself. To feel truly grounded, your brain needs simultaneous feedback from primarily three specific points on your foot:
Centre of the Heel (Calcaneus): The “sensor” for our upright posture. Lose a heel and we’re now “ungrounded” and falling forward.
The Base of the Big Toe (1st Metatarsal): The “accelerator.” As we move through the walking cycle, we “push off” through here.
The Base of the Little Toe (5th Metatarsal): Our lateral “stabiliser,” ensuring we maintain full-foot contact.
When a shoe allows you to sense all three of these points, your brain gets the high-definition picture that it craves. If the shoe is too soft (Alphafly) or too unstructured (Vibram), the “tripod” often collapses and the brain’s signal is altered.
Grounding is Clarity
When we make reference to finding a “grounded” shoe, it’s not a request to run out and hug a tree (though you’re welcome to). It’s an attempt to ask you to give your brain a better map of where the ground is underneath you.
If your brain can’t feel the floor through the heel of your shoe when it strikes the ground, it will find stability elsewhere—this could be through a knee, tightening of hip flexors, or a clenching of the jaw.
Grounding is therefore the absence of sensory confusion.
Next time you try on a pair of trainers, don’t just ask “Does this feel soft?” Ask “Does my brain know exactly where the floor is?” Because if the GPS can’t find the signal, it doesn’t matter how fast the car can go.
AK.