Last week I promised to break down the key functions of the foot and how they impact your patients (and you) every day.
Although I learned the anatomy and basic mechanics of the feet during my university studies, no one ever really emphasized just how much they impact everything else that happens above.
Spinal and pelvic mechanics were covered in detail, but feet were assumed to have only two basic jobs…
Standing and walking/running.
Whilst that may be true, it’s not really useful when it comes to understanding the feet from a functional, whole-body perspective.
Today we’re going to start by looking at the foot as a sensory organ.
This is the first of the four critical foot functions… actually sensing the ground we’re standing on.
I love this quote from Dr. Emily Splichal, Functional Podiatrist & Human Movement Specialist…
“To truly appreciate the foot, we must not look at it as just a biomechanical structure. We must appreciate that your foot is a very powerful neuromuscular structure. This means that your foot is the gateway to your nervous system.”
This goes directly to the heart of why, as chiropractors, we should be paying attention to our patients’ feet.
Did you know that the smallest (therefore most sensitive) branches in the peripheral nervous system are actually in the feet?
And that the tibial nerve has 3x as many sensory fibres as motor fibres?
(That’s why memes like this are a thing…)
Anyone who’s ever stepped on a lego, (or a bindi if you live in Australia) knows that the pain is real.
Why would evolution play this cruel trick on us?
Well, these days life is pretty safe for our feet (lego’s aside), but for hundreds of thousands of years the consequences of a misstep were much more severe. A sprained or broken ankle, or a potentially deadly snakebite, were all very real and dangerous possibilities that would have severely impacted your ability to survive and feed your family.
Not only that…
Resources were scarce, which meant energy was at a premium.
That meant that those who survived were the most efficient…
And there’s no way to efficiently set up your gait, balance, posture or relationship to gravity without accurate information about the surface you are standing on.
The simple scripting I use to explain this to my patients, whenever they are shocked by the instant changes in their hip flexors when they stand on the orthotics is this…
“Your brain is always setting up your posture based on the information it is receiving from your feet. Bad information equals bad posture, bad balance and bad neurology.
Unfortunately, most people are receiving bad information from their feet due to a lifetime of wearing shoes and walking on flat, unnatural surfaces.”
Another way to understand this is to think about the example of someone standing on a hill. If they are facing up the hill, their brain will increase tone in their flexors and decrease tone in their extensors so the person remains upright.
(Again, providing the brain actually receives accurate information from the feet.)
I believe this is one of the mechanisms whereby the orthotics help scoliosis… if the brain is receiving “scrambled” information from dysfunctional feet, the spine is trying to adapt incorrectly to the forces of gravity.
There are 2 types of sensory receptors in our feet- proprioceptors and mechanoreceptors.
The proprioceptors include muscle spindle cells and golgi tendon organs.
These give us our:
- Joint Position Sense
- Joint Centration
- Kinesthetic Awareness
- Peroneal Reaction Time
The mechanoreceptors include:
- SA1 – Merkel Disc (two-point discrimination)
- SA2 – Ruffini Endings (skin stretch)
- FA1 – Meisner Corpuscles (low frequency vibration)
- FA2 – Pacinian Corpuscles (high frequency vibration)
We need both mechanoreception and proprioception to create effective gait, balance and posture.
What’s interesting is that 80% of our plantar receptors are sensitive to vibration.
Vibration translated to bone stimulates an osteoblastic response – increasing bone density in weight-bearing activity.
Vibration also increases growth hormone release, which decreases bone turnover.
Is it possible that a vastly reduced amount of sensory information from our feet to our skeletal structure is at least partly responsible for the modern epidemic of osteoporosis?
This is still speculation at this stage but it certainly seems plausible.
For decades now the trend in shoes has been towards ever more support and cushioning. We have moved from leather-soled shoes, to the rise of rubber-soled running shoes and sneakers in the 70s and 80s and now today to the growing popularity of brands like Sketchers and Hoka… basically people walking on big fluffy pillows!
These might feel nice and cushy on our pampered feet, but what do you think they do to our brain’s ability to sense and react to the ground?
Not only that, but counterintuitively, some studies have even shown that the presence of cushioning in shoes actually increases impact forces (a topic we will cover in much more detail next week when we get into the second critical foot function- absorbing and managing ground reaction forces.)
https://pubmed.ncbi.nlm.nih.gov/30504822
It turns out that as we put on shoes, socks or traditional orthotics we begin to block plantar receptors, skewing our perception of how hard we are striking the ground…
And actually causing us to strike it harder!
This is why running injury rates have not decreased significantly despite ever-more technologically advanced shoes.
So, what are the consequences for our patients when their brain doesn’t receive the expected (and evolutionarily necessary) sensory input from their foot to their brain?
Perhaps the most obvious is that falls risk increases.
This is a huge one, especially for our older patients. The stats on it are frightening.
In Australia alone in 2023-24, there were ~248,211 hospitalisations for fall injuries, representing 43% of all injury hospitalisations.
In 2022-23 there were ~6,698 deaths from falls in Australia, representing 43% of all injury deaths.
Yesterday in practice I saw a 92-year-old patient who had just completed 10 weeks in hospital after breaking her hip in a fall. She’s now moved into a nursing home for a few weeks (which she told me is costing her a fortune) while they assess whether she can go back home.
(I assured her that we’ll get her home safe and sound.)
The impact of an event like this on someone’s life can’t be overstated. She literally looks and feels like she’s aged 20 years in the last few months… and may never get back to the same quality of life that she previously enjoyed.
And she’s one of the lucky ones.
However, not all the effects of lack of sensory function in our feet are as obvious and dramatic as major falls.
Anyone who experiences pain or discomfort while standing or walking is feeling the effects of reduced sensory input from their feet. Without the correct feedback the brain simply can’t coordinate correct muscle action and joint position effectively.
The result can range from short-term, such as acute injury…
To long-term, such as overuse injuries and chronic degeneration.
This affects a massive percentage of your patient population and relates to many of the complaints they come in with every day. Things like…
- Pain
- Osteoarthritis
- Chronic muscle tension and spasm (especially in the lumbar, upper trap and suboccipital regions… although it can be anywhere, even in places you would never usually associate with the feet.)
- Recurrent sprains, strains or overuse injuries
- Joint restrictions
- Subluxation
- Cramps (these are not always just a magnesium deficiency.)
A more subtle, but extremely common symptom is simply fatigue. Remember our brain relies on sensory information from the feet to make our gait and movements efficient.
Without the right input we rely far too much on muscular effort rather than elastic fascial mechanics, with the result that we expend way too much energy just staying upright and propelling ourselves forward.
This can create a real vicious cycle, as it makes exercise or even just daily movement more onerous, with the end result that people ultimately move less and degenerate faster.
Sensory issues are another manifestation of this problem. Interestingly, I’ve seen this go both ways. I’ve seen people with diabetic neuropathy or other lack-of-sensation issues like numbness and tingling in their feet improve…
And I’ve also seen people with spectrum-related sensory processing issues calm down. It seems that we are wired for a certain level of “normal” input (such as from our feet) and when we increase that feedback it modulates some of the more aberrant sensory information the brain is dealing with.
This list could continue but I’m conscious of the length of this email… maybe we can dive deeper another time. However, hopefully it’s clear that having properly stimulated feet, as nature intended, is impactful on our health for much more than just simply foot problems.
Over the next few weeks we’ll look at the other critical foot functions and how they are impacting your patients (and sabotaging your adjustments) every day.
Cheers,
