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Sensorimotor Considerations in the Assessment of Arch Stability

Question: I have been told that I have high arches. Thus, my foot might require support. If my arch collapses, over time, I will develop Plantar Fasciitis. Is there a test for weak arches? I have been wearing my Vibram 5 Fingers. I also frequently practice picking up items with my toes (marbles, towels, etc)?

It is important to think globally when considering how a fallen arch might occur.  Yes, we want the arches to be strong.   Walking around in Vibrams is a great method to develop foot strength, as are the exercises you listed.  Those exercises are modern ways to replicate the gripping and pulling that our toes would otherwise do constantly if we lived in a less mechanized society that forced us to walk over varying terrain to survive.   The real key is how the gripping and pulling coordinates with the input the foot is receiving elsewhere along the kinetic chain, particularly from the ankle and the hip.

For running, the arch must support the body over several thousand low to moderate intensity footstrikes during the course of a run.   Strength means nothing if the movements of the feet aren’t coordinated with signals from the rest of the body.    Many times people will see a collapsed arch as weak, when in reality the problem was not the arch itself but instead an ankle or hip mobility limitation that caused the brain to seek mobility from another source, such as the foot.  If the ankles and hips aren’t doing their jobs, when the brain tells the body to “Go!” the body will find mobility elsewhere. 

Another explanation gaining momentum in recent years is that because of the high concentration of nerves in the feet, a flattening of the arch is a subconscious mechanism for the body to acquire missing sensory input that our brain is hardwired to expect from its surroundings.  A flattened arch brings more of those foot nerves in contact with the ground.  By spending most of our lives shod and driving around in cars, our brains may feel deprived of the sensory awareness our ancestors had come to expect from our feet.   

What Joint-by-Joint Tells Us

Remember the joint-by-joint apporach…our big toe, ankle, hip, thoracic spine, glenohumeral joint, and wrists all crave mobility and are designed as such with the capacity for safe multiplanar movement.  The foot, knee, lumbar spine, scapula, elbow, and cervical spine all crave stability.  If we want to move, but don’t have the requisite mobility in the mobile joints, the brain will find mobility in the stable joints, which can simultaneously reinforce the pattern of immobility in places like the ankle, hip, and thoracic spine.  The brain is the ultimate authority and we must recognize that physical manifestations are the result of neurological input.  To view preservation of the arch as only “strength” issue can lead to undesirable outcomes.    

Instead, think of a supportive arch as a stability mechanism.  We define stability as control in the presence of change.  The arch needs to maintain control of the foot while coordinating the many signals it receives from above.  The difference between “strength” and “stability” may sound like a matter of semantics, but it is a critical distinction to make.  A supported arch is a sign of proper stability and a collapsed arch represents misplaced mobility.   We can run into major problems if we create synthetic solutions where they aren’t needed.  Are there people for whom synthetic corrections, such as orthotics or motion control shoes are appropriate?  Absolutely.  However, the decision to enlist the help of orthotics or motion control shoes should only come after a thoughtful analysis of the global factors behind whatever “problem” we are trying to solve.

Let’s look at the all too common problem of a runner having immobile ankles and hips.  If the arch collapses as a subconscious compensatory mechanism to create mobility that should have been coming from the ankles and hips, adding an extreme support such as an orthotic can create the following pattern:

Big toe – Immobile

Foot – Immobile

Ankle – Immobile

Knee - ?

Hip – Immobile

Low back - ?

Any guess where the body will find mobility mobility?  It probably won’t come from the ankle or hip, since those joints never had mobility to begin with.  It sure ain’t comin’ from the toe and with an orthotic stuck in the shoe.  Now you not only have an arch that has been programmed to relax, you have a knee and back that are called on to perform mobility roles for which they were not designed. 

Summary

If the body can demonstrate satifactory competency in creating mobility from the appropriate sources, then we shouldn’t be afraid to offer outside stability assistance where needed.  However, we run into all sorts of problems in if we bring mobility deficits, such as limited ankle and hip mobility, to stability solutions (such as orthotics).  Although “fallen arches” and their related iterations of “flat feet” and “overprontation” are very real, it is imperative that we confirm the causes with a global assessment to determine whether artificial interventions are indeed appropriate.  Adding extreme artificial corrections beyond those provided by the footwear itself can create a whole new set of problems if these corrections are added in response a localized rather than global analysis.  

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