The Foot Core System

One of many nice things about human movement research is that you get to work with some truly brilliant people, like Dr. Patrick McKeon who published an article, “The foot core system: a new paradigm for understanding intrinsic foot muscle function,” in the British Journal of Sports Medicine. I had the pleasure of mentoring Patrick back when he received his Ph.D. in Athletic Training at the University of Virginia. What’s kind of “small world-ish” is that he happens to be the cousin of another brilliant research colleague I’ve worked with, Dr. J. J. Collins, who is a professor at Boston University and, I like to say, a certified genius, having received at one point in his career, the MacArthur Genius Award.

Patrick is now an assistant professor in Exercise and Sport Science in the School of Health Sciences and Human Performance at Ithaca College, along with his wife, Dr. Jennifer McKeon. When I saw his article, which he co-authored with a couple other colleague friends of mine (Dr. Jay Hertel and Dr. Irene Davis), I was excited to catch up with him.

Through his research, Patrick has always understood certain aspects of foot function that are often not well appreciated by most. In his foot core article, Patrick and his co-authors call attention to what they describe “the foot core”. Pulling together a number of articles and drawing parallels to the well-known “trunk core” in relationship to trunk-hip stability, they describe an essential core specific to the foot that is vital for stability and overall lower extremity health.

So what is your foot core?

Athletic and fitness training professionals already appreciate that in the trunk and hip, small muscles known as the “core” muscles play a critical role in stabilizing bones and joints, accommodating to changing demands that occur with different activities. When the core muscles are weak from disuse, large muscles and bodyweight forces transmit abnormal stresses and strains that lead to injury. To counteract this effect, core strengthening exercises are performed.

While the concept of the trunk “core” and the need to maintain good “core strength” in these small muscles has been broadly accepted in the athletic and fitness community (just google “core strengthening” to see a myriad of exercise programs aimed at improving core strength), the small muscles in the foot have been largely ignored. In fact, there has been a long persistence of an old “truth” that the small foot muscles are not only unimportant, but fragile and in need of constant external support via arch supports.

Patrick commissioned a skilled medical illustrator to draw the four layers of muscles in the arch of the foot along with the deepest layer of muscles on the top of the foot. These are the only anatomy drawings I know of that display just the muscles and bones in each of the layers.

Foot Core Foot Muscles

In another post, The Little Arch Muscles That Could, I reviewed a recent study demonstrating that various of these arch muscles play an active role in absorbing forces to the body that occur when standing, walking and running. In their article here, Patrick and his co-authors review a bunch more studies supporting the significance that these muscles have in controlling load distribution under the foot.

While there are four separate layers of muscles in the bottom of the foot, there are also four separate arches in the foot (the medial and lateral longitudinal arch and the anterior and posterior transverse metatarsal arches). Patrick illustrates with the help of his medical illustrator, Tom Dolan, how these arches effectively coalesce into a half dome as shown below. They credit the idea to J. McKenzie who wrote a little known article back in 1955, entitled “The foot as a half-dome” which Patrick found buried in a university library.

Foot Core Dome of the Talus

Patrick reviews how the muscles in these four layers work synergistically to control this functional half-dome. Moreover, he and his co-authors explain how these small muscles “set the table” so to speak, for the larger structures in the foot and lower leg to work effectively and normally. Specifically, they describe how they provide the core foundation for maintaining and achieving health in commonly unhealthy structures such as the plantar fascia. They also point out that to date, these muscles have been very much under appreciated in the treatment of plantar fasciitis.

How to strengthen your foot core

While foot and toe exercises such as “picking up marbles” and “rolling a towel under the foot” certainly activate some of the muscles in the foot, they don’t fully activate the small muscles in the way that they’re activated during walking and running. How these small muscles work during standing, walking, and running to achieve optimal healthy function upward from the ground, is actually rather complex.

So, Patrick suggests a much more functional exercise, a “short foot maneuver,” pictured below, that is done with weight being borne through the foot. With the foot on the ground, the foot is actively “shortened” by using the arch muscles to pull the ball of the foot near the great toe toward the heel as the arch is lifted upward. The exercise is done with increasing weight being applied through the foot.

Foot Core

You can start doing the exercise just while sitting, then when standing on two legs, and ultimately while just standing on one leg. Jay has done a number of studies showing that doing these short foot exercises for just four weeks, significantly improves muscle strength, reduces arch collapse and improves balance ability.

Ideally, you do the exercise while barefoot. As I was talking with Patrick, I found that I was quite able to do the exercise while standing in my OESH La Vidas. I then tried the same exercise in various traditional, non-OESH shoes and was unsuccessful. Just about every non-OESH shoe out there has a built-in arch support which makes it virtually impossible to activate those small muscles. The fact that the typical built-in arch support in a shoe suppresses small muscle activity in the arch of the foot has been confirmed with fine-wire electromyographic studies.

Shoes and your foot core

Imagine how the typical shoe suppresses this small muscle activity not just during a short foot exercise, but all day long when those small muscles otherwise would be naturally exercised. Over time, those muscles become weak and compromise the normal function of structures in the foot and the lower leg such as the plantar fascia.

Conversely, it’s been shown that switching to a shoe like OESH that has absolutely no built-in arch support, can re-engage those muscles, essentially exercising and strengthening those small muscles just with regular daily activities.

Patrick and his co-authors state “Clearly, a stronger foot is a healthier foot. To this end, we are suggesting a paradigm shift in the way we think about treating the foot….Unfortunately adding permanent support to the foot, as opposed to strengthening the foot core, is the current standard of care. We would like to suggest that perhaps it is time for the Decade of the Foot. This type of attention to a largely ignored, but critical part of our body might help raise awareness of the amazing function of our feet and their under appreciated potential for improvement.”


This article is an updated version of a post originally published April 6, 2014

For more posts about foot health and research, check out the Best of Casey section of the OESH Blog.

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6 replies on “Are You Exercising Your Foot Core?

  • Gerry

    Hi Casey
    As outlined above I wondered if the plantar intrinsic foot muscles (PIFM) located between the bony arch of the foot (BA) and the plantar fascia might be subjected to passive transverse compression (PTC)when acted upon by these structures during early stance .
    I also wondered if ,during mid to late stance when the PIFM are active ,an increase in the stiffness of the “intrinsic core “might provide even greater support to the BA and its articulating joints .
    So the question for me is -Is there an increase in the intra and inter muscular pressure in early stance and can this be attributed to PTC ?
    An in vivo study to investigate this might involve indwelling intramuscular pressure sensors but why go down this road when such a sensor may already be in place in the form of plantar venous plexus (PVP).
    So can the PVP be looked at in this way? Is the pump emptied by inter-muscular pressure or by stretching and necking down ?
    Since the veins of the plexus are elastic longitudinally and viscoelastic transversely the effective emptying of the PVP by stretching and necking down is ,in my inexpert view ,unlikely .
    So if necking down is not the mechanism of PVP emptying then the pump must be emptied by increased inter- muscular pressure .But what cases this ?
    If the pump empties in early stance when the plantar intrinsic muscles are not activated then the pressure must be created by stretching of the PIFM or by PTC.
    A study by BJ Broderick et al(1)showed that the PVP is emptied when a standing individual performs toe curls so it can be inferred that inter-muscular pressure is increased when the muscles become activated and contract. I believe that it is reasonable to think that inter-muscular pressure is therefore not increased when the same muscles become less active and return to their original more lengthened positions .
    So, in my opinion, it is most likely that in early stance the PVP is emptied by the passive transverse compression of the “intrinsic core” and indeed that the existence of a functioning PVP confirms the existence of a significant level of PTC . I also think it likely that the pressure generated in the pump reflects the inter and intra-muscular pressures generated within the “intrinsic core” and hence the pressures generated at the interfaces between the core and the plantar fascia and BA .

    I would welcome any comments on the above

    Kind regards

    Gerrard Farrell

    Ref (1) Broderick et al -Venous emptying from the foot ; influences of weight bearing ,toe curls,electrical stimulation ,passive compression and posture 2010

  • Gerry

    Hi Casey
    Might it be ,during early stance when the bony arch of the foot lengthens and the plantar fascia becomes tensioned ,that the passive intrinsic musculature located between the arch and the fascia becomes compressed between the two structures (transverse passive compression ) providing support to the arch and a reduction in the shearing forces between the articulating bones of the foot in the midfoot area ?
    Also ,might it be that the intermuscular pressure generated through the transverse passive compression of the foot intrinsics ,in the way outlined above , provides the primary force for the compression and empting of the vessels of the plantar venous arch ?
    I understand and largely agree with the “foot core system ” outlined in your article ( although I have to say I am not an expert in either foot anatomy or physiology) but believe that the intrinsic muscles of the foot also act as the core of the foot in a much more literal sense .

    Kind Regards

  • Gerry

    Hi Casey
    I enjoyed reading your article but wonder if perhaps the intrinsic muscles of the foot play an important role in supporting the bony arch of the foot even in early stance when they are in a passive state . That is might forces be trasmitted between the bony arch and an under tension plantar fascia via the passive intrinsic musculature . This mechanism could help reduce harmful shearing forces between between the bones of the foot during locomotion and explain the forces which lead to the compression and empting of the vessels of the plantar venous plexus in early stance .
    I would greatly welcome any comments on the above .
    Gerry Farrell

    • Casey

      Yes indeed, I do think that the intrinsic muscles play an important role throughout the entire stance period, not just when they are actively firing. What we have found is that essentially all the muscles in the lower leg and foot work in a consistent manner: a muscle is first passively stretched, then it begins to fire eccentrically (actively working while the muscle is being lengthened) followed by a comparatively brief time of concentric (shortening) activity. The main contribution of each muscle, I believe, is the passive lengthening and eccentric lengthening that occurs first. I have to think that the intrinsics are no exception to this rule, doing important work as you mention, well before it actively turns on.

  • Lori

    I’d like more specifics on the foot shortening exercise. When you shorten the foot, do you hold the shortened position like you would a stretch or release immediately? How often should you repeat this?

    • Casey

      The typical study protocol that I’d recommend is to maintain the shortened position for 5 seconds on each foot and repeat times 3, which would all be one set. You’d aim to do five sets a day, each separated by a rest of at least two-minutes. So as to save the time of waiting the two minutes in between sets, you could spread out the sets throughout the day, sneaking them in when you have a chance, e.g. get a set in when you’re in line at the grocery store (or two sets if the line is long!) etc.


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