John Davis

Written by John Davis

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Is the Secret to Running Injury Free Foot Core?

New research points to the importance of strengthening the small muscles in your foot to stay healthy as a runner. This article analyzes the data and makes suggestions on how to implement this "foot core" into your training.When you think of core exercises, what comes to mind?

Probably sit-ups, planks, and back extensions.

If you’re really on top of your game, you might be picturing side leg lifts, the glute bridge, and other hip strength exercises, because you know that hip weakness been connected with a litany of running injuries. But a provocative new paper published last year proposed that there’s another core you need to worry about—the “foot core.”

Is Your Foot the Key to Running Injury Free?

Patrick McKeon and collaborators from four American universities laid out their theory in a paper in the British Journal of Sports Medicine.1

In the article, the authors draw parallels between the core muscles of the abdomen and spine and the small muscles within your foot itself.

The authors state that although these “plantar intrinsic” foot muscles are very small and not very strong, their role isn’t to create motion. Instead, they stabilize the foot, providing a solid foundation for the larger, more powerful muscles in the lower leg to efficiently move the foot.

The biomechanics of the foot are a little unusual, because it has to alternate between stiff rigidity and springy flexibility during walking and especially during running.

The human body has developed a number of mechanisms that allow for this, and McKeon et al. argue that the small plantar intrinsic muscles inside the foot are one of them.

Another biomechanical quirk of the foot is that the major muscles which control your foot motion, and even your toe motion, aren’t located in the foot itself. The main muscles that scrunch up your toes, point your ankle down, or roll your foot outward are all in your lower leg, adjacent to your calf muscles.

These so-called extrinsic foot muscles are already popular targets for strengthening in rehab programs—think towel scrunches, theraband ankle exercises, and so on. But, as McKeon et al. point out, these exercise don’t do as much to stimulate the plantar intrinsic foot muscles.

Learning about Foot Core and how it can help you run healthy (and happy!) Click To Tweet

Fatigue in Foot Muscles and Injury Risk

The centerpiece of McKeon et al.’s hypothesis is that proper functioning of the “foot core” is essential to being able to walk and run without injury. With scientific research focusing mostly on hip dysfunction as a cause of injury in the past decade, the paper’s authors worry that researchers are missing an important piece of the puzzle.

There is some evidence that foot muscle function plays a role in biomechanics:

A 2008 study by researchers at the University of Virginia showed that doing an exercise that fatigued the foot muscles causes the arch to collapse slightly,2 and another study of eight people with plantar fasciitis in one foot found smaller and presumably plantar intrinsic muscles in the injured foot than in the healthy foot—though this could also just be the result of favoring the healthy leg.3

Since the idea of a foot core is very new, McKeon et al.’s discussion of the practical implications of this idea is rather brief.

In addition to calling for more research, the authors recommend the use of a special maneuver called the “short foot exercise” to begin strengthening the plantar intrinsics, as well as small, controlled amounts of barefoot activity (e.g. running on grass).

Remember, we interviewed Chris McDougall on our podcast a few months ago, take a listen if you have not already!

 Foot Short Strengthening Exercise for Injury Prevention

The foot shortening exercise is performed by sitting in a chair with your foot planted normally on the ground, then using only your plantar intrinsic muscles (the ones underneath your arch) to “shorten” your foot and raise your arch.

Here’s the deal:

This can be very tough to learn, since your first instinct is to flex your toes or just roll your ankle outward to accomplish this.

McKeon et al. write that establishing control of this muscle can be difficult, but once you’ve mastered it, you can try doing the short foot exercise while standing or even while balancing on one foot. The authors provide no recommendations on how often to do this exercise, or even how many repetitions you should do—this underscores the fact that these are only preliminary recommendations based on McKeon et al.’s hypothesis.

Now:

As for the efficacy of the short foot exercise, McKeon et al. point to a couple of small studies, including a 2010 doctoral thesis by Lindsay Drewes at the University of Virginia.

Drewes found that adding the foot shortening exercise to a standard rehab program for chronic ankle instability resulted in better subjective improvements in foot function among the study’s subjects who included the short foot exercise in their rehab program, though these improvements weren’t measurable through objective measurements, like dynamic balance testing.4

Wow! What an interesting post! Could Foot Core be the way to healthy running? Click To Tweet

 Conclusion

The idea of a foot core in addition to your regular core is an interesting proposition, but there’s far too little research on it yet to fully endorse it.

As the focus of research swings back towards the foot, it will be exciting to see what new findings are discovered, but for now, the most you should do is think about trying out the short foot exercise and perhaps incorporating a little bit of barefoot running on grass into your weekly training routine, if you don’t do it already.

 

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References

McKeon, P. O.; Hertel, J.; Bramble, D.; Davis, I., The foot core system: a new paradigm for understanding intrinsic foot muscle function. British Journal of Sports Medicine 2014, 49 (290), 1-9.
Headlee, D. L.; Leonard, J. L.; Hart, J. M.; Ingersoll, C. D.; Hertel, J., Fatigue of the plantar intrinsic foot muscles increases navicular drop. Journal of Electromyography and Kinesiology 2008, 18 (3), 420-425.
Chang, R.; Kent-Braun, J. A.; Hamill, J., Use of MRI for volume estimation of tibialis posterior and plantar intrinsic foot muscles in healthy and chronic plantar fasciitis limbs. Clinical Biomechanics 2012, 27 (5), 500-505.
Drewes, L. K. Effects of Rehabilitation Incorporating Short Foot Exercises on Functional Outcomes for Chronic Ankle Instability University of Virginia, Charlottesville, 2010.

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6 Responses on “Is the Secret to Running Injury Free Foot Core?

  1. There are too many studies that the proposed model is inconsistent with and contradicted by for it to be a useful model. A good model has to be consistent with the bulk of the evidence and explain a lot. This model falls way short of that. The authors cherry picked the references that supported them, but ignored plenty that did not support them –> very misleading if you not familiar with the whole body of literature.

    There is way too much that the model can not explain (eg the intrinsic muscles do not fire until weight starts to come off the heel, so they can’t actually do what is claimed for them; eg (2) plenty of studies have shown no relationship between arch height and muscle strength; etc etc).

    That does not mean that rehab/ strengthening of the intrinsic muscles should not be done…. it should be done; just don’t base it on this model.

    • Hi Craig, thanks for your input. You bring up some good points, and we are happy to see that you agree the strengthening of those muscles are important. We did mention at the end of the article that there is not enough evidence to make any solid recommendations, but we do enjoy reading your feedback, and if we research more into this in the future, we will be sure to let you know!

  2. Most of the people who are running today have hip and core muscles that are not capable of contracting at the right time, in the right plane, or at the right joint. That is also the case for many of the muscles that go from the lower leg to the foot (i.e., extrinsic muscles). But they don’t have any pain to speak of.

    More often than not, the exercises that are labeled as strengthening are not only putting the cart before the horse, they’re also breaking the person down.

    This is due to the fact that a runner is only as strong as their ability to compensate for the weakest link at that point in time.

    Said another way, when a person is told to perform an exercise, they’re going to get from point A to point B. But how they get there is a whole different story.

    And that scenario is occurring every single day in most rehab clinics throughout the world. Meaning, the person doing the rehab exercises feels stronger, but they’re only relatively stronger. It’s a false sense of strength.

    It’s also important to consider that pronation and supination involve motions that take place in all three planes. Not only in the foot, but throughout the entire chain. So if the foot is not capable of loading (flexing) in all three planes, there will be a limitation in motion at the knee. And when there is motion that a runner can’t take advantage of at the knee, the bigger muscles throughout the hip and core will not be capable of dissipating ground reaction forces efficiently.

    When a runner is capable of pronating at the right time, for a variety of different reasons, their chains ability to go against the pull of gravity will be much better (i.e., supination). So it’s not only what the foot is capable of doing when it is driven from the bottom up, it’s also about what is taking place from the top down.

    It doesn’t matter how skilled a practitioner is at applying force to a muscle; a muscle that is not capable of pulling its weight is not going to get stronger. And determining whether or not a muscle is weak can only be seen when the joint that the muscle crosses is put in a position that emphasizes it more than any other muscle or division of a muscle.

    When a muscle is not capable of contracting optimally, another muscle will be forced to pick up the slack. Therefore, the muscle that is already strong is only going to get stronger.

    This is the brain’s best attempt at protecting the human chain from an injury. And making the conscious choice to go against what the brain has already figured out how to do is not allowing anybody to get stronger for running.

    • Hi Rick, thanks for sharing your insight. Great advice here, you have brought up some valid points. We have talked about how hip weakness contributes to many running injuries and instabilities in a number of posts in the past, and it is good to see you agree. We are merely looking into other areas that research studies have looked into recently. I am sure our readers will enjoy your points, and give them something to think about when it comes to the running chain.

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