So, You Walk Like a Duck: The Evolution of the Collapsed Arch

Is the flat foot a scar of the human evolutionary process, or have we misunderstood our foot’s natural design and brought about the aches and pains we feel today with poor lifestyle choices? This is a hotly debated topic in the physical therapy and orthopedic fields. I have gotten into intense discussions on whether we should be supporting this structure with orthotics and how to go about treating the problem. How do we go about treating them? Is running barefoot an acceptable option? What about the motion control shoe?

Dangers of Collapsed Arch

Today, approximately 25% of Americans have flat feet (about 60 million people).3 The next time you step into sand or out of a pool, look at your footprint. If it looks like a box or a rectangle, your natural arch is nonexistent in a weight-bearing position. This overpronation is likely to cause many biomechanical faults in the human body, starting at the foot and going all the way up to the cervical spine and temporomandibular joint. Because of flat feet, many people commonly experience pain in their heel, knee, hip, low back, and cervical spine.6 Injuries range from medial ankle sprains, to posterior tibial tendon dysfunction, shin splints, Achilles tendinopathy, and patellofemoral pain. MedBridge’s 3D Model Library is a good reference on these injuries.

Evolution of the Arch

Why do so many people have flat feet? I believe it’s largely due to our environment and developmental behavior. Our environment has evolved over the millennia from our hunter/gatherer ancestors to the humans we are today. Our ancestors were running around outside in nature, exposing bare feet to the unpredictable terrain of rocks, sand, grass, and dirt. This gave our feet the proprioceptive training necessary to build strong, durable arches. Even today, our physical terrain has not changed dramatically. Sure, we have sidewalks, streets, carpets, and hardwood floors, but rocks and dirt still remain. Our terrain, however, is irrelevant because of our proclivity towards comfort. What have we given up in our efforts? Bulky and padded shoes with sturdy arch supports, flip-flops, and high heels have negatively impacted the way our feet interact with the ground and changed the biomechanics of our gait. High heels shorten the Achilles tendon and limit dorsiflexion. Flip-flops impair the windlass mechanism. Arch supports limit proprioceptive input while weakening the intrinsic musculature and ligaments that naturally keep the arch strong.5

Society of Sitters

In addition to all of our fancy attempts to make our feet comfortable or stylish, we have also become a society of sitters. Many of us sit at the breakfast table to read the morning paper, sit in our cars on the way to work, sit at our desks working at computers, sit in the car on our way home, and then sit down to eat dinner. Lather, rinse, and repeat. Some of us are lucky to get in a short one-hour workout, but research suggests that this isn’t enough to counteract the negative effects of habitual sitting.8 Why should our feet ever have to worry about being strong? We are naturally weakening them each day. Wolf’s Law states that our bodies will adapt to the loads under which they are placed. By sitting all day and wearing over-padded or heeled shoes, we take away the beneficial stress from our foot’s intrinsic muscles.

Biomechanics: normal arch vs. collapsed

If we walk around with collapsed arches, some work must be done to correct that. A properly functioning foot arch should be a high dome that is flexible and capable of flattening a little, but not completely, when walking. It’s supported by four layers of muscles and more than a dozen ligaments.6 When walking or running, it transfers weight to the big toe in the push-off phase of gait. This transfer of energy through the kinetic chain needs to flow unimpeded. With a collapsed arch, energy and torque bleed from the system into other areas of the body that are not suited to handle such loads, including the medial structures of the knee joint.4,9 Check out MedBridge’s course titled The Running Athlete Part A: Biomechanics and Analysis for an in-depth look at how to better assess these athletes.

Arches are like Bridges

To me, the arch is a non-weight-bearing surface, period. I went to school in Pittsburgh, PA – a city full of bridges. None of them have a support in the middle of the arch. If the bridge were to break down (i.e. the arch of the foot begins to collapse), the engineers wouldn’t just place support beams as a permanent fix. Even when supported, the keystones of the arch would continue to break down, just at a slower rate. Instead, they would repair the failing arch by making the keystones stronger.

The analogy holds true for the arch of the foot. This structure can be rebuilt with proper strength and mobility training. Improvements can be seen in weeks to months when it comes to intrinsic foot muscle strength.2 However, I have anecdotally found that true structural change of the foot takes time. I have found this to be a much slower process due to the years of poor mechanics and sustained postures in some of my patients. What it comes down to is motivation and commitment to make a change. I have literally done at least 10 minutes of work daily on my own feet and, after 2 years, I’m finally starting to receive major dividends for my hard work.

Band-Aid for the arch

As a society, we are essentially slapping a Band-Aid on the symptoms of a collapsed arch. We are merely bolstering crumbling keystones with our padded shoes and custom orthotics. Instead, we should be repairing the weakened structures (muscles, bones, ligaments) by cultivating the natural way our feet should be interacting with our environment. I am not saying we should all be walking and running around barefoot, but we should strive to replicate an environment that fosters optimal foot health. A 2009 study published in the British Journal of Sports Medicine conducted a meta-analysis of literature pertaining to the potential mechanisms of action of orthotics. The researchers concluded that orthotics cause a relatively small (~2 degree) change in foot and ankle motion.9 To me, this does not warrant the $4.7 billion spent on orthotics each year.1

Return to the Natural Ground

Minimalist footwear, for starters, will help bring our feet closer to the natural ground that we were meant to walk on. It can help develop intrinsic control as well as provide better proprioceptive input.7 I recommend a shoe with a 3mm drop from heel to toe or less. Be careful if you’re not used to these types of shoes. Give yourself ample time to get used to a minimalist shoe by gradually progressing wear time from week to week. Many pediatricians recommend tummy time for infants to allow for proper development of the posterior chain. The same should hold true for the feet. Barefoot time is an essential element for adequate arch development.

Walking Barefoot

One day a week, put away your shoes. Walk around your house and pick a safe area in your yard or a park near your residence to challenge your feet in a way that creates positive change. If you ever walk outside barefoot, your gait will change dramatically. You will want to walk more on your forefoot and toes compared to a heel to toe fashion while wearing shoes. If you were to walk on your heels barefoot and misstep on an uneven surface, it really jars your back. A similar feeling is experienced when descending a flight of stairs and expecting there to be one last step when reaching the end. Over time, your feet will get used to handling these new loads, which will inevitably strengthen the joints up the chain, improve knee stability and hip control.6

No Excuse to Have Flat Feet

I have never seen a patient where I couldn’t create an arch in his or her feet. I do believe there are certain populations who simply have gone too far down the rabbit hole of poor foot biomechanics and will only benefit from some sort of external support. This population involves the elderly and those whose feet and ankles are so painful they are unable to walk. The rest of us can and should strive to rebuild our natural foot architecture.

Where to Begin

Examine how you feel after a day of walking barefoot. Do you notice any muscle soreness, areas of pain, or hot spots? These may be clues to a host of problems you could encounter down the road. Take note of these, and then talk to your physical therapist to help you get your healthy stride back. Think about how much money you have spent over the years on custom orthotics and expensive padded shoes “guaranteed” to relieve your nagging running injuries. Don’t you think it is time to save some money and invest more resources to help your foot achieve its natural structure?

  1. Collier, R. Orthotics work in mysterious ways CMAJ 2011;183(4):416-7.
  2. Hashimoto T, Sakuraba K. Strength training for the intrinsic flexor muscles of the foot: effects on muscle strength, the foot arch, and dynamic parameters before and after the training. J Phys Ther Sci. 2014;26(3):373-6.
  3. Kelton Research. “Down at their Heels.” January, 2009. Kulig K, Burnfield JM, Reischl S, Requejo SM, Blanco CE, Thordarson DB: Effect of foot orthotics on tibialis posterior activation in persons with pes planus. Med Sci Sports Exerc 2005, 37:24-29.
  4. Lieberman DE. The Story of the Human Body, Evolution, Health, and Disease. Vintage Books; 2014.
  5. Mills K, Blanch P, Chapman AR, et al. Foot orthotics and gait: a systematic review and meta-analysis of literature pertaining to potential mechanisms. Br J Sports Med 2009;44(14):1035-1046.
  6. Owen N, Healy GN, Matthews CE, Dunstan DW. Too much sitting: the population health science of sedentary behavior. Exerc Sport Sci Rev. 2010;38(3):105-13.
  7. Starrett K, Murphy T. Ready to Run, Unlocking Your Potential to Run Naturally. Victory Belt Publishing; 2014.
  8. Tong JW, Kong PW. Association between foot type and lower extremity injuries: systematic literature review with meta-analysis. J Orthop Sports Phys Ther. 2013;43(10):700-14.
  9. Williams DS 3rd, McClay Davis I, Baitch SP. Effect of inverted orthotics on lower-extremity mechanics in runners. Med Sci Sports Exerc 2003;35(12):2060-2068.