Cultivate your Arch

Use it or lose it

A physiological axiom holds true: If you don’t use it, you lose it. Meaning: inactive muscles atrophy. A longitudinal study measured the change in muscle volume following lower limb immobilization and found, over 6 weeks of immobilization, a 17% loss in lower leg muscle volume. Our muscles are taxed constantly resisting the force of gravity. This is seen in spaceflight, where a lower gravity environment yields substantial atrophy. Over 180 days on the International Space Station, this study observed muscle loss in the range of 35% and peak power loss in the soleus (your calf muscle) by 55%.

Figure 1: A Longitudinal view of Britain's Ouse Valley Viaduct. With its many semicircular arches, the bridge supports over a 100 trains daily.

Mother Nature is an Incredible Architect

Mother nature knows her architecture. Our feet are built with the sturdiest load bearing design --The arch -- to support our bodies. Mother nature designed a foot with properties of firmness and flexibility, to support the demands of upright bipedal movement.

If we subscribe to the value of progressively overloading our bodies, why would it be any different for our feet? The intricate design of our feet demands respect. For starters, a quarter of our total bones are found in our feet; along with 33 joints, 100 muscles, tendons, and ligaments for each foot. The foot is exclusively designed among the animal kingdom, being the only foot with such an emphasized longitudinal arch. There are two arches, one across the top of the foot and the other running the length of the foot. Respectively, these are referred to as the transverse tarsal arch and medial longitudinal arch, they work together to create enough stiffness to allow for upright bipedal movement.

The foot is incredibly well-designed, it even has a group of veins called the plantar venous plexus that, with each step, pumps blood back to the heart. Mother nature got it right. Since Nike’s introduction of the first widely popular cushioned shoe in 1964, we have been babying our feet; depriving them of any chance of adaptation ever since. More cushion isn't always a better thing, without an appropriate level of stress our feet will atrophy. When measuring the frequency of plantar fasciitis in books over time, using google’s handy ngram viewer, there is a sharp increase in usage only a few years after cushioned shoes became popular.

Figure 2: There's a dramatic increase in the usage of plantar fasciitis in literature right around the time cushioned shoes became widely used. However, correlation does not imply causation

The Anatomy of The Foot

Figure 3: The anatomy of the bottom of the foot.

There are many ligaments and muscles that make up the longitudinal arch, including the plantar fascia, or more technically named the plantar aponeurosis. The plantar fascia is connective tissue, attached to the heel, which then runs along the sole of your foot before dividing to connect to the five metatarsal bones. With the major role that the plantar fascia plays in maintaining the longitudinal arch, one might guess that a flat arch would be indicative of a weak plantar fascia, insufficient in strength to support the arch. A flat arch may stretch the plantar aponeurosis, causing inflammation. These aspects may all act in conjunction to cause plantar fasciitis.

How The Foot Supports Those with Flat Feet

The foot’s ability to keep us upright is referred to as the foot’s stiffness. A great study by Dr. Venkadesan out of Cornell isolated the role of the transverse tarsal arch in foot stiffness, finding it responsible for more than 40% of the longitudinal stiffness of the foot. For those with flat feet, i.e. no tension in their longitudinal arch, the transverse arch takes over and provides the foot stiffness that the longitudinal arch can’t, explaining how those with flat feet can still walk upright. The contribution of the transverse arch in foot stiffness may explain why there isn’t a much stronger correlation between flat fee (i.e. a weak longitudinal arch) and plantar fasciitis.

Much attention is given to the longitudinal arch, frankly I didn’t ever consider the transverse arch until diving into foot research. Is there a relationship that an underdeveloped longitudinal arch has on increasing the chances of bothering your plantar fascia, increasing the likelihood of developing plantar fasciitis? Your longitudinal arch acts like a spring, a weak spring is longer, a longer spring pulls the associated muscles and fascia, including the plantar fascia. I don’t know about you, but if I was pulled out of shape for a prolonged time, I would get pretty upset too!

Physiological Indicators of Plantar Fasciitis

Plantar fasciitis is rife in the general population, accounting for 15% of foot injuries. Proper ankle range of motion (ROM), and foot muscle strength, allows for balanced weight loading while walking. Without this, feet are susceptible to developing a thicker plantar fascia from microtears, fiber degeneration, or edema from the added stress. A thicker plantar fascia reduces both plantar fascia flexibility, and the foot’s shock-absorbing function. A plantar fascia thicker than 4 mm thick has been correlated with higher risks of plantar fasciitis, while studies have shown reduction in plantar fascia thickness after plantar fasciitis intervention. A study, published in the Journal of Exercise Rehabilitation, tested the relationship between plantar fasciitis and flat feet. They found a correlation of flat feet with predictors of plantar fasciitis including foot pain, limited ankle ROM, and plantar fascia enlargement.

The Take Home Message

Other than making you feel more self-conscience, this blog is designed to be helpful too. Your feet are stronger than you give them credit for. My message is this: just as you consider strengthening your glutes, quads, and pects; consider strengthening your feet too. However, there is a fine line you walk (or run), between stress and too much stress. The principle of progressive overload applies with your feet as well. Start light, and slowly build up. Perhaps you get a pair of footwear with just a little less cushion. Once you build up to it, you can go for a pair with even less. However, there are not many affordable options for going minimalist that don’t look too dorky. I wear Feiyues, I’ve found that after ripping out the insoles and heel foam, what’s left is a very stylish and flexible sole of thin rubber and an incredibly minimalist shoe for only $25. They work for me, but find what works for you! And lastly, I want to always encourage you to do your own research, and challenge my opinions.

Figure 4: a demonstration of the stylish minimalism of feiyue shoes.

Works Cited

1. Psatha, M., Wu, Z., Gammie, F.M., Ratkevicius, A., Wackerhage, H., Lee, J.H., Redpath, T.W., Gilbert, F.J., Ashcroft, G.P., Meakin, J.R. and Aspden, R.M. (2012), A longitudinal MRI study of muscle atrophy during lower leg immobilization following ankle fracture. J. Magn. Reson. Imaging, 35: 686-695. https://doi.org/10.1002/jmri.22864

2. Fitts RH, Trappe SW, Costill DL, Gallagher PM, Creer AC, Colloton PA, Peters JR, Romatowski JG, Bain JL, Riley DA. Prolonged space flight-induced alterations in the structure and function of human skeletal muscle fibres. J Physiol. 2010 Sep 15;588(Pt 18):3567-92. doi: 10.1113/jphysiol.2010.188508. Epub 2010 Jul 26. PMID: 20660569; PMCID: PMC2988519. https://pubmed.ncbi.nlm.nih.gov/20660569/

3. Manganaro D, Dollinger B, Nezwek TA, et al. Anatomy, Bony Pelvis and Lower Limb, Foot Joints. [Updated 2021 Sep 20]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK536941/

4. Lucy's Flat Feet: The Relationship between the Ankle and Rearfoot Arching in Early Hominins DeSilva JM, Throckmorton ZJ (2010) Lucy's Flat Feet: The Relationship between the Ankle and Rearfoot Arching in Early Hominins. PLOS ONE 5(12): e14432. https://doi.org/10.1371/journal.pone.0014432

5. White JV, Katz ML, Cisek P, Kreithen J. Venous outflow of the leg: anatomy and physiologic mechanism of the plantar venous plexus. J Vasc Surg. 1996 Nov;24(5):819-24. doi: 10.1016/s0741-5214(96)70018-6. PMID: 8918329.

6. "Plantar Aponeurosis." Physiopedia, . 15 Dec 2021, 23:49 UTC. 16 Sep 2022, 18:54 <https://www.physio-pedia.com/index.php?title=Plantar_Aponeurosis&oldid=289145>.

7. Venkadesan, M., Yawar, A., Eng, C.M. et al. Stiffness of the human foot and evolution of the transverse arch. Nature 579, 97–100 (2020). https://doi.org/10.1038/s41586-020-2053-y

8. Rhim HC, Kwon J, Park J, Borg-Stein J, Tenforde AS. A Systematic Review of Systematic Reviews on the Epidemiology, Evaluation, and Treatment of Plantar Fasciitis. Life (Basel). 2021 Nov 24;11(12):1287. doi: 10.3390/life11121287. PMID: 34947818; PMCID: PMC8705263.

9. Chen H, Ho HM, Ying M, Fu SN. Association between plantar fascia vascularity and morphology and foot dysfunction in individuals with chronic plantar fasciitis. J Orthop Sports Phys Ther. 2013 Oct;43(10):727-34. doi: 10.2519/jospt.2013.4774. Epub 2013 Aug 30. PMID: 23886626.

10. Park SY, Bang HS, Park DJ. Potential for foot dysfunction and plantar fasciitis according to the shape of the foot arch in young adults. J Exerc Rehabil. 2018 Jun 30;14(3):497-502. doi: 10.12965/jer.1836172.086. PMID: 30018939; PMCID: PMC6028224.