
FAC Facts and FAQs
The FAC is extremely complex because there are dozens of bones and hundreds of muscles, tendons, fascial components, and ligaments at play. All of these components come together within the FAC to provide stationary support while standing and dynamic spring while moving. So I will do my best to keep it simple, but please forgive me if my inner nerd comes out and I use too much technical jargon. When it comes to movement of the FAC, one major concern is the interaction between the arch of the foot and dorsiflexion of the foot (taking your foot off the gas motion). A lack of dorsiflexion in the ankle can be the caused by several factors, but frequently involves decreased strength of the tibialis anterior muscle (1). The decrease in shin muscle strength can then lead to flat feet, increased plantar flexion (pressing the foot down on the gas) during squatting motions and gait (walking). All in all, the arch can be placed under great amount of stress during the load acceptance phase of gate, if your foot is weak and there is limited dorsi flexion. That’s because during this phase of the walking/running cycle the shin and ankle muscles assist the arch in energy absorption (2). If the ankle is unable to properly dorsiflex, a huge amount of stress will be placed on the foots spring ligament, plantar fascia, and intrinsic muscles which can lower the arch. This lowered arch in turn causes tibial (shin) rotation, hip internal rotation, slight hip flexion, and hip adduction creating a valgus (knock knee) stress (3,4). So what does this mean for you? Well to sum it all up, when we don’t pay attention to the FAC we are more likely to have stiff hips, lower back pain, tight calves, weak feet, weak ankles, altered gait, plantar fasciitis, hallux valgus (a.k.a. bunions), patellofemoral pain, increased susceptibility to medial collateral ligament (MCL) injuries, and an increased likelihood of anterior cruciate ligament (ACL) tears.
There are also some other surprising aspects of foot strength that I’m betting most of you didn’t even think about. Having proper FAC strength means you have developed some proprioception (foot eye coordination in this case). In turn, this means you know where your body is at in space. This is extremely important if you think about it because it’s the same as knowing where my fingers are as I type each letter of this post. I don’t need to look down for each letter, I just know how to move my hands. So, if you practice strengthening your FAC you will know where your lower body is during each step you take. This leads to better performance for athletes, enhancements in the standing and walking positions, and the ever crucial prevention of falls for seniors (5).
Foot Fitness
So I’m going to start this section by being a negative Nancy. To have healthy feet you SHOULD NOT use arch supports or supportive shoes. No, this does not mean you should take out those stinky old things you have put in your shoes for years and start walking around. What I mean is that the arch support is to the feet, what the weight lifting belt is to the back. Yes they are both supportive, but if you don’t let those underlying muscles develop you will end up with some limp noodles for muscles. So instead of opting for the all or nothing path, star weaning yourself off of the arch support and into regular shoes. Or if you’re ready for it, start weaning yourself onto more minimalist shoes. It’s really all about a gradual progression into a more barefoot environment… unless your feet stink like mine ;). You wouldn’t go from lifting 10 lbs dumbbells to benching 225 lbs, so don’t jump too quickly on the minimalist bandwagon especially if you have high arches to begin with (6).
Okay, I know that if you have read this far you might be a little frightened of your weak feet. But I promise you that you don’t have to do that much to whip them into shape! This is because even though you use them all day long, the interaction between your nerves and your muscles may be the real underlying issue. So to re-learn your own feet, there are a few simple steps you need to take. Use your time wisely by standing on one foot as often as you can. This can be done while you wash dishes, make phone calls, eat Ramen noodles, or other things that people who aren’t poor college students do. You can also practice flexing your toes while you’re sitting down. This can be done by simple scrunching your toes together while at your desk, or by picking up objects and putting them into a container while you’re seated (7). Additional exercises include standing on one foot, bunny hops, walk heel to toe, medial (inside) calf raises, resisted ankle inversion exercises, single-leg kettlebell swap, foam rolling the biceps femoris (outside hamstring) and plantar fascia, and walking in a straight line with one foot in front of the other. Finally, you should take care of your hips. The interaction between the hips and the ankles goes both ways. So stiff hips can mean stiff ankles and visa versa.
Resources
1. Chizewski M., & Chiu L. Contribution of calcaneal and leg segment rotations to ankle joint dorsiflexion in a weight-bearing task. Gait & Posture, 3685-89. doi:10.1016/j.gaitpost.2012.01.007
2. Spaich, E. G., Andersen, O. K., & Arendt-Nielsen, L. (2004). Tibialis Anterior and Soleus Withdrawal Reflexes Elicited by Electrical Stimulation of the Sole of the Foot during Gait. Neuromodulation, 7(2), 126-132. doi:10.1111/j.1094-7159.2004.04016.x
3. Hollman, J. H., Kolbeck, K. E., Hitchcock, J. L., Koverman, J. W., & Krause, D. A. (2006). Correlations Between Hip Strength and Static Foot and Knee Posture. Journal Of Sport Rehabilitation, 15(1), 12.
4. Simon, L., Christian, B., Peter, M., Richard, T., Roger, W., & Dylan, M. (n.d). The effect of anti-pronation foot orthoses on hip and knee kinematics and muscle activity during a functional step-up task in healthy individuals: A laboratory study. Clinical Biomechanics, doi:10.1016/j.clinbiomech.2013.11.015
5. 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. Journal of Physical Therapy Science. 2014;26(3):373-376. doi:10.1589/jpts.26.373.
6. McKeon, P. O., Hertel, J., Bramble, D., & Davis, I. (2014). The foot core system: a new paradigm for understanding intrinsic foot muscle function. British journal of sports medicine, bjsports-2013.
7.Siddiqi A., Kumar D., Arjunan S. Age-related motor unit remodeling in the Tibialis Anterior Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS, Volumes 2015-November, 4 November 2015, Pages 6090-6093