The feet: how they move (and when they don’t)

The feet are a fairly incredible feat of engineering (no pun intended). They hold us up, are our initial connection to the ground, and, in conjunction with the lower extremity, propel us forward when we walk. Yet many of us ignore our feet, treating them an extension of the leg rather than a body part which can be mobilized, strengthened, and improved upon. 

The feet are comprised of two longitudinal arches, the medial and the lateral, which allow the foot to respond to the ground and absorb force (1)*; this means they have the ability to flatten and rebound, kind of like one of those gooey toys that splatters on impact, before returning to its original shape and pulling away from the wall (or whatever else it might be stuck to). Unlike the gooey toy, the foot accomplishes this through elastic recoil, strength, and mobility.

This concept is called the Windlass mechanism (2), and can only be understood if you have an idea of a few key anatomical structures of the foot. The arch that we commonly refer toon the inside of the foot is called the medial longitudinal arch (fancy name you probably don’t need to remember). The plantar fascia (a thick band of connective tissue), connects the calcaneus (heel bone) to the phalanges and is instrumental in preventing in preventing foot collapse. 

The arch deals with vertical forces from the body via the tibia and ground reactive forces from the calcaneus and metatarsal heads. These forces act to flatten it out. 

With that much load, why isn’t the foot completely flat?

A windlass is what happens when a rope or cable tightens. The plantar fascia behaves like a cable attached to the ankle bone and metatarsophalangeal joints (the joints that connect the toes to the feet). During the gait cycle, when the back foot is on the ground and about to move forward, the ankle moves into dorsiflexion. This shortens the distance between the calcaneus and metatarsals because the plantar fascia winds around the metatarsals (see picture). Voila! The arch becomes elevated, and gives us the ability to push off and swing the leg forward with minimal effort.

plantarfasciasmall.jpg

When the foot hits the ground, it’s rigid upon impact. This happens through ankle plantarflexion, subtalar inversion, and forefoot adduction. (For those of you whose eyes officially glazed over, just know that this is a triplanar movement). This happens at three different places: the ankle, the subtalar joint and the forefoot (3). We’ll return to this idea a little later, but for now start to appreciate how the foot responds to the ground is affected by both ankle and foot mobility.

Once the foot is on the ground, it flattens, to absorb the ground force. Think about the three movements I named above. If you can come up with movement in the opposite directions, you have figured out what happens during midstance. (If you guessed ankle dorsiflexion, subtalar eversion, and forefoot abduction, you would be correct). Finally, before pushing off, the foot becomes rigid again, propelling us forward. 

This requires no conscious effort, and happens (hopefully), at least 10,000 times per day. 

What happens when fatigue sets in? Or uneven terrain? Or if a person’s feet don’t move through the gait cycle in the way described above?

Let’s say you decide you are going to go for a 10 mile trail run. The only problem with this is your longest run in the last 6 months is 4 miles. Chances are pretty good you will experience a bit of neuromuscular (and physiological) fatigue. What happens to foot strike?

The integrity you normally use during gait will begin to get sloppy. The muscles which control the way the foot hits the ground get tired, and even the act of flexing your hips becomes challenging. Eventually, you will feel like you are slogging along, with your feet slapping the ground. The ability of the foot to effectively absorb the ground reactive forces (GRFs) from the ground is compromised. If your ankles aren’t very mobile and used to dealing with uneven surfaces, late in the run, when you step on an unexpected rock, the ability of the foot to recover will be impacted, and you might twist your ankle or strain your foot. 

The next day, your feet will probably feel a bit sore.

The feet, like any other body part, require progressive overload to adapt and get stronger. Even if you wear the most amazing shoes, they will hurt if you don’t progress your training systematically.

Let’s get into the part where we look at ways to train the feet. Not the toes. The toes we will look at later.

Training the rigid foot:
Before I begin, I should point out that if you are working on someone’s feet, you might want to consider what’s happening upstream at the pelvis. Just like the hand informs the shoulders, the feet inform the pelvis (or maybe the pelvis inform the feet. It’s a chicken or egg debate) (3). 

Pretend when someone stands, the arch lifts away from the ground and you can see a tiny bit of space on the lateral side of the foot. When you ask the person to do a basic step up, you watch as most of the load during movement is on the pinkie side of the foot. The big toe is light during the stepping movement, and the arch remains rigid throughout the motion, with very little give. How can you improve the mobility in the foot? 

First, it’s important to note excessive supination isn’t necessarily a bad thing. Research performed by Hillstron, et.al., looked at gait patterns in people with flat feet, high arches, and “well-aligned” feet. They found no clinically important differences during gait pattern parameters (4). So foot type does not implicate a dysfunction.

Let’s get back to our example above. Her resting posture begins in a high arch, and the arch position doesn’t change during gait. Giving her foot an opportunity to move in different planes (since gait is a triplanar motion), is probably a good thing. Her strategy doesn’t deviate from supination, ankle plantarflexion, subtalar inversion, and forefoot adduction. The goal isn’t to change her resting stance, but to improve mobility and awareness of other parts of the foot, namely pronation, ankle plantarflexion, subtalar eversion, and forefoot abduction.

An easy way to do this is to begin by having the person roll the bottom of her feet on a golf ball. I have written about this before, but basically, it’s a sensory input that has a short term effect on mobility, a bit like foam rolling (4). 

Next, I place a small towel underneath the forefoot and have the person roll from the big toe ball of the foot to the pinkie toe part of the foot. (If this doesn’t make sense, there is a video of the sequence here: https://vimeo.com/205385243).

Finally, I remove the towel and ask the individual to press the big toe ball of the foot down. Another way to think of this is to allow the arch to move downwards. (This tends to feel like a lot of work, possibly all of the way up into the hip).

While this is a blog about the foot, I would be remiss not to mention the ability to invert and evert the ankle should also be addressed in those with rigid feet.

Training the floppy foot:
On the other side of the spectrum are those with “floppy feet.”

Again, a foot that is flat or doesn’t have much arch does not correlate with pain or dysfunction (5). If the foot flops on to a step during a step-up, however, training the stabilizing foot muscles to give the foot a bit of strength will probably improve efficiency.

I trained a client for a while who had arches that spilled into the ground. She had low back pain, and with low back pain clients I always work on their perception of how their feet interact with the environment. After about 6 months of training, that included awareness of the foot and exercises to strengthen various areas, she came in, excited.

“I have an arch,” she said. “I don’t remember the last time I had an arch.”

While this wasn’t my goal, it was a pleasant by-product of the work she had been doing. Her feet no longer spilled over in the middle and she had the strength and mobility to use her feet differently.

Back to training the floppy foot. Typically, people that don’t have a lot of control of their feet feel the weight on the inside heel. They might have trouble controlling how the foot hits the ground, and there might not be any sense of spring when they toe off. 

Training the floppy foot is similar to training the rigid foot in that using sensory input, such as a tennis ball, mobilizing the ankle, and getting movement through the subtalar joint to move the foot through inversion and eversion are helpful tools to increase awareness. 

Additionally, teaching the foot how to make an arch and generate force into the ground with the center of the big toe are excellent ways to improve strength in the deeper, intrinsic muscles of the foot. A few of the drills I commonly use can be found in the short video here: https://vimeo.com/205384165.

What about the toes?
The ability of the toes to press into the floor creates a sense of stability and allows us to maintain our balance. The actions of the toes mirrors the action of the ankle joint; for instance, the toe extensors (extensor hallucis longus and extensor digitorum longus) extend the big toe (EHL), lateral four toes (EDL), and dorsiflexes the ankle. The flexor hallucis longus (FHL) and flexor digitorum longus (FDL) flex the big toe (FHL), lateral four toes (FDL) and plantar flexes the ankle (6). (There are also muscles that further control flexion and extension at the toes, as well as abduction and adduction of the big toe).

What we can take from this anatomical knowledge is the toes have the ability to move, both with the ankle and independent of the ankle. What you will notice if you pay attention is people adopt a myriad of strategies in the toe region to maintain stability. Some people claw their toes, lacking the ability to fully extend. Others have toes that are quiet, not moving much at all. (These are the same people who, when asked to go into a toe point, will find themselves grimacing as the foot goes into an epic cramp). 

There is also the big toe that lives in adduction, completely lacking the ability to abduct, despite having a muscle whose sole function is dedicated to big toe abduction and flexion (the abductor hallucis). 

During gait, just before toe-off, the big toe goes into extension, tightening the plantar fascia, which we learned above via the windlass mechanism, heightening the longitudinal arch which, along with the intrinsic muscles of the foot, provide a stable, rigid structure from which to push off.

Like with any other body part, there is a balance between toes that are active and participate in a movement and toes that drive the movement. If you notice the toes are busy, moving unnecessarily or pre-empting stabilizing movements, teach the person how to differentiate between toe and foot movement. If the toes don’t participate at all and need more strength, check out the sequence from Dr. Spina below that not only differentiates the toes from the ankle, but also strengthens them.
https://www.youtube.com/watch?v=2OOJ9AQ1AEg

The feet are an integral part of our relationship with the ground. By incorporating strength and conditioning drills specifically for the foot and toes, you can help clients and students feel more deeply grounded, improving balance and total body coordination. 

 

*There is also a transverse arch, which provides additional support and flexibility to the feet.
**If you want more practical information on this topic, I have an entire class available here: https://vimeo.com/ondemand/feet
***The Nature and Movement Retreat is happening June 2-4 in the beautiful Mayacamas Lodge in Napa Valley. Early bird registration ends March 1. Check out www.bewellpt.com for more information.

References:
1. Huson, A., (1991). Functional anatomy of the foot. Disorders of the Foot and Ankle, 1, 408-431.
2. Bolgla, L.A., & Malone, T.R., (2004). Plantar fasciitis and the windlass mechanism: a biomechanics link to clinical practice. Journal of Athletic Training, 39(1), 77-82.
3. Dugan, S.A., & Bhat, K.P., (2005). Biomechanics and analysis of running gait. Physical Medicine and Rehabilitation Clinics of North America, 16, 603-621.
4. Mohr, A.R., Long, B.C., & Goad, C.L., (2014). Effect of foam rolling and static stretching on passive hip-flexion range of motion.  Journal of Sport Rehabilitation, 23(4), 296-299.
5. Hillstrom, H.J., Song, J., Kraszewski, A.P., Hafer, J.F., Mootanah, R., Dufour, A.B., Chow, B.S., & Deland III, J.T., (2013). Foot type biomechanics part 1: structure and function of the asymptomatic foot. Gait Posture, 37(3), 445-451.
6. Moore, K. L., Agur, A. M. R., Moore, K. L., & Agur, A. M. R. (2002). Essential clinical anatomy. Philadelphia: Lippincott Williams & Wilkins.