After reading an article about ankle and foot dysfunction and commenting on it, I wanted to do a follow up, especially on running strikes and the appropriate type of footwear.
First of all here are some facts about our feet. Each foot has 24 muscles, 26 bones and 33 joints, mostly in the vertical plane. It is one of the most complex and important part of the body yet we don’t really look after it. A subtle motion on the foot has a significant impact on the rest of the body Imagine a tower with a foundation that starts to collapse. Not only the whole tower becomes wobbly but weak spots start to appear at the upper levels.
The Talus bone is very unique. Beside being the only bone in the body that has no muscle attachment, it is a torque converter as it converts sagittal motion to the transverse plan because it is designed to be energy efficient as opposed to energy expensive. Most of us are borne with a certain degree of arch under the base of the feet (primary curve) but with bad habits, lack of supportive footwear, injuries, walking barefoot on hard surfaces, the muscles of the feet can become inactive and the arch ends up collapsing (secondary curve). I have seen a lot of people coming to me to get fitted for ski boots telling me they were “flat footed” and had all sorts of issues and pressure points in ski boots. The question was: are they really flat footed or do they have a collapsed arch? The answer: almost every single one had collapsed feet. Digging a little deeper I found that most of my clients had experienced at some point some knee pain, back pain, lower back lordosis and even neck pain. Even more for those who were running.
The foot in Motion and the Kinetic pulse:
We are biomechanically designed to pronate (as in motion) but not to live with it (as in position). The foot in motion needs to be rigid as well as mobile and is constantly under stress as it is jammed between the Ground Force (GRF) and Gravity. When we simply walk, our feet take up to twice our body weight. When we run, up to 4 times on each strike. When we jump, our feet need to lift up to 5 times our body weight and when we land it is required to absorb up to 8 times our body weight. Now do the math!
Whether we walk or run, the foot needs to adapt to the ground to keep the body stable, which is mostly done thanks to the many proprioreceptors. They send messages to the brain when the foot hits a surface in order to activate the muscles necessary for movements. This includes all the muscles along the legs, back and even arms. During the landing phase, the bones of the feet unlock to absorb the shock then lock at the end phase for propulsion. Every muscle of the foot decelerate pronation to avoid damage on the body (remember the foundation of the tower).
A study about foot strike done by Pr. Daniel Lieberman at Harvard University showed the impact some footwear had on the whole body and the difference with barefoot running. He found that the shock from the impact of the foot on the ground is energy that gets stored by the muscles to spring back to the propulsion phase. It is called the Kinetic Pulse. Now on heel strike, this Kinetic Pulse is preceded by a rattling which is like an unnecessary vibration that goes straight through the bones rather than stored by muscles. This rattling is even more important when the heel strikes barefoot. The stress of the impact with the ground needs to be put on the muscles and fascia (viscoelastic tissues) to store the energy and avoid a foot distortion which happens when the calcaneus (heel bone) strikes first. We need motion of the foot before stability
When the runner hits the ground mid foot, Pr. Lieberman found that the distortion (rattling) disappears and that the Kinetic Pulse is even smoother, especially if wearing racing flat shoes and Vibram 5 Fingers.
Shoe Guideline:
The footwear industry is a multi billion dollar market and there are pros and cons with every shoe about the amount of cushioning, width, lacing…
As a general rule:
§ The heel cushion should not be wider than the body of the heel as this would increase the moment the foot hits the ground and send the wrong signal to the brain which would create excessive pronation.
§ Too much height difference between the heel and the forefoot will create too much plantar flexion and will lock the talus bone and minimise loading and energy transfer.
§ If the shoe has too much cushion, it will “buffer” the Kinetic Pulse and insufficient energy will be transferred into the body although it may be appropriate for a heavier runner.
§ Having a narrow shoe or lacing up too tightly impedes the navicular and mid foot bones from moving, thus limiting loading of the foot. It also creates a valgus hallux (and big toe bunion).
If you start running and you are not quite sure what shoe to get, it’s probably worth getting a gait test to see how your feet function. Also keep in mind that feet, knees and hips are all related and that tension/dysfunction at one end or the other will automatically have an impact along the lower limb chain. Getting massages in the gluteal area, ITB, calf region and feet will help give back enough mobility for appropriate movement.
Guillaume Tual
If you are more interested about why we are designed to run and the story behind barefoot running, read Christopher McDougall’s “Born To Run”.
