custom footbeds

WHO NEEDS FOOTBEDS? NO ONE

There are some who can benefit from footbeds or orthotics and some who do actually need them. But these groups are the rare exception. And they are unlikely to be skiers.

Orthotics. The pros / cons of orthotics in today’s society!

In a recent YouTube video (1.), Podiatrist & Human Movement Specialist, Dr Emily Splichal, explores the concept of orthotics and their role in today’s society. Dr. Splichal doesn’t pull any punches when she says:

“…..I have been through the conventional podiatric school and been fed pretty much the bullshit from podiatry of how every single person needs to be in orthotics, that our foot is not able to support itself without orthotics……if we do not use orthotics our foot is going to completely collapse  and you are going to lose your arch…….”

“……Our foot is designed to support itself. If we actually needed orthotics, we would be born…..we would come out of the womb, with orthotics on our feet.”

Meantime, The Foot Collective  asks (2.) Are you promoting weak feet?

  • Anything you use for artificial support at the feet (footwear with arch support & orthotics) your brain takes into account and accommodates for it.
  • That means if you provide your foot support your brain shuts down the natural arch supporters to reduce un-necessary energy expenditure.
  • Stop using support to help with pronation and understand why your feet pronate in the first place – because they are weak.
  • Strong feet = strong foundation = strong body.

The Real Source of Support for the Arch

Ray McClanahan, D.P.M. offers a perspective on the issue of Arch Support in his post on the CorrectToes blog (3.)

Are Custom Footbeds and Orthotics better than stock insoles?

In his post of August 20, 2017, Custom Foot Orthotics; No Better Than Stock Insoles (4.), Rick Merriam, of Engaging Muscles, explores the issue of orthotics in depth.

Prior to being told that supportive insoles are the way to go, I think it’s safe to say that all of those people didn’t know what they didn’t know.

The erroneous assumption that every skier needs footbeds or orthotics was made at a time when little  was known about the function of the foot and lower limb, especially in late stance. I was one of those who didn’t know what I didn’t know when initially when down the ‘the foot needs to be supported in skiing’ road up until I realized what I didn’t know and took steps to acquire the requisite knowledge.

Footbeds; is anyone checking what they do?

In 2000, I formed a company called Synergy Sports Performance Consultants (5). Synergys’ product was high quality information. One of my partners, UK Podiatrist, Sophie Cox, was trained by Novel of Germany and was one of the few experts in the world at that time on the Pedar system. Synergy did not make and/or sell footbeds or orthotics. Instead, we checked the effect of footbeds on skier performance. We performed a quick footbed check for a minimal fee of $20 using the sophisticated Novel Pedar pressure analysis technology.

Synergy was one of the first companies in the world to use the Novel Pedar pressure analysis system synchronized to video to acquire data on skier performance and analyze the captured data.  The Synergy team with diverse expertise studied the effect of ski boots and custom insoles on skier performance and identified functional issues in the body that needed to be addressed. It was a common finding that custom footbeds were significantly compromising skier performance, especially the ability to create the necessary platform under the foot on which to stand and balance on the outside ski.

Synergy offered a comprehensive 5 Step Performance Program that started with a footbed check. A key component was item 2., the Biomechanical Check.

With increasing recognition of the negative effect of most footwear on the user and criticism of the unproven claims made for footbeds and orthotics coming hard and fast, credibility in skiing is rapidly going downhill. It is time for proponents of custom insoles for ski boots to support their claims with solid evidence, especially evidence supported with data acquired during actual ski maneuvers. The technology to do this has existed since at least the year 2000.


  1. https://youtu.be/CIRf9WHmMXI
  2. http://www.thefootcollective.com
  3. https://www.correcttoes.com/foot-help/articles-studies/arch-support/
  4. http://www.engagingmuscles.com/2017/08/20/custom-foot-orthotics/
  5. DIGITAL SALVATION FOR THE SOLE [BACK TO THE FUTURE] –  http://wp.me/p3vZhu-24g

THE MECHANICS OF BALANCE ON THE OUTSIDE SKI: PRESS AND POINT THE BIG TOE

A widespread perception appears to exist within the skiing community is that the ability to hold a ski on edge by using the leg to exert force against the side of the stiff shaft of a ski boot and staying upright and not falling, equates with good balance. This ingrained perception presents a challenge in terms of communicating how the world’s best skiers create a platform under the body of the outside ski that they can stand and balance on using the same processes that we all use to stand and balance on a hard, flat level surface.

Last ski season, I developed simple cue to help skiers find the right mechanics and biomechanics as the new outside ski goes flat between edge change and then rolls into the turn on its new inside edge.  At ski flat, if a skier has the right stance, they should feel strong pressure under the ball and the big toe. As the skier extends and inclines into the new turn, the outside leg should be rotated into the turn to point the big toe in the direction of the turn. Hence the cue, press and point the big toe.  This pressure under the ball of the foot and big toe should be maintained through the turn phase until it is released by the transfer or weight to the inside (uphill) ski at the start of the transition to the inside. The strong pressure under the ball of the foot and the force that presses the big toe down flat is passively created by a strong stance, not conscious effort.

The Reverse Windlass

The pressure under the big toe is created by what is called the Reverse Windlass Mechanism. This naturally happens in the late phase of stance when walking barefoot. But wearing shoes with raised heels and cushioned insoles makes it impossible for the Reverse Windlass to function. When the Reverse Windlass is lost, it must be re-acquired by being barefoot as much as possible and walking, running and training in zero drop, thin soled minimal shoes. In some cases, people have to learn to walk naturally by rehearsing the action.

There is an excellent YouTube video by Teodoro Vazquez on Blog del Runner  called Windlass Mechanism and Running Biomechanics – https://youtu.be/y_8SrufgmDk. Vazquez describes the 3 phases of the windlass mechanism, Active (Activo), Reverse (Inverso)  and Passive (Pasivo). Although the video is directed at running, the primary concepts have direct application to skiing and ski technique. The reverse windlass is activated by the weight as shown in the graphic below from Vazquez’s YouTube video.
 This tensions the arch of the foot and presses the big toe down.
As the shank angle increases, the soleus muscle goes into isometric contraction and arrests further shank movement. The results in a heel to forefoot rocker action that dramatically increases the down force under the ball of the foot and the big toe. What I call the Spinal Reflex or SR Stance maximizes the down forces.

It is important that when the big toe (aka Hallux) is pressed down flat, the ball of the foot and big toe feel like one. When the big toe is pressed down properly, you should feel your glutes tighten. The leg you are standing on should be straight and the knee pointed straight ahead.

An important muscle in the Reverse Windlass is the Flexor Hallucis Longis or FHL. When the soleus goes into isometric contraction, the FHL is tensioned. This stabilizes the foot and knee by rotating them away from the center line of the body.

Things that prevent the Reverse Windlass

1. A condition called Hallux (big toe) Valgus
2. Narrow shoes and especially shoes with a pointed toe box.
3. Ski boots, especially ski boot liners.
4. Shoes with elevated heels, cushioning and toe spring (toes raised up). Note: A small amount of ramp angle is necessary for the SR Stance.
5. Footbeds and Insoles.
In my next post, I will discuss fixes to enable and/or restore the Reverse Windlass.

INSOLE/FOOTBED/ORTHOTIC EFFECTS

The big epiphany I had about 1975, was that the foot needed to be supported in the new plastic ski boots and that it was a lack of support that was causing my difficulties skiing after switching from low cut leather boots to the new higher, rigid plastic boots.

Back then, I was an avid runner. As best I can  recall, it was an article in Runner’s World on running injuries caused by over-pronation that served as a catalyst for my conclusion that the foot needed to be supported in a ski boot. I assumed that what was being reported in running magazines was both factual and derived from science-based investigations. While I had not found anything in the literature that suggested that the foot needed to be supported in a ski boot, it seemed logical to me that if runners needed support in their shoes, the need for support in a ski boot was many times greater. But my conclusion was based on the assumption that over-pronation was a pathology and that it was a proven cause of injuries in running. Therefor, it was also a problem in skiing.

Pronation and over-pronation was a new concept to me in 1975. My running partners and I all ran in flats with no arch support. None of us had ever heard of, let alone experienced, knee pain or the myriad of other problems that were fast becoming an integral part of running and were claimed to be caused by overpronation.

Soon after I read the article on overpronation, I made an appointment with a podiatrist in Vancouver to have my feet examined. I was hopeful that he would find the defect(s) in my foot that were causing me difficulties in skiing in the new plastic boots. But after a thorough examination, he pronounced my feet healthy and normal. Undeterred, I made an appointment for my wife and I with a well known sports podiatrist in Seattle, Washington, almost 800 miles round trip to and from Whistler. We made a special trip to Seattle to have prescription orthotics made for our ski boots. But far from helping, they made both of our skiing worse, much worse. Still, I remained convinced that the foot needed support in a ski boot.

Between 1977 and about 1983, I made a lot of footbeds for ski boots. From the first pair of footbeds I made, I received positive feedback. Skiers loved them. Some skiers told me they would never ski again without the footbeds I made for them. Even today, I encounter skiers who are still using the same footbeds I made for them 40 years ago. Did this subjective feedback serve as evidence that my footbeds made skiers ski better? No.

By about 1989, I was still unable to understand why I was continuing to experience difficulty skiing even after trying numerous pair of plastic ski boots. At that time, I was struggling to invent and patent a ski boot based on sound principles of functional anatomy

I finally came to the realization that the only way to arrive at meaningful conclusions about how the human system should ideally function in skiing was to design and fabricate an open-architecture research vehicle, one that minimized any neural noise that was unavoidably caused by interference with the physiologic function of the user by structures of the conventional ski boot. It had become apparent to me that it is the level of ‘neural noise’ and interference to physiologic function caused by a tightly fitting ski boot that prevents anyone from proving how a ski boot affects a skier.

The Birdcage allowed the capture of data during actual ski maneuvers that showed how some of the world’s best skiers skied and especially what happened when specific joint actions were interfered with.

It was was also about 1989 that I was starting to question how an insole or orthotic fit to one ski boot could produce the same result in a different ski boot or with skis with different sidecuts, especially width underfoot and different lift heights of the sole of the foot above the surface of the snow. I was also starting to question how the same stock or custom insole or orthotic could produce the same effect when used in different shoes. A custom insole for a female might be used in casual shoes, flats, running shoes, walking shoes, hiking boots and even spiked, high heel shoes. And what happens to the effects produced by an insole or orthotic when the sole of the shoe it is used in wears unevenly?

It was obvious to me, and should be obvious to anyone, that it is impossible for an insole or orthotic to consistently produce the same effect in widely varying footwear that each affect the foot in a different way. 

Despite the many questions I was having about insoles and orthotics, I continued to believe that they had value in some applications. In the years following the Birdcage tests of 1991, my wife had two different pairs of prescription orthotics made, both by reputable labs, for issues with hip and back pain. Neither pair provided any perceivable benefit. Both pairs were eventually discarded.

The best skiing experience today for my wife and I is with perfectly flat insoles and boot boards that provide no perceivable interference with the dynamics of the arches of our feet. Even the slightest impingement is immediately perceived. All of the shoes I wear have either flat insoles or no insoles. If I purchase a shoe with an insole with arch support, I modify it to remove the support.

 

 

WHAT DO INSOLES AND ORTHOTICS DO?

According to Benno Nigg, no one knows for sure. From 1981 until he retired recently, Nigg founded and was the Director of the Human Performance Laboratory (HPL) at the University of Calgary in Calgary, Alberta, Canada. The Human Performance Laboratory is a multi-disciplinary research centre concentrating on the study of the human body and its locomotion. From 1971 until 1981, Nigg was the Director of the Biomechanics Laboratory at ETH Zurich (Swiss Federal Institute of Technology).

For more than 30 years, Nigg studied the effects of insoles and orthotics on the lower limbs. What he found was that most of the time they didn’t do what was claimed. Often, the effect of the same insole or orthotic varied greatly from one subject to another even though they had the same condition. In some cases, Nigg found that orthotics had a large effect on muscles and joints, increasing muscle activity by as much as 50% for the same movement while increasing stress on joints by the same amount as the body fought to overcome the effect of the orthotic. Nigg also found that “corrective” orthotics do not correct so much as lead to a reduction in muscle strength. He details his findings in his book, Biomechanics of Sports Shoes. The book can be ordered from NiggShoeBook@kin.ucalgary.ca

If no one knows what insoles and orthotics in footwear affect the user, how is it possible for anyone to know insoles and orthotics in ski boots affect skiers? I am not taking about claims made for insoles and orthotics made for ski boots. I am talking about how they affect the skier during ski maneuvers as confirmed by on-snow studies. The pivotal issue is how the CNS manages, or isn’t able to manage, the forces across the inside edge of the outside ski in a turn. This is what any claims should focus on. But I have yet to find evidence that any studies to this effect have been done.

You’ve been to a ski boot-fitting shop or perhaps a foot professional and had custom insoles or orthotics made for your ski boots. You may have been told that these interventions will create a specific alignment of your knees with some aspect of your feet.  You may have also been told that your feet pronate or over-pronate and that insoles or orthotics will correct these issues. In addition, you may have been told that you will ski better with the insoles or orthotics or an expectation was created that you would. This expectation may have been reinforced by the fact that you probably felt very different standing in your boots with the insoles or orthotics fit to them than you did without them.

Out on the ski hill with your boots and skis on you probably also felt different than you did without your new insoles or orthotics. But are you skiing better? You might think you are, especially after paying several hundred dollars or more. But how do you know for sure? You don’t. Unless the person who made your custom insoles or orthotics instrumented your ski boots and captured data during actual skiing both before and after the insoles or orthotics were installed and then compared the data sets to peer reviewed, independent studies that provided compelling evidence that the data captured during skiing conclusively demonstrated a positive effect of the insoles or orthotics on your skiing, any claims made were speculative and any conclusions, subjective. More important, claims tend to be biased because a product is associated with them.

You are probably thinking that none of this matters because there is an abundance of science in support of custom insoles and orthotics. But in a  New York Times article, Close Look at Orthotics Raises a Welter of Doubts – January 17, 2011 (http://www.nytimes.com/2011/01/18/health/nutrition/18best.html?pagewanted=all), Benno Nigg looked critically at insoles and orthotics. His overall conclusion? Shoe inserts or orthotics may be helpful as a short-term solution, preventing injuries in some athletes. But it is not clear how to make inserts that work. The idea that they are supposed to correct mechanical-alignment problems does not hold up.”

In the same NY Times article, Scott D. Cummings, president of the American Academy of Orthotists and Prosthetists, acknowledged that the trade is only now moving toward becoming a science and that when it comes to science and rigorous studies, “comparatively, there isn’t a whole lot of evidence out there.” Dr. Nigg would agree. The proof that orthotics provide benefit? Some people feel better using them than not using them. So any evidence is in the form of highly individualized, subjective feel. What about skiing? Is claiming that the foot needs to be supported and/or especially that the foot functions best in skiing when its joints are immobilized in neutral, sufficient to claim a benefit or implied need for insoles or orthotics in skiing? Hardly.

The first thing to consider is that unless the load W from the central load-bearing axis is transferred to the inside turn aspect of the inside edge of the outside ski it is impossible for the foot to pronate. In addition, in this configuration, the outside foot cannot be ‘supported’ because there is no support in the form of a contiguous source of snow reaction force under the base of the outside ski.

When Lange introduced the world’s first all plastic ski boot in in 1962, biomechanical research on human locomotion was in its infancy. Biomechanical studies of sports shoes, including ski boots, were nonexistent. The first edition of Inman’s seminal work, The Joints of the Ankle, wasn’t published until 1976. What did it take for the new rigid plastic ski boot to be universally accepted? A few trips to the podium.

When running and jogging took off in the early 1970s, insoles and orthotics and were widely promoted in response to injuries that were erroneously assumed to be caused by excessive (over) pronation. Were there any studies to support this conclusion? No. Nor, was there any evidence that I am aware  to support the position of the proponents of insoles and orthotics that the foot needed or would benefit from support in ski boots. As far as I have been able to determine, the need to support the foot in a ski boot was and still is based on a widely accepted assumption. If pronation was a problem in running, then it had to be a problem in skiing. That made sense. Except that it didn’t. In the late 1980s and early 1990s, studies were showing that there was only minimal correlation between high pronation and high impact loading and typical running injuries. Nigg and other researchers suggested that no evidence was found because there was no evidence. Researcher had been trying to prove pronation was the cause of running injuries instead of trying to find the cause.

Two recent studies question the validity of the premise of supporting the longitudinal arch of the foot, especially in ski boots.

_____________________________

Dynamic loading of the plantar aponeurosis in walking http://www.ncbi.nlm.nih.gov/pubmed/14996881

BACKGROUND: The plantar aponeurosis is known to be a major contributor to arch support, but its role in transferring Achilles tendon loads to the forefoot remains poorly understood. The goal of this study was to increase our understanding of the function of the plantar aponeurosis during gait. We specifically examined the plantar aponeurosis force pattern and its relationship to Achilles tendon forces during simulations of the stance phase of gait in a cadaver model.
RESULTS:  Plantar aponeurosis forces gradually increased during stance and peaked in late stance. Maximum tension averaged 96% +/- 36% of body weight. There was a good correlation between plantar aponeurosis tension and Achilles tendon force (r = 0.76).

CONCLUSIONS: The plantar aponeurosis transmits large forces between the hindfoot and forefoot during the stance phase of gait. The varying pattern of plantar aponeurosis force and its relationship to Achilles tendon force demonstrates the importance of analyzing the function of the plantar aponeurosis throughout the stance phase of the gait cycle rather than in a static standing position.

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For years, experts have claimed that skiing is done in the mid phase of stance in what is called the gait cycle. What the preceding study clearly shows is that the strongest stance in skiing in terms of the ability to transfer force to the head of the first metatarsal and functional stability of the structures of the foot occurs in the late phase of stance, not the mid phase. The graphic below provides a simulated representation of the sequence by which Achilles tendon force tensions the plantar aponeurosis and transfers large forces to the forefoot, especially to the head of the first metatarsal.

Foot Dynamcs 3

New studies are questioning the premise of supporting the arch of the foot with anything  because neural activity in the arch of the foot appears to  be potentiated by tension in the plantar aponeurosis and surrounding soft tissue. Rather than being a passive static entity in its role as a support structure for the superincumbent body, the arch is a dynamic, neurally charged system whose height changes in response to changes in perturbations in GRF that challenge the balance system.

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Foot anatomy specialization for postural sensation and control http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3311689/

These findings show that rather than serving as a rigid base of support, the foot is compliant, in an active state, and sensitive to minute deformations. In conclusion, the architecture and physiology of the foot appear to contribute to the task of bipedal postural control with great sensitivity. Here, we show that the foot, rather than serving as rigid base of support, is in an active, flexible state and is sensitive to minute perturbations even if the entire hind and midfoot is stably supported and the ankle joint is unperturbed.

However, support of the body weight in the erect posture involves not only the counterbalancing of the gravitational load, but also equilibrium maintenance, which is dynamic in nature. Accordingly, somatosensory information on local foot deformations can be provided from numerous receptors in the foot arch ligaments, joint capsules, intrinsic foot muscles, and cutaneous mechanoreceptors on the plantar soles (Fallon et al. 2005; Gimmon et al. 2011; Kavounoudias et al. 1998; Magnusson et al. 1990; Meyer et al. 2004; Schieppati et al. 1995).

During standing, the foot arch probe and shin sway revealed a significant correlation, which shows that as the tibia tilts forward, the foot arch flattens and vice versa.

It is worth stressing that the foot represents an important receptive field, formed by numerous skin, joint, tendon, and muscular receptors (including intrinsic foot muscles), and it has long been recognized that damage to the foot, be it either by sensorineural loss or physical damage to the muscles, bones, or supporting tissues, changes posture and gait stability.

A number of cutaneous and load-related reflexes may participate in the fine control of posture or foot positioning during walking.

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Almost any structure that provides even minimal support for the arches of the foot will prevent the arch from lowering and transferring force to the MTs and will  interfere with the function of the arch as an active, dynamic neuro-sensory mechanism.

Claims made for insoles and orthotics create a reasonable expectation in the consumer that what is experienced in an off hill controlled environment will also happen on the ski slopes. Terms of disclosure require that any claims  be qualified with statements like, “These claims have not been confirmed during actual ski maneuvers”.

 

 

 

A NEW PARADIGM: THE FOOT CORE SYSTEM

I can’t think of any application where the universal mentality that supporting the foot is necessary to provide a strong foundation for the foot is causing more problems than in ski boots.

In a ski turn, forces can reach several Gs. In such a situation, interference with the dynamics of the arch of the foot can prevent it from acquiring the intrinsic or fascial tension it needs to oppose the external forces and potentiate the neural processes associated with balance.

After decades of intervention in the form of arch supports and orthotics for feet with weak intrinsic muscles that do nothing to address the underlying issue and in many cases may actually exacerbate the condition, we are now seeing sound thinking prevail in the paper, The foot core system; a new paradigm for understanding intrinsic foot muscle function – Br. J of Sports Medicine dii: 10:1126/bjsports-2013-092690.

One blog that I follow is Dr. Nick’s Running Blog. Dr. Nick is a podiatrist who endorses barefoot function and ways to rehabilitate weak feet. Dr. Nick’s last post was on a two year case study demonstrating an increase in arch height from running in minimalist shoes. The post has a series of before and after photographs of the subjects feet. When standing on a flat, level surface, arch height is a good indicator of foot function.

http://www.drnicksrunningblog.com/two-year-long-case-study-demonstrating-an-increase-in-arch-height-from-running-in-minimalist-shoes/

It has been my observation that unless properly set up, ski boots, and especially any form of arch support, can significantly compromise foot function needed for skiing and may even cause feet to become weaker. When I was a child, the shoes I wore were far too narrow for my feet. Over the years, this caused significant damage to my feet that adversely affected my gait and balance. As the damage progressed, the height of my arches  decreased and my feet got wider. This did not present a noticeable problem for me in skiing until I switched to the new rigid plastic boots.

Over the past 8 years I have gone barefoot as much as possible. I also started wearing minimal shoes such as the New Balance Minimus with zero drop (no heel to ball of foot ramp). As Dr. Nick cautions, one has to make the transition to minimal shoes gradually. Since going mostly barefoot, the height of my arch has increased dramatically and my feet feel very solid to stand on. I now recognizing more of the compact, stiff foot structure that I used to envy in the feet of the best skiers when I worked with Canada’s National Ski Team.

In a future post I will go greater detail on the importance of intrinsic foot muscles and fascial tension to skier balance and ski technique.

 

 

 

PRONATION – WHAT SHOULD IT FEEL LIKE?

Given the widespread confusion and misunderstanding surrounding pronation and it’s role in skiing that seems to exist I am going to provide some drills that will teach you how to assume a functionally pronated position.

Functional pronation is specific to monopedal (one-foot) stance especially as it relates to the ability to assume and move from one dynamically tensioned base of support to another. Once you have a feel for the functionally pronated monopedal position you can go through series of drills standing in your bare feet on a hard flat surface. Next you can stand in your ski boots starting in the boot shell after which you can add the liner with no insole followed by the liner with an insole or custom footbed. By using the feeling associated with standing in your bare feet on a hard, level, flat surface and then comparing the sensations to standing in your ski boots on a hard, level, flat surface you can experience for yourself how the various elements around and beneath the sole of your foot affect your ability to assume a functionally pronated position or even stand properly on two feet. As a prelude to providing drills on how to assume a functionally pronated monopedal stance, I will provide a brief history of the events that contributed to my current position on pronation, footbeds and insoles in general in skiing.

In my initial years of modifying ski boots I was a big proponent of footbeds. In those days, my work on ski boots was very much aligned with conventional views of immobilizing and supporting the foot and leg. But my disastrous experiences with Dave Murray got me rethinking this. By the time I began working with Steve Podborski, I was moving in a direction away from conventional thinking. In 1980, I had a huge breakthrough with a in-boot technology for which I was later awarded a patent. This was the turning point at which  severed any association I had with conventional thinking in ski boots and started fresh with a clean sheet of paper; one that did not include any premises on which existing ski boots are based.

By 1991, when Steve Podborski and I  initiated a research program to test my hypothesis on the mechanics, biomechanics and physics of skiing, my thinking was so far from convention that I insisted on retaining two scientists to provide oversight on the project. This included reviewing everything I put in writing but especially my patent. This process was intended to ensure that the principles I was using were both sound and correct. One of the scientist was G. Robert Colborne, Ph.D, an expert in the biomechanics of the human lower limbs. After reviewing my hypothesis, the initial impression of these scientists was that if it were correct it meant the whole world was wrong. Because I was in uncharted territory it was critical to me to have my findings confirmed before going forward. Once the wheels of a new technology are set in motion and significant money has been invested, it is hard to change direction, and especially to reverse direction. For this reason, we did a series of on snow studies in 1991 on Whistler’s glacier to confirm my hypothesis. I will provide details of the results in future posts.

The image below shows the model engaged in quiet standing Bipedal stance. There four positions of Centre of Mass in relation to the feet with weight distribution as follows from 1 to 4:

1. Centre of Mass is just in front of the base of the shin. The heel which is carrying about 60-70% of the load of each foot. This represents the rearmost limit of Centre of Mass. Should CoM fall behind the base of the shin, a rearward fall will result.

2. Centre of Mass is in the proximate centre of the span of the longitudinal arch. The heel is carrying approximately 50% of the load of each foot. The balls of the feet are carrying the remaining 50% of the load. The ball of the great toe is carrying twice as much load as the other 4 balls of each foot. This position represents the most stable and efficient form of bipedal stance.

3. Centre of Mass is approaching the balls of the feet. The contraction of the muscles that plantarflex (push down) the feet is increasing. The balls of the feet are carrying the remaining 60-70% of the load of each foot.

4. Centre of Mass is almost over the balls of the feet. The contraction of the muscles that plantarflex the feet has further increased. The muscles that push the toes down are now contracting forcefully, pushing the toes against the floor. This is the absolute forward limit of Centre of Mass in quiet standing. The toes act as a fail safe by pressing down onto the support surface in what is called the Reverse Windlass Mechanism. This mechanism tensions the forefoot into a rigid lever in preparation for propulsive phase of gait. At this point, almost all the weight is being carried on the balls of the feet and the toes. Should CoM pass the balls of the feet without evoking plantarflexion of the ankle, a forward fall will occur.

Screen Shot 2014-02-10 at 10.03.33 AMBIPEDAL DRILLS

These should be done in bare feet on a hard, flat, level surface. Start with the second position.

Drill 1. Stand erect with your feet a natural hip width apart and with a small angle of flexion at the knee joint. Release any tension from your body and allow your feet to settle onto the surface of the floor. Do not consciously apply force with your feet. Tune in to the pressures in your feet and buttocks. Sway back and forth slightly using only ankle flexion. Find the point at which the weight feels even between your heels and balls of your feet. You should feel slightly more pressure under the ball of your big toe than under the balls of your other toes. This is normal. Look down at your knees. They should be aligned straight ahead.

Drill 2. Using only the ankle joint, press down on the balls of your feet until you feel most of the weight on under your heels. Do not go too far. This is the limit of the rearward movement of C0P. At this point you are on the verge of a backward fall. Look down at your knees. They should be aligned straight ahead.

Drill 3. Using only the ankle joint, release the pressure under the balls of your feet until you feel more of the weight on the balls of feet than your heel. Look down at your knees. They should be aligned straight ahead.

Drill 4. Using only the ankle joint, release more pressure under the balls of your feet until you feel the weight pressing down hard on the balls of your feet and your toes. Do not go too far. This is the limit of the forward movement of C0P. At this point you are on the verge of a forward fall. Look down at your knees. They should be aligned straight ahead.

FUNCTIONAL PRONATION MONOPEDAL DRILL

1. Start from position 2 above.

2. Move your Centre of Mass slowly towards whichever one of your feet you most comfortable and confident with.

3. As you move towards one foot allow your ankle and leg to relax and roll inward, towards the L-R centre of your body.

4. When you feel the pressure strongly under the ball of your foot move, allow the ankle to relax and your Centre of Mass to move forward into position 3 above. As this happens lift the other foot off the floor. You will feel a pronounced change in the tension of the gluteus muscles in same side as your support foot in your buttocks. If your foot is functionally pronated you will feel most of the pressure under the ball of your foot.

Congratulations. You have achieved functional pronation and a dynamically tensioned base of support. Now try putting insoles and arch supports under your foot and feet. Do the same drills and see what happens.

US PATENT 5,265,350 ON PRONATION

Here is what I said in my US patent (since expired) that I wrote in January 1991 and filed on February 3, 1991 about the existing philosophy in ski boots (aka – the prior art)

“The inventive technology disclosed by the present application, as will be described in more detail below, teaches the importance of accommodating and enhancing both bipedal and monopedal function by providing for freedom of medial movement of the inside ankle bone. This is in direct contrast with the prior art which teaches, in an indirect manner, that the ideal function for skiing will result from fixing the architecture of the foot in a position closely resembling that of bipedal function, thus preventing monopedal function. 

The prior art refers to the importance of a neutral sub-talar joint. The sub-talar joint is a joint with rotational capability which underlies and supports the ankle joint. The sub-talar joint is substantially “neutral” in bipedal function. That is to say that the foot is neither rolled inward or rolled outward.

If the foot can be substantially maintained in a neutral position with the arch supported and with a broad area of the inner aspect of the foot well padded, there will exist a good degree of comfort. Such a state of comfort exists because the foot is not able to roll inward (pronate) to a degree where significant mechanical forces can be set up which would allow it to bear against the inner surface of the boot shell. In effect, this means that initiation of the transition from a state of bipedal to a state of monopedal function, is prevented. This transition would normally be precipitated by an attempt to balance on one foot. If the foot is contained in a neutral position, traditional supportive footbeds (arch supports) are quite compatible with the mechanisms and philosophies of the prior art.

COMMENT: The objective of the conventional ski boot, whether intended or not, is to make skiing exceedingly difficult. Towards this end, the objective is comfort. A ski boot that renders the lower limbs dysfunctional can be very comfortable while at the same time making skiing exceptionally difficult. Although a priority, comfort in itself does not necessarily equate with good balance and control in skiing.

Problems arise when the foot is attempting a transition from a state of bipedal stance to monopedal stance. If the transition to monopedal stance or function can be completed without interference from the structures of the ski boot, all is fine and well. However, if the transition is allowed to proceed to a point where the mechanics associated with the monopedal function can establish significant horizontal forces, and the further movement of the foot is blocked before the transition can be completed, the skier will experience pain and discomfort at the points where the inner aspect of the foot bears against the structures of the footwear. This is the situation experienced by a majority of the skiers with prior art footwear. It is at this point where arch supports, if employed, also begin to cause discomfort. It should be noted that it is the normal tendency of the foot to pronate when weight bearing on one foot.

Footbeds (arch supports) may work in conventional boots (which traditionally do not allow natural biomechanics or movement of the foot to occur), but in a boot which accommodates and supports natural leg and foot articulation and function, arch supports can be detrimental.

When the foot attempts to pronate inside the ski boot, it is often the case that the ankle bone will come to bear against the inner surface of the boot shell. When contact of this nature occurs, pain and other related complications usually result. Since the consensus of those skilled in the art of ski boot design and modification is that pronation or the rolling inward of the foot is detrimental, and, thus, undesirable, provision is not made to allow for such movement. Rather, the structure of the footwear is intended to resist or even prevent it.

Thus, the problem with existing footwear arises due to the dynamic nature of the architecture of the foot. When the wearer is standing with the weight equally distributed between left and right feet so that the centre of mass of the wearer is manifesting itself in the centre between the feet, the architecture of the wearer’s foot assumes a specific configuration. As the wearer begins to shift his weight towards one foot so that the other foot bears proportionately less weight, the wearer’s centre of mass moves over the medial aspect of the weighted foot so as to assume a position of balance.

In order for this movement of the wearer’s centre of mass to occur, the architecture of the weighted foot must undergo a progressive re-alignment. Existing footwear does not adequately anticipate this re-alignment of the architecture of the foot and thus such footwear inhibits the wearer’s ability to assume a balanced position.”

While I am working on the video cited in my last post I will do a post next that describes how to assume a pronated position on one the foot and what it feels like.