Footbed posts

BOOT-FITTING 101: THE ESSENTIALS – SHELL FIT

In this post, I am going to discuss the process I follow to assess what I call the essential foot to shell clearances. This is a 2-step process.

Step 1 – Establish the clearances between the structures of the foot and the inner wall of the boot shell required for the foot to function.

Step 2 – Establish the physical connections between discrete restraint force transfer areas of the foot and the inner walls of the boot shell required for the effective force transfer to the ski, for containment of the foot required to support the processes of balance and for the coupling of the foot to specific mechanical references in the boot shell related to the running surface of the ski.

As a prelude to discussing shell fit, it is necessary to point out that a major shift is occuring in the area of focus on the human foot.

Until recently, most discussions on the human foot have focussed almost exclusively on the rearfoot; the ankle complex, the tibial-talar and sub-talar joints, ankle dorsiflexion and plantarflexion, ankle mobility, inversion, eversion, etc. This limited focus has been at the expense of an appreciation and understanding of the role of the forefoot and the complex lever mechanism that enables the first MTP joint to apply large forces to the ground. A study (1) published in 2004 commented:

The plantar aponeurosis (plantar fascia) is known to be a major contributor to arch support, but its role in transferring Achilles tendon loads to the forefoot remains poorly understood.

 Fascia is a sheet or band of fibrous tissue such as lies deep to the skin or invests muscles or various body organs.

The most plausible reason why the role of the  plantar aponeurosis in transferring Achilles tendon loads to the forefoot is poorly understood is that it has not been given much attention until recently.  

The above cited study concluded:

Plantar aponeurosis forces gradually increased during stance and peaked in late stance.

The almost exclusive focus of attention on the rearfoot has led to assumptions about the function of the foot as a system which are only now being called into question and found to be erroneous or invalid. One result is the erroneous assumption that the arch of the human foot is weak and collapses under the weight of the body. This has spawned a lucrative market for custom made arch supports intended to provide what is perceived as needed support for the arch of the foot.

In boot-fitting, the process of fascial tensioning, in which the height of the arch decreases and the forefoot splays, has been misinterpreted as an indication of a collapsing (implied failure) of the arch due to its inability to support the weight of the superincumbent body during skiing maneuvers. This has led to an almost universal perception and acceptance in skiing of custom arch supports as essential foundations for the foot and the most important part of a ski boot.

The Fascial Tension/SR Stance Connection

Plantar aponeurosis forces peak in late stance in the process of fascial tensioning where they act to maximally stiffen the foot in preparation for the application of propulsive force to the ground. When fascial tensioning of the plantar aponeurosis peaks, forward rotation of the shank is arrested by isometric contraction of the Achilles tendon. This is the shank angle associated with the SR Stance.

Immobilize – Support – Stabilize

Discussions of foot function in the context of the foot to shell clearances necessary for foot function and especially fascial tensioning, tend to be obscured by a consistent, persistent narrative in the ski industry spanning decades that the foot should be supported, stabilized and immobilized in a ski boot. Foot splay, associated with fascial arch tensioning, is viewed as a bad thing. Efforts are made to prevent foot splay with arch supports and custom formed liners in order to the fit the foot in the smallest possible boot size in the name of optimizing support.

In the new paradigm that exists today, the foot is increasingly viewed in the context of a deeply-rooted structure. In the design and fabrication of footwear, attention is now being directed to the accommodation of the  fascial architecture  and the importance of fascial tensioning as it pertains to the science of the human lever mechanism of the foot.

Fascial Tensioning and the Human Foot Lever

Fascial tensioning is critical to the stiffening of the foot for effective force transmission and to foot to core sequencing.

The body perceives impact forces that tend to disturb equilibrium as vibrations. It damps vibration by creating fascial tension in the arches of the foot and the lower limb. Supporting the structures of the foot, especially the arch, diminishes both the degree and speed of fascial tensioning to the detriment of the processes of balance and the ability to protect the tissues of the lower limbs through the process of damping of impact forces.

Dr. Emily Splichal has an excellent webinar on The Science of the Human Lever – Internal Fascial Architecture of the Foot as it pertains to foot to core sequencing – https://youtu.be/_35cQCoXp9U

The DIN Standard is Not a Foot Standard

A major problem for the human foot in a ski boot is the DIN standard toe shape. DIN stands for ‘Deutsches Institut für Normung’ which means ‘German Institute of Standardization’.

The DIN toe shape creates a standard interface for bindings. In a strong, healthy foot, the big toe or hallux should be aligned straight ahead on the center axis of the boot/ski. But as an interface for the human foot, the DIN standard toe shape of a ski boot is the equivalent of a round hole for a wedge-shaped peg.

The graphic below shows a photograph of a foot overlaid over a photograph of the ski boot for the same foot. The outline of the wall of the boot is shown in red. Even though the length of the boot shell is greater than the length of the foot, the big toe will be bent inward by the wall of the shell using the one finger space behind the heel shell length check.

screen-shot-2017-02-09-at-3-55-38-pm

The Importance of Foot Splay

The progressive fascial tensioning that occurs as CoM advances over the foot transforms foot into a rigid lever that enables the plantar foot to apply force the ground or to a structure underneath the plantar foot such as a ski or skate blade. Forefoot splay is important to the stiffening of the forefoot required for effective plantar to ground force transfer.

Ski boot performance is typically equated with shell last width. Performance boots are classified as narrow. Such boots typically have lasts ranging from 96 mm to 99 mm. Narrow boots are claimed to provide superior sensitivity and quick response, implying superior control of the ski.

The outside bone-to-bone width shown in the photo below is not quite 109 mm. The boot shell has been expanded. The 2 red arrows show the 5th and 1st toe joints (metatarsophalangeal joint or MTP joint). A prime hot spot in less than adequate shell width in the forefoot, is the 5th MTP joint. Even a minimal liner will narrow the boot shell width by 3 to 4 mm.

mt-width

Shell Check: Start Point 

I start with a skier standing in both boot shells with the insole in place from the liner then have them claw each foot forward in the shells using their toes until they can just feel the wall of the shell with the outside (medial) aspect of the big toe when they wiggle the toe up and down. If there is a finger space behind the heel, the shell is in the ball park.

A second check is made with the skier standing on one foot. Some allowance for the correct alignment of the big toe  can be made by grinding the inside of the shell where it is forcing the big toe inward. When fully weighted, a fascially tensioned forefoot will splay approximately 3 mm for a female and 5 mm for a male.  The ball shaped protrusion of the 5th MTP joint is typically almost directly below the toe buckle of a 4 – buckle boot.

Once a skier can stand on one foot in each shell with adequate space for normal foot splay, the rear foot can be checked for clearance. The usual sources of problems are the inside ankle bone (medial malleolus) and the navicular and/or the medial tarsal bone. A good way to locate the prime areas of contact is to apply a thick face cream or even toothpaste to the inside ankle bones then carefully insert the foot into the boot shell, stand on it to make contact with the shell, then carefully remove the foot. The cream will leave tell tale smears on the boot shell which can then be marked with a felt pen.

Getting Step 1 successfully completed can involve alternating back and forth between forefoot and rearfoot clearance. Until, both areas are right, full normal foot splay may not occur. Step 2 is done in conjunction with liner modifications which can be a process in itself and is often the most problematic aspect of creating an environment in a ski boot that accommodates and supports foot function especially fascial tensioning.


  1. Dynamic loading of the plantar aponeurosis in walking – Erdemir A1, Hamel AJ, Fauth AR, Piazza SJ, Sharkey NA  – J Bone Joint Surg Am. 2004 Mar;86-A(3):546-52.

FEATURE POSTS: US PATENT 5,265,350 ON PRONATION & PRONATION WHAT SHOULD IT FEEL LIKE?

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.

On February 9 and 10, 2014, I published complementary posts on the subject of pronation as it pertains to skier function and especially balance. The above excerpt is from US PATENT  5,265,350 ON PRONATION Feb 9, 2014. The entire post can be read at http://wp.me/p3vZhu-ey

The second post, PRONATION – WHAT SHOULD IT FEEL LIKE? was published on February 10, 2014. The entire post can be read at http://wp.me/p3vZhu-ey

 

GUEST POST: MICHAEL PUPKO

Since I started this blog with my first post on May 11, 2013, A Cinderella Story: The ‘Myth’ of the Perfect Fit,  (https://skimoves.me/2013/05/11/the-myth-of-th…ve-perfect-fit/), I have had a number of skiers contact me from various parts of the world, either through my blog via a comment (which I don’t post), through a social media site like FaceBook, Twitter or Linkedin, or through contact information provided by someone they know who knows me. One skier who contacted me privately is Michael Pupko. After he started following my blog, he started trying some of my ideas. Most important, he started giving me valuable feedback. Michael has developed some innovative concepts of his own. He started discussing them with me and asking for my feedback. Over the years I had considered some of his ideas. But never got around to trying them. Michael put them into practice and refined them. We have both learned a lot from our corroboration. He recently posted a large comment. With his permission, I am posting it as a guest post with my comments inserted.

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MICHAEL PUPKO

The physics of skiing are secondary to the ability to move within the ski boots. My only contact with David MacPhail has been through this blog and a limited amount of personal emails from which I can guarantee, I don’t have a complete grasp on his ‘alignment concepts’ of ski equipment but am 100% convinced of their validity because applying my limited understanding to what I have discovered myself over the past 20 years has changed what I do with equipment radically for the better. The latest discovery before being given the link to this blog (I can’t even take credit for finding it myself!) was to leave my boots unbuckled to the point where I hit the cuff just before my ankles range of motion is zeroed out so should I happen to need it, my binding would release before my ankle. Upon reading this blog I found someone who knew the why and methods of doing this properly, so I’m grateful to not have to reinvent the whole wheel, just try to build on it and make it better and above all, understand methods already proven by Podborski, etc.

Sometime around 2005 I ‘discovered’ a new method of adjusting footwear and orthotics that is better than any current method THAT I”M AWARE OF (which doesn’t mean there isn’t a better method). Finally after 1000s $ and many rejections I now have a patent on the method because I was finally able to convince the necessary parties that the vertical relationship of the heel to forefoot is different than the lateral (canting wedges) relationship. Since over 99% of humans that have access to fancy footwear walk anatomically incorrectly, the vertical relationship, called toe drop by some, remains a critical aspect of fitting not just ski boots but all footwear for me, guess what? I am now skiing without footbeds/orthotics for the first time in 2 decades with better results than with because what I learned from this blog enabled me to remove the original interference in the arch that was the limiting factor in not only my ski boots, but also other footwear.

In spite of a pile of fancy orthotic blanks and the equipment to create orthotics it will take a strong argument from any one to convince me to make them a pair because MacPhail’s methods are better than what I was doing. So obviously his methods is based upon a more solid ‘principle’ than my methods.

My theory on Ligety’s last season is so silly I never dared to mention it last year; I say it boiled down to his broken hand / wrist. When one is competing at any level, in any sport, anything that can cause one to hold back just a touch will change the standings dramatically.

COMMENT: I agree

We’ll see as the season progresses how far ‘back’ he is, obviously. Nothing could stop Ted though in Beaver Creek last season because his mental strength overcame whatever other issues seemed to be there last seasons. He ‘rose to the occasion!’ Bottom line is that Ligety and Shiffrin are both better aligned for their best disciplines than any other current racer and while they are dialled in them, either they don’t know or their equipment techs won’t allow them to transfer it over to the disciplines. Something we’ll never be able to prove now is that if Bode had MacPhail as his boot-fitter I feel he would have left Stenmark’s records in the dust. As dominant as Ligety has been in GS, he still has a little bit of catch-up when it comes to Stenmark who skied on brands of equipment that no other racer has won consistently on!

COMMENT: I agree

MacPhail’s theory that removing the inner liner of the ski boot keeps one’s feet warmer doesn’t make much sense. I did that and with an extra pair of liners in a pair of used boots I had bought and I’ve never gone back.

COMMENT: I think Michael means he tried his boots with minimal liner and found it works. Racers I worked with like Podborski, skied in shells with no liner except for the portion of the liner that was screwed in the shaft of the boot. They never had cold feet. This is not something I recommend without careful experimentation.

My boots are a joke, I laugh every time I go skiing because I have so much more fun. I challenge any critics to simply apply these ideas to your equipment and then if you want to argue fine. But I’d first ask for MacPhail’s help in what went wrong because my experience has been that my problems were in a mistake that I made.

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.

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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”.

 

 

 

TO SUPPORT OR NOT TO SUPPORT THE FOOT?

To support the foot or not support the foot? That is the question and the subject of this post.

Some followers of this blog are asking  whether they should use custom insoles, aka orthotics or footbeds, in their ski boots. My views on issues pertaining to the structures of ski boots and interventions in general that affect the physiologic function of the user are predicated on whether they accommodate and support the physiological processes of the user and especially whether the proponents of specific structures and interventions can support their positions with explanations predicated on sound principles of science and especially whether the explanations will withstand intense scrutiny. In addition, any explanations, conclusions or claims made should be based on the actual environment in which the use is occurring. Conclusions made in an indoor environment, or even in a controlled laboratory setting where gravity is the sole external force acting on the subject or subjects, cannot necessarily be applied to skiing maneuvers where the forces are both three-dimensional and dynamic in nature.

The question of whether the foot should be supported or not in skiing can only be answered by putting the issue under the high powered lens of the microscope of sound science.

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.