Footbed posts

IS ‘SUBTALAR NEUTRAL’ SKIINGS’ HOUSE OF CARDS?

If you purchased custom footbeds for your ski boots or had your ski boots custom fit you may have been told that your foot was placed in subtalar neutral and that this created the strongest position of the bones of the foot and leg for skiing. Neutral in this context refers to a neutral configuration of the subtalar joint of the ankle/foot complex.

As best I can recall, the term subtalar neutral began to emerge in the ski industry about 1978. The authoritarian manner in which it was presented and promoted suggested that it was science-based and supported with evidence that conclusively demonstrated superior performance. But I never saw or heard any explanation as to how subtalar neutral could create the strongest position for skiing of the bones of the foot and leg and I have still not seen such an explanation.

Back in 1978, I didn’t even know what the subtalar joint was. I couldn’t envision how the bones of the foot and leg could be maintained in a specific configuration while foam was injected into a liner around the foot and leg or through some other custom fit system. But in spite of the lack of even a theory to support the premise of subtalar neutral as creating ideal biomechanical alignment of the bones of the foot and leg for skiing the premise seemed to be readily accepted as fact and quickly became mainstream. By the time The Shoe in Sport (which questioned the principles on which the plastic ski boot is based) was published in 1989 (1987 in German), neutral subtalar was firmly entrenched in the narrative of skiing.

In my US Patent 4,534,122 (filed on December 1, 2013) for a dorsal support system that I called the Dorthotic, I had unkowingly tried to fix the subtalar joint in a static position as evidenced by the excerpt below from the patent:

The system of the invention applies significant pressure to the dorsal (upper) surface of the foot over the instep, including the medial and lateral aspects thereof, and hence to the bones of the mid-foot to substantially prevent these bones from moving relative to each other.

Note: The prior art refers to the current paradigm in existence.

The objective of the dorsal support system was to immobilize the joints of the bones below the ankle in conjunction with the joints of the bones of the midfoot while allowing unrestricted dorsi-plantarflexion of the ankle joint within it’s normal range of motion. But the significant medial (inner) pressure applied by the  system to the bones of Podborski’s foot below his ankle made it difficult for him to stand and balance on one foot with the system in a ski boot shell even on the concrete floor of my workshop. Removing the offending structure from the dorsal support system quickly resolved the issue by allowing his foot to pronate. This made me aware that structures that impede supination did not appear to create issues. This insight raised the possibility of a fit system based on selective constraint applied to specific aspects of the foot and leg as opposed to what I termed indiscriminate (general) constraint.

Even though at the time that I wrote my US Patent No, 5,265,350 in February of 1992 I still did not comprehend the mechanism behind the claimed superior performance associated subtalar neutral, I knew enough to know that attempting to fix the subtalar joint in any configuration in a ski boot would interfere with, or even prevent, a skier from balancing on one foot.

Here is what I said in the patent:

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 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 (balance on one foot on the outside ski).

I later discovered that the above statement came close to the truth.

I also discussed the issue of subtalar neutral in my post NO NEUTRAL GROUND (2.) published on September 1, 2014. But I did not learn about the origins of subtatar neutral and especially the intense controversy surrounding it in professional circles until recently when I came across a discussion on Root and his subtalar neutral theory in an online podiatry forum.

The Origin of Subtalar Neutral

Merton’s Root’s subtalar joint neutral theory was first described in the textbooks, Biomechanical Examination of the Foot, Volume 1. – 1971 (Root, Orien, Weed and Hughes) and Normal and Abnormal Function of the Foot – 1977 (Root, Orien, Weed). The basic premise of Root’s subtalar neutral theory is that a neutral position of the subtalar joint (which Root defined as existing when the foot was neither supinated or pronated), is the ideal position of function in static (two-footed bipedal, erect) stance and in gait where the subtalar neutral theory posited that the foot was pronated in the first half of the stance phase then transitioned through neutral in mid stance to become supinated in the latter half of the stance phase.

Root’s paradigm proposes that the human foot functions ideally around the subtalar joint’s neutral position and that deviations from this ideal position are deformities.

What Root really said

Root and his associates never stated that the joints of the foot should be immobilized in subtalar neutral. The reference to static in subtalar neutral as the ideal position of function in static stance pertained to a subject standing in place in an erect bipedal stance on a flat, level, stable surface with the weight apportioned between the two feet. In this static stance the Root subtalar neutral theory posited that the subtalar joint should rest in neutral. Root and his associates never stated, implied or suggested that the joints of the foot should be configured and immobilized in subtalar neutral. Further, Root and his associates made no reference, of which I am aware, to the application of subtalar neutral to activities other than static stance and gait. Critrics have asserted that a subtalar neutral position in static stance is neither normal or ideal. In defining subtalar joint neutral as normal, Root’s theory implied the existence of abnormal pathologies in the feet of the majority of the world’s population.

The lack of evidence

Critics of Root and his associates “Eight Biophysical Criteria for Normalcy” claim the criteria was nothing more than hunches, that these conjectures were accepted as fact, when, in reality, there was no experimental data or research to support them and that the eight criteria were neither normal or ideal.

 The STJ neutral position problem

One of the early critics of Root and his associates was Kevin Kirby, DPM. He is an Adjunct Associate Professor within the Department of Applied Biomechanics at the California School of Podiatric Medicine at Samuel Merritt College in Oakland, Ca.

Kirby observed a large error range in determining STJ neutral position on the same foot from one examiner to another. In unpublished studies done during his Biomechanics Fellowship at the California College of Podiatric Medicine, Kirby found that the Biomechanics Professors were +/- 2 degrees (a 4 degree spread) and the podiatry students were +/- 5 degrees (a 10 degree spread)  in determining STJ neutral position.

Subtalar neutral appears to be what amounts to a knife edge between pronation and supination where neutral is the border or transition point between the two states. Unless the subtalar neutral position can be precisely and consistently identified, it is impossible to know whether the subtalar joint is pronated or supinated.

The future of subtalar neutral in skiing

Too many times theories of how the human foot functions and therefore how mechanically inducted foot problems are treated have been presented as if they were facts. The dogmatic adherence that sometimes ensues from such an approach has frequently stifled the evolution of foot mechanics. This has been particularly apparent in the field of podiatry which has been dominated by the Root paradigm. (4.)

The long standing controversy and growing challenges mounted against the credibily of Root’s subtalar neutral theory has significant implications for the continued promotion of subtalar neutral in skiing as providing the strongest position of the bones of the foot and leg.

It may eventually be shown to be unfortunate that Root’s influential textbooks were published at a time when the ski industry was attempting to come to terms with the skier/boot interface issues associated with the new paradigm created by the rigid shell plastic ski boot.

In my next post, I will discuss what a ski boot should do for the user or perhaps, more a case of what a ski boot shouldn’t do.


  1. Root ML, Orien WP, Weed JH, RJ Hughes: Biomechanical Examination of the Foot, Volume 1. Clinical Biomechanics Corporation, Los Angeles, 1971
  2. https://wp.me/p3vZhu-Bv
  3. Are Root Biomechanics Dying: Podiatry Today, March 27, 2009
  4. Foot biomechanics- emerging paradigms: Stephen F Albert, 4th Congress of the International Foot and Ankle Biomechanics (i-FAB) Community Busan, Korea. 8-11 April 2014

 

SKI BOOT ASSESSMENT PROTOCOL

Step 1 of the synergy 5 Step performance Program described in my last post is a Footbed Check using the Novel Pedar insole pressure analysis system.

Step 3 of the program is the Ski Boot Assessment detailed below. As with the 5 Step performance Program, the Ski Boot Assessment protocol and report were intended to serve as a template to base future programs on. The assessment report was intended to provide clients with information on the effects of their ski boots on their performance and/or as a work order for them to take to a boot-fitter to have any necessary issues identified in the report addressed.  Synergy Sports Performance Consultants Ltd. did not sell products or perform boot modifications.

 



My next post will be called FOOTBEDS: THE GOOD, BAD AND THE UGLY.

 

 

 

 

A FIVE STEP SKIER PERFORMANCE PROGRAM

Almost 40 years ago to the day, the head of the Whistler Pro Patrol, whose boots I had worked on, introduced me to Nancy Greene in the Roundhouse restaurant on top of Whistler Mountain. The rest is, as they say, history. Nancy asked me if I would work on her ski boots. She was so impressed by the results of my work that she approached the National Ski Team to make arrangements for me to work with some of Canada’s best racers.

Recently, while going through some archived files, I found copies of Nancy’s communication with the Program Director of the National Ski Team, Andrzej Kozbial. When Nancy approached me about working with our National Team, I stressed to her that I did not see any potential arrangement with the team as a job opportunity but instead as a vehicle where I could gain further experience and knowledge while providing a crucial service to the team and furthering the sport of skiing.

The graphic below is an excerpt copied from Nancy’s first letter of April 26, 1978 to the National Ski Team Program Director.

At the time that I wrote my US Patent 5,265,350 in early 1992, the intent and purpose of the detailed and lengthy specification was to provide a repository of the knowledge I had acquired to date to serve as a legacy for skiers and skiing to help advance the sport. While this information was in support of the inventions disclosed in the patent, the majority of the information was not subject to protection under the terms of the patent. The information was open access to the world. This was my intent.

In spring of 2000, I formed a company with 2 partners for the 2000-2001 ski season called Synergy Sports Performance Consultants Ltd. The objective of the venture was to gain further experience and knowledge and create a model that could be used as a template for future skier performance programs.

The following series of graphics are from Power Point presentations synergy made to ski schools.

The following graphic is the poster that described the synergy 5 Step Performance Program.

5 Step Performance Program description

The synergy Analysis Program looks at how your body interfaces with your ski equipment; primarily your footbeds and boots because this is the connection to your equipment and through it to the snow.

Synergy offers the program as a package made up of 5 components. They can either be taken as the complete package [recommended], several components or steps at once, or one component at time. Synergy recommends that you begin at step 1 and follow the sequence in numerical order. But the order can be arranged however you wish to suit your needs. The choice is yours.

1.Biomechanical Assessment

Good foot function is the key to control. That’s why the first thing we thing we assess is your biomechanical function. What that means is that we look at how well your foot and lower limb works. The examination is done by a podiatrist who looks at how your foot functions and how the lower limbs all connect.  Then we see how effectively your feet interface with the ground by putting you on insoles that read the pressures under your feet. We coach you through some balance movements while we watch how your foot functions while our computer records the results

2. Footbed Assessment

Footbeds can have a positive, neutral or negative effect on the function of your feet.

That’s why the next thing we check is how your foot interfaces with your footbed or orthotic.  We make sure that it allows your foot to function as well as it should without one.  And if your foot needs some assistance for optimal function we make sure the footbed is helping your foot do what it needs to do.

3. Ski Boot Assessment

Now that your foot is functioning optimally we make sure your ski boot lets it keep functioning. We conduct a thorough examination of your boot and provide you with a report that tells you how your boot is affecting your performance. Most important, we tell you what has to be done to fix the problem.

4. Kinesthetic Training

Skiing is about making the right moves. Kinesthetic Training is next. It teaches you how to tell when your body is making those moves. What is Kinesthetic Training? In simple terms it means to train your body to associate a feeling or sense with the right movements made at the right time. It is feeling and bringing about an awareness so you know when you are doing it right because we have taken you there and you have felt it. A picture may be worth a thousand words, but in skiing a feeling is worth a thousand pictures. We bring you to understand what you should feel in your foot at the start of the turn and then what it feels like to settle and balance onto the foot that drives the ski. By acquiring this sense you become more aware of how to allow your foot to transfer energy directly to the edge of the ski by using the body the way it was designed to be used. Remember, your body was not made to be a lever.

5. On-Hill Data Collection

This is where everything comes together. We move to the ski hill for this part of the package. We meet up top on Whistler or Blackcomb Mountain. We put our pressure insoles in your ski boots.  A pair of cables from the insoles goes up your ski pants where it connects to the data box [a kind of mini computer] we attached to your waistband.  Then we go out for a run on moderate, groomed terrain.  We record data in three takes in medium radius turns at a speed you are most comfortable with. While this is happening we videotape your skiing. Then we head into the lodge and synchronize the video with your foot pressure data. When this is done we watch your foot function in your boots on the computer screen on one side while we study your ski video on the other side of the screen. This way we confirm that your foot is functioning optimally as confirmed by analyzing your movement patterns and the timing of your skills.

My next post will be on the synergy Boot Assessment program.

 

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

ERROR IN LAST POST ON EVERSION

In my last post, I erroneously stated that the sole turns inward, towards the center of the body, in eversion. I meant to state that the sole turns outward, away from the center of the body, in eversion.

I have revised the paragraph in my post so it reads correctly.

In order for the torso and Center of Mass to stack vertically over the ball of the foot, the sole of the foot must turn outward, away from the center the the body. This is called eversion. It is enabled by the joint that lies below the ankle called the sub-talar joint. The sub-talar joint is tied to the tibia where it acts as a torque converter. When the foot everts or inverts, the sub-talar joint translates this on an approximately 1:1 ratio into internal or external vertical axial rotation of the leg.

I apologize for any confusion this may have caused.

OUTSIDE SKI BALANCE BASICS: STEP-BY-STEP

In view of the positive response to my recent posts and comments I have received, I have decided to take a step-by-step approach to explaining the mechanics and biomechanics of balance on the outside ski.

I am going to start the process by comparing balance on one foot to balance on two feet. I refer to balance on one foot as monopedal stance (one foot) and balance on two feet as bipedal stance (two foot). The graphics are for illustrating general principles only.

The graphic below shows monopedal stance on the left and bipedal stance on the right. Orange hash marks delineate the alignment of major body segments. Black reference lines on the right leg of both figures show the angle of the leg in relation to the ground.

In order to transition from a balanced position in bipedal stance to a balanced position in monopedal stance, either the foot must move towards the L-R center of the torso or the torso must move towards the foot that will become the stance foot, or a combination of the 2 movements must occur. The central issue is the amount of inertia acting on the torso. In skiing, due to the degree of inertia, the new outside foot of a turn is normally guided into position under the torso as the skier or racer approaches the fall line in the top of a turn.

Moving the foot into position under the Centre of Mass so it stacks in line with the ball of the foot usually takes an inward movement (adduction) of the leg from the pelvis of 6 to 7 degrees. In the upper left figure in monopedal stance, the leg is adducted 6.5 degrees and has formed a varus or outward leaning angle with the ground.

If the leg only adducted, then the sole of the foot would end up at an angle of 6.5 degrees with the ground and the figure would end up on the outer edge of the foot; on the little toe side. In order for the torso and Center of Mass to stack vertically over the ball of the foot, the sole of the foot must turn outward, away from the center the the body. This is called eversion. It is enabled by the joint that lies below the ankle called the sub-talar joint. The sub-talar joint is tied to the tibia where it acts as a torque converter. When the foot everts or inverts, the sub-talar joint translates this on an approximately 1:1 ratio into internal or external vertical axial rotation of the leg.

When the foot everts, the subtalar joint rotates the vertical axis of the leg towards the center of the body an equivalent amount; in the subject case, 6.5 degrees.

The combination of eversion/internal vertical axial rotation of the leg is called pronation. If either of these actions is interfered with, or worse, prevented, it is impossible to create the alignment necessary to stack the torso and Center of Mass over the ball of the support foot.

The consistently stated objective of footbeds is either to limit or even prevent pronation. Put another way, the whole idea of footbeds is to make it difficult or even impossible to balance on the outside foot and ski.

If this issue is not crystal clear, please post comments as to what is needed.

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.