Ski boot modification posts


As a segue to my post on Turntable Power and how it cantilevers ground reaction force acting along the running surface of the inside edge of the outside ski, I have decided to post the discussion on the problems with existing ski boots from my US Patent 5,265,350 with associated international patents. The patent was issued on November 30, 1993 (24 years ago) to me as the sole inventor and assigned to MACPOD Enterprises Ltd. (Toronto).

The objective of US Patent 5,265,350 and subsequent patents filed and granted to MACPOD was to identify problems with existing ski boots and offer solutions and a functional criteria for advancing the state-of the art going forward. Some of the problems noted and solutions offered, apply to footwear in general.

The final paragraph raises the issue of the limitations of conventional ski boots in terms of accommodating and enabling biomechanically generated forces such as torque from the mechanical force transfer points of the foot to the structure of the ski boot.

The following material is verbatim from the text of US Patent 5,265,350.

Problems with Existing Ski Boots

Existing footwear (ski boot design) does not provide for the dynamic nature of the architecture of the foot by providing a fit system with dynamic and predictable qualities to substantially match those of the foot and lower leg. 

Although somewhat vaguely stated, a generally accepted theme has arisen over the years, one of indiscriminate envelopment and “overall restraint” applied to the foot and leg within the footwear. The stated position of various authorities skilled in the art of the design and fabrication of footwear for skiing is that the foot functions best when movement about its articulations is substantially prevented or restricted.

To serve this end, inner ski boot liners are usually formed around inanimate lasts or, alternatively, the foot and leg are inserted into an inner liner within the ski boot shell and foam is introduced into a bladder in the liner so as to totally occupy any free space between the foot and leg and the outer ski boot shell. The outer shell of the footwear is closed around this inner envelopment forming an encasement with which to secure and substantially immobilize the foot and leg. This is considered the optimum and, therefore, ideal form of envelopment. The perspective is that the physiologic structures of the foot are inherently weak and thus, unsuited for skiing. Enveloping the foot within an enclosure which makes it more rigid is thought to add the necessary strength with which to suitably adapt it for skiing. The reasoning being, that the foot and leg now having being suitably strengthened, can form a solid connection with the ski while the leg, now made more rigid, can better serve as a lever with which to apply edging force to the ski.

To some degree, the prior art (existing ski boot design) has acknowledged a need for the ankle joint to articulate in flexion. However, the prior art has not differentiated exactly how articulation of the ankle joint might be separated from the object of generalized and indiscriminate envelopment and thus made possible. Therefore, the theme of prior art (existing ski boot design) is inconsistent and lacks continuity.

The only disclosure known of a process wherein the separation of envelopment of the foot from articulation of the ankle joint is contained in U.S. Pat. No. 4,534,122, of which the present applicant is also the inventor. This material discloses a supportive structure (i.e Dorthotic) wherein restrictions to flexion of the ankle joint are essentially removed, support being provided from below the hinge of the ankle joint.

In keeping with the theme of indiscriminate envelopment and overall restraint, the following structures are generally common to all footwear for skiing disclosed by prior art (existing ski boot design):

(a) a continuous counter system which surrounds the foot and provides for the process of envelopment;

(b) an arrangement of pads or padding with which to envelope the foot;

(c) a substantially rigid outer shell which encases the structures employed for envelopment;

(d) an articulation of the ski boot lower outer shell and the cuff or cuffs which envelope the leg of the user, usually accomplished through a common axis or journal;

(e) a structure to brace and support the leg since prior art considers the ankle joint to be inherently weak and in need of support; and

(f) some form of resistance to movement of the cuff (shaft of the ski boot).

The prior art (existing boot design and boot fitting procedures) 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.

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.

A further problem with existing footwear is the fact that longitudinal relative movement between the foot and the footwear may occur. This happens, for example, when the forefoot/midfoot section of the foot is not adequately restrained under certain conditions, such as when flexion is occurring between the lower leg and the foot. Such longitudinal relative movement contributes to the disruption of biomechanical reference points associated with the dynamics of the ski and, in addition, results in a delay in the transmission of force between the leg and foot and the footwear.

Yet a further problem with existing footwear for skiing, in particular the rear entry type, relates to the obstruction of the leg in forward flexion. A relatively freely flexing gaiter or cuff (i.e. shaft) is necessary in order to permit the posterior muscle groups of the lower leg to modulate external force exerted on the footwear. This requires that the axis of the footwear be allowed to rotate so that small degrees of flexion/extension occur at the foot with the lower leg being relatively passive and that large degrees of flexion/extension occur as coordinated ankle, knee and hip flexion. The construction of the prior art requires flexion/extension to occur primarily at the knee and hip joints which is disadvantageous to the user.

While some types of rear entry boots do disclose gaiters or cuffs which provide a degree of relatively free flexion, there remains numerous problems, the most serious of which is the fact that the device employed to secure the foot of the user exerts, in addition to the downward directed force on the foot, a simultaneous rearward directed force on the leg which acts to resist forward flexion in spite of any free hinging action of the cuff. The result is an interference with the physiologic function of the foot and leg of the user.

Yet another problem resides in buckle or overlap type footwear. In order to provide for entry of the foot of the user and for resistance to flexion, plastic materials are employed for the outer shell which have flexural qualities. This is necessary in order to facilitate the aforementioned requirements. Plastic materials by their very nature tend to resist point loadings by a relaxation of the material at the point where stress is applied. This characteristic creates serious problems for two reasons. First, the teaching of this application is that force must be applied and maintained only to specific areas of the foot and leg of the user while allowing for unrestricted movement of other areas. The application and maintenance of such force by flexible plastic materials in the structures of prior art is necessarily difficult, if it is possible at all.

Second, the plastic materials in relaxing under the application of stress assume a new shape by moving into void areas. Thus, the probability is great that the plastic material will change shape so as to inhabit the very area required for the uninhibited displacement of the structures of the foot and leg. The result of these limitations is interference with the physiologic function of the user.

Top and rear entry footwear for skiing and skating necessarily have interior volumes greater than that required by the wearers foot and leg, particularly in the area over the instep, in order to accommodate entry. This additional volume makes the incorporation of structures designed to provide accurate and consistent support to specific areas necessarily difficult and ineffective. This results in reduced support for the foot and leg.

Another problem with conventional footwear relates to the flexion of the lower leg relative to the foot. It is desirable to provide a degree of resistance to such movement to assist in dampening movement of the mass of the skier relative to the ski resulting from, for example, a velocity change due to terrain changes and to assist the user in transferring energy to the ski. Adjustment of such resistance is desirable in order that the user may compensate for different physical makeup and different operating conditions. In present ski footwear, sources of resistance for such purpose are poorly controlled and often produce resistance curves inappropriate for the operating environment (i.e. temperature) thereby adversely affecting the balance and control of the user and creating a need for additional energy to be expended to provide correction. In many applications, resistance is achieved by deformation of shell structures thereby resulting in reduced support for the user’s foot and leg. If indeed provision is made for adjustment of flex resistance in the instances cited, it is very limited in terms of ability to suitably modify resistance curves.

Torque Transfer and The Turntable Effect

Yet a further problem relates to the efficient transfer of torque from the lower leg and foot to the footwear. When the leg is rotated inwardly relative to the foot by muscular effort, a torsional load is applied to the foot. Present footwear does not adequately provide support or surfaces on and against which the wearer can transfer biomechanically generated forces such as torque to the footwear. Alternatively, the footwear presents sources of resistance which interfere with the movements necessary to initiate such transfer. It is desirable to provide for appropriate movement and such sources of resistance in order to increase the efficiency of this torque transfer and, in so doing, enhance the turning response of the ski. 

In my next post, I will discuss Turntable Power in conjunction with the Over-Centre mechanism.


After my last post BOOT-FITTING 101: THE ESSENTIALS – SHELL FIT, I received an email from a Whistler skier asking a number of questions. I have copied and pasted the questions into the post below and inserted my answers

Whistler Skier: After reading your last two posts and going through all the information about boot fit, the tongue and where your shin should contact the boot/liner, I probably need  to punch the shells a bit wider in the ankle area of the navicular bone (it definitely needs more room when I go from bipedal to monopedal stance).

Answer: Make sure forefoot width is adequate first.

Whistler Skier: 

  • Do you want a full finger width between all parts of the shell and your foot?

Answer: No. Just behind the heel. A few mm clearance to 1st and 5th toe joints and inside ankle bones is usually sufficient if the liner is thin enough in those areas.

Whistler Skier: 

  • Should I just experiment with padding of different thicknesses over my forefoot to try and keep my foot in contact with the bottom of the boot?

Answer: TONGUE CHECK will be the subject of a future BOOT-FITTING 101: THE ESSENTIALS post.

Whistler Skier: 

  • When I put the boot on and lightly buckled, I can still ‘stand on my toes’, so:
    • Is that because my foot is not sitting in the heel pocket?

Answer: I suspect you aren’t standing in an SR Stance. If you were, you would not be able to stand on your toes.

Whistler Skier: 

  • I gather from your postings that I don’t want to add foam to the front ‘crook’ of my ankle to hold it in the heel pocket because it will impede the natural ankle movement on flexion?

Answer: Yes. It might not impede the natural ankle movement. But at the same time, L-pads do nothing useful if the foot is stiffened by fascial tension. It is the age old problem of what is easier to nail to a tree, liquid Jello or frozen Jello?

Whistler Skier: 

  • If so, how do I get my heel to stay in the heel pocket? (do I want it there?)

Answer: Wedge fit loading of the instep of the foot with forefoot portion of the boot tongue. The key is ensuring fascial tensioning can occur in the boot because it makes the foot behave as it were solid, not malleable. Conventional boot fitting strategies attempt to achieve this objective by encasing the foot with a form fitting medium. This has the exact opposite effect. It actually prevents fascial tensioning.

Whistler Skier: 

  • Should I hold off on punching the ankle area?

Answer: For the time being. If it is close, skiing will confirm whether or not the space is adequate.

Whistler Skier: 

  • i.e., Is the space already large enough?

Answer:  I don’t know. See above.

Whistler Skier: 

  • Is it the cuff of the boot that provides control in conjunction with the sole of the foot?  My shin seems to contact the front cuff of the boot right about where your diagrams indicate it should and there is no pressure further down the cuff.

Answer: Sounds good.

The key that has literally been under everyone’s feet for decades, while they threw out nonsensical theories on skier balance, is what I call Ground Control. Given the correct sequencing of events, fascial tensioning in combination with pronation of the outside foot in a turn, enable pelvic rotation of the femur to extend the ground (snow) under the inside edge of the outside ski up under the base of the ski.

The mechanics of Ground Control has the effect of bringing the ground (snow) up under the entire ski base and foot thus allowing a skier to actually balance on the outside ski as if they were standing with their outside foot in full contact with solid ground (snow). This was my hypothesis that the Birdcage experiments confirmed in 1991.



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 –

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.


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.


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.


What if you used your hands like you used your feet?

Bind your hands with tape and then try typing. Instead of using the muscles and joints of the fingers (intrinsic), you’d peck at the keyboard using excessive motion of the wrists (and extrinsic musculature), leading to intrinsic muscle atrophy and extrinsic muscle (and related joint) overuse. – Katy Bowman, Nutritious Movement FaceBook Group, April 20, 2016 and author of Whole Body Barefoot: Transitioning Well to Minimal Footwear

Bowman wasn’t talking about what happens when you put your foot in tightly-fitting ski boots. She was only talking about what happens to most people’s feet in their everyday shoes. Binding your feet in tightly-fitting ski boots is infinitely worse in terms of making it impossible to effectively use all the muscles in your legs to coordinate balance and initiate precise movement. But in fact, this is the whole idea behind the ski boot. The holy grail in skiing is the fit of a ski boot that perfectly mirrors the shape of the foot and lower leg. In other words, the objective is to render the human foot completely dysfunctional.

“The bootmaker, ignorant of the relative use and importance of the different parts of the foot, has steadily persisted for centuries, and at this day usually persists, in so shaping the shoe that the great toe is forced upon the other toes more or less out of its right line with the heel. (1)

“The Problems in Existing Ski Boots

Existing ski boots do not provide for the dynamic nature of the architecture of the foot by providing a fit system with dynamic and predictable qualities to substantially match those of the foot and lower leg. Thus, the problem with existing ski boots arises due to the dynamic nature of the architecture of the foot”. (2)

One hundred and thirty years after the article was published in the Scientific American, not much has changed. But it gets worse.

“The foot may have been distorted by wearing improperly made shoes, and the person may have become accustomed to the bad-shaped shoe.” (2)

“The less a shoe does to a foot, the better for the foot. A shoe should stay out of the foot’s way. In it’s most elemental form, shoe has only two functions; as a non-intrusive protective foot covering and as an ornamental dressing. The moment a shoe assumes a therapeutic function for the average foot, the foot is in trouble. (3)

“The worst thing shoes do, according to Bowman, Rossi and others? Tilt the whole body forward by elevating the heel so it is higher than the forefoot. In ski boots, I call this the Net Ramp Angle.

Last ski season, I learned more about skiing than in all the years since I started down this road in 1973. Prior to last season, I knew that a Net Ramp Angle of more than about 3 degrees had an adverse effect on stance, associated balance, ski control and especially the ability to move with precision. But I had no idea just how critical ramp angle is until I reduced the ramp angle of the boot boards in my own ski boots from 3.0 degrees to 2.5 (my bindings are zero ramp). Then the whole world changed. In working with other skiers and racers I found that they were sensitive to changes of one tenth of a degree.

Jessi Stensland, a high performance athlete, talks about how shoes affected her performance and served as the inspiration for FOOT FREEX in a the video in the following link –!about/c1nx6

After working with Whistler Ski Pro Matt since skiing started last fall it is only in the past few days that Matt’s feet were finally set free and after thousands of hours on skis, he finally knows, for the first time, what it is like to truly ski. Mat’s problem was not a lack of fitness and/or athletic ability. Matt’s problem is his large boned feet that cannot function in a ski boot without extensive modifications. I will explain, in graphic detail, what had to be done to Matt’s boots in my next post.


2. US Patent 5,265,350 1992 – MACPHAIL, November 30, 1993

3. Footwear: The Primary Cause of Foot Disorders – Willam A. Rossi – “!references/c19n”>!references/c19n



After the initial slope test on November 11, 2015, Matt was convinced of the merits of the extreme modifications made to the liner of his left boot when he compared his skiing performance to his right foot in the boot shell fit with the stock liner and his custom footbed.

The next step in the step-by-step process was to modify the liner for Matt’s right boot shell so it had the same configuration as the liner in his left boot. With the right boot now the reference boot, I took Matt’s left boot to the next level. It is important that the skier or racer I am working with confirms every change as positive or negative and any corrections made prior to moving to the next step. For this reason, I make a change to one boot then use that boot as a reference for changes to the other boot.

One of the first tweaks I made to Matt’s left boot was to remove the padding from the outside of the liner so that there was no padding in either side. The graphic below shows the shape of the foam pad that was inside the inner or medial section of the liner for his left boot. The stitches were cut to gain  access to the pad. Once the pad is removed, the liner is restitched. Although it can be restitched by hand with a heavy needle and thread, a shoemaker can perform a more robust repair.

Pad Shape

Here is the pad that was surgically removed .

Ankle pad

The next tweak I made was to remove the portion of the padding in the in the bend of the left tongue where it turns upward from the instep to the shin. I discussed this issue in my post, TONGUE TIED. With the tongue disconnected from the liner, it is less likely to obstruct the glide path of the ankle in dorsiflexion as the shank moves forward. But I like to ensure that the center of pressure stays at the top of the tongue/shaft where forward movement of the shank can be controlled by the power strap to limit movement of the shank within the shaft of the boot to about 10 to 12 degrees of ankle flexion. Removing the padding in the area of the transition is not difficult. But care should be exercised to avoid knicking and especially cutting into, the plastic tongue body. I cut the stitches on one side, pull the skin back, cut the tongue pad foam with a box cutter and yank the foam out with needle nose pliers. If necessary, any rough edges can be trimmed with sharp scissors. It helps if you have 3 hands to perform this operation.


After the tweaks were made, Matt went back to the ski hill for more testing. Two issues came up that I have underlined in Matt’s text below.

06/12/2015 14:44

MATT: Notes from today;

-Left boot feels better and no more pressure band.

Both left and right boots, is there a way I can decrease or prevent the tongue from slipping. The top of the tongue will end up out of line after a few runs.

I’m very keen to rivet and connect the cuff of the liner to the cuff of the boot as the liner cuff too will experience rotation throughout the day

Skiing felt pretty strong today. I’m getting more and more aware of the front of my foot and getting a lot of data from the snow.

ME: Tongue issue. With your boots on and buckled to the normal tension, grasp the top of the tongue in one boot and see how easily you can pull it up part, way out of the shaft. If there is not much resistance, the instep portion is not applying enough load to your instep. Another possible issue is not quite enough forward lean. I should have some time tomorrow to remove the padding in your other liner and rivet the liners to the shell.

MATT: Excellent. I’ll connect with you tomorrow then! All in all I love the boots.

06/12/2015 18:07

MATT: Can I cut out the padding on the right foot (outside padding)? So I can have it even for tomorrow?

ME: Sure. You have to peel it away from the skin of the liner then get your hand inside and grab the pad where it attaches behind the Achilles.

MATT: Will I mess up or can I handle this task? I’ll wait it you think I should

ME: Experience helps. But you can probably manage. The trick is to make sure peel pad completely off the liner skin then bunch the pad up, get a firm grip on it and pull on it as close to the rear aspect as possible. Get as much out as you can. I’ll check it tomorrow. Don’t try to rip until you can get a good grip.

Mission accomplished.

With padding removed from the sides of both liners, it usually becomes obvious where the most important area of constraint is lacking; the area between the instep of the foot and the underside of the shell. In the late 1980’s, a husband/wife team of radiologists took some X-rays of the feet of skiers in boots tightly buckled. The X-rays, called Seriograms showed, as much as 2 to 3 cm of free or ‘crash space’ between the top of the boot tongue and the inside of the boot shell that the foot could move upward into.  You don’t want to put high pressure on the instep of the foot. But for reasons I will explain in a future post, the foot needs to be dampened against vertical movement caused by perturbations in GRF from undulating terrain that can cause load/unload cycling that perturbs balance and places stress on the knee.

The graphic below on the left shows the top of the left tongue from Matt’s boot. The graphic on the right shows the same tongue with a shim pad outlined in grey.  A template is made to the approximate shape of the grey area. Then a shim pad is cut from a piece of dense foam about 2 – 3 mm thick. The stitching is cut on the outside of the tongue and the pad inserted between the top of the tongue foam and the plastic outer skin of the tongue. A good source of foam for this purpose is a thin insole from a running shoe.

shim pad

The photo below shows some good sources of suitable padding. It is better to start with a thing layer (2-3 mm) then add a second layer if on snow testing finds the fit still lacking.


Since Matt literally lives in his boots 11 months of the year, he wanted the liners positively connected to the shells. This is easy to do with T-nuts. But the locations need to be carefully chosen so as to avoid causing issues with the foot leg especially when putting on the boots. I placed the fixations on either side of the tongue in a seam in the liners. I got Matt to locate the liners in the shells where he wanted them. Then I clamped the liners to the shells, drilled holes through the shell and liner, inserted T-nuts into the liners facing the shell and inserted screws into the T-nuts from the outside of the shell.

As usual, I did the left boot first so that Matt could use it as a reference to compare to the right boot with the unsecured liner.

The rule of thumb is that if you do something, have a process in place to make sure it works. Only the skiers and racers I work with can make that call. I am only the mechanic.

Liner screws 2-5-16

In my next post, I will provide photos and plans for a Stance Ramp and describe how it works in stance training.


With the shell work completed, Matt’s modified shells appeared to have adequate width in the forefoot and functional clearance for the joints of his ankle/foot complex as did the modified liner for his left foot. But whether the left boot was better than any of Matt’s previous boots, could only be determined during actual ski maneuvers. The dynamic physical environment of skiing with constantly changing forces that can go as high as 3 Gs for recreational skiers, cannot be duplicated in an indoor setting or even in a gait/balance laboratory. In the initial slope tests, Matt compared his left boot shell fit with the modified liner to his right boot shell fit with the unmodified, stock  liner

If CARV were available, it would have been invaluable to help Matt assess his left and right boots and guide him in developing a sound technique. CARV would have also enabled baseline data to be obtained from Matt’s previous boots that could be compared to data derived from his new boots. But since CARV technology is not available until the end of the year, slope testing had to rely on Matt’s perception.

One question that many ask is “what about custom insoles?” The only way to tell is to test them against a reference standard that is the same for everyone, preferably using a system that acquires real time data on the pressures, forces and ski pitch, yaw and roll. In the initial tests, Matt used a stock insole that had been pressed flat in his left boot and the custom insole, made for his previous boots, in his right boot. Once both boots have been modified and Matt has adapted to them, he can try replacing the flat insoles with the custom insoles. I recommend making changes in one boot at a time so the other boot can be used as a reference. This was the protocol used in testing Matt’s boots.

As part of the process, Matt is undergoing kinaesthetic stance training to learn how to tension the arches in his feet and stabilize his pelvis from the balls of his feet up, from the shoulders down and in the abdominal core. The foundation of a strong stance is what I call the Resistive Shank Angle. I will discuss this in a separate post.

18/11/2015 12:30


ME: Please try and capture the initial feelings of your left and right ski boots as soon as you start moving on snow by making slow turns in both directions. Focus on the feeling in the soles of your feet and those in your legs and pelvis. I suggest you either use your phone to record them or take notes as soon as possible. Any initial perceived dffferences may either diminish or increase. So you need to capture them as they happen.

MATT: I will put notes into my phone on each chairlift ride. Looking for feelings in my feet and muscles firing off in my legs, glutes or other. I’ll message you and see what you’re up to at some point.


Matt is on the hill sending me reports on his phone.

19/11/2015 09:48

MATT: I’m warmed up and ready to head and line up for the gondola. Looking forward to some skiing!

MATT: First run…. Terrible! Left foot feels way better. Right feels squashed and like a brick.

ME: Try doing some slow turns on flat terrain while focussing on the feel in your feet. Try making turns while keeping pressure on an imaginary  toonie disk under the ball of your outside foot. Steer the turn radius with the toonie disk.

MATT: It’s ridiculous, my left foot I can feel the entire skis and I’m making cleaner turns every single time. My disconnected right foot is being blocked on top where you’ve removed material on the left equivalent. I can feel the ground on my left foot. Right one (foot) is bad.

As good as the left one feels, the right one still interrupts to good turn as I can feel what it’s doing/ not doing. Can you make the right one as correct as the left?

ME: Of course.

MATT: The difference is unexplainable. The footbed is sh*t too. Stops me getting any forefoot loading. No room for the ankle and the forefoot is being crushed by the liner.  I’ll head down sooner than later. Having a tight supported foot is so stupid if you want to feel anything.

I was expecting some good surprises and changes in the left foot but never thought it would be so dramatic.

In my next posts, I will discuss modifications to Matt’s right boot, tweaks made to the left boot and kinaesthetic stance training.



When a skier or racer changes ski boots, they often change everything. If they had a custom insole or orthotic in their old boot, they may use it in their new boot. But that may be the only thing that is the same. The problem with changing everything is that there is no reference with which to assess whether the new boot enables the same level of skier function as the old boots, let alone determine whether it is better or worse. The underlying assumption seems to be that newer is always better. But when it comes to a promising career of a talented racer, new can sometimes be career ending.

In Matt’s case,  the reason he was changing boots is that he had concluded that his present boots weren’t allowing him to ski the way he was trying to. Setting up his new boots will follow a methodical, step-by-step process; one that will allow Matt to assess the effects of each component and modification. Without such a process, it is virtually impossible to assess the effects on skier performance of any aspect of the boot. The rule is to assume nothing until a benefit has been proven.


Here is the sequence I follow.

  1. Ensure Boot Board is to Specification
  2. Create Functional Space for the Foot and Leg in the Boot System
  3. Position the Foot in the Boot
  4. Adjust Shaft Side Cant and Forward Lean to Support a Functional Stance.
  5. Load Specific Aspects of the Foot and Leg within the Structures of the Boot

Boot Board Ramp Shape and Angle

Boot board ramp angle can have a significant impact on stance and skier/racer function. Yet, it is rare for a skier or racer to know the shape and ramp angle of the boot board in their old boot and take steps to ensure that the specification of the boot board in the new boot is the same let alone optimal.  The standard I use is a boot board that is monoplanar and parallel with the transverse aspect of the sole of the boot with a positive ramp angle of approximately 2.7 degrees. For boot/ski continuity, my preference, is zero ramp angle in the ski binding system.

The boot board in the photo below is not flat. In addition, the ramp angle is 4 degrees. So the first step is to grind it flat and reduce the ramp angle to 2.7 degrees.

The stock Head insole is also not flat. I always start with a flat insole. So the stock insole is heated and flattened in a press. Even when flat, it usually still requires trimming and adjustment based on skier input.

Head Boot Boards


With the boot boards to specification and the shells expanded to create sufficient functional space for Matt’s foot, the next step in the process is liner modifications. A number of issues are flagged in the photos below.

Matt 1

When Matt tried the liners on he found that them very constricting. The first thing I did was remove the panel on the instep that holds the sides or ‘quarters’ of the liner together. With Matt’s foot in the liner, it became obvious that the tongue was attached too far rearward. It was pressing in the glide path of his ankle and not even in contact with his shin in the upper area of the tongue. So the next step was a tongue-ectomy or surgical tongue removal with a sharp Exacto knife. Skiers/racers I have worked with have consistently found significant benefits to having the tongue free floating as opposed to fixed to the liner.

In order for Matt to assess the effects of every modification, I started by modifying one liner. In Matt’s case, I modified the left liner. Matt would ski with one modified and one unmodified liner until it was clear which one was better.

Here is what the stock right liner looked like.


The kind of modification needed at times is not the faint-hearted. But Matt assured me he was “all in” as in “whatever it takes”.

Here is the left liner after removal of the tongue and the toe portion of the liner. After the tongue was removed, the ends of Matt’s toes were still all crunched so that he could not fully weight his foot. This necessitated removal of the toe portion of the liner.


Since clearance on the inner or medial side of Matt’s foot required major shell expansion all padding within the liner was removed on that side only. This was done by cutting the stitching and then grabbing the padding firmly and ripping it out. Later, the same thing was done to the other side of the liner.


As a final modification, the portion of the rubber-like base that turned up along the inner or longitudinal arch was trimmed away.

Arch line

Matt was good to go for a test flight. Some are probably thinking that with toes of the liner removed, Matt’s feet would freeze. Only Matt can answer that question. So I’ll let him respond to that issue in my next post.