Ski boot modification posts

SHOE/LINER HACKS

There is no point in continuing my discussion of the mechanics of balance on the outside ski because the odds are great that ski boots are preventing most skiers from engaging the mechanics required to apply the torsional forces to a ski with which to establish a balance platform under the outside foot.

In the scheme of things, an essential first step is to adapt the ski boots to functional needs of the skier as opposed to forcing the skier to adapt to the limitations imposed on them by the ski boots. Tightly fitting, supportive ski boots and most conventional constricting, cushioned, supportive footwear actually makes the feet weaker while compromising postural alignment and balance. There is an emerging global movement that is recognizing conventional footwear as THE problem behind compromised foot function while creating a ‘perceived need’ for cushioned soles  and artificial support in the form of custom insoles and orthotics which, instead of solving functional issues in the feet, lower limbs and entire body, further weaken the biokinetic chain.

The links below are to 3 articles that speak to this subject.

ORTHOTICS OR NOT => OUR LIMITING FOOT BELIEFS ARE HURTING US – http://kristinmarvinfitness.com/orthotics-or-not-our-limiting-foot-beliefs-are-hurting-us/

YOU WERE BORN WITH PERFECT FEET – https://www.correcttoes.com/foot-help/feet-101/

STRENGTHENING VS. SUPPORTING: THE COMPETING LOGIC OF FOOT HEALTH – https://www.correcttoes.com/foot-help/strengthening-vs-supporting-competing-logic-foot-health/

There is currently a whole series of Foot-Cast Episodes on The Foot Collective site at – http://www.thefootcollective.com

see – THE HUMAN GUIDEBOOK FOR SWITCHING TO BAREFOOT FOOTWEAR


A good starting point is to acquire a sense of how day-to-day footwear compromises foot and lower limb function and the modifications or ‘hacks’  necessary to adapt the footwear to the functional needs of the user.

A recent post on the Correct Toes blog called ‘How to Modify Your Shoes to Better Fit Your Feet’ (1.), comments on a runner who was experiencing distracting numbness and tingling in her feet, but balked at allowing her coach to make a few cuts in the upper material of her shoes to relieve the tension that was causing her problem. Most people are uneasy with the idea of modifying footwear. They tend to readily accept standard, off the shelf shoe size fit and assume that the way a shoe fits (or doesn’t) fit their foot is the way it is supposed to fit.

I recently had a similar experience with a young ski racer whose toes were crunched up in her ski boots that were both too short and too narrow. The liners were especially bad. Like many of today’s young racers, early in her racing career, she had probably grown accustomed to the constraint imposed on her feet by her ski boots and had unconsciously learned to make her feet comfortable by standing with most of her weight on her heels. After a time, her body had come to accept this as ‘normal’. Once this happened, she became reluctant to make changes.

A ex-racer, who I worked with back in the 1970s, loaned the young racer a pair of her boots. The improvement in the racer’s skiing was immediate and remarkable. Her coach commented that she had made 6 months improvement in one day! Unfortunately, stories of skiers and racers whose foot function, balance and even the function of their entire body has been compromised by tightly fitting, supportive ski boots is common. But happy outcomes, such as this young racer experienced, are exceedingly rare.

The Correct Toes post offers some good suggestions on footwear modifications that are remarkably similar to those I have used for decades in both ski boot liners and in my own footwear. The reason the modifications are similar is that the end objective; creating a functional environment for the user by minimizing the negative impact of the footwear on foot function, is the same.

The series of photos that follow illustrate examples of modifications that can improve the functional fit of footwear. An easy modification is to reconfigure the lacing pattern. Just because a shoe has a specific set of lace eyelets does not mean they all are necessary. The 2 photos below are from the Correct Toes article.

Photo with permission of Correct Toes

The photos below are the lace hacks I made on my Xero Prio (left) and Lems Primal 2 (R).

One modification that the Correct Toes article does not mention is the use of lace locks. Lace locks allow lace tension to be regulated and maintained without the need to over tighten laces to prevent them from coming undone.

This is one form of lace locks on my Xero Prio.

This is another form of lace locks on my Lems Primal 2.

I also use Correct Toes to improve foot function.

Correct Toes, The Foot Collective, EBFA, Feet Freex, EM Sports and many others are advancing on a uniform front in lock-step with the makers of minimal shoes in recognizing the damage caused to feet by conventional footwear while moving towards a uniform standard for the design and construction of footwear that creates a functional environment for the foot, while minimizing the negative impacts associated with structures placed on the human foot. Technologies such as NABOSO hold the promise of advancing on barefoot function in what I like to call ‘Beyond Barefoot’.

It has long been my experience that liners are the most problematic aspect of most ski boots. When I worked exclusively with Langes, I often made extensive modifications to liners that included using a liner a size larger than the shell size and re-sectioning and/or re-sewing the forefoot to allow proper alignment of the big toe and adequate width for the forefoot to fully splay.

The biggest problem in ski boot liners is in the toe box, especially the shape of the toe end in that it forces the big toe inwards, towards the center of the foot.

A modification that the Correct Toes article suggests is to make small slits on the side of the footwear opposite the point where the foot needs more room to splay.

Photo with permission of Correct Toes

Cutting small slits along the base of a ski boot liner is the first hack I usually try. But in many cases, I find more drastic modifactions are necessary in order to obtain the width required for the foot to fully splay and the big toe to align properly.

The photos below are before (L) and after (R) modifications that were necessary to accommodate my wife’s feet. These are older race stock Lange liners which I fit to her extensively modified Head boot shells.

The photo below is of the modified liner from my Head World Cup boot.

For ‘shallow’ feet or feet with a low instep the Correct Toes article suggests adding tongue depressors along the top of the foot or under the laces to help fill the void and prevent the foot from lifting or sliding around.Photo with permission of Correct Toes

The photo is of forefoot/instep retention pad that applies a constraining load to the foot that is substantially perpendicular to the transverse plane of the boot board. This device is similar to the one that powered Steve Podborksi to the podium in World Cup Downhill races. Today, Steve remains the only non-European to have ever won the World Cup Downhill title.

I devoted a large portion of my US Patent 5,265,350 to laying the groundwork for a functional standard that could evolve and eventually be applied to all forms of footwear, but especially ski boots. There are encouraging signs that the ski industry has finally started to take baby steps in this direction. I will discuss this in my next post.


  1. https://www.correcttoes.com/foot-help/modify-shoes-better-fit-feet/ 

DIGITAL SALVATION FOR THE SOLE [BACK TO THE FUTURE]

“Any sufficiently advanced technology is indistinguishable from magic.”  – Clarke’s Third Law

Conspicuous hardly begins to describe what I was feeling.  In the early morning rush of skiers grabbing a quick caffeine rush at the Wizard Grill, amid tables full of Ski School twinks waiting to see whether they were going to have any work for the day, an attractive woman was carefully stringing computer cables up the inside legs of my ski pants.  Things like that draw attention even at the base of Blackcomb on a Monday morning.

One end of the cables were attached to pressure sensing insoles in my ski boots, the other to a data recording box I was trying to figure out exactly were to attach.  About the size of an epic Michener paperback, it was just too big to slip into any of my pockets.  Finally clipped to the waist of my pants, it was, in turn, coupled to a high-powered flash unit strapped to my arm, both of which were fired by a button left dangling pretty much nowhere.

Robocop.  I couldn’t get the image out of my head, although at least one person who asked what all the hardware was about accepted my answer that it was a control mechanism to power my artificial leg.

David MacPhail grabbed the digital video camera and we headed up Blackcomb to take some measurements.  Dave — who I’d been working with to document some background on the Rise boot he’s been developing — had only recently launched Synergy Sports Consultants.

I wasn’t clear where exactly he was taking me or what we were going to accomplish, but a more willing guinea pig would have been hard to find.  In the nether world of ski theory, and more particularly in the areas of skiing biomechanics and modeling, Dave MacPhail is riding the cutting edge.  His work with National Team skiers and his understanding of exactly happens to the human body when it straps on a pair of skis has brought him an international reputation as an authority in the field.

On a clear slope under the Solar Coaster, Dave skied ahead to set up the video shot.  Sophie — who’d wired me up — rechecked the cable connections, set a baseline measurement for each of my unloaded feet and told me to point the flash unit down the hill at the camera.

As they signaled their readiness to each other, Sophie fired the flash and told me to ski down toward Dave.

Making my best ski school turns, I skied for the camera.  We repeated the process a few times and then we went back down to the Daylodge to…well, I wasn’t sure to do exactly what.

What, turned out to be mind blowing.  The unit strapped to my waist was a Pedar foot pressure data recorder from the Novel company of Munich, a techy little piece of equipment that, until last year, was the size of a small desk.  On a PCMCIA flash card, the unit was capable of recording about 10 minutes worth of data.  Fed by 80 pressure sensors arrayed throughout the insoles in my boots that each took 50 measurements per second, the Pedar tracked pressure across time as my feet worked to move me like a skier.

Downloaded onto a laptop computer and run through the company’s software, the data could be displayed as images of my left and right foot, colour-coded across the sensing mechanisms to display the changes in foot pressure as I made turns.  With lower pressure readings showing up as black squares and higher pressure lighting up bright pink, the readout was a moving kaleidoscope of colour as it played back my runs down the mountain.


On each colourful foot profile, a small dot traced a red line showing my centre of pressure at any moment in time.  A good skier using foot pressure the way they’re supposed to, would, over the course of a run, track a red line from the ball of their foot back toward their heel.  The track would be true and relatively straight with few variations.  That’s what the tracing on my right foot looked like.  The track of pressure of my left foot looked like someone who had never seen an Etch-A-Sketch grabbed both knobs and started twisting them randomly.

The difficulties showing up in my left foot readout were verified when Sophie explained the graphic display at the top of the screen.  “This line graph shows change in pressure over time for each foot.  When you make a good turn, like you’re doing with your right foot, the graph of pressure shoots up dramatically at the start of the turn, drops down slightly to a plateau, then falls away as you unweight the foot at the beginning of the next turn.  Your left foot comes on very gradually.  Something’s blocking your foot function,” she explained.

The final diagnostic piece of the puzzle — at least as far as the technology end of things went —was put in place when Sophie downloaded the images from the digital video camera and synchronized them with the Pedar display.  There I was, making graceful turns and there was the readout of what my feet were doing — or not doing, as it turned out.

“Neat,” I said.  “Now what?”
“Now you find out what Synergy is all about,” said Dave.

Synergy — small “s” — is about joint action of different substances producing an effect greater than the sum of the effects of all the substances acting separately.

The whole being greater than the sum of the parts. 

In a theological context, synergy is a doctrine that human effort cooperates with divine grace in the salvation of the soul.  I’ve often thought of skiing as a salvation of the frozen Canadian soul and certainly a day in the high alpine making perfect turns in all conditions is as close to divine grace as most of us will ever come.  But it was the more secular meaning of the word Dave had in mind in naming the company.

“The whole concept of Synergy probably came into my mind 25 years ago.  I started thinking about something called bio-integration, bringing people with different important skills together to work holistically on making your body work right.  Five years ago, we couldn’t have launched Synergy because the technology wasn’t quite there.  We needed more sophisticated software and I could see the time coming closer to when we’d reach a point where a lot of things in athletics that are mysteries now were going to be revealed by being able to plug in sensors at key points of interface.  Now, we’re starting to get there.”

But data is just data without something to make it sing.  And that’s where the principals of Synergy begin to make the concept work.  Joanne Younker is Synergy’s president. She’s been working with Dave for 12 years on both the Rise boot and putting together a biomechanical model of how people ski, how joints and muscles and nerves and bones work together to overcome our natural tendency to fall down when the earth starts to slide out from under our feet at an accelerating rate.

Joanne’s a level IV CSIA instructor and a level II CSCF coach and a personal trainer when she’s not on skis.

Sophie Cox and Joanne Younker

She’s been a keen skier since she was fourteen and a student of kinaesthetics since 1989 when she blew her back out squatting improperly in the weight room, an injury leading to temporarily paralysis and a burning desire understand how her body works.

“Working with David, and studying the biomechanics of skiing, I can look at someone skiing and understand what they’re doing wrong and, more importantly, probably why they’re doing it.  That is, what muscles aren’t functioning right or what functions are blocked.  Working with this technology, I can validate my diagnosis with hard data.”

Using a set of dry-land kinaesthetic exercises, Joanne led me through a session designed to help me experience the “feel” of having the right muscles firing and applying pressure with the correct area of my feet.  Once I’d managed to do these correctly, she had me stand on the Pedar’s insoles outside my ski boots.  Connected to the computer, they gave me a real time display of where, in turn, I was applying pressure with each foot. Running me through the exercises again, I could use the display to associate that “feel” with a visual representation of correct pressuring.  There was no guesswork.  When I lit up the right area of the pressure pads, I was having my feet do exactly what they should do to initiate a good turn.

The final step of the exercises was to slip the insoles back into my ski boots and repeat the exercises again.  Within the confines of my boots, I could watch as I pressured the ball of my foot and got my bulk into the right plane of alignment.  I was surprised — as is virtually everyone else who has gone through this exercise — at how far forward I really needed to bring my centre of mass to consistently apply pressure where needed.

All of this might have taken a lot longer to happen if the third member of the Synergy team hadn’t walked into town by accident.  Sophie Cox finished her B.Sc. at the University of Brighton School of Podiatry in, England, in the summer of 1998 and was working in a Podiatry clinic in London.  Her mother brought home a bottle of Whistler spring water  — the same water that gets flushed down toilets in Function Junction, ironically — and she was taken with the idea of goofing off for a year in Whistler.  After some web surfing, she decided to take a job as a bootfitter at Can-Ski and really learn how to ski and party, Whistler style.

A colleague in Boston mentioned the groundbreaking work Dave had been doing in biomechanics and planes of movement associated with skiing to her and she attended a presentation Dave made last March to the Congress of the Canadian Sports Medicine Association.  “After Sophie met David and explained what she’d been doing with the Pedar, he was really excited.  He called me up and said, ‘I’ve met the third person!’ and we went from there,” Joanne explained.

After a summer back in England working , Sophie returned this fall to work with David and Joanne on the biomechanics of skiing and help launch Synergy.  What she brings to the table, in addition to the technology, is an in-depth understanding of the structures and movement of the foot and ankle joints and a wealth of knowledge in diagnosing problems related to feet and lower limbs.

“I look at a skier’s mechanics, what they can and can’t do, and try to decipher why they can’t do it.  Sometimes it’s bad motor skills and that’s Joanne’s part.  But if she’s trying to teach them a skill and they just don’t have the biomechanical capability to do it, that’s where I come in.  I can determine the physiological problem and refer them on to a physio or bootfitter or local podiatrist.”

“The only way of discovering the limits of the possible is to venture a little way past them into the impossible.”  Clarke’s Second Law

For me, the proof of what Synergy was offering was back out on the slopes.  I practiced and visualized what Joanne had shown me, let Sophie make a few modifications to my left footbed and got wired up again a few days later.  Back at the computer after two or three runs, I sat in rapt amazement at the difference.

On the Pedar’s readout, the front of my feet were lighting up at the initiation of each turn.  The tracking line of the centre of force had moved inward — indicating a much stronger pronation, getting the ski on its edge — and my left trace looked like something made by a functioning foot instead of a peg leg.

I know what you’re thinking; almost anyone can help me be a better skier.  That’s like crowing about doubling your money when you only have fifty cents to start with.  But what about good skiers?  What can all this do for them?
Funny you should ask.

In the fall of 1991, during dry-land training in Banff, Rob Boyd blew a disc at the L-5, S-1 joint in his back.  An ensuing laminectomy restricted his mobility and left some nerve damage on his right side— although not enough to keep him off the podium from time to time for the next six years.  “I learned to compensate using different muscle patterns,” he said.

Screen Shot 2017-05-14 at 2.11.09 PM

Three years off the World Cup Circuit now, and away from the daily coaching, Rob wasn’t happy with the way he was skiing this season, nor was he happy with his finishes in the early Ford Pro Series downhill races.  “I saw Jim DeMarco, M.D. wired up to this thing one day and started thinking maybe Dave — who had done a lot of boot work for Rob in the past — could do some testing on me and help me find some answers.”

Sophie and Joanne ran Rob through a gait test, using the pressure pads inside his running shoes while he walked the treadmill at Meadow Park.  “What we saw,” Sophie related, “was Rob had some blockage in the way his foot was functioning.  He wasn’t pushing off the ball of his foot with any force at all but compensating through other muscle patterns.”

Screen Shot 2017-05-14 at 2.10.31 PM

“Right away, from what we saw on the data, my suspicions were confirmed that my right side wasn’t working well,” Rob added.

What they saw when Rob was hooked up to the Pedar for the first time on the slopes was even more surprising.  His heels lit up like a Christmas tree and he was almost never pressuring the front of his boot.  His left turns were strong and crisp but his right turns were nowhere near the same intensity.  “Yeah, that was surprising to see.  It felt like I was skiing alright and using the balls of my feet but I wasn’t even close,” Rob said.

Dave went to work on Rob’s boots, Sophie made some modifications to his footbeds and Joanne got him started on a series of patterning exercises and visualization techniques.  “I could really feel the difference when I started concentrating on using my foot more.  That and the changes in my boot environment made a big difference.  I could feel it right away at Sugarbush (Vermont).  My skis were gliding on the flats; just floating,” Rob said.  He could also see the results in his times: second on his first run and fourth on his second.

 

“The next step will be to set Rob up with a physiotherapy regimen with Allison MacLean,” Joanne said.

And that’s where the remaining synergy of Synergy comes into play.  The company’s goal is to actively work with bootfitters, physiotherapists, chiropractors and other specialists in the community who can treat the whole person.

Allison is just beginning to work with the Synergy people and is excited about the “integrated approach” they’re trying to bring to problem solving.  “The data gathering and testing they’re doing is interesting,” she told me.  “It’s hard sometimes to know exactly what’s not functioning in the case of lower limb injuries and whether what your treatment is as effective as it could be.  When they send someone to me, we’ve got a pre-treatment set of data we can compare to post-treatment performance to really know whether what we’re doing is effective.”

“Every other person you bring into this adds something to the mix and produces even more beneficial results,” Dave explained.  “Sophie and Joanne and I, working together, have a much greater impact than any one of us could have on our own.  That’s the genesis behind Synergy.  But we want to bring the best resources we can to bear and make it so everybody looks like a hero.”

This obviously includes some of the best bootfitters in town.  George McConkey is sold on the idea.  “What Synergy is doing validates a lot of my own ideas about foot function and bootfitting,” he said.  “I still believe 99% of most peoples’ problems are in their boot and with any luck, what we’re starting to see in the way of data coming out of this will get the manufacturers interested in designing boots that work.”

Scott Humby, one of the owners of Fanatyk Co., isn’t so sure what’s going on is going to shake up the industry, but he sees potential benefit.  “I think what they’re doing can help you by really proving what’s going on in your boots.  If it make you feel better about your skiing; you’ll ski better.  If, as bootfitters, we’ve done all we can for someone and they’re still struggling, we’ll definitely send them on to Synergy because there may be something we’re just not seeing.  There’s a huge benefit in being able to refer someone on to a team of specialists.”

It seems axiomatic that what Synergy is doing is the way sports will go in the future.

The advances in sports in the last 25 years have largely come about because of a refinement in coaching techniques and technological innovations in equipment.  But most of what’s being done on the coaching front still relies on what a coach can see and how he or she interprets that visual data.  The advances in coaching and teaching in the next 25 years will probably be realized through the application of measurement technologies only now being brought into the field.

Some people in town and on the mountains think what Dave’s up to is another bit of high-tech quackery, other’s are true believers.  But whether coaches and instructors and others who guide athletes embrace the kinds of tools is probably more a matter of when, not if.  Elite athletes will demand it; the wired generation coming up will assume its presence. And guys like me who just want to get better and shorten the distance between muscle pattern and muscle memory will embrace it the same way we embraced those shapely new skis we can’t live without.

In the meantime, Arthur C. Clarke’s Law of Revolutionary Ideas is probably apropos:

Every revolutionary idea — in science, politics, art or whatever — evokes three stages of reaction. They may be summed up by the three phrases:

1. “It is completely impossible — don’t waste my time.”

2. “It is possible, but it is not worth doing.”

3. “I said it was a good idea all along.”

Watch out for number three.

author- J.D. Maxwell


reprinted with the permission of Whistler Piquenewsmagazine

published on February 18, 2000

A SKIER ASKS QUESTIONS ON BOOT-FITTING 101: THE ESSENTIALS

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.

 

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.

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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 POST – ASSESSING CHANGES TO SKI BOOTS

Since the summer and fall is a time when racers and serious skiers make changes to ski boots, I will describe the strategy I use to assess changes. It is important to make changes in a manner that controls variables and provides a baseline to make one-on-one comparisons against. However, after viewing video provided to me by several followers of my blog that graphically shows the effect on technique of changes made to ski boots over a number of years, it became apparent to me that few, if any, racers or elite skiers have any idea of what a ski boot should ideally feel like and especially how it should affect them in terms of performance.

Without clearly defined end objectives and a sequential process for achieving and confirming successful implementation, skiers and racers can only think in relative terms of better or worse, not optimal.

ASSESSING CHANGES TO SKI BOOTS was originally published on July 11, 2015. The entire post can be viewed at  http://wp.me/p3vZhu-15C

It should be read in conjunction with BOOT-FITTING 101: THE ESSENTIALS – BOOT BOARDS

 

BOOT-FITTING 101: THE ESSENTIALS – BOOT BOARDS

Those who went through the 9 exercises in TRANSITIONING THE SR STANCE TO THE SKI BOOT  probably ended up with a number of red flags. Starting with this post, I will go through what I consider to be the essentials of boot-fitting.

While I use the term boot-fitting, I prefer the term boot-modification. Boot-fitting and fit of a ski boot imply a fit of the boot with the foot and leg that results in a degree of dysfunction of the foot. The key to skiing with minimal effort and maximum balance and comfort is a ski boot that creates a functional environment for the foot and leg as opposed to a ski boot that creates an environment that results in a significant degree of dysfunction of the foot and the entire lower limb.

Achieving a functional environment in a ski boot for the foot and leg is about sequence. The fastest route to a ski boot that provides the best functional environment for the foot and leg is a step-by-step process; one that assesses the effect of each essential component in a systematic manner. A minimalist approach makes it easy to assess the effect of changes such as substituting a custom footbed that supports the arch for a baseline flat insole. The gold standard in studies to assess the effect of interventions such as insoles and orthotics is to compare barefoot balance on one limb to balance on the same limb in a specific form of footwear to balance on the same limb in the same form of footwear fit with an insole or orthotic. This protocol enables the effect of a compounding series of interventions to be assessed against a consistent baseline; in this case, barefoot balance on one limb.

Where I Start

At the bottom. By at the bottom, I mean the boot board (aka, the Zeppa).

I prefer to start with a monoplanar boot board. Monoplanar means flat in both the long and transverse axes of the boot board with the plane of the transverse axis parallel to the base plane of the sole of the boot.

Why monoplanar? Because the shape of the boot board can significantly affect foot function and the fact that the shapes of boot boards and materials and construction can and do vary considerably from one boot brand to another and sometimes even among different models in the same brand. The shape of a boot board can also act to compound the shape of custom footbeds and orthotics. A monoplanar boot board establishes a baseline with which to assess the effects of foot function irrespective of the boot brand or model. A monoplanar boot board and a flat insole serve as a baseline reference with which to assess the effect of any changes to that alter the monoplanar surface form of the boot board.

In my opinion, boot boards are one of the weakest components of a ski boot. Boot boards are one of the first things I check when I am considering purchasing or working on new ski boot. In future post, I will discuss a recent study that raised significant issues with boot boards.

What I Look For

Ramp or Zeppa angle is important. But before I even consider this aspect, I check the construction and materials of the boot board. Although I have not conducted an extensive review of boot boards, I consider both the boot boards and the insoles (after heating and pressing them flat) in Head Raptors some of the best I have seen to date.

The photo below shows a boot board from an Atomic boot (upper 2 photos). A boot board from a Head Raptor is shown in the bottom photo.

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The 2 photos below are of side and top views of a boot board from a Head Raptor SD. One thing I deem important is continuity across the heads of the metatarsals, especially the head of the first metatarsal (ball of the foot). With the boot board in place, no break in surface continuity should exist between the interface of the boot board and the surface of the boot shell. It is especially important that there is no step at the interface where in the boot board or shell base are at different elevations.

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The photo below shows a boot board from a Salomon SX 90 rear entry boot. This type of boot board construction is still found in some recreation boots. I would not consider a ski boot with this type of boot board.

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The main reason I prefer boot boards like the one shown in the photo below is that it is fabricated from dense hard foam. Any contour can be quickly and easily removed with a sharp block hand plane. Ramp angle can also be easily and quickly adjusted with a sharp block plane. I use a belt sander to finish the surface

plane-bb

When the front portion of a board needs to be raised to correct zeppa angle, I use a material like dense gasket cork. The photo below shows boot board from a Head recreational boot with a layer of cork added to the front half to reduce ramp angle.

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With the boot board in place in the shells, the insoles from the liners should be placed on top of the boot boards in order to ensure that the foot is sitting at the correct elevation in relation to the shell walls when checking for clearances.  The insoles shown in the photo below are from a Head Raptor.

head-insoles

In terms of resiliency and surface texture, the Head insoles in the above photo are some of the best insoles I have found to date. I heat and press them flat in order to create a baseline insole.

Once a skier or racer has adapted to the baseline fit of a ski boot they can replace a baseline insole in one boot with a custom insole or orthotic and compare it to the  baseline insole in the other boot. If the boot is perceived to be better with the custom insole or orthotic, the baseline insole in the other boot can be swapped. If there is any doubt after a ski-in period, the process is easily reversed.

The protocol I follow is to make one change at a time and always ensure is quickly and easily reversible.

My next post will be on BOOT-FITTING 101: THE ESSENTIALS – FOOT TO SHELL CLEARANCES

UPDATE ON THE FREEMOTION SKI BOOT PROJECT

On December 9, 2016,  Simon Zachhuber from Austria posted the following comment on my blog.

Dear David! While researching for a university-project (FH-Salzburg, Austria) I discovered your blog! Clearly you are an expert on ski boots, and I thought maybe you can provide some feedback! At least it’s worth a try

I’m a product designer and our task is to analyze a specific ski boot and try to figure out ways to improve it! The ski boot we work on has a new concept of dealing with the occuring forces. Instead of providing stability and flex with plastic shells, the forces are applied to a metal spring. So the area of the tong and the shin doesn’t have to be covered with hard plastic, but with leather or fabric. You can see the concept on their website http://www.freemotion.cc

I am currently working on a project as a student for the FH Salzburg, Austria! We have the task of analyzing a specific ski boot and implementing improvements! Since this is a short project and we are not experts on ski boots, I wanted to ask you for profound feedback on this boot! It can be seen on the website http://www.freemotion.cc

The boot’s concept is that instead of having a hardplastic-shell to deal with the forces, it uses a metal spring that starts at the forefoot and goes through the ankle-axis all the way back over the heel! We already tested it and were quite surprised, how well it worked, but maybe you can add a few thoughts that come to your mind when you check the boot?
I know, it’s very hard to give feedback without having the boot to test, but maybe you can still give some feedback? Thank you very much!!!

With greetings from Austria
Simon Zachhuber


I replied to Simon by email

Dear Simon,

Greetings from Whistler, BC Canada.
I would be glad to assist you in any way I can with your project.

Do you know of the work of Dr. Martin Pfeiffer of the University of Salzburg? He was committed to the development of a ski boot designed along anatomical principles. Two Canadian radiologists of Austrian descent made me aware of Dr. Pfeiffer’s work in 1988 when they gave me a copy of Der Schu Im Sport. Part 6, The Ski Boot, features a chapter by Dr. Pfeiffer called Kinematics of the Foot in the Ski Boot. Dr. Martin Pfeiffer was a source of valuable knowledge that influenced my work. I had personal communication with him in the early ‘90s.

Dr Pfeiffer concluded his chapter by stating, “This goal (a ski boot designed along anatomical principles) has not yet been achieved”. I do not know whether he is still with us. But I would appreciate you recognizing his contribution to skiing by making his vision a reality and by recognizing his work.

Best regards,
David


Due to the urgency of Simon’s deadline (which was fortunately later extended to January 17, 2017), I made providing my assistance a priority with the following series of posts.

NEW AUSTRIAN SKI BOOT: THE FREEMOTION – http://wp.me/p3vZhu-1CB

SIMON RESPONDS TO MY PRELIMINARY OBSERVATIONS ON THE FREEMOTION SKI BOOT – http://wp.me/p3vZhu-1D9

POTENTIAL SOLUTIONS FOR THE FREEMOTION SKI BOOT – http://wp.me/p3vZhu-1Dt

THE FREEMOTION SKI BOOT:  FLEXURAL BEHAVIOUR – http://wp.me/p3vZhu-1FB

FREEMOTION FLEX CURVE OPTIONS – PART 1 – http://wp.me/p3vZhu-1Gj

FREEMOTION FLEX CURVE OPTIONS – PART 2 – http://wp.me/p3vZhu-1Gy

FREEMOTION FLEX CURVE OPTIONS – PART 3 – http://wp.me/p3vZhu-1GI


On January 18, 2017, the following video was posted on YouTube on the FreeMotion site with the text below translated from German.

Kooperation Freemotion mit der FH Kuchl

The results of our successful cooperation with FH Kuchl are here! We are delighted about the great input of the students and professors. We are already working on the implementation of the ideas. Once again a big thank you to the students #Feelgoodskiboot

 


I sincerely hope that my efforts have assisted the students of FH Kuchl. The design of the ski boot needs fresh young thinking and a new direction with design based on the functional requirements of the human system. The most satisfying aspect of the design exercise at FH Kuchl was to see the large female component with students Marlene Arabjan and Evelyn Obermuller taking an active role.

Gut gemacht Simon  Zachhuber und die anderen studenten von FH Kuchl!

Viel Gluck und Best Wunsche