Foot orthoses and skiing

Well, I can't believe I missed this thread. I was holidaying in the North Island (December is summer here.) Skiing was my first "thing" in podiatry.

When Kevin was still in college, Paul Rasmussen at Precision Intricast (where Kevin now writes the newsletters) made orthotics for me for the US Olympic Ski Team. I travelled with them to New Zealand for their training camp, where we did the first study. Paul and I were good friends. I am aggrieved of his passing.

One thing I noticed early on is that [/B]everyone[[/B] on the team had rigid forefoot valgus (cavus) foot type. This relatively rare foot type made for incredible medial edging power and "foot feel." The average foot uses the rigid lever of the plastic boot against the ankle and leg to edge onto the medial edge of the ski. This is a sloppy, imprecise way to ski, not allowing elite level precision.

So, although for the elite skiers the orthotics spread the contact area (they commonly had sub 1st met head problems), for the average footed skier, the orthotic immediately improved everything. They skied better immediately, and would come back to my office (in the base lodge of Squaw Valley) like excited children. This was really great fun. I never had anyone so excited to have orthotics. People flew in from around the country after I was featured in an Aspen Airways inflight magazine.

So, what are some tricks? Simple really. You want the foot in the rigid lever ("ready stance" in tennis) all the time. You cast in neutral, and want the orthotic to invert the heel to neutral. (The forefoot valgus foot innately does this.) Normal arch fill. Rearfoot post with no motion in a thick, stiff polypropylene shell. You may add a flat forefoot post to spread the contact area and stiffen the orthotic. A Spenco cover is nice if there is room in the boot, and with any sort of flexibility or hypermobility (oops, haha) in the first ray, you can add a korex Morton's extension (oops again).

All of the correction for the foot is done in the orthotic. Forget about canting bindings, or grinding boot soles.

Tibial and proximal correction is done with the angle of the cuff of the boot. Some boots have adjustments on the boot itself for this, sometimes they need to be fixed by the good boot fitter you need to work with.

Boots are all different. They have different heel heights, different centre of pressure, forward lean, flex, etc. That being said, the cuff varus is probably the most important. Langes have a high built in tibial varum of 6 degrees. Most other boots are about 4 degrees.

Recreational skiers like a little extra varus correction, as they ride on their inside edge, even when shussing, for directional stability.

Downhill racers need to ride a flat ski for speed, and have their cuff adjusted so they are "square" (the ski is flat) in a tuck.

Slalom, GS racers need less varus in their cuffs (a second pair of boots) so they can hip angulate (dropping their body inside the turn) without over edging.

These are some of the basics. Limb length discrepancy makes a big difference, as does heel height and forward lean.

You can fix the skier's technique problems so that even the coach is impressed. Very cool!

Anyway, I'm probably talking to myself here, by now.

Cheers

Frederick

 

Again, all good info if we are talking long, stiff, straight skis and old style technique i.e. using lots of hip angulation. With today's technique the foot and ankle control turn radius and turn shape, this is due mainly to the use of greater side-cut in skis, compared to skis in the early 80's - early 90's.

As a visual, if you have seen a snowboarder laid out on the snow carving a phat arc, then you were looking at a balanced structure able to control turn radius and shape with most likely a very flexible soft boot combined with flexible soft binding and ankle motion and propreoceptors (sp) firing off on all cylinders. Yes there are many other things going on.

In skiing today with a two-footed style technique and skis that are softer in flex, shorter in length with higher taper angles and side-cuts using a ski boot shell shape that matches the foot shape, allows full range of motion in the ankle combined with a semi ridged flexible insole and proper alignment will yield a higher degree of balance and control.

Mid-foot flexibility (some call it pronation) is a really good thing in today's skiing.

Coup

 

Dear Coup

Nope, I'm afraid I have to disagree with you. Snow boarding and skiing are not closely related biomechanically, primarily because of the stance. Ice skating and skiing are much more closely related, with two edges in rectus under the foot.

Carving skis with greater sidecut haven't changed what's needed for foot feel control. "Motion," like pronation, gets you nowhere. It's like "slop" or "play" in the steering wheel of your car. Exerting pressure precisely under the foot into the ski is what's necessary. Excess "slop" pronation just means that when the skier changes pressures through his foot there is motion in the foot, but not immediate pressure change transmitted into the ski. Conversely, when the ski hits a rut, etc. the ski doesn't transmit back up into the foot precisely. The foot needs to be moved until the "slop" is used up. The foot has to overcorrect to regain control.

Softer, or semi-rigid insoles are just easier to fit, not better. A ski shop can fit a generic device and claim it's the best thing. And they feel good in the shop, with an enthusiastic salesman.

Cheers

Frederick

 

Fredrick....maybe skiers in NZ are still all using straight skis, with all due respect technology has moved on a hell of a long way since those days....... excessive pronation in a ski boot is very much a bad thing, flexibility of the foot in the boot is critical, if the foot is locked rigid in a cast then it cannot use fine balance to adjust to the constant changes of pressure through the ski as the terrain changes...many world cup downhill racers do not use any footbed/orthotic in their boots because they do not want to have the foot rigidly held, they want the ability to roll the foot ever so slightly in the boot, if they are held too rigidly then they would never make it to the bottom of the course.

just look at the one of the most common modifications we carry out to race boots... punch the shell at the navicular to allow for some natural roll, in fact more and more boots are comming with this space built in

 

Dear CEM

All these assumptions about NZ, and from the great skiing nation of Britain! How patronising.

I couldn't figure out why you were using this vague, useless, layman ski shop jargon, and I was going to try to explain to you how the body (quite old technology) biomechanically works when skiing. Then I looked at your homepage, and saw that you were just a web retailer, and you sell Chris Smith's old cheap and nasty Superfeet orthotics.

So, now I understand your promotive language.

Cheers

Frederick

 

fredrick, very nice if you want to insult people go do it in the bar rather than on a web forum, because if i were in a bar i would have no respect for you based on the comments you make above.

if you took the time to go to my website and actually read it properly you would see that

A] i am a certified pedorthist [do they have that in NZ]
B] the work i do with skiers i highly regarded, i work with many skiing professionals both top level instructors and racers, currently i work with our number one skier cross skier [8th in the world] and number 1 bumps skier [predicted to be on the podium at the next olympics] and have just returned from a working trip in France with 2 colleagues who work with the world cup tour...i don't see them using anything other than a conformable or superfeet insert and they have several podiums in world cup and olympic medals between them
C] yes i sell some product on line, OTC devices and shoes, but you may notice that you can't buy any custom product on my website, but then you couldn't be bothered to read past what you wanted to.
D] whether you like it or not the superfeet product works for lots of people and just because we don't charge $100s for it doesn't make it bad, it is not professing to be something it is not

to be honest i am sick of having to defend my position on here to you, you sound very much like you are stuck somewhere in the past, whilst i 100% agree that biomechanics is biomechanics is biomechanics, ski boots and skis have changed dramatically over the past 10 years.

anyway if all you are able to do is to being insulting and patronising then i am done with this forum and hopefully you are satified that you have ousted a non podiatrist, i have felt welcome here until now but not any longer

good bye

moderators feel free to remove this post if it upsets any of the delicate souls, but then please delete my account and send me an e mail to say that it is done

 

A question: In skiing, to turn, do you just want to get increased medial edge pressure, or do you actually want to evert the ski to get medial edge pressure.

If you want to get eversion of the ski, then one possible contributer to that motion is eversion of the foot. So, you could use pronation of the STJ to turn. If a boot did not allow for internal talar motion, it would be difficult to use the STJ to evert the ski.

I can also see how filling the boot so that there less room between foot and boot can be considered to remove "slop" from the system. When you pronated the STJ and the forefoot everts, there will be a sooner upward pressure on the lateral side of the boot. Downward pressure on the medial side of the ski and upward pressrue on the lateral side of the ski (boot and bindings) will create an eversion moment on the ski. An eversion moment on the ski will increase medial edge pressure.

The slop in the steering wheel argrument was often used when applying the rigid lever mobile adapter thoery of the MTJ. The theory went when the STJ pronates, the MTJ becomes a "loose bag of bones" or "a mobile adapter" because there is increase in range of motion of the STJ. I know of no research supporting a decrease in stiffness of the MTJ with STJ position. Fred, why do you think pronation is creating slop?

Regards,

Eric Fuller

 

Dear CEM, senior member

You are the one that made the patronising assumptions. And you still are, saying that I am stuck somewhere in the past. I don't care what your degree is, but when you use vague nonbiomechanical, commercial language, with all the new whizbang nonsense, and then sell the old Superfeet soft orthotic, I mean come on! You don't expect me to take that seriously!

Do you know how many different boot fitters with their great new technology I have seen in various countries, while I was travelling with ski teams? Why would you think I don't know about the newest technology? Have you designed ski boots for major manufacturers? Do you have any patents for ski boots? Do you have any idea how equipment has evolved over the years? If you think the last 10 years brought changes, you should have seen the previous 20 years. Technology has changed, not always for the best, but the foot remains the same.

If you start talking knowledgeably about how you are treating or improving a particular foot type for a particular event or type of skiing, I might listen. I understand this forum has been used by others in the past to promote their product. This smells of that.

So, are you going to take your marbles and go home? After being a contibutor for 4 years?

You must really be embarrassed.

But remember, if you are going to dish out the insults to me, you can expect a response.

Cheers

Frederick

 

Hi
Well, for me guys (not a moderator), I think you have both had your moment of a spat (for your own reasons). Any more of this is really unacceptable in this playground so please, dust yourselves off, resist the temptation to move into any more levels of personal retaliation because it will then reflect upon both of you.

Regards
Ian

 

Dear Eric

For precise skiing, you want to evert the ski/apply pressure to the inside edge through the bottom of the foot. Excessive pronation doesnt exert pressure.

A pronated, forefoot varus, or Morton's foot won't do this effectively, and the ski will be everted by pressure on the inside of the boot by the navicular, medial malleolus, tibia.

There is little precision or foot feel with this, and as the snow is jerking the ski around, the carving of the turn will be imprecise, with skidding.

Most recreational skiers ski this way, because the average foot isn't very good for skiing. A soft generic footbed (Superfeet) will help them, but a custom orthotic is much better.

Cheers

Frederick

 

Ian,

believe me i don't want a spat i was only making points in resonse to another poster, but obviously fredrick wants a fight, and if he is going to cherry pick out lines from my posts and twist them then i can't stop him

please do not be condescending in your response, i made two commnets about history and straight skis due to the content of your post being related to a time when they were the market norm, they were not intended as condescending, however your response is very much in that tone!

but in answer to some of your points

1 i don't know how many boot fitters you have met, know doubt you will tell me.
2 have i works on the design of ski boots for major manufacturers..well in fact yes i have worked with the designers on a few projects, the most basic that i had an input in was the partially fixed water dam on the salomon x wave/course boots for retention during the foam injection process ...not the biomechanical structure of the boot, i agree, but input we have given has also gone into the toe box designs in the salomon X3 and the Lange W/C160, i am in regular contact with the design teams and product managers of these and other brands.
3 patents no sorry you got me there, input yes, full physical rights and £250,000 of legals not my thing
4 i have no intention of promoting any product here, please tell me where and when i have done so
5 non biomechanical ,commercial language and modern whizzbang stuff, well that is a very intelligent thing to say, again please tell me the terms you disagree with and why, prehaps i can get you a biomechanical definition which you will accept

i don't have a lot more to say to you, this thread ran along quite sensibly for a year or so, then you came in and don't like what i said....

oh and just while i remember, could you possibly answer Eric's question, it appears that you have missed it

 

fredrick

apologies, you answered Eric's question while i was posting, just one point, you said earlier that superfeet were old and crappy, in the last post you said they will help, but a custom orthotic is better...what about a custom superfeet [the full kork type]?

 

Dear CEM

I said that Superfeet were cheap and nasty, not crappy. A kiwi term for something that's not good quality and inexpensive. They were designed to be sold in the ski shop by personnel with no knowledge.

Anything that fills the arch will probably help someone with the average foot.

But that's a long way from treatment of choice.

This forum mostly seems to be for the exchange of leading edge, best ideas.

Cheers

Frederick

 

In a bid to extend my personal knowledge base I recently obtained employment at a very well known and highly regarded ski shop here in Vancouver. But, they do things a little differently to other ski shops I have worked for in the past. They have many stories of their sucsess from world cup racers to average joe skiiers (which i guess you can only take on face value).

Their theory revolves around allowing the foot to pronate, they believe it will facilitate in internal rotation of the tibia and therefore make turn initiation easier. They also believe that you can exert a greater force on the medial edge of the ski because of this. They do use footbeds, but with no RF post and are not molded in STJ neutral.

I would argue that:

1) allowing that motion in the boot is an inefficient transfer of forces and will actually reduce medial edge pressure and any rotational force exerted by the tibia.

2) the result of the above would in most cases lead to less force being applied to the uphill edge - which, if you were to use the race coach formula of: 60% downhill/medial edge pressure, and 40% uphill/lateral edge pressure for the ideal carve.

your thoughts...

Marc

 

I'm with Frederick on this one.

The idea that an orthotic cast in neutral with the intent to hold the foot in neutral will prevent pronation is false anyway. How often have you seen a device that completely blocks pronation...(this would be a cast?!) The idea is just to get the foot to operate around a theoretical neutral, It's still going to pronate over the device...How much it does seems to be question at hand? (But my experience is that even with a super aggressive device, the foot is still able to pronate over it somewhat.

Surely someone has tested this by making a whole serious of gradually more controlling devices and seeing how they perform on the same skier?? (hmmm, tax deductible ski holiday sounds good to me)



Cheers


Tom

 

Marc,

You must be working at Snowcovers!

1) If we were all skiing on long, stiff, straight skis I would agree. However with today's skis turn radius and turn shape are controlled with foot and ankle. Allowing motion in the boot on a shape ski is a very good thing in that it allows the skier to balance better as their feet move further away from the centerline. Proprioception is enhanced, and the skier is able to pressure the ski.

2) Actually if the ankle is locked in the boot or pinned if you prefer, you stand no chance of effectively pressuring the skis.

A pretty good acquaintance of mine owns an Olympic Gold and Silver medal, he won these while using an incredible rigid and vague custom insole. He asserts you cannot ski without moving your ankle. Another WC athlete tells me that "at 80 mph, you have to be able to move your ankles, or you can't stand up".

Everything changed when shape skis came out.

coup

 

Coup,

Can you please provide me with a better description of what 'moving your ankles' entails?

Can you describe the 'ideal' motion of the MTJ, STJ, AJ and Tibia(rotation) for a linked turn?

I would agree with Tom, it seems like it would be better for the foot to funtion around a more neutral position.

What about those with a medially deviated STJ Axis etc, isnt it going to be much harder for them roll over to their uphill edge? Wouldn't a footbed/orthotic better facilitate this?

Craig, I saw you posted in another thread that internal tibial roation drives pronation/supination. What do you think happens if we apply a force to resist pronation?

Interesting thread!

 

I have been around the ski game since 1982 and spent some years fitting boots for all sorts of skiers and have used all sorts of materials prior to qualifying as a pod and have some perspective on the changes in design of boots and skis that have occurred in that time. What we appear to be seeing here is a bit of "mine's bigger than yours" contest.?? It may be more correct to accept that there is no one right answer for all skiers due to the huge difference between skiers anatomy and ability and purpose of skiing. I for one would not want to ski with the same skis, boots and orthoses on an icy slalom course as I would want heli skiing in 4 feet of fluff. Every one has valid experience and happy users of equipment I'm sure. I enjoy a good non-abusive discussion of skiing theory as well as anybody but I don't think you'll convince me there is one right answer that works best for every one in all conditions. It may be more productive to approach the discussion from some other perspective. The Harb kind of technique is quite different to what was taught prior to shaped skis coming on the market. The materials changes alone have allowed huge improvement. In the seventies it was impossible to make a ski that was vibrationally damp at 60 mph unless it was also quite stiff and for a ski to be torsionally rigid it was also stiff along its length. This began to change quite a lot with the introduction of the early
(Saloman etc) moncoque construction and visco-elastic dampening compounds. This change in materials allowed for new designs to be possible, like much increased side cut skis that actually steered well and flexed well but stayed damp and stable at speed. These design changes allowed the development of new ski driving techniques which were previously just not possible. Having spent many years skiing in telemark boots helps give insight into boot function weight and balance centering etc......there are many ways to ski, many of which are a lot of fun.......but won't win you a gold medal on a World Cup race course.
regards Phill Carter

 

PG,

All very good points and this thinking is more or less right in the wheelhouse of what is happening at the highest and entry levels of our sport. I'll write more when I get a chance.

coup

 

I was chatting to Mark on the side about some of this stuff will repeat some of it here...I have thought for years that most downhill ski boots are too stiff and with too much forward lean, this is about sagittal plane motion, not lateral or coronal plane motions. To get onto and off your control edges you need very precise transmission of lateral control movements....but to make these lateral control movements smoother transitions from flat base onto an edge and then back onto the flat base, and then onto the other edge, you need free and full range of ankle movement and full knee extension available. This is for nearly every skier (not World Cup slalom or GS skiers), back in my past I listened to some of the worlds best racers, like Weirather and others.
Weirather skied full Downhill events in special boots made for him with leather cuffs over plastic lower shells....said it worked better for him at really high speeds not to have so much rigidity around the ankle.??? There was another legend of skiing whose name I now struggle to remember(Klammer maybe?) (Alzheimers I'm sure ) who when asked what he felt when he was racing said " I feel nothing" and proceeded to explain that the pressure between your skiis and the snow should be almost nothing all the timeand that in any sort of turn the force between the ski and the snow will naturally build much too high, and that his job was always to keep these forces to the absolute minimum......but still go in the direction that he needed to go. This was saying that it was the absorption of forces that was by far the most important job that your legs do, not the application of forces. Absorption of forces occurs in the legs via available range of motion in the sagittal plane .....hence less forward lean and not so stiff in the flex.
As far as subtalar function , pronation and turning forces I think that the newer big side cut skis have changed things a bit but I think you want people near to neutral because any pronatory range should be used to transmit edge pressure to the ski, if you are already pronated or even partly pronated but still on a flat ski then edge pressure will be driven by knee translation and rotation, which kind of works but does put more stress on the knees, and also tends to use knee flexion range up earlier in the turn radius, making it more difficult to finish nice long round turns smoothly......just my theory based on other peoples stuff
regards Phill Carter

 

Phil,

This is absolutely the best presentation I have heard on this subject in years. I can not add anything, other than to say...

Everything really changed with shape skis in that we ski with our feet further away from our bodies more than ever before. With shape skis turn radius and turn shape are controlled by the foot and ankle.

Having an active supportive insole, footbed or orthotic and a ski boot set up so that the ankle can function much as it does outside the boot is critical for balance and to enhance proprioception.

Skiing today is about balance, not strength. If the ankle has limited range of motion (either fore and aft or side to side) due to shell design or the use of a rigid insole, balance is lost.

coup

 

Marc,

1) Fore and aft, medially less so laterally. Critical for balance and edge control when skiing on shape skis.

2) No I cannot, as I have no background in podiatry, only skiing, ski instructing, racing a and boot fitting for the last 30 years or so.

3)Seems better yes, but the traditional idea of neutral just does not work as effectively on shape skis as it did on long stiff straight skis, where we really needed to make big movements to engage the sidecut of the ski.

4) Not really as difficult as it seems, if the ankle has a full range of motion pressuring the uphill edge is actually pretty easy.

Or put another way, Applying force to the boot wall can only be achieved if the muscles that tip - evert - the foot can function. The peroneal muscles that run up along the outside of the tibia must be able to move the foot through some range of motion.

I deal with boot fitters and Cpeds everyday that set up orthotics and ski boots based on what appears to be podiatric concepts, and generally the outcomes are poor to ok from a comfort level, but the real test is when I get them on snow and they are not able to access their skills due to limited ROM.

Coup

 

One of the things that begins to occur as the forces of turns begin to reach very high levels, at high speed or in short radius in hard pack (ice etc), steep powder barrels is that a more marked separation between the centre of your travelling mass(body) and the base of support (skis)that you use to stop your bum hitting the snow. In lower speed ,lower difficulty skiing the challenge is to balance over the top of your skis and not fall off them. As athleticism? and technical skill increases skiers move into situations where the forces, speeds and angles involved require that base of support to be put where ever it needs to be in order to maintain the required direction of travel and maintain a separation between your body and the snow. As things get more extreme the separation between centre of mass and base of support gets larger and larger.
Eg a slalom skier with monstrous lateral projection ripping a slice an inch deep into a solid ice race course to get his skis around the other side of a gate post without having to shift his body mass all the way "over there" in order to bring it all back again moments later to pick up the next gate going the other way. The body mass travels a much straighter path than does the skis. Tha balancing of all the forces at speed is a ballet all of it's own and a sensation that I have spent years hunting for and never tired of, although the knees are no longer good for much. And for me the most satisfying of all is to do it with no heel binding.
regards Phill Carter

 

I have continued to think about this a bit and I think that it is not so much that "everything changed" with the advent of shaped skis, but what has changed is the small but necessary turn initiation movements that have changed. Granted on a heavily side cut ski you can begin turns using pretty much only "ankle rolls" but gravity, physics, body weight, and human anatomical function have not changed. One of the major effects of heavily side cut and relatively short skis is that they don't like to run on their flat bases in a very stable way so in order to ride them it is generally better to be on an edge (one or the other?) pretty much all the time. When teaching beginners during the early days of big side cuts I felt that the bigger curves in skis gave a bigger feel for using the edge and it became easier to get people to ride the rails in turns rather than skid in and out of them all the time. I am recently a bit out of touch with what is happenning with full downhill planks or speed skis but I think these purposes still require longer firmer less side cut designs. What does this lead me to think?? that sliding on snow is fun and there are an increasing number of ways to do it and the equipment choices are increasing and that you can choose equipment that is more or less suitable for you want to do. There is no one correct answer.
regards Phill Carter

 

I have continued to think about this a bit and I think that it is not so much that "everything changed" with the advent of shaped skis, but what has changed is the small but necessary turn initiation movements that have changed. Granted on a heavily side cut ski you can begin turns using pretty much only "ankle rolls" but gravity, physics, body weight, and human anatomical function have not changed. One of the major effects of heavily side cut and relatively short skis is that they don't like to run on their flat bases in a very stable way so in order to ride them it is generally better to be on an edge (one or the other?) pretty much all the time. When teaching beginners during the early days of big side cuts I felt that the bigger curves in skis gave a bigger feel for using the edge and it became easier to get people to ride the rails in turns rather than skid in and out of them all the time. I am recently a bit out of touch with what is happenning with full downhill planks or speed skis but I think these purposes still require longer firmer less side cut designs. What does this lead me to think?? that sliding on snow is fun and there are an increasing number of ways to do it and the equipment choices are increasing and that you can choose equipment that is more or less suitable for you want to do. There is no one correct answer.
regards Phill Carter

 

From Sports podiatrist 2017

"Treatment of Plantar Intrinsic Stress Syndrome in Downhill Skiers with Pes Planus The treatment of plantar intrinsic stress syndrome in downhill skiers is focused on two primary areas: 1) Stabilization of the feet with proper orthotic devices 2) Strengthening of the intrinsic musculature, in particular, the abductor hallucis."

I wonder how many sports podiatrists prescribe strengthening exercises along with orthotics when skiers develop arch pain . Snow boarders who take the summer months off seem to suffer from the same type of arch pain .

 

Here is part of the strengthening regime recommended in the Sports Podiatry article.

"A proposed progressive plan for strengthening the intrinsics follows:
• Begin the program two months prior to ski season.
• Continue the exercises through the ski season if not skiing more than once a week.
• Spend five to ten minutes per day on the exercises.
• Begin the program with the patient sitting in a low chair and performing the short foot exercise one foot at a time. • When the patient can perform the short foot exercise on one foot while sitting for five minutes, then perform the short foot exercise on both feet simultaneously. "

We know that habitually wearing shoes weakens the feet and it seems likely that skiing places demands that strengthen them . Go skiing and your feet may get stronger after 2 weeks, just in time to go home from that holiday ruined by arch pain .But strengthen the intrinsic foot muscles before you go and you might get little or no pain at all . Certainly strengthening is recommended in the Sports Podiatry piece by two senior podiatrists.

 

Frederick,
Hope you’re still out there! Thank you for all of your valuable knowledge that you shared from your experiences to this thread over ten years ago. I believe everything you have said still stands true today even with the technological advancements in orthotic manufacturing, scanning and ski boot design. Question for you or anyone else that is knowledgeable in this field, if orthotics are so successful in making ski boots fit better and in turn allow the end user to perform better, why aren’t orthotics recommended/used more often in all sports and also in everyday life for everyone that has feet, regardless of foot issues or not? Curious to hear some thoughts here…

 

Interesting response . No one had posted on this thread since 2009, until I did yesterday . Prior to that the thread contained nothing about foot strengthening . Many podiatrists do now recommend strengthening for skiers, along with foot orthoses, so things have progressed .

 

“And that’s why we can’t have nice things…” as someone once said.



Pronation is not a skiing movement. Missing all the three plane movements. Pronation is based on absorption of GRF in the landing phase of walking and running.

https://en.m.wikipedia.org/wiki/Pronation_of_the_foot

Pronation is a negative work deformation of the foot upon landing. It’s not a method to apply force out through the leg to the snow in alpine skiing. The ski boot restricts these walking gait type movements at the ankle. The ankle is primarily a net negative joint.

https://www.nature.com/articles/s41598-017-15218-7


We start from an athletic stance and use eversion stabilizing movements at the foot and shank. The stabilizing foot movements are coupled with larger flexion and extension limb movements using internal hip rotation from the adduction of the femur while in a flexed whole body position to control the pressure to the ski and the resultant forces back to the skier.

Movements
Fore-aft
Lateral
Vertical
Rotational

•Hip passive stiffness is associated with foot passive stiffness 2021
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8536852/

•A ski instructors guide to the physics and biomechanics of alpine skiing 1998
https://www.thesnowpros.org/download/Physics_And_Biomechanics_Of_Skiing.pdf

Turn cycle structure 2022
https://mdpi-res.com/d_attachment/s...eploy/sensors-22-00902.pdf?version=1643098591

Pages 12-22
https://cdn2.sportngin.com/attachments/document/35cb-2033401/L100_Alpine_Manual.pdf

 

Take a look at:
•Biomechanical analysis of alpine skiers performing giant slalom turns

Introduction
3. Main results in the analysis of alpine skiing turning techniques
https://www.researchgate.net/profil...nt-slalom-turns.pdf?origin=publication_detail


•State of the art in alpine skiing research modeling
https://www.xsens.com/cases/peak-performance-capturing-the-movement-of-alpine-skiing

 

The most recent research in skiing is published in the most recent addition of:

Science And Skiing
A book is published about a year after the International Congress on Science and Skiing where oral presentations are given after peer review.

2020
https://www.researchgate.net/publication/340982840_Science_and_Skiing_VIII

Three books are currently cited as research often in alpine skiing:

George Joubert (translated)
Skiing an art… A Technique 1978

John Howe
Skiing Mechanics 1983

Ron LaMaster
Ultimate Skiing 2010

 

Pronation happens in other activities than walking. You should watch someone standing on one leg. You will see pronation and supination of the subtalar joint. Good skiers happen to be very good at this task and you may not see much movement with them. Now if you take someone who is not very experienced at standing on one foot you will see a lot of motion of the STJ. Skiers are very good at this task because their sport requires them to shift the center of pressure under the foot for ski control.

The reason that you will see subtalar joint movement, while standing on one leg is that the movement is required for medial lateral balance. Shifting the location of force under the foot is more important that actual motion. It is possible to shift the force with very little motion.

Pronation is a skiing movement.

 

The chicken or the egg?
The hip or the foot?

The foot and hip are connected, it’s one movement, according to the research I just provided.

We can’t control amount or duration of pronation.

If so,
Can you explain what muscles allow voluntary control of pronation of the foot on demand?

It’s pretty easy to describe which muscles allow control of eversion and where the movement comes from.

Pronation
rear foot use to stabilize and balance -negative work (inside a ski boot?)
vs
Eversion
whole foot use to apply a force -positive work (in alpine skiing)

•Pronation vs eversion Nigg
https://www.footwearbiomechanics.org/wp-content/uploads/2020/09/WhitePaper1_Pronation.pdf


•Ankle is energy neutral 2017
https://www.nature.com/articles/s41598-017-15218-7


It would be helpful if someone provided some real evidence of exactly how I would pronate my foot voluntarily and how I would control the amplitude and duration of that movement at the foot level for all the different turn radiuses and speeds we use in alpine skiing.


I also looked for it…

 

AP balance control and the ankle
ML balance control and the hip

•Unified theory regarding A/P and M/L balance in quiet stance, Winter 1996
https://edisciplinas.usp.br/pluginfile.php/5245117/mod_resource/content/1/winter_1996JNP.pdf

 

Yes, and the knee is in between the hip and the foot. The joint surfaces at the knee are in a very poor position to translate torque from the hip to the foot or vice versa. The hip and the STJ don't always move in the same direction. During stance phase of gait some people will exhibit pronation and others will exhibit supination.

The peroneal muscles both brevis and longus will pronate the STJ and the posterior tibial muscle will supinate the STJ. You can see this in pretty much any anatomy textbook. I believe the earliest I saw it was in Duchene's text from the 1860's.

Did you see it? If you didn't, keep looking. You are more likely to find it in people who are not experienced skiers.

 

I saw David Winter give a talk on this concept. He talked about inversion and eversion torque at the ankle (subtalar joint) and hip abduction and adduction torque. His talk was consistent with what I have been saying.

 

My post were not about what you have said. They we adding info to the post topic.

But if you want to play opinions with me, then it would be even more fun if you addressed the evidence (research) I presented instead of me personally. Compare and contrast the evidence presented with other real examples of evidence would demonstrate your points even better.

 

“Overall ground reaction forces are transferred through the boot's cuff and spoiler”, (Cf. Lüthi et al., 2005; Stricker et al., 2010). Nakazato et al. (2011)
•Studying Force Pattetns in a Alpine Ski Boot
https://www.frontiersin.org/articles/10.3389/fspor.2021.557849/full#F4

It’s currently fashionable for some ski instruction to use the terminology: “pronate the foot to start the turn”

= pronation as an active motion which you can control the amount and speed of the movement?

Yet no research on skiing technique ever uses the term pronation as a skiing action. Why?
Meta research
https://www.frontiersin.org/articles/10.3389/fphys.2019.00111/full

I looked, maybe the experts are better at looking??

The phase of gait in which we see pronation (unloading), is not the same position as in skiing. The foot-ankle-shank is placed in the ski boot well forward of the ankle-foot position compared to the phase when foot pronation happens in walking/running gait.

 

What is your definition of Pronation at the foot?
Eversion, abduction, dorsiflexion -Open chain
Inversion, adduction, plantarflexion -Closed Chain

The tri-plane movement of pronation don’t add up to any skiing combinations.
The pressure is clearly plantarflexion to make a ski turn, not dorsiflexion.
Eversion is pressure used to increase inside ski edge angle, not inversion.
Adduction would be the rotation movement to the inside to add angulation, not abduction.


Why would eversion not be the correct term?


The ankle has a few functions in a ski turn. It provides fore-aft balance reactive movements (AP), and active lateral edging angulation control movements (ML). The ankle is also involved with absorption (- work) flexion, and power (+ work) extension of the limbs above.
Anterior posterior control (AP) is mostly a ankle reactive to aid balance
The medial lateral control (ML) is mostly a hip movement

Why would we advise skiers to use a tri plane movement in a ski boot?
What are the benefits of using that term to explain skiing movements?
Pronation does not happen by magic??
What exact movements do I use to achieve that tri-plane movement?

Can I control the amount and the speed of my pronation? Can quicken my pronation speed in a more aggressive rotated short turn? Can I slow my pronation speed to match the edging movements of the longer carved high speed turns? Can I eliminate the use of pronation when the condition don’t require it like in skiing deep powder, or when skiing switch in freestyle park moves? HOW?

From what most all research now states:
-The rotation of the femur from the hip using coupling everts the foot to apply pressure the plantar pressure. What is refer to as: “Rolling the ankle in”.
The movement of the coupled thigh rotation is the action, the foot everting to pressure against the boot shell is the reaction to balance that coupled movement above. Why would a skilled skier focus on the reaction to the movement itself?

Eversion is a movement where amplitude and duration of the movement can be controlled at will.
Pronation tri-plane movements varies by foot type and other factors. You would not have consistent results teaching skiers to ski using the term pronation (varies by individual).
The term eversion is a movement which is controlled more consistently by the simple movement of the limb.

Why is eversion the wrong term?
We can kinda see why pronation is not a perfect word used to teach lower extremity alpine skiing movements.