Drill Deb Armstrong/center of mass, weight shift

[Erik Timmerman]

Simple to do, maybe not so simple to learn.

Skiing is simple. That doesn't mean it's easy, but it is simple. - Stu Campbell

 

[JESinstr]

Skiing is simple. That doesn't mean it's easy, but it is simple. - Stu Campbell

Stu was my Certification Examiner Assistant under Cal Cantrel back at Stowe in 1973. Got with him a couple of times when he was VP of skiing at Heavenly. What a great guy and he is missed. I know, I am dating myself.

 

[justplanesteve]

Thank you.
I like those drills for independent feet. Stork was a metanoia for me, because it is dynamic & does not work if everything is not balanced. It forces you into where you need to be to attain it, and re-inforces with fail when something is off.

 

[Sledhead]

I have been aware of the PSIA fundamentals over the last 20 years or so (2014 last updated) and, as I got further and further away from the org and its fundamentals, they became less and less relevant to me on both a technical and corresponding developmental basis. First I find it to be categorically unbalanced in a way that branches out ineffectively, second, I find it a bit “top-down” and, third, somewhat redundant. This is not a criticism or complaint in any way. While I am not privy to the long term planning around the adoption of these 5 specific fundamentals and cannot attest to all the factors that were considered by what was probably quite a large and experienced panel, that is why it has taken me so long to come to certain contrary conclusions. That said, I feel that their determinations may have been made with certain organizational priorities that do not always cater directly to pure development. They have so many other things to consider. Apparently there was some sort of pressure to put out a lot of academic text for their training manual. I suppose it was in order to substantiate itself as a training and education org. Jesinstr’s comment of skiing’s actual simplicity does seem to fly in the face of such a thick manual. I believe that it may be best in terms of serving the masses of customers that show up to their ski schools across the country and especially that they represent the lower echelon of skill.

The third PSIA fundamental is representative of why I feel that they are designed or built to teach only ‘up to’ the advanced intermediate levels. While intermediates may “control edge angles through a combination of inclination and angulation” as written - to angulate and incline the CoM in order to tip the ski is a top-down operation. That is technically crude (in terms of lacking kinesthetic refinement). Advanced skiers, instead, “ski into” angulation and inclination. (they also “ski into” flexion, extension and rotation) In other words, the outcome of angulation, inclination rotation, flexion and extension is produced by the movement of the BoS. Not the CoM. The ski “pulls” the body into extension and inclination in turn phase one, “pushes the body into flexion and angulation in turn phase three and rotates the feet under the CoM throughout the turn cycle. Not the CoM. Carvers leave the CoM alone. They fly it straight and steady. So much so, you can hang your rifle on either side of that horse and it won't make a difference. (yee-ha). Straight and steady momentum is a vehicle that the skier can count on. Of course the faster it is moving, the more you can count on it as long as you are piloting it in the right direction. The path of the ski vs the position of the CoM is the only reason for any movement other than perhaps a pole touch but that which is timed with these paths taken.

After a couple decades of boiling things down in my head, I have come up with my own technical model which, for me, rewrites the fundamentals and corresponding developmental process for the higher level skiers that ski schools typically do not see. This is what I’ve got left burnt to a crisp at the bottom of the pot:

1. Control the relationship of the center of mass to the base of support to direct pressure along the length of the skis
Yes, a fundamental requisite: maintain dynamic fore/aft balance over ski.

2. Control pressure from ski to ski and direct pressure toward the outside ski
Yes, a fundamental requisite: maintain outside pressure dominance.

3. Control edge angles through a combination of inclination and angulation
Advanced skiers do the opposite: edge angle produces inclination and angulation up the chain, not down.

4. Control the skis rotation (turning, pivoting, steering) with leg rotation, separate from the upper body
Yes, but rotary separation is only one of the five fundamental movements of separation also including
flexion, extension, angulation and inclination, all of which are used to meet the top two fundamental requisites that, therefore, deserve a separate categorical designation from the top two fundamental requisites.

5. Regulate the magnitude of pressure created through ski/snow interaction
Yes, but just another way to say number 2.

Perhaps think of the above as freebasing technique. Freeing it from its base of other elements that a training institution is going to apply such as a thick academic training manual, more fundamentals than necessary, program branding and marketing, a large training structure that is going to meet the needs of thousands of people down to the few bare bones that would actually matter to an individual and their dev.

As a technical and developmental model for advanced intermediates and up, seeking the athleticism of high performance carving, I would categorically branch this technical model from the trunk which are I. the two fundamentals outcomes out to the, II. the five fundamental movements that manage the CoM to BoS relationship and then out to, III. the technical skills/direct inputs, a category associated mostly around foot/ankle/boot use, tipping and edging (to answer Matt Merrit’s & Geeper’s question). I see it as pyramidal with I. on the bottom, II in the middle and III at the top. (a developmental pyramid, not a skills pyramid but that which would follow the same lines). Most drills, directives and tasks are presented in spiraled progressions that would be focused on this model by A. challenging the relationship between the CoM and BoS in order to meet the requirements of the two fundamental outcomes and B. by training inside/outside ankle movements/skills associated with tipping and edging as now, at this skill level, it is the BoS that is in charge of the CoM/BoS relationship. Granted, my model uses the most basic and generic elements of the biomechanics of alpine skiing that, for one, respects the actual simplicity of good ski technique and two, is in respect of the athletic development that typically corresponds with higher levels of technique.

Jamt has, as he states, in no particular order: “-1. Start the turn before the fall line, - 2. Balance on the outside at will, - 3. End the turn facing down, &, 4. - Accelerate up or down, always. (dynamics)”. While I would not be surprised that these proposed fundamentals could be boiled down and reconstituted into the relevant fundamental biomechanics that we all find important, the issue I would have is this list’s accessibility to the public. It is esoteric to himself in that most of it would require an in depth explanation to other ski pros, never mind your average student or layman as has been demonstrated in these threads. If, like toppling and hip leveling, an explanation to the layman requires more than two attempts, I won’t like it for program modeling. I do know that: 1. & 2. are universally agreed upon (in most cases), 3 is only relevant to short turns and, 4. Is complicated, unique, subtle and, otherwise, esoteric. That said, I don’t think Jamt is saying that he would base a teaching program on this and it is his personal list that he may base his own lessons on. He has held this as his own technical model for quite some time, something I find uniquely commendable in this space. As well, it may be an example of how far a PSIA instructor may stray from their PSIA manual. If everybody did that, it would not bode well for the PSIA. That everything boils down to the same fundamentals, I would not have an issue.

As another few examples, I think Razie, if I am correct, has things broken down a certain way on his website, Effective Skiing: 1. Balance, 2. Carving and, 3. Speed control. He further categorically differentiates this model between planes of motion (fundamental movements) and essentials (skills). Included in this website is Greg’s (Hellivaskier) comments on the importance of a technical framework followed up by thirteen questions, listed twice, one with questions and the other with the answer - I think. It may be a lot of writing about the benefits of a technical model without the few words that an actual technical model would be composed of. That said, a randomly listed technical model can be found within his article. Presumably both Razie’s and Greg’s take on things have strong derivatives associated with the PTMS model (all 3 w/derivatives from racing, like Armstrong) which has a list of a number of essentials (fundamentals) which are: 1. tipping, 2. flexion and extension, 3. fore/aft, 4, counterbalancing and, 5. counteracting. These are categorized as primary and secondary movements. I do like this as it represents what I think are close enough to the five fundamental movements we use to manage the relationship of the CoM and BoS: flexion, extension, rotation, angulation and inclination.

Ultimately, I believe that everybody is saying the same things, however, how we say it, classify, categorize, encapsulate, what we choose to emphasize/prioritize over other arguably important elements, how simple/complicated it is, and what language we use is what will make the difference in how it is absorbed by the public, students and ski pros alike. Fundamentally, I agree with almost every argument proposed in these threads. The facts are easy. Thoroughly describing the melding of the three sciences of biomechanics, physics and engineering associated with skiing with few words is not. Structuring them into a functional teaching program is even more difficult.

 

[LiquidFeet]

I have been aware of the PSIA fundamentals over the last 20 years or so... I am not privy to the long term planning around the adoption of these 5 specific fundamentals and cannot attest to all the factors that were considered by what was probably quite a large and experienced panel ....I find it a bit “top-down” ....Apparently there was some sort of pressure to put out a lot of academic text for their training manual.
.....Thoroughly describing the melding of the three sciences of biomechanics, physics and engineering associated with skiing with few words is not. Structuring them into a functional teaching program is even more difficult.

Agree. Excellent summary of alternative organizational models for ski technique.

Last time I checked, PSIA-AASI is working with Penn State University to provide teaching resources associated with ski instruction for a new degree (or certificate, not sure) in SnowSports. I have heard members of the National Team present on this project. There's probably a textbook in the works. This Penn State priority asserts certain parameters on how PSIA structures its fundamentals.

PSIA's choice to describe fundamentals focusing on moving the torso around over the feet rather than moving the feet around under the torso may be because skiers in the US are intermittent lesson takers. Ski weeks, where there is a lesson every day, are not so much a thing here. Results need to happen fast for learners to feel like they are getting their money's worth. In my experience, "top-down" teaching and learning, as you phrase it, is faster in generating results. Learning to move the torso around is easier than learning to move the feet/skis around. Happy customers who want to see results fast are probably driving this decision. It may also be a hang-over from the straight ski days.

Beginners and intermediates (talking about adults here) could be taught from the beginning to work from the feet upward, moving the feet around under the torso to maintain dynamic balance and to generate edge angles. Then, as you point out, success would mean angulation and inclination happen as a byproduct. But teaching this to beginners and intermediates probably would not produce easy-to-recognize results as fast for a lesson taker who will be in class only for one-two hours, or for only for one day a year.

I may be wrong about the relative ease and speed of teaching top-down vs bottom-up and would welcome personal experience-driven discussion to the contrary.

You also talk about the need for good communication when creating a functional educational program. Choosing the right words, choosing to make them brief enough to hold learners' attention, and making those words memorable, is extremely important. I think of such words and phrases as mantras. Surrounding those words and phrases with short sentences is also important, so they don't get lost in wordiness. Not every educator is good at this. John Clendenin, Stephen Karp/Karpy, Lito Tejada-Flores come to mind and I'm sure there are others.

 

[Jamt]

Jamt has, as he states, in no particular order: “-1. Start the turn before the fall line, - 2. Balance on the outside at will, - 3. End the turn facing down, &, 4. - Accelerate up or down, always. (dynamics)”. While I would not be surprised that these proposed fundamentals could be boiled down and reconstituted into the relevant fundamental biomechanics that we all find important, the issue I would have is this list’s accessibility to the public. It is esoteric to himself in that most of it would require an in depth explanation to other ski pros, never mind your average student or layman as has been demonstrated in these threads. If, like toppling and hip leveling, an explanation to the layman requires more than two attempts, I won’t like it for program modeling. I do know that: 1. & 2. are universally agreed upon (in most cases), 3 is only relevant to short turns and, 4. Is complicated, unique, subtle and, otherwise, esoteric. That said, I don’t think Jamt is saying that he would base a teaching program on this and it is his personal list that he may base his own lessons on. He has held this as his own technical model for quite some time, something I find uniquely commendable in this space. As well, it may be an example of how far a PSIA instructor may stray from their PSIA manual. If everybody did that, it would not bode well for the PSIA. That everything boils down to the same fundamentals, I would not have an issue.

You are absolutely right- I actually use these concepts in clinics that I give to other coaches, and this part usually takes 1-2 hours.
In addition to these fundamentals I also talk about what movements are used to accomplish them which takes a similar amount of time. Then on the hill a lot of time is spent taking it into practice, including a lot of drills.

Also my context is race turns, primarily SL and GS, which kind of narrows the scope. A GS turn usually takes 1.5-2 seconds so it is not really a "long" turn in the context of recreational skiing.

For example, in recreational skiing it may be totally fine to ski with very little dynamics if you e.g. do slow skidded turns, but for racing it is very seldom a good idea, except perhaps for glide sections.

 

[Erik Timmerman]

1. Control the relationship of the center of mass to the base of support to direct pressure along the length of the skis
Yes, a fundamental requisite: maintain dynamic fore/aft balance over ski.

2. Control pressure from ski to ski and direct pressure toward the outside ski
Yes, a fundamental requisite: maintain outside pressure dominance.

3. Control edge angles through a combination of inclination and angulation
Advanced skiers do the opposite: edge angle produces inclination and angulation up the chain, not down.

4. Control the skis rotation (turning, pivoting, steering) with leg rotation, separate from the upper body
Yes, but rotary separation is only one of the five fundamental movements of separation also including
flexion, extension, angulation and inclination, all of which are used to meet the top two fundamental requisites that, therefore, deserve a separate categorical designation from the top two fundamental requisites.

5. Regulate the magnitude of pressure created through ski/snow interaction
Yes, but just another way to say number 2.

I won't pretend that I love the fundamentals as they ar enow. Personally, I was happy with BERP. But I do think you could look at the fundamentals differently and you might find that they do describe good skiing.

Number 3 isn't telling you that you must move your body first it's just describing what good skiing would look like. And btw, the way I think of it, if skiing does start with the feet inside the ski boots, then the angulation starts with the ankle joint and then as the body moves away from the skis other joints become involved.

Number 5 isn't a rehash of #2, it is talking about flexion/extension.

Anyway, for me teaching a lesson, I boil it down to even less - Balance on outside ski, change edges to start the turn, allow the skis to turn more than the body. Obviously there is plenty of room to expand on those three points.

 

[Jamt]

Presumably both Razie’s and Greg’s take on things have strong derivatives associated with the PTMS model (all 3 w/derivatives from racing, like Armstrong) which has a list of a number of essentials (fundamentals) which are: 1. tipping, 2. flexion and extension, 3. fore/aft, 4, counterbalancing and, 5. counteracting. These are categorized as primary and secondary movements. I do like this as it represents what I think are close enough to the five fundamental movements we use to manage the relationship of the CoM and BoS: flexion, extension, rotation, angulation and inclination.

I think it is important to differentiate the fundamentals of a good turn with what movements are used to accomplish them.
For example PMTS has a strong focus on outside balance, but it is not one of the essential movements. All the 5 essential movements affect outside balance in various degrees.
Another example is the popular topic extension vs flexion (vs toppling). Both movement patterns can be used to make a good turn fulfilling e.g. my fundamentals (probably also PSIA?).

Then you also have skills and abilities. For example fore-aft. It is not the case that you always have to be fore to make a good turn, but it is essential that you can use fore-aft appropriately. It is not done with a single movement so it is not a movement essential either.
Not sure how to categorize that.

 

[markojp]

Potayto, potahto.. we do all our training, and I do all my coaching starting with the feet, and then working up the chain. It's not hard, nor contradictory in my mind, to frame our focuses into PSIA'ese. Like the original post, I address angulation as a resultant of how the the CoM moves in relation to the BoS to manage, rather than resist forces at our feet and commensurately, along the length of the ski. One funny comment after a recent clinic, someone said, "you didn't say 'your skis' once. My answer was that for what we needed until we figured out what our feet need to do and where to be to make our skis work, it seemed natural to only mention the feet, and think of skis as an extension of them. Honestly, I hadn't thought about it until it was pointed out.

I do like the order and framework of the 5 fundamentals. If I wanted to pick an argument, I'd probably say that Balance is still a skill, but to clarify, I'd say the 4 skills (now 3 these days, edging, rotary, and pressure) would be: edging, rotary, and pressure while moving in dynamic, functional balance. Honestly though, I'm not really worried or wanting to go to the mat about it about it one way or the other.

 

[Sledhead]

I can’t disagree with any of the responses to my post. Liquid feet, you are correct that my model is targeting the athletic advanced intermediate seeking to bust through to the next level. I think that this is a very relevant demographic in these forums and on YoTube. Yes, top down is the way to get started as a beginner for all the reasons you outline. And, yes, in today’s World, messaging is everything. Wait … it has always been that way. Ever since we drew that first buffalo getting speared on the cave wall. Perhaps a good ski graphic … so we can continue that messaging. It is programmed in our genes for survival purposes. We don’t want to think for ourselves. We prefer to choose a predesignated platform of thought in order to automate these aspects of primitive survival. I digress.

Jamt, not surprised that you are race influenced. My racing background is my foundation, but it is not everything. As technical freeskiers, we can take this foundation of fundamentals and open it up to having control of where we want our skis to go. A lot of very good racers that are very good because they have drilled in the fundamentals all the way through and, as a result, can have problems with transitioning to the enhanced dynamics that technical freeskiing offers over a strict racing technique. I like Helluva skier’s race inspired technical model very much. When I compare him to a skier like McGlashin, I appreciate them equally, however, Helluva is a bit more severe and McGlashin is a bit more relaxed. Sometimes I am in the mood for severe and sometimes I’m in the mood for relaxed.

I agree with Erik regarding the target simplicity of BERP. If #5: “ Regulate the magnitude of pressure created through ski/snow interaction”, however, is about flexion and extension then, why wouldn’t it indicate that? “Ski to snow interaction” could mean tipping the ski which is what creates and diffuses pressure under the ski for a carved turn. While flexion and extension may be subsequent outcomes, that is a far stretch from how fundamental 5 is written. While tipping up creates pressure, tipping down releases it. It is also released by skidding. Either way, all we have to go by is what words are used, not the ones surmised.

In the end of it all, I do agree with Markop’s sentiment of semantics in that we are all working with the same facts and describing them differently as we see them from our unique perspectives.

The technical model outline I use is categorized by fundamental outcomes, fundamental movements & fundamental skills (for alpine skiing, I define the term fundamental as factors that must occur for a high performance carve to happen). When I pull the bones from any program, I find the simple, boring and generic aspects of biomechanics, physics and engineering and avoid anything that sounds more like pretty packaging. You can have the colorful cookie jar, just give me the cookies.

This is a simplified technical model that is in respect to the actual biomechanical simplicity of advanced skiing. It also provides a certain strategic ambiguity that allows for the anatomical and intellectual differences from skier to skier.
Lastly, nothing I write such as this technical model is mine, new or meant to be creative in any way (except for a little reorganization) AS a technical model, it serves as the foundation of a developmental model that would fill only one page.

1. Fundamental concepts/outcomes which are ski to surface interaction outcome and controlling the location of the center of pressure mathematically located within the footprint of the pair of skis.
2. Gaining and maintaining dynamic fore/aft balance
3. Gaining and maintaining outside pressure

1. Fundamental CoM/BoS movements, separation mobility to achieve the above outcomes.

1. Rotation - ankles, hips, pelvis, spine, shoulders, navicular in response to separate paths of CoM & BoSi.
2. Angulation - Hips and spine (closely associated with rotation)
3. Inclination - static gravity fed tipping of CoM/BoS
4. Flexion - ankles (dorsiflexion), knees, hips
5. Extension - ankles (plantar flexion), knees, hips.

1. Fundamental tipping and edging skills to achieve the above fundamental movements.

1. Tipping from subtalar pronation/inversion of outside ankle & supination/eversion of inside ankle.
2. Fore/aft control from dorsiflexion and plantar flexion.
3. 360 degrees of cuff pressure from a blend of these six motor patterns.

Note: I use three turn phase timing to identify the duration, intensity, rate and timing of the five fundamental movements.
While the 5 fundamental movements can be plotted separately, they are blended and overlapping as they are “designed” to work together to achieve one unified outcome.
Duration - how much of a turn cycle is used by a particular movement pattern such as an entire turn cycle of ski rotation.
Intensity - the quickness or speed in which a particular motor pattern reaches maximum rate or magnitude
Rate - the magnitude of a movement such as degree of angle for flexion, degrees of rotation, angles of inclination, etc.
Timing - where in the turn cycle and along with what other movements such as the “timing fundamentals” of inclination with extension in turn phase one and angulation with flexion in turn phase three.

 

[Chris V.]

The technical model outline I use is categorized by fundamental outcomes, fundamental movements & fundamental skills (for alpine skiing, I define the term fundamental as factors that must occur for a high performance carve to happen).

Good stuff, all, including the detail you go into. Teaching novices and intermediates, I put those fundamental movements and skills first. When those are improved the outcomes will come. If a skier is making wedge turns, but lacks the commitment to outside ski balance, or lacks foot tipping ability, or is out of balance fore-aft, you can't just force a parallel turn outcome. The underlying movements have to be there first.

 

[James]

Tipping from subtalar pronation/inversion of outside ankle & supination/eversion of inside ankle.

Should be pronation/eversion - outside foot
Supination/inversion - inside foot

 

[Sledhead]

Yes James, you are correct and thank you. Between inside/outside, supination/pronation, inversion/eversion, frontal/transverse, abduction/adduction and plantar flexion/dorsiflexion, I will often trip up at least once. Let me get this straight:

Inside: pronation & eversion
Outside: supination & inversion
Frontal plane: supination & pronation
Transverse plane: inversion & eversion
Pronation: eversion, abduction & dorsiflexion
Supenation: inversion, adduction and plantar flexion ... Ugh!


Markop, if sole pressure equated directly to ski pressure, I would agree with you. However this is not the case because we also have cuff pressure that, along with sole pressure, controls the pressure along the length of the ski through the triangulation of leveraging the boot against the ski between the sole and cuff. Technically, the ski is part of the entire kinetic chain from the ground up and its contact with the ground is the most important of the performance elements of skiing. Unfortunately, there are very few conveniences of singularity related to the systemic nature of ski technique. The actual “chain of force” being utilized through the entire turn cycle also includes the ground and the force it provides as well, so if you are going to leave the ski out, you might as well leave the ground out of the discussion also. Ending the discussion at the sole while ignoring the cuff and ski at either side of the sole is like going through all the trouble to rob a bank and then leaving the cash at the door and laying face down with hands spread on the sidewalk. Now, do you want to make a good turn or go to federal prison? The choice is up to you. While some people believe that the body and its positional outcome is at the core of ski performance, others consider the ski to snow interaction outcome (control of the location of the center of pressure under the skis) as the ultimate and final words of performance outcome. We cannot do that w/o reference to the ski and the ground.

While there is often discussion on whether we pressure the cuffs, I believe the discussion should be about whether the cuff is pressuring us based on what the ski is doing. Based on your definition of the force derivative of angulation, I suspect you would agree. In addition to “pressure”, I also prefer the terms: tension and leverage rather than “push”, “crush” or “force”. Without good cuff tension, that shovel will slap you in the face. As far as I am concerned, cuff pressure and sole pressure are nothing without each other. The triangulation of tension/leverage mentioned above comes in two forms: rear cuff, ball of foot and forward center of pressure (CoP) during plantar flexion in turn phase one - and - front cuff, heel of foot and rearward CoP during dorsiflexion in turn phase three. As per usual, a mouthful to say the least. No need to worry, I've got James to double check that for me. We are not leaning back and forth on the boot, we are just creating and managing the triangulation of tension with the other two components. It is the geometric triangulation where the power comes from, not the individual sources. Perhaps we can think of the sole as the brains (balance) and the cuff as the brawn (force) in their triangulation relationship with the CoP under the ski. In skiing as in life, balance is nothing w/o force and force is nothing w/o balance. With power comes responsibility.

Of course, as liquidfeet states, not much of these technicalities is relevant to the students a typical ski school will see. Even when you are coaching other ski pros, you are coaching them, primarily, to teach beginners and intermediates. I agree that restricting/simplifying this discussion to the soles at these levels may be best. Those are the students that most instructors who are born to teach prefer to work with. In my opinion, that skill level is at the core of teaching skiing and where the connection between student and teacher is at its most involved and most rewarding. When we start teaching advanced skiers, that is when things really start to become coaching where we are forced to work with where the skier is coming from much more and where we help the skier to delegate their development rather than to commandeer it as we do with beginners and intermediates. Most of what interests me regarding the technical aspect of skiing is far and away from where the ski meets the snow, so to speak. When I am working with someone on snow, I will say very little. One thing about teaching/coaching/mentoring ski technique is that, the more we know, the less we have to say. Just like when getting caught robbing a bank, you have the right to remain silent. Anything you say can and will be used against you in the court of the law of physics. You have the right to speak with an L4. If you cannot afford one, one will not be afforded to you. They are just too damned expensive.

 

[James]

Inside: pronation & eversion
Outside: supination & inversion
Frontal plane: supination & pronation
Transverse plane: inversion & eversion
Pronation: eversion, abduction & dorsiflexion
Supenation: inversion, adduction and plantar flexion ... Ugh!

How are inversion/eversion in a different plane from supination/pronation?

They’re all fontal, no?

 

[Chris V.]

Of course, as liquidfeet states, not much of these technicalities is relevant to the students a typical ski school will see. Even when you are coaching other ski pros, you are coaching them, primarily, to teach beginners and intermediates. I agree that restricting/simplifying this discussion to the soles at these levels may be best.

At low speeds on gentle green terrain, is crushing the cuffs even possible? Other than by leaning the whole body into the cuffs in a straight run, which I doubt is something we'd encourage. It's only when skiing becomes dynamic that the larger fore-aft movements come into play.

 

[markojp]

Yes James, you are correct and thank you. Between inside/outside, supination/pronation, inversion/eversion, frontal/transverse, abduction/adduction and plantar flexion/dorsiflexion, I will often trip up at least once. Let me get this straight:

Inside: pronation & eversion
Outside: supination & inversion
Frontal plane: supination & pronation
Transverse plane: inversion & eversion
Pronation: eversion, abduction & dorsiflexion
Supenation: inversion, adduction and plantar flexion ... Ugh!


Markop, if sole pressure equated directly to ski pressure, I would agree with you. However this is not the case because we also have cuff pressure that, along with sole pressure, controls the pressure along the length of the ski through the triangulation of leveraging the boot against the ski between the sole and cuff. Technically, the ski is part of the entire kinetic chain from the ground up and its contact with the ground is the most important of the performance elements of skiing. Unfortunately, there are very few conveniences of singularity related to the systemic nature of ski technique. The actual “chain of force” being utilized through the entire turn cycle also includes the ground and the force it provides as well, so if you are going to leave the ski out, you might as well leave the ground out of the discussion also. Ending the discussion at the sole while ignoring the cuff and ski at either side of the sole is like going through all the trouble to rob a bank and then leaving the cash at the door and laying face down with hands spread on the sidewalk. Now, do you want to make a good turn or go to federal prison? The choice is up to you. While some people believe that the body and its positional outcome is at the core of ski performance, others consider the ski to snow interaction outcome (control of the location of the center of pressure under the skis) as the ultimate and final words of performance outcome. We cannot do that w/o reference to the ski and the ground.

While there is often discussion on whether we pressure the cuffs, I believe the discussion should be about whether the cuff is pressuring us based on what the ski is doing. Based on your definition of the force derivative of angulation, I suspect you would agree. In addition to “pressure”, I also prefer the terms: tension and leverage rather than “push”, “crush” or “force”. Without good cuff tension, that shovel will slap you in the face. As far as I am concerned, cuff pressure and sole pressure are nothing without each other. The triangulation of tension/leverage mentioned above comes in two forms: rear cuff, ball of foot and forward center of pressure (CoP) during plantar flexion in turn phase one - and - front cuff, heel of foot and rearward CoP during dorsiflexion in turn phase three. As per usual, a mouthful to say the least. No need to worry, I've got James to double check that for me. We are not leaning back and forth on the boot, we are just creating and managing the triangulation of tension with the other two components. It is the geometric triangulation where the power comes from, not the individual sources. Perhaps we can think of the sole as the brains (balance) and the cuff as the brawn (force) in their triangulation relationship with the CoP under the ski. In skiing as in life, balance is nothing w/o force and force is nothing w/o balance. With power comes responsibility.

Of course, as liquidfeet states, not much of these technicalities is relevant to the students a typical ski school will see. Even when you are coaching other ski pros, you are coaching them, primarily, to teach beginners and intermediates. I agree that restricting/simplifying this discussion to the soles at these levels may be best. Those are the students that most instructors who are born to teach prefer to work with. In my opinion, that skill level is at the core of teaching skiing and where the connection between student and teacher is at its most involved and most rewarding. When we start teaching advanced skiers, that is when things really start to become coaching where we are forced to work with where the skier is coming from much more and where we help the skier to delegate their development rather than to commandeer it as we do with beginners and intermediates. Most of what interests me regarding the technical aspect of skiing is far and away from where the ski meets the snow, so to speak. When I am working with someone on snow, I will say very little. One thing about teaching/coaching/mentoring ski technique is that, the more we know, the less we have to say. Just like when getting caught robbing a bank, you have the right to remain silent. Anything you say can and will be used against you in the court of the law of physics. You have the right to speak with an L4. If you cannot afford one, one will not be afforded to you. They are just too damned expensive.

To clarify, I do talk about skis, but not until people understand what their feet need to be doing in their boots.

 

[Sledhead]

James, this is where things can get even a bit more subtle. Technically, pronation & eversion as well as supination & inversion are the same movement in that they always happen together. You can’t have one without the other. While pronation and supination reflect this movement in lateral form or, in the frontal plane, eversion and inversion reflect this movement rotational form or, in the transverse plane. In other words, while the subtalar tips the inside foot towards the inside of the turn, it rotates that foot to the outside of the turn at the same time and within the same movement. While the subtalar tips the outside foot to the inside of the turn, it rotates that foot also to the outside. While both feet tip inwards, they rotate outwards at the same time. Conversely, if the intent is to rotate the feet outward, that will also result in tipping the ankle into the turn. I believe that this distinction is made in biomechanics in order to reflect the relative direction of movement of the weighted ankle in a walking gait. I also believe that it is, by extension, relevant to skiing as the subtalar is the most important and nuanced joint in advanced skiing.

 

[LiquidFeet]

James, this is where things can get even a bit more subtle. Technically, pronation & eversion as well as supination & inversion are the same movement in that they always happen together. You can’t have one without the other. While pronation and supination reflect this movement in lateral form or, in the frontal plane, eversion and inversion reflect this movement rotational form or, in the transverse plane. In other words, while the subtalar tips the inside foot towards the inside of the turn, it rotates that foot to the outside of the turn at the same time and within the same movement. While the subtalar tips the outside foot to the inside of the turn, it rotates that foot also to the outside. While both feet tip inwards, they rotate outwards at the same time. Conversely, if the intent is to rotate the feet outward, that will also result in tipping the ankle into the turn. I believe that this distinction is made in biomechanics in order to reflect the relative direction of movement of the weighted ankle in a walking gait. I also believe that it is, by extension, relevant to skiing as the subtalar is the most important and nuanced joint in advanced skiing.

Regulars on this forum are aware of this anatomical phenomenon. It comes up regularly in technical discussions. But the RoM for rotation of the foot associated with eversion and inversion is small. Its effect is subtle, and escapes most recreational skiers. Its importance grows however when the discussion is whether or not to teach beginners to rotate the feet in the direction of the turn.

 

[Yepow]

Regulars on this forum are aware of this anatomical phenomenon. It comes up regularly in technical discussions. But the RoM for rotation of the foot associated with eversion and inversion is small. Its effect is subtle, and escapes most recreational skiers. Its importance grows however when the discussion is whether or not to teach beginners to rotate the feet in the direction of the turn.
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I find "roll your ankles" the most overloaded piece of advice I've ever received OR maybe I've just never actually understood what people mean by it. Sometimes people seem to mean "initiate with your ankles but follow through with knees and then rotation in your femurs", maybe they actually mean roll your foot inside your boots (inversion/eversion), maybe they mean "treat your foot as a block, then push the whole block to the inside..."

Roll your ankles as blanket advice has not yet clicked for me

 

[Sledhead]

I like the thematic strategic ambiguity of "use your feet, soldier".

I think of the tipping and rotating of the ankle as a compliance that compliments the arc of the turning ski. Technically, it is the ski that is operating the subtalar, not the skier. We need that rotational and angular separation wherever we can get it from the bottom to the top of our chain. Even though we are only discussing millimeters of movement from within the boot, because it is in the boot directly over the ski, those few millimeters replaces inches of movement up the chain at the CoM in order to produce a similar desired effect whichever that may be.