BALANCE IN SKIING: ONE STEP FORWARD, TWO STEPS BACKWARD


What is balance in skiing?

It depends on who you ask. The only limitations seem to be the imagination of the various authorities in skiing.

Typical explanations of balance don’t differentiate between balance associated with staying upright by any and every means and the sophisticated, subconsciously mediated, processes of balance responsible for the maintenance of upright postures and locomotion. The latter involves the management of forces in the feet or foot between the soles of the feet or foot and ground. The coordination and orchestration of these forces by the CNS, maintains the position of center of mass (COM) within the physiological limits of the base of the support in a state of dynamic equilibrium. In laboratory environments, where balance has been studied so throughly it can be analyzed and quantified, balance is expressed by the relationship of the center of pressure or COP (the point center of ground reaction force) with COM. The location and excursion of COP is indicative of the position of COM as expressed by the gravity line, G, or resultant force, R. No physical forces associated with balance activity are present in the sagittal (side-to-side) or coronal (front-to-back) planes. The balance process is mediated entirely by the central nervous system (CNS) at a subconscious level. Given the extreme sophistication of the hard-wired  mechanisms of balance we were born with, there is no valid reason why balance in skiing should be any different.

Without knowing where the forces in the feet should be and how and where they should move, we have no idea how to balance perfectly on our outside ski as those such as Marc Giardelli and other world class racers and elite skiers have alluded to for decades; let alone have any idea of what balancing on the outside ski should feel like.

Two studies done in 1998 by a team from the University of Ottawa provide some insights.

ANALYSIS OF THE DISTRIBUTION OF PRESSURES UNDER THE FEET OF ELITE ALPINE SKI INSTRUCTORS: Dany Lafontaine, M.Sc.1,2,3, Mario Lamontagne, Ph.D.1,2,3, Daniel Dupuis, M.Sc.1,2, Binta Diallo, B.Sc.1,2,3. Faculty of Health Sciences1, School of Human Kinetics2, Department of Cellular and Molecular Medicine, Anatomy program3, University of Ottawa, Ottawa, Ontario, Canada.

“Thanks to recent developments in biomechanical instrumentation, research on alpine skiing can now be performed in on-piste situations. Therefore it would be of interest to determine what is happening under the feet of high level non-racers, such as ski instructors (my emphasis added).

“Three highly skilled ski instructors (CSIA level IV) consented to serve as subjects for this study. Their usual ski boots were fitted with pressure sensitive insoles linked to the PEDAR mobile system which they wore on their backs (Novel corporation, Munich). With their boots so equipped, the subjects performed a variety of turns of controlled radii on a groomed piste. The turn radii were controlled by markers on the snow surface, and were consistent with the guidelines of the Fédération Internationale de Ski, for turn size. Subjects skied on a groomed piste, while the PEDAR system recorded pressure data (sampling rate 50 Hz) onto a memory card. A video (60 Hz) recording of their ski runs was also made to facilitate analysis.

Results:

“What has come out of the results at this point of the study, is that the pressure recorded under the feet can be quite high. The highest pressures are measured on the medial parts of the heel, as well as the medial parts of the forefoot (under first metatarsal). The centre of pressure travels from under the first metatarsal joint down to under the medial part of the heel of the skiers, as they make their way through the turn (my emphasis added), These highest pressures reach up to 30 newtons per square centimetre. Force-time histories reveal that forces of up to 3 times body weight can be attained during high performance recreational skiing (my emphasis added).

Conclusions/Discussion:

“It is quite likely that the type of equipment (skis and boots) worn by the subjects had an effect on the values obtained (my emphasis added). The individual technical adjustments of the skiers may have also had an effect on the measurements. One thing is certain, the centre of pressure moves from the front medial part of the foot, back towards the medial side of the heel as the skiers progress through the turns.”

 

ANALYSIS OF THE DISTRIBUTION OF PRESSURE UNDER THE FEET OF ELITE ALPINE SKI INSTRUCTORS: Dany Lafontaine, Mario Lamontagne, Daniel Dupuis & Binta Diallo, Laboratory for Research on the Biomechanics of Hockey, University of Ottawa, Canada – Proceedings of the XVI International Symposium on Biomechanics in Sports (1998), Konstanz, Germany, p.485.

“In alpine skiing, the feet are used as both a steering device and an important source of sensory input (my emphasis added). It has become quite common for instructors and coaches to ask their pupils to feel pressure under certain parts of their feet in order to ski better. It has also been a trend in skiing to inform students to initiate turns through the application of pressure in the forefoot area and to progressively “roll” from the front to the back of their feet. All of these instructions rely on master instructors’ perceptions of what they feel while executing a ski turn. Historically, it has been quite complicated to perform biomechanics research on alpine skiing on-site. This fact is so because of the environment where the sport is practised which does not lend itself well to biomechanical measures using traditional equipment.

The trajectory of COP was consistent between both feet for all turn types (my emphasis added). Results showed the COP following a near linear trajectory for the Dynamic Parallel, Short Radius and Basic Parallel turns. This trajectory had the COP move from the head of the first metatarsal at the beginning of the turns, and progressively migrate towards the medial aspect of the longitudinal arch near the end of the turns (my emphasis added). However, the COP travelled from the head of the first metatarsal to the medial aspect of the heel during Giant Slalom turns

“A factor that was not controlled during data collection was the equipment worn by the subjects. The skiers wore different boots, and used different skis, although two of them had the same brand and model of skis and boots. It still has yet to be determined if that factor had any effect on the results. A point that all the skis that the subjects used had in common is that the skis were all sharp side-cut skis (also called shaped skis). Another equipment variation which may have affected in-boot measurements, is that some subjects (n=5) wore custom designed footbeds, while the other did not (my emphasis added). As was stated for the skis and boots, it has yet to be determined if this piece of equipment affected results or not.”

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COMMENTS

  • Every instructor in both studies, without exception, initiated their turns with high pressure under the head of the first metatarsal of their outside foot in the turn. This is a clear indication that not just pressure, but high pressure under the first metatarsal, is fundamental to the technique of elite skiers.
  • These studies were published 17 years ago. Yet even though Shiffrin stresses the importance of ‘getting over it’ (the head of the first metatarsal) and Ligety talks about ‘creating pressure’, there is little or no mention in the technical narrative of skiing of the need to establish pressure under the head of the first metatarsal at the initiation of a turn.
  • All the instructors in the two studies were elite skiers. Yet there were significant differences between the two groups of instructors in each study. In the first study, the data showed that COP at the beginning of a turn was under the head of the first metatarsal and moved to the medial (inner) aspect of the heel near the end of a turn whereas in the second study COP at the beginning of a turn was under the head of the first metatarsal and moved only slightly rearward to the medial aspect of the longitudinal arch near the end of the turn.
  • The studies did not look for forces in other planes so did not confirm that the instructors were in ‘balance’.
  • It was only in the GS turns that COP moved to the medial aspect of the heel. The question is why did COP move rearward at all towards the end of any turn types?
  • The only way COP can act under the head of the first metatarsal is through pronation. This requires that the foot be flat on snow either between edge change at the end of the transition or from a flat landing on the outside foot/ski in the fall line. Even then, the boot must not interfere with the ability of the the foot to pronate.

In my next post, I will discuss the implications of the University of Ottawa studies.

20 comments

  1. Merry Christmas and how I hate it when I can’t ski on this day!!

    Reflecting more upon the study issue, it occurs to me that if David MacPhail does the updated study there will still be the accusation of bias, lack of science etc. So my theory is that we should do an ‘independent’ study and I’ll volunteer to be part of that. Now I’m biased, because I feel that his theories are MacPhail-proof! so what I need is one of the skeptics to get together with me and work together using David’s theories to the best of our understanding and see what the results are. As an added bonus I have some equipment that he doesn’t so this individual would have the added pleasure of experimenting with these things and another set of off-the-beaten-path theories to attempt to discredit or validate.

    David and I know each other only through his blog. I have never had the honor of receiving, on site, formal training from him so essentially have virtually the same information anyone else would have access to. This is why I’m biased and feel that what is being presented is as much a law as gravity because if I can take this info off the posts I read and transfer that consistently to not only myself, but others it has to have a concrete basis. Whereas all of the formal training in the past always had one step in it that reads like a favorite tee shirt I have; it’s a cartoon with a student doing a calculus problem with the second step reading ‘and then a miracle occurs’ and then the answer. Just ask David for my contact info and we’ll see what we can arrange.

  2. How did I miss all of this exciting dialogue? Guess I had other fish to fry unfortunately but it’s great to get caught up here. The interchange with Cookie has helped my understanding so I’m grateful for both sides of it. My thought on why the minute analysis and ‘engineering’ analytics that David presents are important is because a lot of great skiers are great athletes and don’t know what they’re doing, they simply fit into the boots and so achieve those pressure points that David is describing because they happen to right in place. Those that understand that stay with the ‘same old’ equipment and stay at the top for long periods of time, see Stenmark!! If you You-tube him you’ll see him making remarkable turns back 30 years ago and looks to me he has found the perfect spot that David talks about and no one could touch him. The only difference is that todays skis with a bit more side cut but way better flexibility would have allowed him to ski with the great angles of today and he’d most likely still be winning just as consistently because he wouldn’t have Shiffrin to ski against!! The reason David’s work is so important, at least for me is because I’ve had the great fortune to ski with some superior skiers on the bump side of the mountain. I could never ski like them because I was doing way too much ankle foot movement because the ski boots had me so locked up that even with all that effort it was still about all I could do to make the damn ski turn because it was always ‘railing’ (wanting to go straight) on me. I still did too much movement up until the finish of last year, even though I’ve been able through my own discoveries and now this blog to take this hopeless situation to the point that other than the slippery boot soles, I can hike in my ski boots as comfortably as my regular hiking wear. Even though I skied with those great skiers a lot they A) never explained adequately what they were doing because it turns out I (and too many other skiers) can’t get that pressure point in their current set up. And B) they never showed me how to adjust my equipment to get to that pressure point. I finally got into radical experimentation during my teaching career because 5 different trainers told me to do the same thing and none of them could coach me into doing it because THE EQUIPMENT wouldn’t allow it and they couldn’t figure that out. I can ski better today skiing 100 less days a year than 20 years ago because I can actually get onto the inside edge. I’m so excited to get on the snow this year because now understanding how to most efficiently use my equipment with most of the final tuning coming from this blog, I feel positive I can eliminate all the extra movements needed and left over from the ski shop/industry set up boots that I used to ski in. If I can’t do what David is explaining I now know how to adjust the boots to do so. How do I know that? Because I can do that with my regular footwear using those methods. This is the million dollar question for all detractors; why does all foot wear in addition to ski boots hinder the wearer and many times injure them? I swear, the major reason for knee and hip replacement and back injuries is the misalignment the footwear inflicts upon the skeletal system.

    I’ve learned more from this blog in the last year and a half than in the previous 50! And most of the previous stuff turns out to be wrong!!!!!!!

  3. Would be nice to see a more recent similar study with a variety of skis and professional skiers from various countries and disciplines.

    Also would like do see how it looks on the CoP map of a foot when the foot pronates while simply balancing on that one foot… Maybe having a hand on a wall to keep from falling over when you pronate…

    1. I find it interesting that although the functional principles of the foot have been known and irrefutably accepted for at least 50 years, you seem to be implying that in skiing the foot somehow functions differently from country to country and from one skier to another. It doesn’t. The principles I am discussing in my coming post will reveal what the world’s best skiers have being doing, literally right under the feet of the so-called experts, since the 1930s. Why is that no one in skiing has ‘discovered’ what to me was drop-dead in-my-face obvious 30 years ago? And why didn’t the ski industry discover the foot pressures of elite skiers or the detrimental effect of ski boots on medial-lateral (side to side) CNS mediated balance of racers at the highest level, that could predispose them to injuries from falls in every day life.

      1. How the CoP moves will depend on not only boot setup, but ski type, terrain, snow, turn type, speed and the technique of the Skier.

        Ski technique alone has greatly changed from the dates on the studies that you cite.

        Why are you not open to trying to research this further? You have made some assumptions, why not verify them?

      2. “Ski technique alone has greatly changed from the dates on the studies that you cite.”
        Of course. Why didn’t I think of that? The laws of mechanics and physics are ancient as are Newton’s Laws. Gravity? I heard a rumour that the high priests of skiing, who hold domain over the powers of the universe, met recently and unanimously voted to rescind the law of gravity. Gravity no longer applies in skiing. As for humans, they have probably undergone enormous evolutionary changes in the past 3 or 4 years and no longer bear any resemblance to the skiers in the Ottawa tests.

        Let’s get serious. I have been around long enough to know how the ‘systemic ignorance in the name of keeping it simple’ con works. When I started skiing in 1970, the best racers were the model for recreational skiers to emulate, except that most skiers couldn’t even come close to making the grade. What to do? Call in the marketing gurus to apply a liberal application of BS to skiing. Freestyle (as in no style) became the order of day. Anything went. The ways to ski were unlimited as were the techniques. No technique was superior to another. Every country had a different technique. Heck, every skier had their own technique. And the really great thing at least from a marketing perspective as in $$$$$$$$? All techniques were equally good.

        The issue that has been on the table since man (or woman) made the first downhill descent on skis and had to turn out of the fall line in order to avoid killing themselves, was how the central nervous system could negotiate a solution through which to balance forces across the inside edge of the outside ski. By all indications, the CNS of the world’s best skiers had figured this out by the 1930s. That this process remains one of the greatest problems ever facing man or woman kind suggests that either the ski industry is populated with some of the most incompetent people on the planet or some of the most gifted actors at feigning stupidity.

        Assumptions? I don’t think so. One of the smartest people I have ever had the privilege of meeting is Alex Sochaniwskyj, P. Eng. When I first met Alex in 1991, he had 12 years of biomedical and rehabilitation engineering research experience at the Hugh MacMillan Rehabilitation Centre in Toronto. Alex was also teaching computer science at the University of Toronto. In those days, he was designing and fabricating analytical technologies that remain state-of-the-art even today. In his letter of support for my nomination for the gold medal in applied science and engineering in the 1995 British Columbia Science and Engineering Awards by the new technology officer of the National Research Council of Canada, Alex said of me:

        “During 1991 and 1992, I had the opportunity of working with David MacPhail in the realization and testing of conceptually innovative sports footwear, in particular a ski boot. Design of this type requires knowledge, understanding and experience in a combination of disciplines including anatomy, physiology, biomechanics, sports dynamics, physical mechanics and design. David MacPhail exhibited this unique combination of skills throughout all aspects of the project, and continues to research and explore developments in: the influences of footwear on the kinematics and kinetics of human movement; the design of athletic footwear; and the etiology, occurrence, frequency and prevention of athletic injuries.

        “Unlike other designs, David’s theoretical model described skiers’ biomechanics in a realistic, uncompromising, dynamic situation. Analysis of the results validated the original hypothetical model and provided additional insights.The design and development strategies used by David MacPhail are very holistic in nature, placing the human system as the central and most critical component in the biomechanical system. His intent is to maximize human performance and efficiency, while foremost preserving the well-being and safety of the users and minimizing biomechanical compromises.”

        Realistic? Holistic? Uncompromising? Validated the original hypothetical model? These hardly represent ‘assumptions’. And what led you to ‘assume’ that I don’t have recent studies?

        Here’s a suggestion. Apply yourself to the single greatest problem facing man or woman kind and see if you can come up with a solution that actually works and, more important, can be defended against rigorous scrutiny. Then we can engage in a meaningful dialog.

      3. I can choose where and when to pressure different parts of my foot. If this were not a variable, then went are you bothering to write about where you believe the CoP is and how it moves?

        Why do you not want to further investigate this with a variety of skiers, skis, terrain , turns, etc.? The studies you cite are not new. Everything you refer to is old data.

        I think recent data would be interesting, especially consider how the foot acts like a tripod and the new skis are skied more centered than we used to.

        What I feel is pressure under the first meta when I pronate, roll into my arch, but I also feel pressure under my heel at the same time. The pressure under the first meta is not due to moving forward onto that part of my foot, but rather due to pronation to edge and steer the ski.

        I know of other pros who do move onto their forefoot and pressure their tips. These same pros have problems skiing our Jackson powder and steeps… They go over the handle bars…

        Just saying that there are other ways to look at this and it would be great to have some recent studies.

      4. You fail to appreciate, let alone understand, the difference between applying pressure with the foot on a conscious level to the base of a ski boot and COP as a term that pertains to the interplay of COM and the point center of GRF (aka COP) in the context of CNS mediated balance. Pressuring your foot not only has nothing to do with CNS mediated balance, it is actually antagonistic to balance.

        COM is where you are in relation to the base of support within a defined area in the feet or foot. COP is the point center of ground reaction force. Since studies of balance and locomotion in laboratory settings are always performed on a contiguous, level ground or a surface that is an extension of ‘ground’, such as a floor system of a building that is supported on walls that are supported on foundations that are supported on ‘ground’, ground is assumed when COP is shown on a system such as the Novel Pedar (which I have considerable experience with). This issue went over the heads of the University of Ottawa researchers at about 100 miles up just as it continues to go over the heads of other researchers. It is deeply troubling to me (and should be to any intelligent person) when accredited scientists are guilty of such glaring omissions.

        When a ski is on edge, there is no ground under the foot to support it with the exception of perhaps a tiny segment of the head of the first metatarsal and only then, if the minimum width profile underfoot is narrow enough. Even when the foot is supported on ground, you do not create COP. You position COM where you want COM to be positioned. Since COM cannot exceed the limits of the base of support without precipitating a fall, it can be behind and close to the head of the first metatarsal so long as it does not pass it. So until you can explain how ground is created under the structure that is under the foot, you do not have a leg to stand on metaphorically speaking.

        Old data, old physics, old laws of gravity. This scripted ski industry ruse does not work on me. Unbalanced moments of force is basic science that any 3 year old who has used a teeter-totter can easily understand. The fundamental issue, which the experts in skiing have scrupulously avoided for almost 100 years, and which you continue avoid is the issue of the unbalanced forces that are present across both the inside and outside skis when they are on edge. So stop spouting nonsense and deal with the reality that is or should be in your face.

      5. Maybe I fail to go with mumbo jumbo, but if there is to be any value regarding discussing and learning various ski techniques, it has to be something someone can actually do, and have some internal awareness of.

        This translates to feeling and doing as well as understanding objectives and cause and effects.

        If people can’t feel and understand what you are talking about, of what value is it outside of an ivory tower?

        Why not try explaining things in terms of what people feel and do, including variable factors such as timing and direction…

        If what you believe cannot be translated in such simple language, what is it worth?

        Also, experiments place sensors under the foot sole to record data. Don’t you think we can feel and be aware of what our foot soles feel like? I can get high edge angles and I know what I feel in my feet. I don’t give a crap about what is or is not under the bottom of the ski or what vectors go where. I know that it works and I know what it feels like. I also know how to help others learn to get high edge angles…

        So, how about talking in language skiers can understand?

      6. I structure my information on the hat my target audience is wearing. My blog is for serious skiers, ski pros and ski coaches. The information is not for the average recreational skier who just wants to make it down the ski hill to the bars and shops in the valley. Walking is typically described as as an incredibly complex activity by those with the requisite knowledge to understand it. The constantly changing dynamic environment of skiing makes it infinitely more complex. It takes an enormous amount of knowledge and cognitive horsepower to make it simple and especially to analyze what is causing people to ski at less than their potential. So, it depends on which hat you are wearing. If you just want to ski better or ski to your true potential, I can usually make this happen just by creating a functional environment in your equipment that allows your brain and body to do what it is designed to do. When I did this with racers such as Steve Podborski or Rob Boyd, I never had to say a word……..not ONE WORD about their skiing. Within a few runs, Boyd was transformed from an average technical skier to a sophisticated skier who trained with the Germans when they were the Super G power house and was 3rd in the first run on a course when Boyd had never been any good at Super G. I never said ONE WORD to Rob who went on the next WC season to be a regular on the podium. NOT ONE WORD.

        If I set up a skiers equipment and their body doesn’t respond or fails to fully respond, I give simple cues but only after a careful, thoughtful, insightful analysis. Only after that do I give cues, usually of ONE or TWO words. Then I watch and wait to see…… if the brain figures it out. Stance training is usually required for recreational skiers. I invented the Roll Over trainer as a simple device that trains skiers in the feel of the proper stance which must be established at ski flat in the transition. The stance “go for turn initiation” ‘cue’ is the feeling of a disk of pressure under the ball of the outside that is about 1.25 inches in diameter or about the size of a looney in Canada which skiers can place under the ball of their foot to get a sense for the right feel of pressure. I teach a skier to find the disk at ski flat to the point where they don’t even have to think about it then keep the pressure under the ball and steer it along the line that takes them in the direction they want to go. After a short time skiing is like walking. I find it humorous when skiers talk about making all kinds of adjustments when they are travelling at 50 fps. The only thing I think about when I am skiing and I mean THE ONLY THING is where I want to go.

        THE PROBLEM that is destroying skiing is that it is overrun with egomaniacs who actually boast about their ignorance claiming, “I (am sooooo great… me, me, me, me) that I can just watch Ted Ligety (who spent 8 years perfecting his technique) and copy him (because, I am sooooooo great). I don’t need to know anything (because, I am sooooooo great). Some of the ski pros in Whistler came up with a thing called the FIGJWME Award – F, I Am Good, Just Watch Me.

        “Don’t you think we can feel and be aware of what our foot soles feel like?”
        No, I don’t.
        “I can get high edge angles and I know what I feel in my feet. I don’t give a crap about what is or is not under the bottom of the ski or what vectors go where. I know that it works and I know what it feels like. I also know how to help others learn to get high edge angles…”

        Can I assume that you also don’t give a crap whether or not what you teach could create unbalanced moments of force on the outside leg that can predispose the knee to serious injury? Here is where I am coming from.

        “His intent is to maximize human performance and efficiency, while foremost preserving the well-being and safety of the users and minimizing biomechanical compromises.

      7. So, why do you make so many unfounded assumptions about other people, their skills and even what and how they might coach?

        Like yourself, I keep my method of helping others really simple. Like yourself, I focus on where you want to go and when. I ask questions to help people discover things. I focus on keeping your lower body functional so you can use it and not hurt your knees and back. I aim to help people stay loose, so they can feel and move in and with the forces. I want people’s bodies to figure it out so they can learn and own it…. Timing and direction, where they want to go and when.

        Learning and doing hardly ever depend on a cognitive understanding of either theoretical or applied physics. You don’t have to know things with your conscious, logical brain. Your body feels, knows and does many things without cognition. You seem to agree with this by how you describe how you help others.

        It appears you are quite successful in understanding ski boots and feet and setting them up.

        Serious skiers are not always curious about the physics behind what they do. Some are and some are not. Knowing does not necessarily help them improve.

        I think of the physics and body mechanics more as a curious, but not that important issue. I do like to learn these things… Others don’t.

        The main question I have has not been answered via scientific data. You have made an assumption based on old data. I would like to see some new data that is more inclusive. Why are you opposed to this?

        I know that I can feel and apply pressure to that first meta in two very different ways. One is actually moving forward onto it and the other is remaining centered around my arch and pronating. The moving forward method limits what my ankle joint can do, whereas centered and pronating can occur while either opening or closing my ankle.

        Thoughts?

      8. “Thoughts?”
        Sure

        “I know that I can feel and apply pressure to that first meta in two very different ways. One is actually moving forward onto it and the other is remaining centered around my arch and pronating. The moving forward method limits what my ankle joint can do, whereas centered and pronating can occur while either opening or closing my ankle.”

        Your perception is not functional reality. Dorsiflexion is intrinsically coupled to pronation. But rather than waste time in a one-on-one monologue, I suggest you wait until I post on these issues. For now, consider the absurdity of the idea of rolling the ankle to make the edges hold or consciously everting the foot with the very weak everter muscles when it is the much more powerful Inverters that control pronation, not create it or the patently absurd idea that skiers can flex a boot when the shaft is mechanically integrated with the shell lower and that this actually has some sort of purpose or that knee angulation, which is literally means opening the inner aspect of the knee by shearing the MCL and ACL is part of a good technique. As a step towards meaningful communication, how about purging the BS from the technical narrative?

        As for new studies, what leads you to believe that any researchers have any idea of what they are looking for. I have lots of studies where the conclusions demonstrate a distinct lack of understanding of the real issues. The U Ottawa team had no idea what the pressure patterns the found meant. When it comes to problem-solving skills, I consistently rank at the top in both theoretical and practical applications. When I was a problem solver in a position where problem, solving outcomes were tracked by computer and ranked in a division of a 1010 technicians who were selected for their problem-solving skills, I was #1 by a wide margin.

        Let’s take a time out. I have other work to do.

      9. More assumptions. Who said anything about knee angulation, ankle rolling and the rest of the BS? You did. I never think those concepts… Even your assumption about dorsiflexion and pronation in a ski boot…

        Just saying data and not assumptions goes further for understanding reality. This is not a competition. Who cares who is number one in problem solving.

      10. Problem-solving skills are important because solving problems requires the ability to recognize problems. Most can’t recognize problems even when they are standing on them. When those who have minimal problem-solving skills try to solve a problem, they usually create a new problem. The big problem that is eventually going to kill skiing is that when those such as yourself claim that they can apply pressure to different parts of the boot this almost always creates unbalanced moments of force that predispose the lower limbs and especially the knee to injury. It is obvious that that there is not a fit with you and my blog. So I will no longer approve your comments or waste any more of my time.

  4. Just wanted to truly thank you for your impressive, solid, original work which help us so much as professionals
    A reader

  5. Good article Dave. Do you think that no pressure is applied to the 1st met head during supination? Like In propulsion phase in Gait the CoP migrates more to the 1st met head. Also what are your thoughts on the foot moving from pronation to supination? Just as the rest of the body moves dynamically through a ski turn, so shouldn’t the feet? Not just be held in pronation. Only wondering this as pronation opens most of the joints under the bottom of the foot making the foot very mobile and adaptive to pressure and terrain. However staying in pronation and not entering supination leaves the bones on the plantar surface in this open state, where as supination locks the bones in place creating a rigid lever.

    Just interested In your thoughts as I’m trying to map out more of the whole body’s joints movements in efficient skiing and this involves the foot doing far more than just pronating.

    Cheers Tom

    1. Good questions Tom. The dynamics of the human foot and lower limb in general was a major focus of my US Patent 5,265,350. The fast answer to your question is no pressure is applied to the first met head. The established narrative in skiing precludes recognition of pronation and supination by taking the position that the foot is reduced to a simple hinge by the ski boot and that the knee should track straight ahead in ankle flexion. These positions are based on uninformed opinion and, as such, are not supported by irrefutable biomechanical principles established over 50 years ago by those such as Inman (The Joints of the Ankle). Supination involves, inversion, external rotation of the leg and plantarflexion. Pronation involves, eversion, internal rotation of the leg and dorsiflexion. Plantarflexion and dorsiflexion are intrinsically tied to supination and pronation by the everter/inverter muscles. Attempts to make the knee track track straight ahead create a degree of dysfunctional imbalance in the lower limb. In addition, the normal kinetic flow is from supination to pronation. The normal unweighted state is supination and the normal weighted state in monopedal function is pronation.

      Foot dynamics in a turn. For reasons I will provide in future posts, the 1st MT should be loaded at ski flat and the load maintained until the end of the turn where it is released by moving to the inside foot while the inside ski is still on its current (uphill) edge. Extending on the inside leg releases the old outside ski from the snow by lifting it and initiating the same swing phase as occurs in walking. Unloading causes the foot to plantarflex and supinate within the constraints of the ski boot. Extension of the new outside leg is done in conjunction with internal rotation of the whole leg. This rotates the skis across the skiers line and into the fall line. It also has the effect of aligning COM so the load can be applied to the head of the 1st MT. The new inside leg must rotate externally to match the internal rotation of the outside leg. In effect, the inside leg swings past the new stance leg. In one of the slalom races before she was injured, Shiffrin was shown rehearsing this movement in the start area.

      “Only wondering this as pronation opens most of the joints under the bottom of the foot making the foot very mobile and adaptive to pressure and terrain. However staying in pronation and not entering supination leaves the bones on the plantar surface in this open state, where as supination locks the bones in place creating a rigid lever.” This is the myth perpetrated in skiing by those who sell custom insoles. The reality is the exact opposite of what you state. The human foot is a 3-dimensional truss. Trusses function in compression/tension. The human foot becomes maximally pronated and maximally rigid just prior to heel lift that initiates the propulsion phase. When the foot unloads, it resupinates and becomes maximally lax. At foot strike, the ankle is plantarflexed (supinated) in order to absorb the shock. There is absolutely no conjecture on these issues except in skiing where any and everything seems to go and go unchallenged. I was running in flats when knee pain and injuries emerged with the introduction of jogging shoes. All of a sudden, all the running magazines were citing studies by foot specialists who claimed overpronation was causing the knee problems. While this was never proven, some saw a lucrative market for mass produced custom insoles. As this market was beginning to be tapped into, the new plastic ski boots hit the market. For consumers who had already been conditioned to believe pronation was a bad thing, it was an easy sell in skiing.

      1. Thanks for the reply. I understand the mechanics of pronation and supination and their movements in all three planes. Wasn’t looking for clarification there. What I’ve been trying to figure out is more than just what the foot is doing. Given it is a 3D truss and functions through tension and compression, so shouldn’t the rest of the body? Pronation and especially the timing of it as you mentioned at ski flat, Would be the trigger for the whole body to enter a tensioned state. Wondering your thoughts on movements at the pelvis, spine, arms etc as a result of the pronation?

        I personally don’t feel my foot continues to pronate throughout the whole turn of a well executed ski turn. It does at the initiation but as the pressure builds, and I continue to move inside the arc, my whole body moves differently than that of pronation. For example as my CoM moves inside my outside hip is abducting keeping my balance over the outside ski. This hip abduction would be eccentrically loading the adductors of my outside leg. This would result in hip external rotation at the joint. This movement matches supination mechanics and not pronation mechanics.

        I’ve been working on making my skiing feel as fluid and effortless as possible and therefore am definitely thinking of my whole body working as a tensegrity structure and trying to figure out what goes on beyond just the pronation. It’s a very important movement but not the whole picture in my opinion. You’ve put up lots of posts about pronation and I think
        We all get the importance of it, but what about after that point? I really admire your efforts and understanding of skiing and biomechanics so that’s why I’m interested to hear your thoughts on areas like the middle of the turn where big angles are created. I don’t think it’s just more pronation that gets you there.

        Cheers Tom

      2. “Pronation and especially the timing of it as you mentioned at ski flat, Would be the trigger for the whole body to enter a tensioned state. Wondering your thoughts on movements at the pelvis, spine, arms etc as a result of the pronation?”

        Bingo! Exactly. One of the reasons I started working on a one-on-one with a small group of skiers again was to be able to monitor them and engage in a dialogue on their progression and especially the issues that arise that impede their progress, like misconceptions and erroneous information. In order for me to progress to the issues you have raise, which are right on target, I need to first establish how elite skiers create a platform on the outside ski that is a source of ground reaction force that they can stand on and balance on. This is a prerequisite to create the maximum tension in the processes in arch of the foot to allow the metatarsal heads to act as buttresses for eccentric soleus-grastroc-hamstrings to pull on the achilles which is an extension of the plantar-apoeneurosis. This chain of muscles running from the heads of the MTS to the pelvis creates what I refer to as the pelvic-plantar pull. The high tension in this chain enables COM to approach the limits of the head of the first MT without breaching it. With the pelvic-plantar pull established, the next step (pun intended) is to extend the plantar pull to the shoulder girdle. How? By pulling the shoulders out and forward into a bow-like shape and rounding the back; the gorilla stance. This tightens the glutes and renders the entire muscle-skeletal system into what amounts to a giant shock absorber. Weak stance, as characterized by too little hip and ankle flexion and too much knee flexion, is epidemic in skiers, even in most ski pros. The problem is that there is a whole industry working 24/7 to make sure most skiers can’t create the necessary high pressures in the foot. Once I get past the next few posts in which I will discuss the secret of the world’s best skiers, the diagonal load axis, I will review my work with local ski pro Matt Williams. This involved major modifications to his ski boots beyond anything most could imagine.

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