The processes of balance that configure the joints of the lower limbs originate in the feet in what is referred to as a bottom-up process.

The following text is excerpted from my US Patent No. 5,265,350 which was published in the major developed countries of the world on or about February 3, 1993. I have added emphasis with bold text to highlight key statements

The foot articulates in order to facilitate muscle function. Muscles respond in opposition to loads imposed upon the foot. A process ensues wherein the chain of articulations, initiated at the foot, are continuously mobilized so as to maintain a state of dynamic balance across the plantar-ground interface.

COMMENT: Structures of a ski boot that interfere with or otherwise impede the articulation of a joint or joints will reduce or even prevent a muscle or muscles from effectively contracting and shortening.

Bipedal function or bipedal stance, in the context of the invention disclosed, is defined as being a weight-bearing state wherein the feet are neither supinated (rolled outward) or pronated (rolled inward). This is described as a “neutral” state of the foot. It is usually associated with weight-bearing on two feet wherein each foot bears an equal proportion of the weight of the body.

Monopedal function or monopedal stance is defined as being the state achieved at the conclusion of a progressive weight transfer from two feet to the medial aspect of the plantar surface of one foot. As the weight transfer occurs, the foot to which the weight is being transferred undergoes pronation until a physiologic state of balance is achieved on one foot. Monopedal function distinguishes itself from other possible states of balance on one foot in that the ability to mobilize the joints of the body required to re-orient the centre of mass relative to the foot is possible while simultaneously maintaining a state of balance in relation to the forces acting on the user.

As an example, one can bear weight on one foot without having that foot pronate and, thus, not assume the position required for monopedal function, thus there is no significant inward movement of the ankle bone. This is done by shifting the weight to bear on the lateral aspect of the foot, and using the extrinsic leg and intrinsic foot musculature to support its medial arch. However, this form of balance produces a relatively static position in terms of ability to re-orient the centre of mass of the body relative to the supporting limb. This static quality is typical of states of balance on one foot achieved by other than monopedal function. With monopedal function, medial movement of the inside ankle bone is involved.

Monopedal function is a physiologic state wherein balance is achieved with the weight of the body borne on the medial plantar aspect of one foot. It has been recognized that the ability to balance on one foot (usually the one to the outside during a skiing or skating turn) is superior, in terms of balance and control, to balance on two feet, in sports such as skiing and skating wherein an instrument such as a ski or ice blade is affixed to the sole of the footwear. Monopedal function is extremely relevant in such applications for the following reasons:

(i) Balance on one foot, achieved through pronation, provides superior control of the articulations over balance on two feet. This translates to superior control of the ski or skate blade. It also translates into superior dynamic or kinetic balance. The mechanics of monopedal function permit the centre of mass of the body to be accurately placed and its relative position maintained, if necessary, with regard to the ski or skate blade affixed to the sole of the footwear.

(ii) A dominant position on the outside foot in the arc of a turn affords more efficient and precise control of the instrument since the inner limb, being relatively passive, is utilized primarily for the purpose of assisting balance.

(iii) The most important source of rotational power with which to apply torque to the footwear is the adductor/rotator muscle groups of the hip joint. In order to optimally link this capability to the footwear, there must be a mechanically stable and competent connection originating in the plantar processes of the foot and extending to the hip joint. Further, the balanced position of the skier’s centre of mass, relative to the ski edge, must be maintained during the application of both turning and edging forces applied to the ski. Monopedal function accommodates both these processes.

(iv) In skiing, the mechanics of monopedal function provide a down force acting predominantly through the ball of the foot (which is normally almost centred directly over the ski edge). In concert with transverse torque (pronation) arising from weight bearing on the medial aspect of the foot which torque is stabilized by the obligatory internal rotation of the tibia, the combination of these forces results in control of the edge angle of the ski purely as a result of achieving a position of monopedal stance on the outside foot of the turn.

(v) The edge angle can be either increased or decreased in monopedal function by increasing or decreasing the pressure made to bear on the medial aspect of the foot through the main contact points at the heel and ball of the foot via the mechanism of pronation. As medial pressure increases, horizontal torque (relative to the ski) increases through an obligatory increase in the intensity of internal rotation of the tibia. Thus, increasing medial pressure on the plantar aspect of the foot tends to render the edge-set more stable. The ski edge-set will not be lost until either the state of balance is broken or the skier relinquishes the state of monopedal function on the outside ski.


  1. That’s so out of context. Some unshod feet can absorb GRF quite well, in the short term. Shoes were invented so feel could absorb GRF in the….long term. 90% of the patients I have seen over the past 3 years with stress fractures of a metatarsal had been running in minimalist shoes. Some had stable feet and some did not, but it seems that the overload of the forefoot, takes its toll. You ignore the fact that the classic running shoe has evolved to address and prevent these types of injuries. They do not cause them. A functioning TCJ is all important.

    A gait cycle is not what the foot is put through in most of gymnastics. This is another example of taking a little bit of science, and misapplying it. Gymnastics is done on a mat, for a very good reason. The foot cannot withstand that much punishment. You also seem to be applying bits and pieces of gait cycle biomechanics to the function of the foot and ankle, while skiing, with your assumptions being based on your own premise, not science.

    1. Correct. This discussion is off on a few too many tangents. It’s getting a little nasty, too, which is unfortunate. You’re right… the moments around, and work done across the various foot/ankle joints is vastly different in different contexts. Any ski boot is going to constrain the foot and ankle within limits, but a boot that completely prevents motion at the foot/ankle joints is going to compromise the skier’s ability to turn, and to respond to high frequency perturbations by the ski. A boot that allows pronation of the foot is not allowing the foot to do anything that is not within its normal physiological limits…as I said before, it’s not an extreme movement. Likewise for dorsiflexion of the ankle and internal rotation of the tibia…normal physiologic movements. Any extreme torque of the limb, caused by crossing the ski tips, or catching an edge is going to destroy knee ligaments irrespective of the boot.
      So, what we’re saying, is that performance can be enhanced for skiers that have ‘normal’ feet by allowing those feet to behave in a normal physiologic way. And what I’ve said a few times is that people with poor foot conformation will not be able to take advantage of this mechanical benefit.

      1. It’s important for readers of this blog to recognize that I mostly worked on boots of elite skiers and racers. Every once in a while I would have a racer whose boots I had worked on tell a friend who was struggling with their skiing and having all kinds of boot issues to come and see me with the expectation that I could solves their problems. In some cases, I could help. In other cases I could only help them ski after a fashion knowing that they would never ski like the elite skiers. As you say, it is unfortunate that the discussion has gotten a little nasty. One thing I learned long ago was to never fall in love with your great idea. It could be your great wrong idea. When I was teaching boot clinics my thinking was evolving. I would try a refined version of something very conventional only to have the skier tell me that whatever I had done to their boots had messed up their skiing. I never tried to represent that I was right and they were wrong. If what I did, didn’t work for an elite skier I was wrong, period. For lesser skiers it was sometimes a matter of adaptation. What I found disturbing was that as I gathered a following, those who I had influenced started to behave as if what I said was an unassailable truth. When I tried to adjust my position these people became annoyed, even hostile. Once they bought into a concept they tended to resist change. To me knowledge is tentative. Any time a person takes the position that they know everything in my mind they know nothing of importance.

      2. So you say. Still, you are hiding. Why? As far as I can tell, you did not start this blog for elite skiers only.

        At least now I know you have not actually tested your theories on the core demographic of the skiing population.

      3. Coming soon to a footwear application near you. The trick is that you need something to put the technology in that doesn’t bury the data you want in neural noise.

    2. In a series of studies Benno Nigg asked what orthotics actually do. He found that they have little effect on kinematics but that they can have a large effect on muscles and joints often making muscles work as much as 50% harder for the same movement and increasing stress on joints by a similar amount.

      1. Nigg has done a great number of studies. He is very well known. Correlate the specific study you are citing, to this discussion. Also, what Publication, issue and date, did his study appear. I’d like to read if for myself and make my own interpretations.

        For suggested reading; Lower Extremity Biomechanics: Theory and Practice: Volume 1, Albert, Stephen & Curran, Sarah

        What’s your degree and field of study?

  2. Yes, Bob, it’s all a plot to discredit boot fitters. Now I wonder, why wouldn’t boot companies want to listen to the average boot fitter?

    Your arguments are counter-intuitive. It is in the best interests of the boot companies, to make as many skiers happy with their product, as they can. It’s in their best interests to use Best Practices in designing boots. It’s also in their best interests to help boot fitters. “T” nuts and pre-punched holes to move latches, are some examples. Then there are the multi-density, heat molding liners. Stop acting the the boot companies are the enemy. It’s absurd.

    I have watched boot design evolve, without any built in prejudices.

    1. Jeez Robert you crack me up. I haven’t had such a good laugh in years. Where is the science to support the idea of interfering with the triplanar joint system of the ankle complex and preventing coordinated muscle function? You expect someone to take you seriously?

      Actually Robert if you profit or benefit in any manner from boot sales (I don’t) and related products you are prejudiced. Plain and simple.

  3. OK, We get that part. Do you think most skiers can’t flex their boots while skiing because they don’t know how to, or the boots are too stiff? What’s your solution?

    1. Robert you seem to be the self-proclaimed penultimate expert of the solar system, enlighten me. Which muscle or muscles does a skier use to flex their ski boot. Over to you.

  4. So Bob is not a boot fitter? Wow. What is he?

    So, you guys experiment on a national team members, eh? Wow! Can you get your head out of the clouds and think about who buys most of the ski boots?

    skikinetics, Did the cuff “rotate” or hinge? If the cuff rotated, did the ankle rotate, as well? From what I can understand in your post, softer flexing boots activated the posterior muscles groups….of the leg, enabling the leg to better absorb bumps in the snow —- until fatigue sets in, I suppose?. You’re saying this is better than skiing a sifter boot, that would take ecentric load —- off — the posterior muscle group?

    Are the ski instructors in CA, telling everyone to buy 70 flex ski boots?

    1. Robert, the last time I did any boot work was 20 years ago. Even then it was at the request of the head coach of the Canadian Men’s Ski Team who asked me to come out of retirement. BTW, the racer the coach asked me to work with credits me with putting him on the podium. The only boot work I do today is for my wife and I. As far as I know ‘Bob’ has never done any boot work. Bob? Have you? As for experiments on team members, I have a box full of letters from racers I put on the podium. I have no idea what ski instructors or racers are doing today or what they are telling people.

    2. Jesus. I hit a nerve. Take a Valium…
      Again, we need to differentiate between ‘normal’ feet that can function perfectly well without orthotic interference, even at high loads, and those ‘abnormal’ feet that don’t function at all well, even at low loads.These are probably the people you see most often. People with poor foot/ankle conformation are not likely to be superior athletes… irrespective of whether their sport is marathon running, or skiing. And you’re correct when you say that most people who buy ski boots only care about comfort when they’re wearing them. There isn’t anything more snuggly than a ski boot that completely encases the foot and ankle. However, most people who buy ski boots have no concept of how the foot and ankle function, and probably don’t care. Sadly, most of the people who sell ski boots likewise have no concept of anatomy or foot function. They’ve been trained to sell custom insoles with boots so the footbed completely fits their foot shape, and further immobilises the foot/ankle in the boot. Then, they go out on the hill and are taught to ski by instructors who likewise have been trained to teach people to ski with their knees and hips. I cringe when I see it.

      Dave’s perspective is that racers with ‘ideal’ feet…size 8-9, reasonable arches, not too wide (me, I’m proud to say…) … get the best performance on skis when their foot is allowed to pronate in the boot, which allows the medial movement of the centre of pressure to effect good medial edge control. And then, when they come off that edge, the foot returns to its neutral position. This movement is unlikely to cause the suite of injuries you list…subluxation of all the joints of the foot/ankle and destruction of the knee. The foot/ankle complex is entirely capable of managing this loading paradigm. Interfering with it is just as likely to cause problems.
      People who don’t have this ‘normal’ or ‘ideal’ foot will not perform at a similarly high level. They won’t be able to use their feet in the boot as effectively, and would probably be more comfortable with insoles to shore up their foot.

      Not to slag off your profession, but there are a fair few salesmen out there who routinely prescribe expensive, custom insoles to everyone who crosses their path…in their view, any evidence of pronation of the foot is a recipe for disaster, and people don’t know any better. Research is pretty bipolar when it comes to the value of orthotics. Half the papers you read will say that pronation results in ‘overuse injuries’ and the other half demonstrate that orthotics generate entirely random and unpredictable effects between subjects, and are therefore not very beneficial. Some show that orthotics don’t change the articulation or path of excursion of joints (ie. they don’t affect ‘alignment’) but change the balance of muscle activity across that joint. Some papers indicate that people with poor foot conformation that already suffer from joint pain benefit from orthotics, in that they relieve the pain, and I’ve read some papers that suggest that proximal muscle activity around the hip and knee is the actual culprit when limb joint injuries have been attributed to pronation of the foot.

      So, rather than flinging poo at each other, can we agree to disagree? Next time you go skiing, try taking out the molded insole. Put a foam wedge across your instep so your foot is restrained and forced down and back by the second buckle, and leave the cuff loose so you can dorsiflex more freely. See if it changes the way you ski…when you want to turn, just flex your knee and drop your arch. If you don’t like it, switch back. When you take out the arch support, you’ll probably find your foot doesn’t get as cold.

      By the way, I’m not a boot fitter. I teach human and veterinary anatomy in medical and vet schools, and my research area is biomechanics of gait. I work mostly on horses and dogs now, but still do a bit of work with human orthopedic surgeons, most recently around patellofemoral pain.

      1. Take a Valium? Really? Now you’re a doctor? You have put yourself out there as a expert. Now, stand to the test. Your theories go against conventional wisdom.

        You guys are great at quoting out-of-context and paraphrasing other scientists’ research, but you are still leaving your theories unproven. What works for you is not the end of scientific research!!

        And, skikinetics is still too bashful to say who he/she is. Who are you hiding from? Why is it necessary to hide? This leads to an inevitable conclusion, you have reason it hide.

      2. ‘Conventional wisdom’…the biggest part of the problem. Efforts to challenge the design of conventional boots by people involved in fitting them to racers on national ski teams have been shut down by the manufacturers supplying the boots.

    3. Yes. A prerequisite for shock absorption at a joint is the ability of the joint to move. The articular surfaces of a joint are not effective at attenuating shocks…these are transmitted through the various soft tissues (ligaments, muscles, tendons…) and dissipate eventually as they cross more joints. If a joint is constrained to its physiologic range, those structures will not strain under load. If a joint is fixed in place, like the ankle and foot in a boot that does not allow normal physiologic motion of those segments, then those loads will simply be transmitted up to the knee without attenuation.
      The normal forces in skiing are large, but are managed by the musculoskeletal system to a point. The knee ligaments will be damaged when those forces are large enough, and if you can reduce the magnitude of those forces by attenuating them to some extent at the foot/ankle then you will protect the knee.

      1. Exactly Bob. There are excellent studies that show that the lower limbs can absorb shocks better when the feet are unshod than they can when even minimally shod. This is the main reason most gymnasts are barefoot. For years I have warned racers about landing jumps on the flats in high speed events like Super G and Downhill because the ski boot limits the ability to absorb shocks. Those who claim that stiffening the joints of the ankle complex and supporting the arch is beneficial should demonstrate their position by jumping off the top of 8 foot step ladder wearing tightly buckled ski boots, something I would never attempt. Having 911 on speed dial is a good precaution prior to jumping. Tally ho!

    1. The time zone was wrong. It was at default UTC 0. Thanks for that.

      Here is an interesting Australian paper that was published recently that studied intrinsic foot muscles under arch loading. To the best of my knowledge I was the first to use the arch loading principle in 1980 (34 years ago) in the form of an in-boot technology I invented that and later patented that allowed Steve Podborski to compete and win about 4 months after reconstructive knee surgery. Back then, a minimum of 9 months recuperation was required before a skier could even think about skiing. Arch loading changes the way the foot functions in a fundamental manner.

      Intrinsic foot muscles have the capacity to control deformation of the longitudinal arch
      Luke A. Kelly, Andrew G. Cresswell, Sebastien Racinais, Rodney Whiteley and Glen Lichtwark
      J. R. Soc. Interface 2014 11, 20131188, published 29 January 2014

      In 1991, as part of an effort to develop a ski boot that permitted the normal range of joint articulations associated with skiing, I designed a device with a biomedical engineer from the University of Toronto that allowed us to study the 3-dimensional forces applied by a skier’s foot and leg to instrumented interfaces of the device which we called The Birdcage. The Birdcage also used the arch-loading principle. Some of the data is posted on this blog. With the Birdcage we could consistently and predictably transform an Olympic champion (we had two as testers) into a struggling beginner or enable a neophyte to use their native balance programs to ski. In fact once we captured the balance signature or profile of a skier we could study the effect of ski design on the ability of the CNS to negotiate a balance solution with SRF.

      1. I’ll have one of my residents order the article from the the hospital librarian, but from the title, the idea that intrinsic muscles of the foot can have any powerful balancing affect, defies, and will quickly exceeds, the physiology of these rather small muscles. Expecting the intrinsic muscles, in the plantar of the foot, to attempt to maintain arch height, against the centripetal forces skiing placed through the medial column, is what most often leads to cramps in the arch. Efficiency is achieved through limiting the over use of muscles. I propose that when the intrinsics of the foot, do not have to “fight”, there is better biofeedback, making it far easier to “finesse the edge”

      2. As a bit of background, after being reduced from an expert skier to a beginner after switching from my low cut leather boots to the new higher rigid plastic boots one of the first epiphanies I had after started modifying boots looking for answers was that my arch needed help; it needed support. I made an appoint with podiatrist in Vancouver who examined my feet and told me he saw no functional issues that would affect my ability to ski. I sought out a sports podiatrist at a university in Seattle who made custom orthotics for my ski boots. I put them in my ski boots and had zero control. I tried them for several days with no improvement. Today I take steps to ensure the boot board of my ski boot is dead flat. In a high speed GS turn my edge underfoot on my outside ski is so solid that I feel like I am standing on concrete. And I ski with far less energy and muscle effort than the average recreational skier. The central issue is depending on a number of factors there will either be an STF inversion or eversion moment of force on the outside foot of a turn. Until such time as someone changes the fundamental laws of the universe there will always be an eversion moment of force on the inside foot of a turn.

      3. I can tell you that the theory and principles of medial “arch loading” , (medial column biomechanics) were taught in colleges of podiatric medicine, in the early 70’s, and maybe earlier.

  5. Your quote was not new or unique information.

    Boot setup is all about managing load deforming, foot and ankle deforming, pressures throughout a turn. It starts with a non weightbearing biomechanical exam of the foot and ankle, followed by an open and closed chain comprehensive lower extremity biomechanical examination. A boot fitter needs to know what is abnormal, before they ever put a boot on a customer’s foot. Most bootfitters cannot accomplish this, as they have no formal training, or at best, have only taken a couple of weekend boot fitting seminars, which at best, only provide a certificate of attendance.

    1. Here’s more information that isn’t knew. The balance system uses ground reaction force or in the case of skiing, snow reaction force, to generate postural responses In skiing the central issue is the ability for the CNS to negotiate a balance solution with SRF through the stack of equipment that resides between the plantar aspect of the skier’s outside foot of a turn and SRF. If this can’t be done there will be unbalanced moments of force across the ankle complex and through STJ coupling an unbalanced moment of force at the knee. The latter is new information but it shouldn’t be given that STJ moment of force coupling is ancient history. My question to you is how do you address this issue?

      1. The aim is to …mechanically…. control deformation of the foot and ankle, including internal rotation of the tibia, when the medial column is loaded. The posterior tibialis muscle cannot be relied upon to hold the arch up, as that is not what it was designed for. Yes, muscles balance us, but if we depend on them to correct bad biomechanics, they fatigue, quickly. BTW, using the term, “single leg stance”, is better than using, “monopedal stance”

    2. I council skiers not to put a gait plate in a ski boot, but way back when, when you had a pair made, not that much was known about skiing mechanics, and the foot’s relationship to those mechanics. You referenced the boot board. What do you mean by flat: fore to aft, or medial to Not since the Salomon Equipes was there a non neutral rearfoot area of a boot board. A properly constructed custom insole is a must, before boot fitting, stand and balance.

  6. A somewhat convoluted attempt to describe the biomechanics of the lower limb, that I feel, fails to correctly describe lower extremity biomechanics in alpine skiing. This quote, “The foot articulates in order to facilitate muscle function. Muscles respond in opposition to loads imposed upon the foot. A process ensues wherein the chain of articulations, initiated at the foot, are continuously mobilized so as to maintain a state of balance.” is absolutely NOT new information. Clearly, there is a basic lack for formal training in biomechanics.

    1. So where do you propose the loads come from Robert? I am all ears. I never said this was new information. This was excerpted from my US Patent 5,265,350 where it was cited in support of the invention.

    2. I think everyone is overthinking this. All Dave is proposing is that the medial arch should be allowed to flatten under load…thereby allowing the foot’s centre of pressure to move medially. He’s also proposing that the tibiotalar joint should be freer to dorsiflex than most boots allow, again facilitating medial centre of pressure movement and also some anterior movement of the centre of pressure toward the first metatarsal head. The point he makes is that contemporary boots, by locking up that motion and preventing it, interfere with the capacity of the foot to function to its potential in a skiing turn. And that’s about the end of the story. So don’t put arch supports in ski boots, and don’t let the tongue of the boot interfere with dorsiflexion of the ankle.
      Getting into a discussion of the functions of the intrinsic foot muscles is unlikely to be all that illuminating, as it’s correct they would only augment the elastic mechanisms afforded by the ligaments of the foot and the more powerful post-tibial muscles. The arch is compressed by forward motion of the shank and upper body, and returns to its neutral position (mostly by elastic ligaments) as the ankle plantarflexes when the limb straightens again and the load is removed.
      Dave and I already had a conversation about people with normal feet, who can capitalise on this mechanism, and those with abnormal feet who can’t…and so may never be elite skiers.

      1. Bob, Thanks for speaking for Dave. 🙂

        No, I think you and Dave are under thinking this. And your statement, “…the medial arch should be allowed to flatten under load…” is absurd. Why punish the subtalar and ankle joints, shin, knee and patella, in that manner? The abnormal foot, ankle and knee biomechanics, for the unsupported medial column, are huge. Suggesting to a skier that you want them to collapse the medial column, and that it’s good to do that, is…well…. putting the skier at higher risk for injury. Maybe you think it’s cute for the right knee to point left, and the left knee to point right, but it’s malpractice

        I read your post on net ramp angle. I have been entering those degrees in an equation with the static forward lean of the upper cuff since I first used a Campbell Balancer, many years ago. My thinking went beyond the balancer, on this point, as the balancer did not account for boot flex. Without getting too involved; after a proper custom insole is made, give skiers a few different sets of heel lifts and let them see which heel height allows them to more easily flex the boot. Voila! Knowing where the boot hinge point is, in relation to ankle’s hinge point, makes things a whole lot easier.

        Thanks for the discussions. I feel like it’s still ski season, instead of pre-ski season.

      2. Robert what if anything does flexing the boot have to do with skiing? And what research have you done during actual ski maneuvers that substantiates your position?

      3. skikinetics, Why are you hiding? You do have a name, do you not?

        I said, “Bob, Thanks for speaking for Dave. 🙂 No, I think you and Dave are under thinking this. And your statement, “…the medial arch should be allowed to flatten under load…” is absurd. Why punish the subtalar and ankle joints, shin, knee and patella, in that manner? The abnormal foot, ankle and knee biomechanics, for the […]

        You said,

        Robert ,”what if anything does flexing the boot have to do with skiing? And what research have you done during actual ski maneuvers that substantiates your position?”

        My question to you is what does my comment about the medial column, have to do with boot flex, or ramp and cuff angles? What do you think pes planus does for the windlass mechanism. BTW, how many patients have you treated for chronic plantar fasciitis specifically caused by changing running shoes, from a 12º “heel drop”, to 8º or less. How much forced dorsiflextion do you think a pes planus foot can absorb? What would such a foot look like?

        As for your question, “what if anything does flexing the boot have to do with skiing?” It’s called transfer ability.

        So why do you think the industry has moved from an ankle high leather lace up boot, to the new plastic wonders, besides lower wind resistance, and lowering the incidence of tib-fib fractures that were so common in ankle high lace-ups?

      4. And why do you think the incidence of knee injuries went from essentially zero prior to the introduction of the rigid plastic boot and followed the sales in perfect lockstep? This was reported very early in the game by a team of Spanish orthopaedic surgeons. Do you have any knowledge of the history of the plastic ski boot. You might want to do some research. Hint. It didn’t come out of a science lab. The Shoe in Sport has a whole section on the ski boot. Here’s a few quotes:”It is hoped (that the author’s criticism) that they are a contribution to the development of a ski boot based along anatomical principles (translation: existing boots are not based on anatomical principles).This goal has not yet been established.” Here’s another, “Investigations by (Professor) Pfeiffer that the foot maintains some degree of spontaneous mobility in the ski boot. Thus the total immobilization by foam injection or compression by tight buckles are unphysiologic”. And yet another; (Referring to flex of the modern boot) “With respect to the safety of the knee, however this is a very poor solution. The increasing stiffness of the flexion joint of the boot decreases the ability of the ankle to compensate for the load and places the entire load on the knee.” The authors of these statements have some pretty impressive credentials.

      5. Robert, At this point I am putting out what works for me. Are you saying trading broken legs for ruptured knee ligaments was a good move? Count me out. You are entitled to your views of issues and I am entitled to mine. Let’s leave it at that.

      6. Nicely said Bob. To gain an appreciation of where I am coming from you need to read all my posts, not just a few. One of the issues I recognized 35 years ago was that there were some skiers who could and did ski very well in the rigid plastic boots that I and a lot of other skiers were struggling in. In fact I attended an event over the past 2 days where I had this very discussion with elite skiers and they talked about how they often start their ski day by skiing with all their buckles undone and that they never have any conscious perception of the boot cuff as in never. Most skiers do not understand how they can ski without the boot supporting their leg and ankle. In my considerable experience I found that the shape of a skier’s foot and leg and especially the structure of their feet in combination with the boot acted as a filter in determining how well someone would ski, athletic ability aside. This process determines who rises to the top.In 1991 to prove out my hypothetical model of the mechanics, biomechanics and physics of skiing a company called MACPOD (MAC Phail and PODborski) spend about $130,000 on a research project that used an instrumented device that replaced the ski boot to study the 3-dimensional forces of skiing and how skiers applied forces to the interfaces of the boot to balance moments of force on the outside limb. What these tests confirmed is that the elite skiers only use the boot cuff to align forces expressed by their foot and that the key force was CoP at the head of the first MT. If we blocked the joint actions that facilitated pronation their skiing ability disintegrated. There are only two ways the rotational forces can go, into a turn or away from a turn. At the end of the day if the rotational forces go out of the turn the implications are that there opposing forces at the knee.

      7. Bob, You stated: “I know a bit about the mechanical behavior of feet and knees, and you’re part of an occupational group that has been indoctrinated to believe that the foot needs to be protected from deforming under load, which, in my view, is something it has evolved to do”.

        Bob, the foot has evolved ………….do to man’s new ability to ski, eh? Darwin would be so happy 🙂

        OK, in what biomechanics journal have you published a peer reviewed article that supports the replacement of the standard and accepted theory of foot and ankle biomechanics, with your “theory”? I really want to know what you know.

        I will accept that you appear to be a master in boot modification. Did you happen to take photos of the guy’s foot, and then the boots, after your modification?

        Bottom line, your “ballsy” statement about my profession being indoctrinated — meant in a degrading tone — is pure BS. You are free to read my CV:

        As for your “theory” of what is a “good” foot, leaves a lot unsaid. Good for what; running, tennis, skiing, standing on your head, etc? In your world, is a foot that pronates no more than 4º, a good foot? If running can put 5-6 times your body on your feet, is it your understanding that it should be on the medial column or lateral column?

        But who knows, maybe the biomechanics experts around the world could be wrong, and only you are correct. It’s possible, but not probable.

        I stand by my professional opinion that our foot is not meant to be ridden with the medial column completely collapsed. Which means the following: 1) the midfoot is unlocked. 2) the first ray is unlocked, 3) the talus is completely pronated and internally rotated, 4) the dome of the talus is twisted within the now compromised ankle mortise, 5) the leg is internally rotated, 6) the knee in genu valgum, greatly increasing the chance of a knee injury. There’s a medical reason a pes planus is listed as a deformity.

        Another way to look at this is that the further from mid-line you move a body part, the longer it takes to re-center, to then be able to move in the opposite direction. Or, in others words, if your turn is late-at-the-gate, you’re screwed. And “screwing” is what you are doing to the biomechanics of the foot and ankle with your “Earth is flat, the foot is flat”, theory.

        Still I am open minded. I would like to read the peer reviewed biomechanical research you have published.

        As for proper “modeling”, is it possible the ski boot companies are missing all the science, and are really just making fashion-ware? If I understand your idea, you feel we need no more support than that given by an old pair of lace-up, ankle top leather boots, right?

      8. Robert, I will let ‘Bob’ respond to your comments. Curious though, where did you get the idea that ‘Bob’ is a boot-fitter and that the ski boot makers have science supporting the design of ski boots? You really have my attention here. The best way to make the foot and leg functional for skiing is to make it completely dysfunctional? Seriously? What a paradigm shift!

      9. Robert… I think we’re arguing from completely different perspectives, and that’s fine. Don’t take anything I’m saying personally… I know a bit about the mechanical behavior of feet and knees, and you’re part of an occupational group that has been indoctrinated to believe that the foot needs to be protected from deforming under load, which, in my view, is something it has evolved to do. And in real terms, when we talk about the medial arch flattening transiently during a skiing turn, and then returning to its neutral position, it is not an extreme movement or something that is going to damage the foot or knee. Dave’s central thesis is that there are skiers with ‘good’ feet that can behave mechanically very well in the right conditions, and his boot/liner design capitalises on that ability. We’ve already agreed that there are others (probably the patients you see, with poorly conformed feet) who cannot make their feet and ankles perform in that way, because they’ve got collapsed arches, or some other performance-limiting orthopedic abnormality. Their comfort might be improved by shoring up their arch, and they will be entirely reliant on hip and knee mechanics to make their ski turn…something I’m sure they can do perfectly well at the lower-to-middle boundaries of recreational skiing performance. No problem.
        Turning on the downhill ski can be accomplished any number of ways. These days, with extreme sidecuts, you just need to think about turning and you do. Those skiers with immobilised, neutrally positioned ankles in contemporary boots can only use their hips and knees to turn, whereas Dave’s boot design allows an additional level of control, probably with shorter reaction time latency. I did a back-of-a-napkin inverse dynamics calculation comparing the frontal moment at the knee in two scenarios…one where the foot was pronated and the foot’s centre of pressure was medial, close to the edge of the ski, and one where the foot was neutral. The pronated position reduced the frontal knee moment…not by a lot, because the forces are large regardless, but still. The three-dimensional forces around the knee are huge when skiing, and irrespective of boot design the foot, ankle, knee and hip are going to work in combination to effect the turn. If some of that effort can be applied through foot/ankle mechanics, it has to remove some of the stress from the knee, which is largely constrained to sagittal motion. If, as the ankle dorsiflexes and the foot pronates, the tibia rotates internally as the knee flexes, that achieves the same superincumbent body position as a neutral ankle and abducted knee. I would say the first mechanism is healthier for the knee.
        It would be nice to have some real force and positional data to do some proper modelling. I’m starting to get to grips with the OpenSim modelling program to look at breakdown of the lumbosacral joint in police and search/rescue dogs, and am planning to look in the near future at stifle joint mechanics relating to cruciate injuries in dogs…which is a huge problem. When I find some time, I’ll see what I can do with this problem…

      10. Thanks for that Bob. There are definitely people with foot conditions that limit how well they will be able to ski. People in this category need all the help they can get. I recall one skier who came to me who had feet so wide they looked like swim fins. There was no way I could stretch the shell enough to get the width he needed. I ended up cutting the lateral side of his boots along the footboard well, pulling the shell wall outward and plastic welding in a section to make the boot about an inch wider across the metatarsals. For the first time in his life he was able to ski pain free. I saw his daughter recently. Her father still talks about how I fixed his boots. On a similar problem I had to take two pair of boots, cut them into sections and plastic weld them together for a skier on the National Team who had broken both ankles. I am going to do a post on the Birdcage research vehicle that we did our study on in 1991. The biomedical engineer who oversaw the research designed a series of protocols to study such things as the effects of cuff resistance in 1 and 2 segments and especially the range in degrees of very low resistance lead segment flexion. At one point when the range of low resistance flexion had reached the highest number of degrees an ex National Team racer asked if he could try skiing with a free cuff. With no springs the cuff could rotate anteriorly to 45 degrees from vertical. I thought there was no way he would be able ski. The first run he was skiing through icy moguls like he was skiing on perfectly groomed hard packed. Soon everyone was trying it. The beginner skier in our test team did not have the finesse of the elite skiers. But he could still ski with a free hinging cuff. The goniometer and the strain gauges under the met heads showed that the posterior muscles in EC were absorbing the energy from perturbations in snow reaction force. The peak forces are very short in duration and not even consciously perceived. When the range of low resistance cuff movement was limited this was not possible.

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