THE FUTURE OF THE SKI BOOT – PART 2


The introduction of the rigid shell ski boot served as a foundation for the evolution of what became a science of immobilization and splinting of the joints of the foot and a leg of a skier. By creating an encasement for the foot and the portion of the leg within the rigid shell, mediums such as foam could transfer force to the ankle and leg to substantially immobilize its joints. Supporting the foot in a neutral position with a rigid footbed or orthotic in conjunction with form fitting mediums ensures maximal immobilization that is described as the Perfect Fit. The science of immobilization has evolved over the years to include thermoformable liners and even thermoformable shells.

Even though the medical textbook, The Shoe in Sport, cautioned 30 years ago that “the total immobilization by foam injection or compression by tight buckles are unphysiologic (against physiologic function)” the proponents of immobilizing the joints of the ankle continue to claim that this puts the foot in it’s strongest position for skiing.

The paper, Recent Kinematic and Kinetic Advances in Olympic Alpine Skiing: Pyeongchang and Beyond,  published on February 20, 2019, cited better transfer of the skier’s action to the skis through improved boot-fittings with individual liners and insoles. If in fact, skier performance is improved due to improvements in the science of immobilization through boot-fitting then it should be evident in studies that look at skier performance.

One such study, Challenges of talent development in alpine ski racing: a narrative review, published in March of 2019 found:

Youth and adolescent ski racers report lower injury rates compared to World Cup athletes. The knee was the most affected body part in relation to traumatic injuries. The most frequently reported overuse injuries were knee pain (youth) and low back pain (adolescent level). Athlete-related modifiable risk factors were core strength, neuromuscular control, leg extension strength and limb asymmetries.

Neuromuscular Function (NMF) affects Neuromuscular control (NMC). NMC is an unconscious trained response of a muscle to a signal associated with dynamic joint stability. This system of sensory messages (sometimes referred to as “muscle memory”) is a complex interacting system connecting different aspects of muscle actions (static, dynamic, reactive), muscle contractions, coordination, stabilization, body posture and balance. The movements of the lower extremity, including the knee joint, are controlled through this system, which needs correct sensory information for accurate sequential coordination of controlled movement.

It has been known for decades that restricting the action of a joint or joint system, especially immobilizing the joint, will cause the associated muscles to atrophy. But a study, Effect of Immobilisation on Neuromuscular Function In Vivo in Humans: A Systematic Review, published in March 2019, suggests that the effects of immobilizing joints of the body are far greater than simply causing muscles to atrophy. This is the first systematic review to consider the contribution of both muscle atrophy and deterioration in neuromuscular function (NMF) to the loss of isometric muscle strength following immobilisation. The fact that the study, Challenges of talent development in alpine ski racing: a narrative review, cited core strength and neuromuscular control as issues in the development of talent is significant. The feet are part of the core in what is called foot to core sequencing. Immobilizing the joints of the foot can affect lower limb and core strength.

Immobilisation in the study the Effect of Immobilisation on Neuromuscular Function In Vivo in Humans: A Systematic Review, was achieved by using casts, braces, slings, unilateral suspension, strapping or splints with the following locations immobilised: knee, ankle, wrist and finger. All studies measured isometric muscle strength. No studies were cited that involved bilateral immobilisation of both ankles such as occurs in form-fitting ski boots. However studies did find that multiple joint immobilisation was likely to produce the largest change in the NMF of segments consisting of both mono and biarticular muscles. Other key findings were:

  • The greatest changes in all variables occur in the earliest stages of immobilisation.
  • The loss in muscle strength during immobilisation is typically greater and occurs faster compared to the loss of muscle volume.
  • The choice of joint angle for immobilisation using the brace or cast method appears likely to play a large role in the outcomes.

I started this blog six years ago for several reasons. A primary reason was to identify whether any influences existed in skiing that would serve to change the focus from immobilizing the joints of the foot and leg with the associated claims to a science-based focus. Since the future of the ski boot appears to be continued refinement of the science of immobilization this will be my final post.

I have learned a lot over the past six years that led to huge breakthroughs on skis for myself and those who I have worked with. Thank you to those who commented and contributed to The Skier’s Manifesto.

17 comments

  1. David,
    Thank you so much for your contributions. Even though I’ve been an follower for less than a year, I’ve learned so much that has helped my skiing. You will be missed sir – well done.

    Would you please give me some idea of how long you will leave your site up? I’d like to learn as much as I can so I can continue my own research and modifications.

    One last question, if I may: It seems to me that for proper foot function, the boot should be flexible in the fore-aft plane. But you stress the importance of stiff boots. Is that because you mean stiff laterally as opposed to fore-aft? Or am I missing something…

    Thanks again for all your contributions.

    Jeff Bruckner

    1. Hi Jeff,
      I apologize for the lengthy delay in responding.
      The subscription for my web site is good until almost the end of December at which time I will decide whether to renew it. If I don’t it will disappear.
      In response to your question about boot flex, it is not so much a case of the boot needing flex (read: deform) but a case of having space for low resistance dorsiflexion, plantarflexion of the ankle between it’s fore/aft limit of about 12 to 14 degrees. The rear limit provided by the cuff must be rigid while the forward limit must have progressive resistance of about 8 degrees for a total ankle range of motion of 20 to 22 degrees. The sides of the cuff must be rigid. Please let me know if this is still not clear.

      1. You are very welcome. The biomechanics of balancing on the outside ski of elite skiers uses the same basic hard-wired loading sequence as walking. As COG moves forward over the outside foot of a turn the ankle dorsiflexes (flexes forward). This tensions the calf muscle by stretching it. When the sufficient tension is reached the ankle stops flexing and the knee and ankle go into extension to move COG over the ball of the outside foot and tension the chain from the forefoot to the pelvis. The problem is that we aren’t consciously aware of the process.

        I spent countless hours walking slowly barefoot to develop a conscious awareness of what is happening. Once I knew what should happen I found that I couldn’t replicate it in my ski boots. I later learned that the sequence is ‘ramp sensitive’ within a fraction of a degree. My bindings have zero ramp and the boot boards in my ski boots have 0.1 (one tenth) of a degree. Most skiers need about 2 to 2.5 degrees. But elite skiers usually need 1.5 degrees or less.

        Boot flex became an issue when elite skiers who skied well in low cut leather boots found that the new rigid plastic boots which at straight shafts did not low allow them to load the ball of their foot with ankle flexion. Instead of recognizing the problem a boot flex mentality prevailed. It was a ‘good story’ (nothing more) that generations of skiers fell for.

  2. David
    Your research and study has brought forth many realities that would otherwise never be mentioned let alone discovered .
    I can’t thank you enough for all of your help over the years, for without it I never would have been able to have the success nor the longevity I have enjoyed as a full time ski professional.
    Best wishes
    Cam Watson.

    1. Cam, the feeling is mutual. Seeing what you did to your boots that enabled you to be a great skier confirmed that I was on the right track when I started removing padding and cutting away parts of liners instead of adding things. Unfortunately, skiing is a survival of the fittest in the context of having the right shape foot and leg to be able to function with the constraints of what amounts to a coffin for the feet. The odds of winning the right shape lottery appear to be about a million to one. Best wishes, David

  3. Hi David,

    Many apologies for my absence from commentary. The end of the season was hectic as I worked to build a functional tongue and test it before long planned hernia surgery on April 12 (postponed from last September). My last ski day was April 10 with a two piece “tongue” and was quite positive. For all the boot work I did this season I did not ski much but, that last day was a real boost in reinforcing the value of your principals ie:1. Ramp angle; 2. Forefoot fit for metatarsal and toe splay; 3. Instep loading for secure neuromuscular function; 4. Ankle flex for proper stretch reflex engagement, and, of course; 5. Space to pronate fuctionaly.

    Ramp angle stood out once again as I adjusted my new boots. I flattened the bootboard and then shimmed the forefoot in 1mm increments. It was a shock, in a good way, to add 1mm to what I had and instantly fire up my stretch reflex. I think ramp angle is the real key to skiing with ease. Despite not skiing much, I could easily make non stop runs on bulletproof ice and not feel beaten up at the end of the day because I could ski more upright, balance comfortably, and keep my body (COM) stacked vertically over the inside edge with maximum pressure on the head of the first metatarsal in the turns.

    David, your blog has reignited and redirected my skiing in the direction I had always hoped to go but, never had the knowledge and awareness to find. This knowledge and information must not be lost to skiers and the skiing world. There must be a way to archive and store this wellspring of information somewhere so that it is available for future generations of skiers and ski equipment designers. I understand your reluctance to write a book but, perhaps this blog could become that book. I am not very computer savy but, I believe there are data storage devices to which this could be downloaded for future reference.

    Do you have a more definite date of termination? I, and perhaps others, would like to copy this information for personal use as we try to make our boots functional.

    Thanks again for the privalidge of reading your work and communicating with you in these comments.

    Best regards as always,

    Herb

  4. Dear David
    thanks for all your interesting comments and explanations and time devoted to the subject. I have enjoyed reading your posts and my boot liners have received a severe hacking along your suggestions. I feel that my skiing has been significantly improved.
    I was waiting with interest for your advice on remoulding the boot boards at a lower ramp angle, I suppose that I will just have to work that one out myself.
    Enjoy pastures new.

    1. This can either be an easy issue to address or a complex one depending on the construction of the ski boot which is all over the map from boot to boot. An easy way is to remove the existing boot board, place the shell on a flat surface tilted to the angle you want the boot board to be (2.2 degrees or ?) then pour in a resin based urethane like Smooth-On https://www.smooth-on.com/products/smooth-cast-325/. You need to be careful not to overfill the boot shell or the boot board will be too high. It is better to pour the boot board in stages and ski test between each stage. When the height is close you can use thin cork gasket material to make insoles for your liners to adjust the height. You can get cork gasket in varying thicknesses at an automotive supply.

      I am appalled that makers of ski boots seem to have no interest in addressing this important aspect. But that’s reality. Good luck and good skiing. Thank you for following my blog and commenting.

  5. David:

    I echo Dr. Hewson’s response on May 19, 2019, “Why now?” After attending his “Foot and Ankle Biomechanics in Alpine Skiing” seminar at PSIA-Rocky Mountain Fall Training in November 2017, I found my way to your blog and Naboso insoles. After many years of trying to get my boots right and save my diabetic neuropathic feet, I was elated to finally connect to the truths of foot an ankle biomechanics.

    The most important and somewhat embarrassing truth I came to was fact that I had previously experienced skiing at a lower ramp angle, but had not paid attention to it since 2004 when I got a pair Lange WC130s with a ramp angle of 4 degrees. Lowering my ramps was first suggested to me back in the early 1990’s by one of my examiner-mentors, when I was working on my PSIA Alpine Level 2 and 3 ski instructor certifications to help me achieve a more upright biomechanically correct stance. I did as was suggested, and my improved skiing enabled me to pass my certification exams. I religiously moved those ramps from boot to boot (all Langes); starting with my Lange Pink Panthers. I also removed or ground off the spoiler inserts that increased the forward lean. However, in 2004 when I got a pair Lange WC130s, I did not move my lower angle ramps into these boots (or grind down the WC130 ramps); mistakenly assuming that ramp angle did not make much difference. My body and my skiing adjusted to the steeper 4-degree ramp angle, and l have skied well, but, not nearly as well as I am skiing now, since I went back to a lower ramp angle of 2-degrees (possibly going lower) and not buckling my boots so tight. Ramps and heel lifts in our foot ware (sandals, shoes, ski boots, etc.) contribute to physical problems for everyone as very well explained in your posts and in The Barefoot Book by Daniel Howell, PhD. We should be lowering our ramp angles in every type of foot ware we use, and we should be pursuing ski boot design(s) that allow our feet and ankles to work as nature intended.

    I am just a lowly ski instructor and resort trainer attempting to give my clients and my fellow instructors the best instruction and training I can give. In spite of your frustration about what is currently going on in our industry, I believe what you are doing is very important. So, as Dr. Hewson said in his post, “Please, let’s keep the foot and ankle in motion!” At the very least, I hope we can still have access to you and your information.

    John R Taylor, PSIA

    1. Thank you for your comments.

      After 45 years I finally accomplished what I set out to do when my change from low cut leather boots to the new plastic boots ruined my enjoyment of skiing. The big breakthrough for me came in 2018 (5 years into the Manifesto) when I made the Achilles connection and reduced total ramp angle to about 1.2 degrees. My dogged persistence finally paid off in spades for my spouse and I and several of our friends.

      One of the reasons I started this blog was to ‘test the waters’ so to speak to see if there was interest within the ranks of the ski industry in developing a science-based approach where equipment would be adpated and refined to meet the functional requirements of the individual skier. The loud and clear message written in the persistent ‘Perfect Fit’ evolution says there isn’t. It costs me money to provide this blog, not to mention many hours of my time. It is time to call it a day and move on. The Manifesto will be online for a period of time after which it will be permanently deleted.

      I am glad and happy to have helped you reach a higher level in skiing.

  6. I enjoyed reading your blogs. Thank you for the effort. I continue to ski without footbeds. I was thinking about trying the Nabiso, based on your blogs, but wondered if you would have to be barefoot in the ski boot to get the benefit…

    1. NABOSO works very well in ski boots if you have the right socks. I tried a number of different socks until I found one with the right thread a weave; very fine thread with no fuzziness and thin well defined texture. Barefoot is best. But it is very difficult to insert my foot into my very stiff Head World Cup competition ski boots. Through subjective experiments with minimal zero drop shoes I found that the correct ramp angle in ski boots is critical. The whole world changed when I reduced my boot board ramp (zeppa) from about 2.8 degrees to 1.2 degrees. Suddenly the nerves under the balls of my feet that are critical for balance came alive.

  7. David,
    Sad day. Why now? You are on a pedestal for bringing the truth to the public through your blog.
    Your work has influenced many. Please, let’s keep the foot and ankle in motion!
    Dr. Kim Hewson

    1. The past 4 years have been very tough as I witnessed talented racers abused and destroyed by the system and then discarded like soiled diapers. Dreams and careers were destroyed while the racer’s parents suffered extreme disappointment and financial hardship. The path to success or failure is a veritable walk on tightrope where one slip can end a promising career. All too often the fatal slip is a change in ski boots with rigid footbeds and custom fit liners that severely compromise NMF. Even Shiffrin proved vulnerable tio changes in gher ski boots. I credit her mother for Shiffrin’s success.

      The 3 recent studies I cited in my last post were the final 3 strikes against the ski industry. Thirty years ago, they were given an opportunity to change direction after the constructive criticism in the Shoe in Sport. But instead they appear to have engaged what I term willing ignorance and stayed the course with the “foot functions best for skiing when its joints are immmobilized” if for no other reason than it is a good marketing story. At this point I don’t see any way for the ski industry to change direction without serious consequences. They will probably keep ignoring emerging studies that prove them wrong. If I could see even a slightest glimmer of signs of change I would continue with my blog.

  8. There must be times when you feel as if you are a lone voice crying in the wilderness, to use one analogy. While as a coach and boot fitter for our local market my theme with my clients and athletes is often first to ensure that they are not going into boots whose rigidity is simply far greater than their ability to balance forward in one plane (shin pressure and direction), I am always left keenly aware that there is so much more to this problem and your articles and investigation have been the basis of many of my own forays into this territory. Even just starting with the victims of the stiffer is better syndrome which for the vast majority of consumers is clearly a marketing tactic or a misguided link to performance in my mind and not always born out by my on-snow experience, and then try to find ways to accommodate the foot, not only making enough room for the bumpy bits without creating so much room that there are other unintended consequences, but also trying to allow the foot and body to perform in harmony is a continual challenge with the modern array of products. The fact that so much needs to be done to inform the consumer as well as try to modify their existing product is a clear sign to me that the industry has been down the rabbit hole so long it did not start the evolution of the ski boot from the same place (the foot) as it should have. This was made even clearer to me when in a short seminar a medical professional who was working for our national ski team described his experience with the testing process at a major boot manufacturer in Europe while on a visit. It is certainly disquieting to recognize how many other variables impact performance and how much variation exists and has existed in the manufacturing world to address the need to connect the body to the binding and by extension the ski, with the boot and yet we’ve still not arrived at a universally understood position. Being in the retail industry has given me perhaps a negative perspective on how footwear products, in general, are designed and evolve and how easy it is for the current fad to overwhelm any basis of scientific validity or carry design concepts to an extreme. While I hold no hope that there will be a significant change in many of these accepted “truths during my lifetime I appreciate your willingness to buck traditional thinking and strike out on your own voyage of discovery.

  9. David I am very sad to hear that you will not post anymore. I am an italian ski teacher. I am conducting research in how a person can learn more on the psychological level but your posts have been always very valuable. Will miss them.

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