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.

5 comments

  1. 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.

  2. 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.

  3. 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.

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