INFORMATION FOR ACADEMICS AND TECHNICAL AND MEDICAL PROFESSIONALS


With the increasing evolution and availability of microsensor technologies, some which can work with smart phones, there has been a corresponding increase in both the level of interest and studies on the science aspect of skiing.

One of the best studies I have found to date is the study (1) by Michał Staniszewski, Przemysław Zybko and  Ida Wiszomirska of the Józef Piłsudski University in Warsaw, Poland. As a preliminary step to the design of a study, researchers typically conduct a search of the literature for existing papers in the field. Researchers who design studies for such things as skier balance are typically surprised when results of searches find that few, if any studies exist.

Thus, the authors of the Polish study (1) commented:

Publications on issues related to the biomechanics of a descent, with particular emphasis on the balance parameters, are rare in the literature on alpine skiing.

The authors of a 2014 Polish study (2) on skier balance, similarly commented:

Our results were in agreement with the scarce information available regarding balance changes during or after a ski training camp.

The authors of a 2013 Italian study (3) on materials, designs and standards for the ski boot made a similar comment:

Despite the large market of ski equipment, not many scientific papers have been published on this subject in the past.

If not many scientific papers have been published on issues pertaining to skiing, the question arises as to what, if any, process was used to influence the design of the modern ski boot. The authors of the paper (3) comment:

The development of alpine ski equipment has been done, in the beginning, mainly by trial and error, using on-snow tests.

In other words, the process appears to have been largely subjective and artisan driven as suggested by the comment:

The first skis were only plank of woods with laces to link the traditional leather boots used in the Nordic and Alpine regions. At that time skiing was mainly performed in flat areas to help the transportation of loads and for this reason the first recreational activity with skis was cross-country skiing. Alpine skiing was born only afterwards and, therefore, the first equipment used to ski down the steep terrains of the Alps was developed starting from those already used for skiing in flat snow-fields (thin skis, leather boots and heel free bindings).

This comment suggests that the modern plastic ski boot was an outgrowth of the artisan leather hiking boot with advancements being mainly in the form of new plastic materials in place of leather.

While the authors acknowledge that research in the field of plastic materials and the optimization of new software for the design of sport equipment have permitted the development of new materials and designs that have increased the level of performance, security and comfort of ski-boots, no mention is made of advancements in the understanding of the physiologic aspects of alpine skiing. The lack of existing studies places researchers who wish to investigate this issue in the awkward position of having to rely to a significant extent on established ski industry positions on such crucial aspects as skier balance as the authors of the 2014 Polish study did when they cited LeMaster’s definition of balance:

He or she is in balance and will not fall as long as the total of all of the forces acting on the center of gravity passes through the body’s base of support.

Not falling does not conform to the text-book postural response paradigm wherein the opposing forces associated with single balance align across the plantar/ground interface with CoM maintained within defined limits of the foot.

Although studies in the field of the mechanics, biomechanics and physics of alpine skiing are rare, the number of studies in related fields that are directly applicable to skiing is steadily increasing.

Recent studies (4) on forefoot loading (fascial tensioning) found that peak plantar aponeurosis tension occurs in late stance, suggesting that it was an error to not include the late stance phase in gait and balance studies and positions in general on the phases of gait.

The plantar aponeurosis transmits large forces between the hindfoot and forefoot during the stance phase of gait. The varying pattern of plantar aponeurosis force and its relationship to Achilles tendon force demonstrates the importance of analyzing the function of the plantar aponeurosis throughout the stance phase of the gait cycle rather than in a static standing position. 

This and similar studies have significant implications for skiing because the late stance phase of the gait cycle stabilizes the subtalar and knee joints in preparation for the application of high ground forces for propulsion. The implications of such findings  to alpine skiing is that the late stance phase (SR Stance) allows high loads to be applied by the 1st and 2nd MPJs and the application of reverse subtalar joint translated vertical axial rotational torque generated from the pelvis to the ski.

Understanding and appreciating these mechanisms opens the door to new opportunities for research projects.


1. Influence of a nine-day alpine ski training programme on the postural stability of people with different levels of skills  (April 2016, Biomedical Human Kinetics (DOI: 10.1515/bhk-2016-0004) – Michał Staniszewski, Przemysław Zybko and  Ida Wiszomirska,  Józef Piłsudski University, Warsaw, Poland.

2. Changes in the Balance Performance of Polish Recreational Skiers after Seven Days of Alpine Skiing – Beata Wojtyczek, Małgorzata Pasławska, Christian Raschner

3. Materials, Designs and Standards Used in Ski-Boots for Alpine Skiing: Martino Colonna *, Marco Nicotra and Matteo Moncalero

4. Dynamic Loading of the Plantar Aponeurosis in Walking: Ahmet Erdemir, PhD; Andrew J. Hamel, PhD; Andrew R. Fauth, MSc; Stephen J. Piazza, PhD; Neil A. Sharkey, PhD – J Bone Joint Surg Am, 2004 Mar; 86 (3): 546 -552 . http://dx.doi.org/

Intrinsic foot muscles have the capacity to control deformation of the longitudinal arch – Luke A. Kelly1,2, Andrew G. Cresswell1, Sebastien Racinais1,2, Rodney Whiteley2 and Glen Lichtwark1⇑

 

4 comments

  1. Hi, I have been reading many of your posts with great interest for several months now.

    Avid recreational skier for around 20 years and now 61 year old, I have tried to apply what I thought I understood from your Ligety and Shiffrin posts (step on it, rotational movement from the pelvis), SR stance posts and boot design posts (loosening them a bit to allow freer foot action). I found them all to be helpful (or at least not hindering) and contributing significantly this year to my never ending quest for improvement. Thank you, very much, for that.

    I have a question regarding the linking of the “step on it” phase and the SR stance. Am I right to assume that the SR stance takes place between the release and the ensuing “application of reverse subtalar joint translated vertical axial rotational torque generated from the pelvis to the ski”, as you described it in your post? Would that torque “application” be what Ligety described as “stepping on it”?

    If so, it seems to me that the moment between the release and the application leaves very little time to assume the SR stance effectively which makes it, I feel, sort of an instantaneous feeling rather than a phase in itself.
    Could you please comment on the flow, integration or linking of these phases?

    Keep writing!

    1. Hello François, Thankyou for writing. It is always both satisfying and rewarding to me when someone writes to tell me I have helped them enjoy our great sport. After all, the Skiers Manifesto is for skiers.

      I think you may have meant you were 61 years young when you said you were 61 years old. N’est ce pa? Mai oui!

      To your question, “regarding the linking of the “step on it” phase and the SR stance. Am I right to assume that the SR stance takes place between the release and the ensuing “application of reverse subtalar joint translated vertical axial rotational torque generated from the pelvis to the ski”, as you described it in your post? Would that torque “application” be what Ligety described as “stepping on it”?

      “instantaneous feeling rather than a phase in itself”.

      Answer: Yes, the feeling is more like a rush. I attempted to speak to this issue in my last post. I am not being arrogant when I say that I don’t think Ted Ligety or even Mikaela Shiffrin, who I greatly respect and admire, fully understand the forefoot loading issue. I think it more a case of them making a connection, working on it and refining it. If you are like most skiers, you probably have elusive days when skiing is effortless only to feel like a beginner the following day. My efforts and attention are focussed on learning how to make every day, every turn, every second on skis magical.

      “If so, it seems to me that the moment between the release and the application leaves very little time to assume the SR stance effectively which makes it, I feel, sort of an instantaneous feeling rather than a phase in itself.”
      ANSWER: Exactly. The extension pulse loading I am trying to articulate is a trigger mechanism that sets in motion a series of reflex driven actions that are the turn sequence. In this scenario, the only required conscious action is when to make the extension pulse that sets the events in motion.

      Your comments are helpful and appreciated. Please keep them coming. The only way my efforts can succeed is if skiers like you succeed.
      Could you please comment on the flow, integration or linking of these phases?

  2. You promised, two posts ago, that your next posts would detail the two moves to balance on the outside ski – when do you plan to do that?

    1. In the next few days. My challenge is that my message tends to get lost in the sea of misinformation in the ski industry. The real time flow of stats tells me what countries are following my blog and what posts they are reading. So to some extent, I try to tailor my posts to the areas of interests.

      One of the things I needed to establish is that omitting the late stance phase from the gait cycle, where the fascial tensioning of the forefoot, ankle and knee joints essential to the second step of skier balance caused everyone to miss this key aspect. This is why the discussion about ski stance refers to mid stance which is weak. No one knows that late stance exists. I did in 1990. It is only recently that studies have discovered the peak tension in late stance. Shiffrin definitely uses 2-step outside ski balance. That is why she is demolishing her competition. I am going to use some screen shots and video of her from St. Moritz as a lead-in to the 2 steps to outside ski balance post.

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