SUPER PETRA VLHOVA’S EXPLOSIVE IMPULSE LOADING IN ASPEN SLALOM


I am blown away by the explosive impulse loading of her outside ski that Petra Vlhova displayed in winning today’s World Cup Slalom in Aspen, Colorado. Vlhova’s powerful impulse loading made other racers, including Shiffrin, look like they were in slow motion in comparison. There are several videos of Vlhova in action on YouTube already.

For those who don’t know how to change video speed and definition in YouTube, the screen shot below shows the range of speed options available from 0.25 to 1.5 times Normal. To select the speed option, click on the gear that says HD then select Speed. I usually watch race videos in several speeds, including pulse frame stepping using the space bar on my keyboard.

Vlhova’s rapid and explosive loading of her outside forefoot at edge change literally supercharges the small nerves in her feet and the muscles in her foot to pelvic core in a way that transforms her into a literal super racer.

Petra; on it – all over it.

Here’s a short video clip in reduced speed of Super Petra in action. In one word; WOW!

Bravo Petra Vlhova! You made my day.

 

6 comments

  1. RE: GIRARDELLI AND STENMARK DEMONSTRATE BALANCE ON THE OUTSIDE SKI
    March 8, 2017

    Dear Dave,

    Boy that post is packed with 100 years of ski pedagogy and translators of language to describe it.

    One can see the elements of the old down up down to unload the skis to set up the transition between edge sets. If I am not mistaken, in English this became “weighting” the new outside ski or eventually “unweighting” the new inside ski. What you seem to be postulating is there is much more complex set of elements that must be understood and incorporated in ski pedagogy.

    Please advise if I am miss characterizing your thesis.

    What I am hearing you say is that these instructor tricks are really about creating ground reactive force with the new outside ski by rapid muscular exertion generating intense ground reaction force GRF (knee extension) at a key point in the transition. It is the physical ability of the skier to pre-activate this muscular loading (re Dr Emily Splichal) and the muscular chaining within the body (re Dr. Vladimir Janda) over short foot (plantar aponeurosis (PA), hard arch, stable base of support) that allows for the necessary force (inclusive of lateral body aliment) to be developed that starts the turning action of the ski. The ski/snow physics of that action being described in your post “THE MECHANICS OF BALANCE ON THE OUTSIDE SKI: TIMING OF EDGE CHANGE” March 12, 2017, is actually what allows the femurs to rotate.

    In racing and recreational skiing, the elements are: neurologic pre-activate (Splichal), rapid generation of intense GRF, ability to develop Janda’s short foot, ability to engage the inside edge of new outside ski (COP on first metatarsal), with neurologic chaining from the feet to the head (Janda) thus creating effective lateral aliment and general stability, plus the physical turning action of the ski when conditions are met with exact timing and sequencing of all elements.

    When looking at the transition “GIRARDELLI AND STENMARK DEMONSTRATE BALANCE ON THE OUTSIDE SKI” video March 8, 2017 one sees 1) the observable up motion of the body as it uncoils upwards from G-force and high edge angle then recoils into the next turn, and 2) the belief that the observable rotation of the femur turns the ski are both spurious correlations that set the new turn in motion. If I’m getting your thesis, femur rotation is a by-product exact timing of force applied to the first metatarsal (setting new inside edge of new out side ski) that sets this rotation of ski and femur in motion. thomas

    1. Thomas has invested significant time engaging in critical thinking on the issues I discuss. I am posting his comment with some minor editing on my part to correct a few errors.

      Thomas is very much in the right direction. I will write a post based on his comments with my comments and graphics inserted in his text.

      Nicely done Thomas!

      1. Dear Dave,

        Thanks for the kind note. I am so glad you took what I wrote as my attempt to hear the meaning of what you want known.

        To:
        To the more general audience reading this blog the practice of hearing and understanding meaning is part of a age old practice of achieving mutual understanding often used as the first step in understanding conflict including bitter conflict in order for members of a community to find a way forward to work and live together.

        In this case, I am just using the first step of reflective listening to see if I understood Dave and giving him an opportunity to try again if he felt I did not reflect his meaning the way he wanted it understood. There is no conflict between us either painful or otherwise. It might be when we reach mutual understanding we find areas of disagreement or agreement. Those areas are likely to be fully understood by each of us, we will be able to define and take responsibility for them and continue the dialogue in community as how to live and work together side by side.

        My reflection is really only one paragraph. It summarizes much of Dave’s writing over the years. Does it contain my own biases and interpretations with my own prejudices? Sure, that is the filter through which we hear others! Are there omissions like ski boot design? Yes. But that is implicit when talking about Janda’s short foot. Was there verbal clumsiness in my reflection which may distort the way in which he wanted to be known? For sure.

        Note I am not attempting to assert legal or rhetorical argument which would tend to separate the connection and divide this on-line community. We have seen such communication here and it did not seem to advance understanding, intellectual curiosity or the sense of belonging to a community. People can belong to a tightly knit community and be in conflict – disagree as long as there is mutual understanding, meaning people know enough about their actions the consequences thereof, that they are willing take responsibility for their disruptive actions and willing to move forward with agreed action. That action may be a compromise, it may be an apology and action which symbolizes what has been lost, and it may be how diametrically opposed ideas can exist in community.

        Dave and I are not in conflict. We are just using a restorative practice to explore and better understand the dynamics of skiing. And in that endeavor, it takes a lot of work to understand everyone’s meaning as we attempt to learn more about these dynamics in community, thomas

      2. Further to what Thomas has alluded to, I started this blog in 2013 for the purpose of advancing the sport of alpine skiing as a credible science based on principles of applied science and the application of the findings of the latest research. While there appears to be a widespread perception that skiing, especially the teaching coaching aspect is based on solid science, there is little evidence to support this. When researchers who investigate such fundamental aspects of skiing as skier balance look for existing studies they are consistently surprised to find such studies rare. What researchers typically find is that most of what forms the basis of ski technique and ski equipment, especially ski boot design has resulted from a subjective trial and error process. In short, it is mostly a process of guessing.

        The problem with this process is that conclusions based on uninformed observation may be the exact opposite of what is really happening. Thus, when a world class racer or even an elite skier makes a quick extension movement in the top of turn as they approach the fall line, the assumption by an influnental figure in skiing that this is an unweighting action is readily accepted by the majority without question even when it contracts principles of mechanics physics. This does nothing to advance skiing as a credible science

        If skiing is to advance as a credible science, it is essential to critically review, question and analzye what makes up the current state of what is regarded as the knowledge of skiing. The first country, or even the first racing team to successfully perform this task will own skiing and line will be drawn in the snow between them and those who have chosen to remain firmly entrenched in the dark ages of ignorance.

  2. Hi David, just a note to say how much I look forward to your articles. They are well written, informed, and just plain enjoyable to read. Augmenting with video significantly helps my understanding as I try to incorporate your thoughts into my skiing and inline skating.The fact that you have given us a real time insight and analysis of the race yesterday is a bonus. Thank you for making the effort, it is much appreciated.

    Best
    Peter Collins

    1. Hi Peter, thank you for your feedback and compliments.

      One of my challenges is trying to find ways to initially create an awareness of an issue, such as impulse loading, that is currently not on the radar screen of official ski teaching and coaching narrative that I am aware, then find a simple way to effectively communicate a complex mechanism. It is a natural tendency of the human brain to filter out information that does not support what is believe. It is also common for people to assume if something is not in an official narrative of an association, that it is not important. Feedback from those such as yourself, helps guide my efforts.
      Best regards, David

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