COMMENTS ON SUPER PETRA VLHOVA


As time permits, I analyze the movement and loading patterns of elite skiers such as Mikaela Shiffrin, Lindsey Vonn, Ted Ligety, Tessa Worley and others. Occasionally, a source sends me video of these racers training.

I have identified a specific movement and loading sequence pattern that I use to analyze technique. This requires decent quality video and specific camera angles. In a future post, I will describe the process, the key metrics I look for and what they indicate.

Up until I saw the video of Vlhova, that is the subject of my post, SUPER PETRA VLHOVA’S EXPLOSIVE IMPULSE LOADING IN ASPEN SLALOM, I rated her as one of the better technical racers on the World Cup circuit. But I did not consider Vlhova to be in the same class as a Shiffrin or a Worley.

When someone posted a link on FaceBook to Vlhova’s winning run in the Aspen slalom, I was stunned by what I saw in first few gates. This was not the same Vlhova I had analyzed earlier in the season. Vlhova has definitely changed and it is for the better.

8 comments

  1. Loosening upper boot buckles for restricted ankle dorsiflexion is palliative but not a good long term solution. A snug containment of the shank and continued contact with the boot tongue is necessary to activate foot pronation. A jerky to and fro shank motion with a loose upper cuff can occur in crud and bumps or any irregular snow. Ankle motion must be smooth and controlled to initiate proper foot pronation and supination. A softer boot flex with snug leg containment aided by a booster strap is my solution.

    1. Boot flex is really an index of deformation potential. In addition to deformation being uncontrolled, it causes the center of force on the shank to drop causing what I term the stair trip effect because it is similar to what happens when one catches the toes of their foot when ascending stairs. The external forces create a dorsiflexion momnent of force. Shank angle is maintained by the triceps surae/hamstrings biokinetic chain applying an opposing plantarflexion moment of force. Introducing a source of resistance to shank dorsiflexion requires a corresponding decrease in muscle contraction in the triceps surae/hamstrings biokinetic chain which will cause a corresponding decrease in Achilles/forefoot load transfer and a decrease in fascial tension in the plantar aponeurosis. This is easy to demonstrate with an in shoe pressure analysis system such as the Novel Pedar or Tekscan. As the boot shafted is flexed (read deformed) by anterior shank movement, the CoP will retreat to the heel and forefoot pressure will disappear from the grid. The negative effects of limiting shank movementwas demonstrated by preiment safety experts and sports scientists in the mid ’80s.

      A study 2005 study by Italian engineering group using instrumentation that measured shell deformation during actual ski maneuvers found that significant deformation of the boot base occured at modest loads of about 1.6 times body weight.

      Values of (inversion) drift angle of some degree (>2-3°) [drift angle is the change in the angle of boot and outside ski with the snow surface under load] cannot be accepted, even for a small period of time, because it results in a direct decrease of the incidence of the ski with the ground (edge angle). As a consequence, the skier stability and equilibrium could be seriously compromised, especially when the radius of curvature is small. An imperfect condition of the ski slope will emphasize this problem, leading to difficulties maintaining constant turning radius and optimal trajectory.

      Studies by M. Pfieffer of the University Salzburg concluded that ski boots should have a total range of ankle motion of about 20-22 degrees of which about half should be low resistance. This is easily achieved within the limits of a stiff boot shaft provided the cross sectional area of the skier’s leg is within specification. A power or booster strap acts in the capacity of a sling to arrest forward shank movement with a consistent, progressive resistance curve that uses the stiff rear spine and which maintains the center of load on the shank.

      1. David’s reply carries the weight of the pioneer of ‘ankle glide path.’ I had just started playing with truly loosening the top 2 buckles on my ski boots when introduced to The Skier’s Manifesto about 3 years ago. The info provided cut back on a lot of wasted time on my own blundering, part. My learning has been ‘experimental’ mostly on self and have to say that I haven’t as yet attained the ability to really dial in the cuff flex so leave a very unimpeded ‘glide path’ by hardly buckling the top two buckles. Ironically this works best on hard surfaces that are consistent in regards to not being sticky and fast. In other words, even in moguls I don’t need the tongue to prop me up; actually love the ability to adjust the ankle joint as needed so skiing the bumps is great with that because I can adjust so quickly. The craziest thing to me is that I can carve on ice better with the cuff really loose than I’ve ever been able to; I now realize I never carved prior to the total opening up the glide path because I could never truly adjust the skis’ edge angle. The biggest string attached is being well aligned and that the first step is Manifesto stuff (toe spread, no arch impediment). I don’t like Booster straps even in the moguls because every time I tried to press my tips down over a bump, the Booster sucked the toes up. When I got them loose enough to not have that issue it never engaged so I have no Booster or power strap. Then the net ramp angle has to be very close because if (I’m throwing a dart at a figure here) if the NR is off by 2* high one needs the cuff tight, literally holding oneself up. If the NR is too low it won’t matter because the skier will never be able to properly pressure the length of the ski even with all the ankle flex in the world because can never achieve the ‘stacked’ position of late load stance (as has been described in those great, recent posts.)

        The bottom line is that one doesn’t need to use the boot cuff as a lever (where have we read that before?:) to tip the ski on edge. So the only place I’ve had to tighten my boot cuff was in deep , heavy powder. That could be potentially dealt with if I ever figure out the secret to holding the foot down without impeding ankle glide path. Currently my heel easily comes up , either if I decide to raise it as I pressure the ‘loonie’ (ball of big toe) intentionally which I find makes a great turn happen, or in the heavy powder where I’m not pressuring the ‘loonie’ because the ski tips get buried thus I end up getting bucked around.

        Due to a number of factors including the looseness of my cuff buckles, this season I skied the best ever in the tightest, steepest, places in my life. Having evolved from race fit plug boots (2 sizes too small), stone hard foot beds, over filled foam liners; to a size larger, very soft, boot, a large portion of the liner has been removed, and no foot beds. I can ski better and longer using less energy.

        Allow the body to get in the correct position and the less one has in ski boots the better it is, that’s what I’m finding out!! If anybody can help me improve on the current situation, great! I’ve tried so many things why stop now?

  2. Lito, a legend:) I liked what I read of his writings. When I first began teaching moguls in Telluride in the ’90s I had many a prospective student say they wanted to ski with Lito!! All I could do was apologize that I wasn’t him!!

  3. Not having watched the ‘before’ and ‘after’ skiing I’ll take your word for the magnificent change in Petra’s skiing. My thoughts for what they’re worth;

    1. You’ve worked with a lot more ‘elite’ skiers than I have (!!) but the fact is that they can ski incredibly on equipment that is rather marginal if not a downright impediment to athletic movement.

    2A. 2A and 2B are interchangeable; if any skier learns the proper ‘loading’ of late stance=’pressing on the loonie’ (that you posted a while ago) it will help their skiing. An elite skier should adjust quicker than a beginner. I just moved over from an instructor thread where it was mentioned in writing that the pressure should be on the calcaneous (essentially heel of the foot) or just ahead of it which was something I’d always been instructed to do in official ski circles until David changed that for good.
    2B. If the equipment by accident or through scientific knowledge is set up correctly the skier will out-perform the competition. If the equipment doesn’t allow one to pressure at ‘late stance’ phase because the heel is too high and one has to drop body parts such as hips back just to stay upright, then the pressure in the correct place is impossible to accomplish/used to the degree needed. For example, I could start turns with the pressure @ late stance but had to move to the heel too early to pressure the tail/whole ski. One ski coach did talk about being on the balls of my feet which I attempted but still found myself leaning back at the same time!!!!

    3. So if one combines both; the equipment allows the movement pattern and the knowledge of how to apply the pressure will translate into a consistent outcome for the racer, and should happen overnight given their athleticism. It’ll be interesting to see if Petra becomes a ‘consistent’ contender or is a ‘one hit wonder.’

    T appreciate that The Skier’s Manifesto teaches how to set up the equipment, test it to make sure it functions for the individual skier, and then how to use it properly. If that works for me it should be just as easy for someone (i.e. racer) who lives on their skis to make the changes needed. Then the real fun begins because someone else (see Mikaela) may have been practicing the proper technique/position for longer.

    This was the best year of my life skiing ever (since last year!) and need to share a couple things when I get them written up. I like the posts on gait/stance because I think it’s very little understood by most and is totally ‘where it’s at.’

    1. One skier who influenced my thinking is Lito Tejada-Flores. His first book, Breakthrough on Skis led to a number of articles by Lito in ski magazines. Recently, when I reread his last book published in 2001, Breakthrough on the New Skis, here is what he said:

      “in a sense, everything in skiing begins with the feet…… Perhaps it isn’t surprising that the biggest obstacles to developing expert balance are out ski boots — not all boots, but many that are too stiff that they don’t allow any movement at all at the ankle”.

      Wow, right on the money. The only thing I would change is to say “the biggest obstacles to accessing the expert balance we all have…”

      Then Lito says, “The fluid graceful combination of postures and poise, foot-to-foot and fore-and-aft balance that adds up to an exert’s stance isn’t just important; it’s essential. Most of the time, as I watch skiers slide across the slope, I can predict exactly how they will turn, just by watching the way they stand and balance on their skis”.

      “The first thing I do with ski students who exhibit no ankle flexion is ask them if their top buckles of their boots are tight. They usually are (nodding my head in agreement). So we begin by loosening the top buckles to see if it permits the ankles to flex; often it will.

      “THIS IS WHERE GOOD BALANCE BEGINS. You need a fair amount of “give” (the ability to flex and stretch each joint) from the ankle on up–but especially at the ankle”.

      What Lito Tejada-Flores was preaching as far back as 1986 begs the question, Where were the experts of skiing? On the far side of the moon?

      So Michael when you say:
      “If the equipment doesn’t allow one to pressure at ‘late stance’ phase because the heel is too high and one has to drop body parts such as hips back just to stay upright, then the pressure in the correct place is impossible to accomplish/used to the degree needed.”
      we are on the same page.

  4. David, If you looking for quality video of World Cup alpine athletes, may I suggest you explore the opportunities currently available through the video analysis site Sprongo. They have recently made available to their subscribers those high quality video of World Cup runs, even with the capability to slomo the selected piece. Hope that might help!

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