ROLL THE ANKLE? SHIFFRIN GETS IT RIGHT


It is rare for a skier or even a racer at the World Cup level to have more than a very basic knowledge of anatomy. When I ask an elite skier or racer to describe what they do to initiate a turn what they tell me invariably has nothing to do with what they are really doing. Often, what a skier describes they are doing is physically impossible. “Rolling the ankle” to initiate a turn is a classic example. Rolling the ankle or “pronating the foot require a conscious effort that uses concentric muscle contraction. This bears no resemblance to what racers like Mikaela Shiffrin or Marcel Hirscher are doing.

Watch the video of Mikaela Shiffrin Flat Lining at the Westin Riverfront Resort & Spa in Beaver Creek (https://www.youtube.com/watch?v=StrKDP92qxQ). Listen to her describe what she really does in her ski boots at the initiation of a turn.

“Once you figure out how to loosen up your ankle and kind of just go with the rope a little bit……”

When she says “kind of just go with the rope ….”, Shiffrin is really saying that she is relaxing her ankle to allow the central load-bearing axis to transfer her weight W to the flat line so her CNS can modulate her balance at a subconscious level.

Notice how Shiffrin positions her heel and ball of her foot on the flat line on order to balance. This enables the load transfer process to induce pronation and align the principle load points under the heel and ball of the foot on the monopedal balance axis. A key movement necessary to allow the ankle to loosen (relax) so the foot can pronate is a subtle coordinated flexion of the ankle, knee and hip joints as the stance foot assumes the load W transferred by the central load-bearing axis. As the ankle loosens, the Centre of Pressure should be felt to move to the ball of the foot. This is the hot button that tells Shiffrin that the load transfer process has tensioned the biokinetic chain between the balls of her feet and her pelvis, that she is stable, balanced and go to load the edges of her outside ski.

 Shiffrin flat lining

BioMedical Perspective:
This is an excellent example of lateral learning using tactile and deep joint proprioception to improve balance. This input leads to synergistic reflex proximal muscle responses. Vestibular inner ear sensory uptake and cerebellar (brain) proprioception sites elicit a reflex controlled overall postural response creating a balanced stance. Some so-called “natural athletes” have an inherent higher level of balance. However, it should be emphasized that most athletes can improve body control through balance training.

– Dr. Kim Hewson is a Telluride Ski School Alpine Instructor and Staff Trainer in the Biomechanics of Alpine Skiing

6 comments

  1. This video was shot 9 years ago. Bad skiing too.?
    Come on Dave, you know exactly what I am aiming at. Someone with your analytical skills cant miss it. The question is. Can you accept it and integrate it in your system.?

  2. I am glad Mikaela got off easier than me.

    That is her free skiing.

    What do you think she working on?

    j

    1. Mikaela is commentating. Bridget Currier is the first demonstrator. The objective of the exercise is to learn to move COM over the ball of the foot at ski flat. Hence the title, Get Over It. ‘It’ in this case is the ball of the outside foot of the new turn. Contrary to the common perception in skiing the problem is not the outside foot in a turn pronating. It is making the skimove at ski flat to create a gravity like force to induce pronation with load transfer. The only time this can happen is when the foot has contiguous GRF under its load transfer points. A skier probably has less than 1/10 of a second at ski flat to allow load transfer to induce pronation. If the load doesn’t end up on the inside turn aspect of the inside edge it will default to the outside turn aspect. This will cause the ski to invert (base rotate into the slope or out of the turn).

      When the foot pronates it everts (rotates in the opposite direction to inversion). Interventions intended to stop or reduce pronation can end up ensuring there is an unbalanced inversion moment of force present 100% of the time on the outside foot of during a turn. The problem is that for every degree that the foot rotates in inversion the inversion moment of force will result in a degree of external rotation of the leg. An unbalanced inversion moment of force on the outside foot in a turn is a predisposition to injury.

      1. Thanks for the explanation, David. My question was in relation to this video which I forgot to include in my post

        ttps://www.youtube.com/watch?v=5nkwr9Dglf0

  3. Dave
    I have been a manufacturer of sports equipment and I’m a “die hard” skier. My partner also” lives to ski” and has been the top mechanical engineer at United Technologies for 25 plus years. We understand your boot concept and we think we have refined and added to it. We know how to make the boot. I would like to talk to you as soon as possible. Email me and I will give you my phone number.. We are going to Asolo and Montebelluna on December 14>
    Walter Lautz

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