SIMON RESPONDS TO MY PRELIMINARY OBSERVATIONS ON THE FREEMOTION SKI BOOT


NOTICE TO THE READER

I have never met Simon Zuchhuber or, to the best of my knowledge, any of the people associated with the FreeMotion ski boot project. Nor, do I have any involvement or financial interest in the FreeMotion ski boot project or do I expect to receive any form of compensation for any contributions I might make. My sole motivation in assisting Simon is to advance the design of ski boots based on anatomical principles and objective science and further the understanding of the mechanics. biomechanics and physics of alpine skiing, in particular, the informed analysis of skier technique.


Simons’ Response to my preliminary observations

To your summary of your observations I can make a few statements.

1.The primary innovation appears to be a U-shaped spring that opposes forward rotation of the Exo Cuff thus transferring force to the front of the shell lower.

This is completely true, even without German language knowledge you summed it up completely correct!


2.There does not appear to be any hard limit to the rearward movement of the shank of the skier.

This is perfectly true as well and was one of the first things I realized when testing the boot! I had a feeling of falling back when I was trying to lean back (both when standing and driving) In our concept we already added a “stopping element” to prevent too much shank movement backwards.


  1. There does not appear to be a forward lean (forward angle) adjustment for the exo cuff.

True again. There is no forward lean adjustment for the exo cuff. They only offer plastic elements that you can place beneath the liner inside the boot to change your forward lean angle. Would you think it necessary to have an adjustment for the exo cuff?

MY RESPONSE: Yes. An adjustment that allows the correct shank angle for isometric contraction of the soleus is essential. In a future post, I will discuss the Birdcage findings on this issue.


  1. There does not appear to be any means to adjust the resistance curve of the spring.

True, you cannot adjust anything when it comes to the spring. Do you think there’s a possibility to make it adjustable?

MY RESPONSE: Absolutely.


  1. If the Heel Retention Mechanism is securely tensioned, it is likely to obstruct the glide path of the distal tibia on the talus. This can cause the center of force on the shank at the buckle secured to the Exo Cuff to rapidly drop down the shank.

This heel retention mechanism is in the patent, but has not been applied to the existing boot series. You can see in the video that on the outside there’s only the buckle to tighten and the zipper to close, they did not apply this heel retention mechanism.

MY RESPONSE: An instep restraint system is essential. I will present several options that can be incorporated into the FreeMotion ski boot.


6.The resistance to forward movement of the shank provided by the spring mechanism appears to be introduced too early and rises too quickly.

What countermeasures would you take? Give the spring more distance to bend for example? 

MY RESPONSE: I will sketch and post some options.


 Thank you once again for your time, I’m looking forward to hearing from you!

Greetings, Simon


Simon has advised me that the timeline for his project has been extended. I will make every effort to accommodate Simon.

For those with an interest in the application of principles of functional anatomy to the design of the ski boot and this project, I suggest that you obtain a copy of The Shoe in Sport (orginally published in German in 1987 as Der Schu Im Sport) and read the section on The Ski Boot, in particular, the paper by Dr. Martin Pfeiffer of the University of Salzburg whose teachings contributed greatly to my knowledge and the success of the Birdcage research. I would like to recognize the dedication and committment of Dr. Pfeiffer to a ski boot based on anatomical principles.

6 comments

  1. Thomas hit the nail on the head, in my current configuration I fine tune my fore/aft position with a self regulated ‘stop’ on ankle flex rather than depending on the boot cuff. I have a tendency to ski a lot of moguls and crud which is where I use ankle flex to fine tune on the go. I now realize (within the last 3 years) that the reason I never was comfortable carving on groomers, mellow or steep was because the ramp/delta angle (steeper) that worked the best for me in the steep moguls doesn’t allow me to pressure the whole ski for the race style turns, even if the same pitch. I’ve also been looking at more world cup racing vids and feel there is a correlation (general not universal) that the gs racers in Head boots seem to do better due to a more upright cuff and I suspect bit of a lower ramp angle. I have yet to find anything within my boot that I could do to change that so I have the proper ramp angle for all terrain and all disciplines, maybe David can illuminate us on that issue!!

    1. “I’ve also been looking at more world cup racing vids and feel there is a correlation (general not universal) that the gs racers in Head boots seem to do better due to a more upright cuff and I suspect bit of a lower ramp angle.”
      > I suspect it is a case of more optimal ramp and cuff angles since the two are interdependent.

      “I have yet to find anything within my boot that I could do to change that so I have the proper ramp angle for all terrain and all disciplines, maybe David can illuminate us on that issue!!
      > it is on my agenda.

      Here are two quotes from ‘Flexural behavior of ski boots’ that appear to confirm that different events such as alpine racing and moguls/freestyle require different boot setups and characteristics.

      1. “During the XXII Olympic Winter games two different boot designs were used in racing disciplines and freestyle events [13]. Significantly different flexural behavior could be found for the two models. The 3-piece design used in freestyle events offered a much more linear increase in stiffness making it more efficient in absorbing landings and bumps on the slope. Whereas the overlap boot design (racing) provides a faster power transmission from the skier to the ski.”

      2. “Elite mogul skiers showed an improved performance when using a boot with much more forward flex (and probably more forward lean) than their normal boot. They were able to keep a more centered skiing position and knee bending moments were reduced.”

  2. Responding to some of the items by #.

    3. There has to be a ‘hard’ limit to forward ankle flex so one hits the end of the cuff’s range before the ankle gets to maximum flex so that the binding releases in a forward fall before the ankle hits its’ limit.* The ‘plastic elements’ under the liner change ramp angle if they extend at least to the ball of the foot which is a wonderful, necessary addition but is different than ‘forward lean.’ If the ‘plastic elements’ are only under the heel it is ‘toe drop’ and again completely different from the other two e mentioned adjustments.

    Have to complement both sides for being willing to discuss and explore improvements on ski boots!! Long overdue……..

    * I currently flex as far forward as possible and then stand up a bit and buckle the cuff there. I have a rigid back of the cuff which is easily adjusted using ‘spoilers.’ It is amazing when one gets things like net ramp proper one doesn’t have to buckle the boot into full ‘lock-down’ mode to stay standing in ones ski boots even on double black terrain!! I admit this is an interim cuff arrangement (only a two years so far!) until I figure out how to keep the cuff from impeding my balance on my quirky left leg when it is buckled tighter.

    1. Actually, the hard limit to forward ankle flexion be introduced well before maximum dorsiflexion is attained. The reason a skier has to configure the SR Stance barefoot and acquire a kinesthetic feel for it outside the ski boot is so they can go through a progressive step-by-step that ensures that they can assume the SR Stance in the ski boot. Without a structured process that used barefoot monopedal balance as the gold standard, even the most athletically talented skier has no idea of how the ski boot is affecting them.

      1. Michael brings up and interesting point about the boot cuff, “There has to be a ‘hard’ limit to forward ankle flex so one hits the end of the cuff’s range before the ankle gets to maximum flex so that the binding releases in a forward fall before the ankle hits its’ limit”
        And Dave notes, “the hard limit to forward ankle flexion be introduced well before maximum dorsiflexion is attained. The reason a skier has to configure the SR Stance barefoot and acquire a kinesthetic feel for it outside the ski boot is so they can go through a progressive step-by-step that ensures that they can assume the SR Stance in the ski boot.”

        I want to check my understanding about the limit. There are two things going on here. 1) As Michael says there has to be a hard limit in order for the binding to release properly. 2) There has to be a limit to keep the foot from going into the propulsive phase of the stride. (see FOOTWEAR DAMAGED FEET https://skimoves.me/2016/12/04/footwear-damaged-feet/)

        The part Dave talks about how to train the skier’s brain out side of boots because the neurologic system has to learn how to arrest, stop, normal gait with the onset of a tensioned arch. In normal locomotion there is rapid progression from pronation to supination the propulsion phase. There is nothing in walking/running workouts or usual dry land training that will queue the brain to stop and hold the tri-planter tension to give proper GRF to the new stance ski.

        I was playing with this the other day in two pairs of old rental boots. What I noticed was when I was intentioned to move COM forward to create the strong arch and stopped at that limit the turn happened (all be it with other necessary body mechanics). What I’m guessing as the dry-land work and deliberately paying attention to the mechanics of my body feet, I have trained my brain to arrest the forward shank movement to stop the progression into the propulsive phase of a stride. That training was set work like Dave’s SR, practice tipping, and running dry-land slalom etc. In doing I have trained my neuromuscular systems activate and hold a strong arch without continuing on into a propulsive phase of the stride.

        If one looks at old movies of Hannes Schneider in ski shoes he seems to arrest at the point we are calling here the hard stop because to move the center of mass to farther forward would result in a summersault. Modern ski boots build in a hard stop for various reasons but the modern skier like Schneider must still train the brain to activate the neuromuscular systems properly for skiing. I’m guessing that is what Dave meant by, “Without a structured process that used barefoot monopedal balance as the gold standard, even the most athletically talented skier has no idea of how the ski boot is affecting them.” thomas

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