Existing footwear does not provide for the dynamic nature of the architecture of the foot by providing a fit system with dynamic and predictable qualities to substantially match those of the foot and lower leg.

MacPhail, US Patent 5,265,350 – November 30, 1993

Of all the figures who have influenced the development of the plastic shell ski boot over the years, the Australian, Sven Coomer, stands tall as one of the most significant and innovative. More recently, Coomer was involved with the development of Atomic’s race boot, the Redster, used by Marcel Hirscher and Mikaela Shiffrin. Coomer claims that the Redster allows the skier’s forefoot to flex and move naturally within the confines of the shell.

A 2014 article by Jackson Hogen quoted Coomer as saying:

This liberation of the previously stunted, frozen and crushed forefoot is what allows for the subtle edging and foot steering that initiates the slalom turns of World Cup champions Marcel Hirscher and Mikaela Shiffrin. (1.)

Four years, later Hirscher and Shiffrin are dominating the technical disciplines of the World Cup circuit.

The ability to establish balance on the outside foot and ski in milliseconds is dependent on the ability of the forefoot to fully spread and acquire fascial tensioning that extends to the ankle and knee. This is called time-to-stabilization. Although Coomer doesn’t mention them, a myriad of other factors are also critical; including the alignment of the big toe on the long axis of the foot and the optimal ramp angle.

Coomer suspects that if racers would only fit their boots more accurately, coupled with a dynamic molding inner boot medium between the foot and shell, and without down-sizing into short, narrow, thick-sidewall shells, their results just might improve. (1.)

In order to realize their maximum potential it is critical that racers and even recreational skiers have a ski boot fit with dynamic and predictable qualities that substantially match those of the foot and lower leg. Yet Coomer readily acknowledges:

Many racers believe they need downsized, super-stiff, ultra-narrow boots. The most accomplished alpine ski boot designer of the plastic era, Sven Coomer, believes that’s changing.(1.)

But then, he seems to retract his optimism when he says that after forty-five years as the Cassandra of the ski boot world, he knows all too well that just because you can prove you’re right, it doesn’t mean your advice will be heeded.

My observation is that since Hogen’s 2014 article, the situation with downsized, hyper-restrictive ski boots that severely compromise the dynamic nature of the architecture of the foot, has gotten worse. I have seen instances where after having ski boots properly fit, it took several full seasons for the competence of the balance to be fully restored after a skier or racer’s feet and legs were constrained for years in ski boots that were too small and too tightly fit.

Marcel Hirscher and Mikaela Shiffrin have heeded Coomer’s advice. Others choose to ignore him at their own peril. In so doing, they handicap their efforts and limit their race results.

In my next post I will start a series of posts on how to build a ski boot from the snow up; one that provides a fit with dynamic and predictable qualities that substantially match those of the foot and lower leg.

  1. The Master Boot Laster by Jackson Hogen: The International Skiing History Association – Article Date: Tuesday, June 3, 2014


  1. Hi David,

    It is good to see that Atomic has been willing to listen to Sven Coomer and incorporate toe splay into the design of the Hawx boots. I almost purchased their Hawx Ultra XTD model this year but was concerned that it would be too difficult to get into. It was one of the best out of the box fits I have experienced as far as the shell is concerned. The liner is ridiculous, in my opinion, being poorly sewn together and with a rigid tongue. A real mismatch for such a good quality shell. I may revisit that boot since I have yet to find any boot with both a good liner and a good shell.
    An innovative boot company would offer a range of liner options for its products as they do for their race stock boots.

    Recently, when visiting a local bootfitter, I learned that the cost of injection molds for boots had dropped drastically since I last heard which was probably ten years ago. He suggested that they now are in the $10,000 to $15,000 range per size and not $150,000+ . If this is true why are there not more new designs or a corresponding price drop for existing designs or liner options, boot board ramp angle options,etc.? I can now see why the Alpine Touring market has exploded with a plethora of new (somewhat) innovative designs, except for the liners which are universally thermofit type, not easily modified but easy to fit, if you call perfect envelopment fitting.

    While shopping on line for liners, I called the Zip-Fit number from their website and was very surprised to be talking to Sven Coomer. He was gracious and helpful even though he was at the factory in Italy at the time. He is quite approachable if you are inclined to contact him, David, I am sure you would have much to discuss.

    Best regards,

    1. Hi Herb,

      Thank you for your comments. I apologize for the delay in responding. You raise a lot of good issues.

      When MACPOD was trying to make a ski boot based on the principles of the Birdcage (which was an open architecture minimal platform research vehicle), my recollection is that the cost of molds for one shell size was about $350,000. This does not include the design and CAD components. The limitations and the costs associated with injection molding remove any incentives to address individual requirements. One option to get around this is a modular shared component format where boot shells could be assembled at point of sale from shared components. Another option which is fast becoming viable is 3D printing. Some forms of 3D printed footwear are already available. Liners could be made now.

      “An innovative boot company would offer a range of liner options for its products as they do for their race stock boots.”

      Race stock boots typically use 3rd party liners. Most companies today don’t manufacture their products. They use OEM facilities to make parts or even the whole product. Their domain is marketing, sales and distribution. Until they come under pressure to change, I don’t see boot makers taking steps to make products that support human performance.

  2. I like where this is going, small boots do work better no doubt. However the foot needs to function in the environment. Where is the “win” point ?

    1. The win point is the equivalent of barefoot which is minimal constraint.

      Minimal constraint applied to discrete aspects of the foot and leg equals maximum neurobiomechanical function. This was the objective of the 1991 Birdcage research vehicle.

  3. Sven Coomer sells a liner called zipfit which allows a cork like gue to be added or removed in different parts of the liner. I haven’t handled one but I think the neoprene forefoot area may be made out of a neoprene that holds its new shape once stretched. Similar to a world cup liner but looks a little more customizable.

    1. Some boot companies appear to be using ZipFit liners. But I have not been able to find them in any ski shops in Whistler. So I don’t know where the construction of these liners are at today.

      The only liners I can still have good success with is the original Lange tricot (soft fabric) liners. When I built Lange race boots from raw parts I used to reconfigure the toe box and sew in a Spenco panel so that the liner matched the shape of the boot. But THE big problem in ski boots is the DIN standard toe shape which makes it very difficult to modify sufficiently to allow the big toe to align straight ahead which is critical.

      1. From the zipfit website: info@skiconnexions.ca – I believe they are near Whistler. The liners are expensive, at least $400. I agree about the DIN standard, I had to punch the life out of the plastic to get enough space for the big toe. Could the boot manufacturers shape the boot properly and keep the DIN standard on the sole? The reason I ask is that Lange has a 100mm wide version of their RS race boots that appears to be the same mold except they have widened the boot in the forefoot, if only they would straighten the toe.

      2. The real question, one the industry should answer, is why the purchaser of their ski boots has to buy after market products and spend hours and/or hundreds of dollars to modify it so it allows the user to use the natural processes of balance and movement they were born with. I can’t think of a single product where the manufacturer sits back while third parties claim you need their liner because the one that came with the product is no good. Would you purchase a new car and on toly have to put a new transmission, engine or drive train in to make it function properly? At the very least, makers of ski boots should be disclosing up front that their product may have limitations that require modification and/or third party products.

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