GETTING SHAFTED BY THE (SKI BOOT) SHAFT


In order to appreciate how and why I fabricate a tongue system that works with my minimal shell, a requisite knowledge of the key aspects of the underlying issues and fundamentals of the science of human balance are essential.

By 1979, through a series of experiments, I had arrived at a tentative conclusion that the concept of attempting to immobilize the joints of the foot and support it within the confines of a rigid shell ski boot was unsound and not conducive to physiologic function. One of the issues that I had identified was the incompatibility of the fixed plane of the front of the shaft (aka the cuff) of the ski boot with the dynamic plane of the front of the shin or shank of the skier’s leg. There was also the issue of inadequate or even the absence of loading of the instep of the foot within the forefoot portion of the ski boot shell. It is one thing to arrive at a conclusion that a concept is flawed. But unless one can come up with a better solution, a tentative conclusion is moot.

In the spring of 1980 I came up with a solution that addressed both issues. It was an innovative, in-boot technology that was granted US Patent No 4,534,122.  The effect of this technology on Podborski’s skiing far exceeded any expectations I held. Although it appears I was first out of the gate in recognizing problems associated with the ski boot shaft, it was soon to turn out that I was not alone in identifying this issue. Here is what I said in my patent filed on December 1, 1983, granted on August 13, 1985 and assigned to Macpod Enterprises Ltd. (Squamish) MACPOD was David MACPhail and Steve PODborski.

Designers of ski boots intended for downhill (alpine) skiing have recognized the need to provide support for the leg, ankle and foot, but have tended to produce boots that are uncomfortable, that do not give the skier proper control, and that restrict those movements of the ankle joint that are necessary during skiing.

Fore and aft movements of the leg at the ankle joint (i.e. plantarflexion and dorsiflexion of the foot) are often restricted or prevented in prior art ski boot by the boot tongue or other structure designed to restrain movements of the foot. Typically, a boot tongue extends from near the toes to the lower shin and, in order to provide good padding and support, is relatively inflexible. Such a tongue presents considerable resistance to dorsiflexion of the foot.”

It is important to note that at the time that the patent was filed I was still in the paradigm of immobilizing the foot and the use of supportive footbeds.

Four years after the filing of the patent my position on the shaft of boot interfering with the physiologic function of the ankle joint was confirmed in four articles contained in the section, The Ski Boot, in the book, The Shoe in Sport (1989) – Published in Germany in 1987 as Der Schuh im Sport. ISNB 0-8151-7814-X (27 years ago). It appeared that as a Canadian I had laid down a gauntlet on issues with the shaft of the ski boot and, in so doing, had led the world in drawing attention to this issue. The response from boot makers? Deafening silence.

In the first article, Biomechanical Considerations of the Ski Boot (Alpine), Dr. E. Stussi,  Member of GOTS – Chief of Biomechanical Laboratory ETH, Zurich, Switzerland, explains that the ski boot must represent an interface between the human body and the ski and that more than simply enabling the skier to steer the ski as well as possible, the boot must also allow direct (neural) feedback from the ski and from the ground (snow) to the skier. In other words, in order to function in a rapidly changing dynamic environment, the balance system must have access to accurate neural feedback from the snow in order to generate what are called postural responses (ergo – balancing processes). Dr. Stussi states, These conditions can be met if the height, stiffness, angle  and functions (rotational axes, ankle joint (AJ)/shaft) of the shaft are adapted, as well as possible  to the individual skier (my emphasis added). Dr. Stussi warns of the problems associated with the loading of the ankle such as occurs when a boot is tightly fit in what is often referred to as ‘The Holy Grail of skiing; the perfect fit of the boot with the foot and leg,, Improvements in the load acting on the ankle make it biomechanically very likely that the problems arising in the rather delicate knee joint will increase.” Dr. Stussi seems to have called this right. Knee injuries did increase. But the loading of the ankle not only continues unabated today, the state-of-the-art in ankle loading continues to evolve.

In the second article, Kinematics of the Foot in the Ski Boot, Professor  Dr. M. Pfeiffer of the Institute for the Athletic Sciences at University of Salzburg, Salzburg, Austria, presents the results of a number studies using  x-ray video tape imaging on the effects of the shaft of the boot on the shape of the foot and the displacement of bones towards and away from each other during flexion of the ankle. These changes disrupt the normal physiologic function of the ankle necessary for balance. Based on these studies Dr. Pfeiffer concludes, “The shaft of the boot should provide the leg with good support, but not with great resistance for about two thirds of the possible arc, i.e., (12 degrees) 20 to 22 degrees. Up to that point, the normal, physiologic function of the ankle should not be impeded.” The response of the ski industry? Power straps to further impede the normal physiologic function of the ankle, the very thing Dr. Pfeiffer warned against.

Dr. Pfeiffer points out that it is misconception that the role that the role of the shaft is to absorb energy and that this misconception must be replaced with the realization that, shaft pressure generates impulses affecting the motion patterns of the upper body, which in turn profoundly affect acceleration and balance. He advises that the lateral stability of the leg should result from active muscle participation and tonic muscular tension and that if muscle function is inhibited in the ankle area (which is the seat of balance – my comment added), greater loads will be placed on the knee (my emphasis added).

Dr. Pfeiffer concludes his article by stating that “the ski boot and it’s shaft must be adapted to the technical skill of the skier, and the technical skills of the skier must be adapted to the preexisting biomechanical functions of the leg and the foot.” Dr. Pfeiffer ends by expressing the hope that his studies will lead to the development of a ski boot design based on anatomical principles. It seems that Dr. Pfeiffer’s hope was in vain.

In the third article, Ski-Specific Injuries and Overload Problems – Orthopedic Design of the Ski Boot –  Dr. med. H.W. Bar, Orthopedics-Sportsmedicine, member of GOTS, Murnau, West Germany mentions that Dr. Pfeiffer’s studies have found that the foot maintains some spontaneous mobility in the ski boot and that because of this, the total immobilization by foam injection or compression by tight buckles are unphysiologic“. Translation? Tightly fitting and compressing the foot especially with foam injected or form fit liners screws up the function of the foot. This is not a good thing. Along this line Dr. Bar goes on to state, Only in the case of major congenital or post traumatic deformities should foam injection with elastic plastic materials be used to provide a satisfactory fixation of the foot in the boot.” Based on the amount of foam injection being done these days it seems that there must be a lot skiers with major congenital or post traumatic deformities.

In the final article,  Sports Medical Criteria of the Alpine Ski Boot – W Hauser & P. Schaff, Technical Surveillance Association, Munich, West Germany, Schaff and Hauser discuss the problems caused by insufficient mobility in the knees and ankles of most skiers and especially much too small a range of motion in the ankles. The authors speculate that “in the future, ski boots will be designed rationally and according to the increasing requirements of the ski performance target groups.”

I’ll conclude this post with some excerpts from my US Patent 5,265,350 filed on February 3, 1992.

Skis, ice skate blades, roller skate wheels and the like represent a medium designed to produce specific performance characteristics when interacting with an appropriate surface. The performance of such mediums is largely dependent on the ability of the user to accurately and consistently apply forces to them as required to produce the desired effect.

In addition, in situations where the user must interact with external forces, for example gravity, the footwear must restrain movements of the user’s foot and leg in a manner which maintains the biomechanical references with the medium with which it is interacting. It is proposed that in such circumstances, the footwear must serve as both an adaptive and a linking device in connecting the biomechanics of the user to a specific medium, such as a ski, for example. This connective function is in addition to any type of fixation employed, in this instance, to secure the footwear to the ski.

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.

More that 2o years later, existing footwear (ski boots) still do 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. Since it is unlikely that ski boots will be available any time in the near future that meet the preceding requirements, I had to find a way to work within the limits of presently available ski boots. In my next post I will explain how I avoid getting shafted by the shaft of my ski boot.