biomechanics

THE MECHANICS OF BALANCE ON THE OUTSIDE SKI: PRESS AND POINT THE BIG TOE

A widespread perception appears to exist within the skiing community is that the ability to hold a ski on edge by using the leg to exert force against the side of the stiff shaft of a ski boot and staying upright and not falling, equates with good balance. This ingrained perception presents a challenge in terms of communicating how the world’s best skiers create a platform under the body of the outside ski that they can stand and balance on using the same processes that we all use to stand and balance on a hard, flat level surface.

Last ski season, I developed simple cue to help skiers find the right mechanics and biomechanics as the new outside ski goes flat between edge change and then rolls into the turn on its new inside edge.  At ski flat, if a skier has the right stance, they should feel strong pressure under the ball and the big toe. As the skier extends and inclines into the new turn, the outside leg should be rotated into the turn to point the big toe in the direction of the turn. Hence the cue, press and point the big toe.  This pressure under the ball of the foot and big toe should be maintained through the turn phase until it is released by the transfer or weight to the inside (uphill) ski at the start of the transition to the inside. The strong pressure under the ball of the foot and the force that presses the big toe down flat is passively created by a strong stance, not conscious effort.

The Reverse Windlass

The pressure under the big toe is created by what is called the Reverse Windlass Mechanism. This naturally happens in the late phase of stance when walking barefoot. But wearing shoes with raised heels and cushioned insoles makes it impossible for the Reverse Windlass to function. When the Reverse Windlass is lost, it must be re-acquired by being barefoot as much as possible and walking, running and training in zero drop, thin soled minimal shoes. In some cases, people have to learn to walk naturally by rehearsing the action.

There is an excellent YouTube video by Teodoro Vazquez on Blog del Runner  called Windlass Mechanism and Running Biomechanics – https://youtu.be/y_8SrufgmDk. Vazquez describes the 3 phases of the windlass mechanism, Active (Activo), Reverse (Inverso)  and Passive (Pasivo). Although the video is directed at running, the primary concepts have direct application to skiing and ski technique. The reverse windlass is activated by the weight as shown in the graphic below from Vazquez’s YouTube video.
 This tensions the arch of the foot and presses the big toe down.
As the shank angle increases, the soleus muscle goes into isometric contraction and arrests further shank movement. The results in a heel to forefoot rocker action that dramatically increases the down force under the ball of the foot and the big toe. What I call the Spinal Reflex or SR Stance maximizes the down forces.

It is important that when the big toe (aka Hallux) is pressed down flat, the ball of the foot and big toe feel like one. When the big toe is pressed down properly, you should feel your glutes tighten. The leg you are standing on should be straight and the knee pointed straight ahead.

An important muscle in the Reverse Windlass is the Flexor Hallucis Longis or FHL. When the soleus goes into isometric contraction, the FHL is tensioned. This stabilizes the foot and knee by rotating them away from the center line of the body.

Things that prevent the Reverse Windlass

1. A condition called Hallux (big toe) Valgus
2. Narrow shoes and especially shoes with a pointed toe box.
3. Ski boots, especially ski boot liners.
4. Shoes with elevated heels, cushioning and toe spring (toes raised up). Note: A small amount of ramp angle is necessary for the SR Stance.
5. Footbeds and Insoles.
In my next post, I will discuss fixes to enable and/or restore the Reverse Windlass.

STANCE HACK: TUNE UP YOUR FEET

Biohacking Your Body with Barefoot Science

“…… hacking” or finding a way to more efficiently manipulate human biology.  This can include areas of sleep, nutrition, mental health, strength, recovery. (1)
– Dr. Emily Splichal – Evidence Based Fitness Academy

 

Last ski season, I developed some simple cues or hacks to help skiers and racers quickly find the body position and joint angles required to create the pressure under the outside foot with which to impulse load the outside ski and establish a platform on which to stand and balance on through the turn phase –  THE MECHANICS OF BALANCE ON THE OUTSIDE SKI: IMPULSE LOADING

The primary source of information that helped me develop these cues are the exercises developed by Dr. Emily Splichal. Her exercises also helped me to appreciate the extent to which traditional supportive footwear with raised heels and cushioned soles has damaged my feet and deadened the small nerves responsible for maintaining upright balance and the ability to initiate precise movement. Since implementing Dr. Splichal’s evidence based science, I am not only skiing at a level beyond what I considered possible, I am starting to walk naturally for the first time in my life.

The information contained in Dr. Splichal’s videos will challenge everything you know or thought you knew about what we have been conditioned to believe about our feet and the footwear we encase them in. Contrary to what we have been told, cushioning under the feet does not reduce impact forces on the lower limbs and protect them. Instead, it actually increases impact forces while slowing what Dr. Splichal refers to as the time to stabilization; the time required to stabilize, stiffen and maximally protect the joints of lower limb from impact damage – THE MECHANICS OF BALANCE ON THE OUTSIDE SKI: TIMING OF EDGE CHANGE

The Best Surfaces to Train On

A good place to start is to learn which surfaces are best to train on. Again, while it may seem logical and intuitive that surfaces with cushioning are best because they will protect the body from shocks, studies show the exact opposite to be true. Over time, support and cushioning in shoes can diminish the sensitivity of the rich small nerve matrix in the feet that acts as a neural mapping system for balance and movement. In her YouTube video, Best Surfaces to Train On (https://youtu.be/gvJjIi3h1Bs), Dr. Splichal discusses the effects of different surfaces on plantar small nerve proprioception and explains how barefoot training is a form of small nerve proprioceptive training designed to activate the plantar foot. Balance training is best done barefoot.

The Power of Plantar Proprioceptors

Watching Dr, Splichal’s webinar presentation Understanding Surface Science: The Power of Plantar Proprioceptors – https://youtu.be/t5AU-noqMFg will further your appreciation of the power of plantar proprioception.

First Stance Hack – Plantar Foot Release for Optimal Foot Function

Dr. Splichal’s 6 Minute Plantar Foot Release for Optimal Foot Function – https://youtu.be/zyrKgFwsppI will dramatically improve foot function.
Dr Splichal explains how to use RAD rollers (golf ball or other firm balls will also work) to optimize foot function by releasing tissues in the plantar foot by applying pressure to the 6 areas shown in the graphic below.
Dr. Splichal advises to focus on using a pin and hold technique  (not rolling the foot on the balls) to apply pressure to these 6 spots on each foot holding for about 20 seconds on each spot with each of the three different sized rounds for a total time of about 6 minutes. The foot release should be done 2 times and day and prior to each training session.
In my next post I will talk about the second Stance Hack: Pressing Down on the Big Toe to Impulse Load the Ski and Power the Turn

1.  https://barefootstrongblog.com/2017/04/28/biohacking-your-body-with-barefoot-training/

OFF SEASON POST ACTIVITY

With ski season coming to an end in many parts of the world, I am going to start posting on what I have learned over the past ski season and changes that can be made to components such as the boot board (aka Zeppa) to improve performance and why how these changes work. I am also going to post on the implications on skiing of recent studies as well as the application and impact of technologies such as CARV and Notch. If these products become available soon enough, I plan to some testing before next ski season so I can write posts on how these technologies can be used to improve ski technique and technical analysis as well as identify problems caused by ski boots.

For the time being, I have decided to hold off on discussing the rocker impulse loading mechanism of the mechanics of balance on the outside ski because limitations imposed by the ski boot prevent the majority of skiers from generating the high transient impulse load within the 2 millisecond window that occurs during roll over through ski flat during edge change (see THE MECHANICS OF BALANCE ON THE OUTSIDE SKI: TIMING OF EDGE CHANGE) that is required to engage the mechanism that enables a skier to balance on the outside ski.

For academics, researchers and others with an interest in the science aspect of the design of ski equipment and the formulation of ski technique, I will be posting studies that have application to both.

WHY THE OPTIMAL STANCE FOR SKIING STARTS IN THE FEET

In this post, I am going to discuss why the optimal stance for skiing is dependent on the loading sequence of the new outside foot of turn, how this must start in the transition phase and why it is critical to the rocker impulse loading mechanism that engages the shovel and inside edge of the outside ski at edge change. This issue was introduced in THE MECHANICS OF BALANCE ON THE OUTSIDE SKI: TIMING OF EDGE CHANGE. The rocker impulse loading mechanism and the ability to balance on and control the outside ski is dependent on the ability to rapidly tension the biokinetic chain that stiffens the forefoot and torsionally stiffens the ankle and knee joints. This process enables top down, whole leg rotational force, into the turn, to be effectively applied to the foot and ski from the pelvis.

A Middle Ground on Stance

Although there is much discussion in skiing on the subject of stance, it is rare for discussions to include, let alone focus on, the foot.

The red rectangle in the graphic below shows the mid stance phase in the 8 component Gait Cycle.

A common position amongst the various authorities in skiing on stance, is that it is represented by the mid stance phase of the Gait Cycle. The 8 component Gait Cycle is the universal standard for discussion and analysis of gait in human movement. During the turn phase, the sole the outside foot or stance foot is in substantially constant contact with the zeppa or boot board. Since the ski stance does not involve initial heel contact or terminal phases, it was reasonable to conclude that skiing must be a mid stance activity.

Assuming that stance skiing is a mid stance activity also meant that the joints of the foot are mobile and the foot is still pronating and dissipating the shock of impact. The fact that the foot is not yet fully tensioned in mid stance, while still pronating, appears to have led to the conclusion that the foot is unstable and in need of support. Towards this end, form fitting footbeds, liners and, more recently, form-fitted shells were introduced and soon became standard. I described what has become known as the Holy Grail of skiing; a perfect fit of the boot with the foot and leg; one that completely immobilizes the joints of the foot in my post, A CINDERELLA STORY: THE ‘MYTH’ OF THE PERFECT FIT.  This objective, precipitated the premise that forces are best applied to the ski using the shaft of the ski boot as a handle with the leg acting as a lever. In this paradigm, the foot was relegated to a useless appendage.

The Missing Ninth Component – Late Stance

The problem with the assumption that mid stance is the defacto ski stance is that it has only recently been suggested that a critical ninth component, Late Stance, is missing from 8 components of the Gait Cycle.

Although it has been known for decades that the foot undergoes a sequential loading/tensioning process that transforms it from what has been described at initial contact as a loose sack of bones, into a rigid lever in terminal stance for propulsion, the effect of fascial tensioning on late stance has remained largely unexplored until recently when the exclusive focus on the rearfoot began to shift to the forefoot. I discuss this in BOOT-FITTING 101: THE ESSENTIALS – SHELL FIT.

As recently as 2004, Achilles/PA loading of the forefoot was poorly understood. Under Background, a 2004 study (2.) on the role of the plantar aponeurosis in transferring Achilles tendon loads to the forefoot states:

The plantar aponeurosis is known to be a major contributor to arch support, but its role in transferring Achilles tendon loads to the forefoot remains poorly understood.

The study found:

  • Plantar aponeurosis forces gradually increased during stance and peaked in late stance.
  • There was a good correlation between plantar aponeurosis tension and Achilles tendon force.
  • The plantar aponeurosis transmits large forces between the hindfoot and forefoot during the stance phase of gait.
  • The varying pattern of plantar aponeurosis force and its relationship to Achilles tendon force demonstrates the importance of analyzing the function of the plantar aponeurosis throughout the stance phase of the gait cycle rather than in a static standing position.

Changes in Muscle-tendon unit (MTU) and peak EMG increased significantly with increasing gait velocity for all muscles. This is the first in vivo evidence that the plantar intrinsic foot muscles function in parallel to the plantar aponeurosis, actively regulating the stiffness of the foot in response to the magnitude of forces encountered during locomotion. These muscles may therefore contribute to power absorption and generation at the foot, limit strain on the plantar aponeurosis and facilitate efficient foot to ground force transmission.

Transmits large forces and foot to ground force transmission means large downward forces directed at the ground or to a ski and from there to the snow.

Although I did not understand the esoteric details of fascial tensioning back in 1993, I was sufficiently aware of the relationship between peak tension in the plantar aponeurosis (PA), to be able to construct a simple model that illustrates how peak PA tension results in peak Achilles tension and how this causes the soleus muscle to go into isometric contraction, arresting further forward movement of the shank. I discuss this in detail in my series of posts on the SR Stance.

The photos below shows the simple model I made in 1993. Simple models of this nature are finding increasing use today to model what are called Anatomy Trains.

In late stance, the foot gets shorter in length and the arch gets higher and tighter as intrinsic tension transforms the foot from a mobile adapter in early stance into a rigid lever in late stance so it can apply the high force to the ground necessary for propulsion in the terminal stance phase that occurs at heel separation. The graphic below shows how the arch height h to foot length L ratio increases as the foot is getting shorter and the arch gets higher in late stance.

What has only recently being recognized is that the fascial tension that occurs in stance maximizes balance responses, neuromuscular efficiency and protection of the lower limbs through a process of  foot to core sequencing; one that stiffens the forefoot and torsionally stiffens the joints of the ankle and knee.

Loading/Fascial Tensioning Speed

A 2010 study (4.) found:

Early-stance tension in the PA increased with speed, whereas maximum tension during late stance did not seem to be significantly affected by walking speed. Although, on the one hand, these results give evidence for the existence of a pre-heel-strike, speed-dependent, arch-stiffening mechanism, on the other hand they suggest that augmentation of arch height in late stance is enhanced by higher forces exerted by the intrinsic muscles on the plantar aspect of the foot when walking at faster speeds.

…… or, by more rapid, forceful impulse loading at ski flat – see SUPER PETRA VLHOVA’S EXPLOSIVE IMPULSE LOADING IN ASPEN SLALOM

A 2013 study (3.) found:

Although often showing minimal activity in simple stance, the intrinsic foot muscles are more strongly recruited when additional loads are added to the participant.

A 2015 study (5.) found:

Changes in Muscle-tendon unit (MTU) and peak EMG increased significantly with increasing gait velocity for all muscles. This is the first in vivo evidence that the plantar intrinsic foot muscles function in parallel to the plantar aponeurosis, actively regulating the stiffness of the foot in response to the magnitude of forces encountered during locomotion.

These muscles may therefore contribute to power absorption and generation at the foot, limit strain on the plantar aponeurosis and facilitate efficient (vertical) foot to ground force transmission.

…….. or foot to ski to snow force transmission.

The Optimal Ski Stance is Unique

While the optimal stance for skiing has the greatest similarity to the late phase of stance, I am not aware of any stance that has requirements similar to the ski the stance where a specific loading sequence precedes rocker impulse loading as the outside ski changes edges in the top of a turn.

As with the gait cycle, the movement pattern associated with a turn cycle also involves loading and swing phases.

Time To Cascade

There are two intertwined rocker mechanisms that impulse load the forefoot at ski flat between edge change. These rocker mechanisms rely on what the 3 components of what I refer to as the Time To Cascade which is only possible when the plantar aponeurosis is rapidly fascially tensioned.

  1. Time to Fascial Tension which affects,
  2. Time to Stabilization which affects
  3. Time to Protection which protects the lower limbs 

In my next post, we will Meet the Rockers and continue with the discussion of the mechanics of balance on the outside ski.


  1. http://musculoskeletalkey.com/gait-and-gait-aids/
  2. Dynamic loading of the plantar aponeurosis in walking –Erdemir A1, Hamel AJFauth ARPiazza SJSharkey NA. J Bone Joint Surg Am. 2004 Mar;86-A(3):546-52.
  3. Dynamics of longitudinal arch support in relation to walking speed: contribution of the plantar aponeurosis – Paolo Caravaggi, Todd Pataky, Michael Gu¨ nther, Russell Savage and Robin Crompton – Human Anatomy and Cell Biology, School of Biomedical Sciences, University of Liverpool, Liverpool, UK – J. Anat. (2010) 217, pp254–261
  4. The foot core system: a new paradigm for understanding intrinsic foot muscle function – Patrick O McKeon1Jay Hertel2Dennis Bramble3Irene Davis4 Br J Sports Med doi:10.1136/bjsports-2013-092690
  5. Active regulation of longitudinal arch compression and recoil during walking and running Kelly LA, Lichtwark G, Cresswell AG – J R Soc Interface. 2015 Jan 6;12(102):20141076.

INFORMATION FOR ACADEMICS AND TECHNICAL AND MEDICAL PROFESSIONALS

With the increasing evolution and availability of microsensor technologies, some which can work with smart phones, there has been a corresponding increase in both the level of interest and studies on the science aspect of skiing.

One of the best studies I have found to date is the study (1) by Michał Staniszewski, Przemysław Zybko and  Ida Wiszomirska of the Józef Piłsudski University in Warsaw, Poland. As a preliminary step to the design of a study, researchers typically conduct a search of the literature for existing papers in the field. Researchers who design studies for such things as skier balance are typically surprised when results of searches find that few, if any studies exist.

Thus, the authors of the Polish study (1) commented:

Publications on issues related to the biomechanics of a descent, with particular emphasis on the balance parameters, are rare in the literature on alpine skiing.

The authors of a 2014 Polish study (2) on skier balance, similarly commented:

Our results were in agreement with the scarce information available regarding balance changes during or after a ski training camp.

The authors of a 2013 Italian study (3) on materials, designs and standards for the ski boot made a similar comment:

Despite the large market of ski equipment, not many scientific papers have been published on this subject in the past.

If not many scientific papers have been published on issues pertaining to skiing, the question arises as to what, if any, process was used to influence the design of the modern ski boot. The authors of the paper (3) comment:

The development of alpine ski equipment has been done, in the beginning, mainly by trial and error, using on-snow tests.

In other words, the process appears to have been largely subjective and artisan driven as suggested by the comment:

The first skis were only plank of woods with laces to link the traditional leather boots used in the Nordic and Alpine regions. At that time skiing was mainly performed in flat areas to help the transportation of loads and for this reason the first recreational activity with skis was cross-country skiing. Alpine skiing was born only afterwards and, therefore, the first equipment used to ski down the steep terrains of the Alps was developed starting from those already used for skiing in flat snow-fields (thin skis, leather boots and heel free bindings).

This comment suggests that the modern plastic ski boot was an outgrowth of the artisan leather hiking boot with advancements being mainly in the form of new plastic materials in place of leather.

While the authors acknowledge that research in the field of plastic materials and the optimization of new software for the design of sport equipment have permitted the development of new materials and designs that have increased the level of performance, security and comfort of ski-boots, no mention is made of advancements in the understanding of the physiologic aspects of alpine skiing. The lack of existing studies places researchers who wish to investigate this issue in the awkward position of having to rely to a significant extent on established ski industry positions on such crucial aspects as skier balance as the authors of the 2014 Polish study did when they cited LeMaster’s definition of balance:

He or she is in balance and will not fall as long as the total of all of the forces acting on the center of gravity passes through the body’s base of support.

Not falling does not conform to the text-book postural response paradigm wherein the opposing forces associated with single balance align across the plantar/ground interface with CoM maintained within defined limits of the foot.

Although studies in the field of the mechanics, biomechanics and physics of alpine skiing are rare, the number of studies in related fields that are directly applicable to skiing is steadily increasing.

Recent studies (4) on forefoot loading (fascial tensioning) found that peak plantar aponeurosis tension occurs in late stance, suggesting that it was an error to not include the late stance phase in gait and balance studies and positions in general on the phases of gait.

The plantar aponeurosis transmits large forces between the hindfoot and forefoot during the stance phase of gait. The varying pattern of plantar aponeurosis force and its relationship to Achilles tendon force demonstrates the importance of analyzing the function of the plantar aponeurosis throughout the stance phase of the gait cycle rather than in a static standing position. 

This and similar studies have significant implications for skiing because the late stance phase of the gait cycle stabilizes the subtalar and knee joints in preparation for the application of high ground forces for propulsion. The implications of such findings  to alpine skiing is that the late stance phase (SR Stance) allows high loads to be applied by the 1st and 2nd MPJs and the application of reverse subtalar joint translated vertical axial rotational torque generated from the pelvis to the ski.

Understanding and appreciating these mechanisms opens the door to new opportunities for research projects.


1. Influence of a nine-day alpine ski training programme on the postural stability of people with different levels of skills  (April 2016, Biomedical Human Kinetics (DOI: 10.1515/bhk-2016-0004) – Michał Staniszewski, Przemysław Zybko and  Ida Wiszomirska,  Józef Piłsudski University, Warsaw, Poland.

2. Changes in the Balance Performance of Polish Recreational Skiers after Seven Days of Alpine Skiing – Beata Wojtyczek, Małgorzata Pasławska, Christian Raschner

3. Materials, Designs and Standards Used in Ski-Boots for Alpine Skiing: Martino Colonna *, Marco Nicotra and Matteo Moncalero

4. Dynamic Loading of the Plantar Aponeurosis in Walking: Ahmet Erdemir, PhD; Andrew J. Hamel, PhD; Andrew R. Fauth, MSc; Stephen J. Piazza, PhD; Neil A. Sharkey, PhD – J Bone Joint Surg Am, 2004 Mar; 86 (3): 546 -552 . http://dx.doi.org/

Intrinsic foot muscles have the capacity to control deformation of the longitudinal arch – Luke A. Kelly1,2, Andrew G. Cresswell1, Sebastien Racinais1,2, Rodney Whiteley2 and Glen Lichtwark1⇑

 

THE MECHANICS OF BALANCE ON THE OUTSIDE SKI

In the next series of posts, I am going to focus on the single most important, but least understood, aspect of skiing; skier balance, in particular, the ability to balance perfectly on the outside ski. Given its univerally recognized importance in the ski culture, it is both perplexing and disconcerting that little attention appears to be given to the study and analysis of the mechanics associated with balance on the outside ski.

For decades, the worlds greatest skiers, including Patrick Russell and Marc Giardelli, have stressed the importance of standing on the downhill (outside) ski. Giardelli said that once you can balance perfectly on the outside ski, everything else follows. The ability to stand on the outside ski and balance perfectly on it, implies the same mechanics of balance we engage in when we balance perfectly on one leg when we take a step to move forward in locomotion. Balancing perfectly on one leg requires a stable surface under the entire plantar aspect of the foot to provide a source of GRF. The reason why the ankle-foot complex has a triplanar joint system is so the tripod-like structure of the foot can seek stable ground. This is the classic text book definition of one-footed or monopedal balance and the standard for studies on balance performed on one foot.

The problem is that there is no ground or any form of stable GRF under the outside foot of a turn when the ski is on its inside edge other than the GRF acting along the portion of the edge in contact with the snow surface and a small portion of the base of the ski adjacent the edge. If elite skiers such as Russell and Giardelli really can stand on their outside ski and balance perfectly on it the question is where is the source of GRF coming from that acts to support weight of the body expressed on the plantar foot?

By 1990, I had an explanation in a hypothesis I had articulated. According to my hypothesis, elite skiers extend GRF acting along the portion of the inside edge of their outside ski from the snow to the base of the ski by rotating their outside leg and foot into the turn. This action causes the base of the ski on the outboard side of the inside edge to pivot upward about the portion of inside edge underfoot with sufficient force to support the weight of the body. The Birdcage studies done in 1991 were designed to find out if my hypothesis were right.

Balance on the outside ski is a Two-Step process

Having seen great skiers like Nancy Greene Raine and Toni Sailor ski with ease on pistes that would be difficult, if not impossible, for most skiers to hold an edge on, I was convinced that some skiers really could balance perfectly on their outside ski when it was on its inside edge, the same way that every skier could easily balance on one ski when the base of the ski was fully supported on a firm, stable surface.

I set out to try and figure out how this was possible. It took me about 10 years between 1980 and 1990, to formulate a hypothesis that explained the mechanics. Once I had an explanation, I understood why no one else had been able to figure it out.

Balancing on the outside ski does not adhere to the text book descriptions of single leg balance where a stable source of GRF under the plantar foot is assumed. The ability to stand on the outside ski when on its inside edge and balance perfectly on it, is a Two-Step Process. The key is that the Second Step is dependent on the First Step.  The First Step makes the Second Step possible. Without getting the First Step right within a very short window of opportunity, the Second Step is not possible.

Since my hypothesis predicted that sequence and timing is the critical, it was quite simple to prove my hypothesis with strategically placed strain gauges mounted in the Birdcage on discrete force plates positioned opposite the predicted force transfer points of the foot. The critical nature of the sequence was easily confirmed by preventing the First Step from occurring.

In my next post, I will discuss the Two Steps of the balance process and provide examples using screen shots and video clips from recent World Cup races showing the sequence in a turn where racers such as Mikaela Shiffrin make the two steps to balance on the outside ski.

 

 

FREEMOTION FLEX CURVE OPTIONS – PART 1

For those who are new to the Skier’s Manifesto, welcome.

I became involved in an effort to design a new ski boot at the request of Crazy Canuck, Steve Podborski. Steve was (and I think still is) the only non-European to win the World Cup Downhill title. Steve also won a bronze medal at the 1980 Lake Placid Olympics. After he won the World Cup Downhill title he asked me if I could design a boot that would do for every skier what the boots I had built from components that used a new fit technology I had invented did for him. I saw this as an opportunity to advance skiing. I accepted.

I did not take on this project to make money. I took it on because I saw problems with equipment, especially ski boots, that were significantly affecting the enjoyment of the sport for the majority of skiers. I wanted to try and solve these problems and contribute to the betterment of a great sport.

In 1978, I started down the road to try and improve the ski boot by working with world class racers such as Steve Podborski. Today, my focus and mission remains unchanged. I am still working with skiers and racers and I am still learning. When Simon Zucchuber asked for my assistance with the Freemotion ski boot project, I did not hesitate to offer my assistance.

You can learn more about me under the HOME heading on the opening page.


Over the past week, I spent time going through my US Patent 5,265,350 trying to recall the events that influenced my thinking.

The first patent awarded to me was US 4,534,122. It was filed on Dec 1, 1983 and issued by the US Patent Office on August 13, 1985. The patent is for an innovative in-boot fit system that constrains the forefoot without obstructing the glide path of the ankle joint.

When I invented the fit system disclosed in the patent, I knew I was headed in the right direction. But I also knew that I did not have a full understanding, let alone a solution, for the flexural aspect of the ski boot. Between 1973 and 1983 I had come to understand that boot flex was affected by material stiffness, temperature and closure tension. But two of the biggest issues were that buckle boots flexed by deformation of what is a U-shaped tube (which made flex unpredictable) and the angle of the rear cuff that had minimal or no adjustment. This meant that the angle of the shank of a skier was determined by the mass of the calf muscle at the top of the shaft. Attempts by others to address flex had typically focussed on one issue at the expense of another or even caused new problems.

Devising a system for boot flex that would solve all issues and especially one that did not rely on shell deformation led me to the exo-skeleton format around 1987. A patent for this format was not filed until April 25, 1989 because of the time it took to work with lawyers and try and figure out how to define and describe the technology so it would meet the novel requirement for a patent.

Figure 1 below is from the initial patent filing for the patent that was eventually issued on November 30, 1993 as US 5,265,350. This figure and the material in the application established a priority date for the length of the eventual patent. This initial patent was later abandoned in favour of newer iterations.  All of the ‘improvements’ are described in the patent which can found by searching the patent number US 5,265,350 in the US Patent or Google Patent web sites.

 

fig-1

The device is a exo-skeleton arrangement with a tube for the leg attached to the base by arms on each side that rotate about an axis (23) on the base structure (11). A single wide band secures the front portion of the tube (shaft) about the leg of a user to the rear portion.

A bendable spring (40) is affixed to the base on the outside (lateral aspect) of the base (11). An adjustment (42) allows the spring to be moved closer or further away from the two contact arms (43 and 46). The contact arms slide up and down in a channel on the arms so as to allow for an amount of low consistent low resistance cuff rotation before higher resistance is introduced or allow spring resistance to be introduced earlier.  Contact arm (46) can be adjusted up or down the arm so as to change the resistance curve.

An adjustment means (generally shown at 30) allows the angle of the cuff to be adjusted. This enables a user to obtain the correct forward lean angle for the shank which I knew by then was critical (see the posts on SR Stance).

Figure 1 is a rough or what is called a schematic concept of the exo-skeleton system. The next step was to try and come up with a design with aesthetic qualities. Figure 5, below, shows the exo-skeleton of Figure 1 with a soft liner. The attachment for flex spring has been incorporated into the axis journals for the arms of the exo-skeleton.

fig-5

About 1989, I was approached by a husband and wife radiology team. They taught radiology at a university. They were both keen skiers. They heard about my project to develop a ski boot based on anatomical principles and offered their assistance. They presented me with a copy of a recently published book called The Shoe in Sport – Supported by the Orthopedic/Traumatologic Society for Sports Medicine (OTS).  The Shoe in Sport was initially been published in Germany in 1987 as Der Schu Im Sport. They were of German background. That was how they knew about the book.

I found the knowledge contained in The Shoe in Sport invaluable, especially the article the ‘Kinematics of  the Foot in the Ski Boot’ by Professor Dr, M. Pfeiffer of the Institute for Athletic Sciences at the University of Salzburg, Salzburg, Austria. The information contained in The Shoe in Sport helped crystallize many of the issues I had been struggling with and profoundly influenced the thinking behind the Birdcage and the Birdcage experients conducted in the July of 1991 on Whistler Mountain’s glacier.

For the first time, I felt I was on solid ground with my thinking. I was ready to go boldly forward and break new ground.

… to be continued in Part 2.