podborski

THE SHOCKING TRUTH ABOUT SKI BOOTS

In this post, I will expand on the content of The Shocking Truth About Power Straps (1.) which was by far the most popular post since I started this blog in 2013.

While the truth about what power straps can potentially do if improperly adjusted is shocking, the lack of support in principles of applied science for the basic premise that I describe as indiscriminate envelopment as the approach to achieving a fit of a ski boot with the foot and leg of the user with the objective of substantially immobilizing it’s joints with unknown consequences, is even more shocking. Little or no consideration appears to be given to the effects of indiscriminate envelopment on the balance and motor control systems of the skier.

What is done to the foot and (lower) leg can affect the entire body. In his post, Foot biomechanics is dead. Discuss (2.), Professor Chris Nester states:

The foot is not a compilation of interconnected mechanical components that respond precisely to the laws of mechanics. It is a complex matrix of at least 11 biological tissues (i.e. skin, fat, muscle, tendon, joint capsule, ligament, bone, cartilage, fascia, nerves, blood vessels….) that responds to external loads through the symbiotic relationship between the motor control system and tissue properties.

Professor Nester goes on to state:

I believe the integration of our current foot biomechanics knowledge with insights from motor control, neurophysiology and related domains (e.g. tissue biology) will drive advances in foot function more than pursuing a pure mechanics paradigm.

Professor Nester proposes that the term biomechanics be replaced with the term Neurobiomechanics. I concur.

How Does the Ski Boot Affect the Human Performance of the Skier?

The short answer is that when the structures of a ski boot indiscriminately envelop the structures of a foot and a portion of the leg (aka the Perfect Fit or the Holy Grail), no one knows. While it is essential that a ski boot create a secure connection of the foot of a skier with the ski, it should not achieve this connection at the expense of natural neuromuscular function, especially balance.

In 1980, when I was about to prepare a new pair of Lange race boots for Steve Podborski, I asked myself whether it was possible to obtain a secure connection of the foot with the ski without compromising natural neuromuscular function or, even better, was it possible to enhance natural neuromuscular function?

I took a significant step towards answering this question in 1980 when I designed and fabricated a device I called a Dorthotic. The Dorthotic supports the upper or dorsal aspect of the foot as opposed to supporting the plantar aspect (i.e. the arch). My theory that loading the top of the foot or dorsum with a force perpendicular to the transverse or medial-lateral plantar plane of the foot has positive benefits for motor control and balance has begun to be recognized. The Dorthotic enabled Steve Podborski to compete and win on the World Cup Downhill circuit mere months after reconstructive ACL surgery and to eventually win the World Cup Downhill title, a feat no non-European has repeated. US and international patents for the dorsal device were awarded to me (David MacPhail) in 1983.

The success of the Dorthotic gave me a start towards answering the question of whether a secure connection of the foot with a ski was possible without compromising natural neuromuscular function. But I knew that I needed to learn a lot more. I realized that finding the answers I was seeking and especially unraveling the secret that enables the world’s best skiers to stand and balance on their outside ski, would require a multi-disciplinary approach.

The Missing Factor in Skiing: A Multi-Disciplinary Approach

A significant influence that served as the impetus for the design of the Birdcage research vehicle and the on-snow studies, was the work of Dr. Benno Nigg. In 1981, Dr. Nigg accepted an invitation to move from ETH Zurich, where he was the director of the biomechanics laboratory, to the University of Calgary, where he founded and developed the Human Performance Laboratory (HPL), a multi-disciplinary Research Center that concentrated on the study of the human body and its locomotion.

The publication of the Shoe In Sport in English in 1988 served as a seque to introduce me to Nigg’s research at HPL. Studies done at HPL found that any interference with the function of the human foot, even a thin sock, extracts a price in terms of the adaptive process the human body has to undergo to deal with what is really an externally imposed disability.

The Effect of Footwear on the Neuromusculoskeletal System

There is an excellent discussion in a recent post on the Correct Toes blog (3.) on the impact of a narrow toe box, toe spring and elevated heel of traditional footwear on the human body. Elevating the heel in relation to the forefoot will predictably cause a realigment of the ankle-knee-pelvis joint system with a corresponding adjustment in the tension of the associated muscles with a global effect on the Neuromuscularskeletal System. This has been known for decades. Elevating the heel in relation to the forefoot, will cause the ankle joint to plantarflex (reduce dorsiflexion) in relation to the support surface under the foot in order to maintain COM within the limits of the base of support.

Ramp Angle Rules

Due to the unstructured nature of the indiscriminate envelopment characteristic of the fit of the majority of conventional ski boots, it is extremely difficult, if not impossible, to determine the effect of constraint of this nature on the Neuromusculoskeletal System. So I’ll focus on the one aspect of the ski boot that has consistent and profound implications on skier human performance, especially motor control and balance; boot board ramp angle or zeppa. Binding ramp angle or delta compounds any effect of zeppa. For the sake of simplicity we’ll assume zero delta.

Contrary to the widely help perception, raising the heel of a skier in a ski boot does not cause CoM to move forward. In fact, it usually has the exact opposite effect. It puts a skier in the back seat with the weight on their heels. Worse, it can disrupt the competence of the biokinetic chain that dynamically stabilizes and protects the joints of the lower limbs. Excessive heel elevation can render a skier static and cause the balance system to resort to using the back of the shaft as a security blanket.

As of this writing, I am unaware of any standard within the ski industry for zeppa. It appears to be all over the map with some boots having as much as 6.5 or more degrees. The default zeppa for the human foot on a hard, flat level surface, is zero.

Through subjective experiments in 1978, I arbitrarily determined that zeppas in excess 3° had a detrimental affect on skier balance. In 1991, zeppas of 2.3° and 2.5° were chosen for the large (US 8-12) and small (US 4-8) Birdcages based on an analysis of the effect of ramp angle on COM and neuromuscular activity. This range appears to work for a majority of recreational skiers. But recent tests with a dynamic ramp angle assessment device that I designed and fabricated is finding the stance of elite skiers optimizes at much lower zeppa angles, with some skiers below 1.5°. Interestingly, when NABOSO insoles are introduced for the assessment, zeppas decrease even further. With minimal training, most skiers are sensitive to dynamic changes in zeppa of 0.1 degrees.

Implications for the future of skiing

A tectonic shift is underway on a number of fronts (see A Revolution) that is challenging the mechanical and static premises that form the underpinnings of the key positions in ski teaching and the design of equipment such as ski boots and the fit process. In my next post I will post recent material by Dr. Emily Splichal, functional podiatrist and inventor the revolutionary NABOSO small proprioceptive stimulating insole.


  1. https://wp.me/p3vZhu-UB
  2. https://talkingfeet.online/2018/01/18/question-3-foot-biomechanics-is-dead-discuss/
  3. https://www.correcttoes.com/foot-help/footwears-impact-musculoskeletal-system/

EPICSKI ARTICLE – THE BIRDCAGE EXPERIMENTS

The following is an article that I posted on EPICSKI (www.epicski.com) on June 18, 2010. The article states that the tests were done on the Blackcomb Glacier. In fact, the tests were done on Whistler Mountain’s summer glacier • Last updated 12/15/12 • 1,380 views

The Birdcage Experiments by David MacPhail

In the summer of 1991 a science team that Steve Podborski and I had assembled to develop a new ski boot conducted pioneering experiments on the Blackcomb Glacier with a device we affectionately named the “Birdcage.” The Birdcage connected a rigid structure to the foot at very specific points while leaving the remaining areas of the foot free of any constraint. The object of the experiments was to study the effects on balance of specific forms of constraint applied to the mechanical points of the foot we had previously identified. The experiments were designed according to a scientific protocol that standardized conditions from test to test while varying one component at a time.

Birdcage
For example, to study the effects of cuff forward lean angle on specific muscles, the range of rotation of the cuff was kept the same from test to test while the initial angle at which the cuff was set was varied from test to test. The cuff was fit tightly about the leg so as to reduce to a minimum any effects of movement of the leg within the cuff. Other aspects of the test such as position of the heel and ball of the foot in relation to the centerline and inside edge of the ski were kept the same.

By using such test protocols we could study the firing order and pattern of specific muscles. This data could then be used to determine the order of events such as balancing, steering and edging. It was discovered that by varying the conditions that affected the firing and effectiveness of the soleus muscle, it could be played like a musical instrument. For example, if the cuff angle were set so it was too erect the soleus would make multiple attempts at the start of each turn to try and get CM over top of and in front of the ankle.

Our primary tester for the experiments was Olympic bronze medallist and World Cup downhill champion Steve Podborski. Steve is shown to the left trying on the Birdcage. The cable coming out of the rear of the device is connected to a Toshiba optical drive computer (remember, this is 1991) that Toshiba loaned us in support of our program. Since telemetry was too costly and less positive we used a 1200 ft cable that linked the Birdcage to a computer that was set up in a tent. Although the technician could not see the skier, he could easily assess their technical competence within a short period of time by assessing the data generated. This was even more remarkable considering that the technician had no background in skiing or ski teaching.

The testers wore a harness to keep the cable from interfering with their movements. A chase skier ensured that the cable remained behind the testers and did not pull on them. Of interest is the fact that this work was universally regarded within the ski industry as completely irrelevant to skiing.

Here is the link to the original article – http://www.epicski.com/a/the-birdcage-boot-experiment-by-david-macphail

In a series of future posts I will discuss the findings from these ground-breaking, on-snow, real-time experiments. As far as I know they had never been done by anyone else before I did them and have never been done by anyone else since the Birdcage experiments.

LIGETY AND SHIFFRIN: HOW I KNOW WHAT THEY ARE DOING

In order to know what to look for, one has to first have a theory that explains what is happening. In order to see what I see, one needs to know something about my theory and how I validated it. With all due to respect to Ted Ligety, in order to fully leverage the potential of the technique he is using, it is necessary to know the basic theory and especially the working principles behind it. Although I could wrong, based on the NY Times video, it is questionable whether Ligety fully understands all the relevant issues associated with the technique he using. Here is one thing that  he gets full marks for.

Ligety: “I step on the new (uphill) ski while it is still on the edge it was currently on in that turn (ergo the uphill edge).”

The question is why is this so important? The answer is that Ligety needs to initiate what I call the pronation flow when his uphill ski is still on its uphill edge. In addition, he needs to initiate a movement sequence that rotates his uphill foot into a foot flat position on the slope. In other words, Ligety (and Shiffrin) need to momentarily literally stand on the slope of the hill. Three things make this possible, 1) extension, 2) pronation and, 3) momentum. Momentum is tending to keep Ligety’s C0M travelling along a fixed path. Gravity is tending to pull Ligety’s CoM down towards the centre of the earth. Ligety and Shiffrin both push back against momentum and gravity by extending their uphill leg with muscle force.  While it may not be obvious from the camera angle of the photo below, Shiffrin is literally standing on the slope of the hill. Although the photo is blurry, you can see that she has started to pivot her left ski across her trajectory. Shiffrin is approaching maximum extension of her left leg. She will extend it further in conjunction with the pivoting of her foot in order to maximize the loading of forces into the turn. Ligety loads his ski more than Shiffrin through the timing of his extension.

Shiffrin initiation

There are several reasons why no one has figured out what Hess, Ligety Shiffrin and in fact all the world’s best skiers have been doing for decadeas. The main reason for the inability to see is that everyone has been focussing their attention on where the action is, at the apex of the turn where the outside ski is maximally loaded. Once the prevailing wisdom saw the downhill ski of the turn as the outside ski they were blinded in terms of the ability to see what the best skiers were doing. The prevailing mentality became to maximize the loading of the outside ski at the apex of the turn. The video below of Guenther Mader in 1987 shows the maximum loading technique. Mader literally pounces on his outside ski and uses the reaction force to catapult him into the next turn.

 

Loading the outside ski of a turn was the right idea. But the mechanism was wrong. It could not possibly work because the Centre of Pressure under the sole of the foot in the technique Mader is using is on the outside turn aspect of the inside edge of the outside ski. In this configuration, loading the outside ski will tend to push to foot to the outside of the turn and rotate it and the leg (more on this later) away from the turn.  These issues led to further serious errors. Trying to fix the foot in neutral and attempts to use the leg as a lever to hold the ski on edge. Today, a whole industry is working 24/7 trying  to make it impossible for skiers make the same Ski Move that Ligety and Shiffrin make.

By the time I saw Hess in 1987, I knew that the world’s best skiers were making a move that  pushed the Centre of Pressure on their uphill foot from under the heel to under the ball of their foot and kept it there through the apex of the turn.  The only mechanism with which to move Centre of Pressure to the ball of the foot is pronation. The pronated configuration associated with the Ski Move allows the leg to absorb energy while enabling the injury defence mechanism to be active.

By 1990, I had formulated a hypothetical model of the mechanics, biomechanics and physics of skiing that predicated that, among other things, the world’s best skiers would move Centre of Pressure to the ball of the foot of their outside ski prior to pivoting the ski and that if the associated movements were impeded technique would be degraded. In order to test this hypothesis we did studies in 1991 using the instrumented data capture device shown in the photos below. The device replaced the conventional ski boot. It recorded the 3-dimensional internal forces applied by the foot and leg of the skier to the interfaces of the device during actual ski maneuvers as well as degrees of cuff movement. Data was acquired through 17 data channels. After only a few runs, a technician in a tent could assess the quality of the turns of a skier was making based purely on  real-time, unfiltered data flow. In a future post, I will present and discuss the data. For now, it is suffice to say that the studies confirmed my Ski Move hypothesis.

Bird Cage Sensors

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This is the device Steve Podborski’s used. Birdcage

That is Steve Podborski’s foot in the device in the lower right hand photo. Testers, who ranged from World Cup Champions and Olympic medallists to neophytes, reported that the device was the best ski boot they had ever skied in. US Patent No. 5,265,350, a document of almost 200 pages, was based on the results of these studies. The focus of this patent, which was granted internationally, is structures of a ski boot that permit the user to assume a dynamically balanced based of support on one foot and use it to move to a dynamically balanced based of support on the other foot. In other words, to allow the average recreational skier to make the same efficient, effective Ski Move that Hess, Ligety, Shiffrin and other elite skiers use.

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PODBORSKI’S BALANCING ACT

“The support system allows proper flexion of the ankle joint while providing firm support for the bones of the mid-foot. When used in ski boots, the system gives the skier good balance and control of the boot even during fast downhill skiing.” United States Patent Number 4,534,122 – Inventor: David MacPhail

Thirty-four years ago, Steve Podborski won a Bronze medal for Canada in the downhill race at the Lake Placid Olympics. When he did, he was wearing a pair of Dynafit ski boots that I had modified. While it was also a great day for me, I was not satisfied that Steve was performing to his full potential. In my perspective on human performance, it is the often the limits of the equipment, not the limits of the athlete, that is the decisive factor in winning or losing.

In Putting the Boot to the Europeans – Part 3: A New Direction, I told how I had recommended to Steve that he change to Lange ski boots. I also had a new idea that I wanted to try. The plan was to put my new idea together when Steve came to my Whistler shop in June of 1980, then test the it against a pair of boots without the new idea and see if my new idea worked as expected. It was a good plan except that it didn’t work out. Before he could test my new idea Steve tore his ACL in Austria in July while testing new skis. After thinking he was out for the season, Pod went to France to be with the team for the opening race of the 1980-81 World Cup season. Although he had not been on snow since he tore his ACL,  he decided to try the new boots to see if he could ski. The rest is, as they say, ‘history’. Steve was third in the opening race at Val D’ Isere. He would have won the World Cup Downhill title that season had he not come down with the flu before Aspen. The unusual characteristics of Steve’s style was his incredible smoothness on course and his ability to stay in a tuck in perfect balance and especially to absorb terrain changes. On course, he looked more like a Formula One driver driving a race car than a typical on-the-edge downhiller.

In the 1980-81 World Cup Downhill season, Steve was using an innovative in-boot technology that I invented and was granted a patent for. Excerpted pages from the patent document follow below. Dave Murray was the impetus for this invention.

Mur was the first National team racer I worked with. Since we lived close to each other he often ended up acting as a Guinea pig testing my new ideas. In  1978 I tried  building a custom tongue for Mur by laminating thin layers  of heat formable foam together and then shaping the assembly into a conventional tongue form. The finished tongue was a perfect fit to Mur’s shin and the instep of his foot. But it caused huge balance issues in that Mur had no balance on his skis. Since this made no sense to me I started reading books on the anatomy and biomechanics of the human lower limbs in an attempt to find out why. I eventually figured out what the problem was. The ankle is a gliding hinge with the centre of rotation well below the ankle bones. When the ankle joint flexes forward, the base of the shin is blocked by the static shape of a conventional boot tongue. In a future post I will describe all the problems this causes.  But the main problem is that when the shin encounters a strong source of resistance, the muscles in the back of the leg turn off. This has the effect of disconnecting the foot from the leg and turning off the muscles that cross the knee joint, exposing it to stress and worse, exposing it to injury. Here is another excerpt from my patent:

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. Rather than concentrating on providing a new boot design, the inventor has studied ways of overcoming the above problems by providing a fit and support system which can find application in many ski boots of current design, as well as in other types of sports footwear.

The solution was a two component system joined by a flexible link. The forefoot component secures the foot in the ski boot in a manner that doesn’t interfere with ankle flexion. The shin portion ensures that the force applied to the boot cuff is consistent. Because the foot is secure in the boot shell, the cuff does not need to be tightened securely about the leg. This allows for correct and adequate ankle flexion to absorb the shocks of downhill skiing without disrupting skier balance.

US 4,534,122 1

US 4,534,122 2

US 4 3

Here are some photos of a version of the in-boot system I made for another skier. It is not exactly the same as the system Podborski used. But the concept is the same.

IMG_3703 IMG_3706 IMG_3705

PUTTING THE BOOT TO THE EUROPEANS: A NEW DIRECTION

While waiting for Poborski to return to Whistler in June so I could assemble and tune several pair of race boots for the 1980-81 World Cup season I spent a lot of time thinking about how I could fit the foot differently from the conventional method of supporting the ankle with foam pads inserted between the ankle and the interior boot cuff walls and squeezing the sides of the forefoot together. After discovering that the forefoot of the boot tongue was applying little or no pressure to the instep of most skiers I was trying to find a way to pad the tongue so as to close the gap between the instep of the foot and the forefoot of the shell.

There are three challenges to attempting to pad the tongue of a conventional liner in order to load the instep with the forefoot boot closure. The stiff nature of the plastic and the inability to open the seam of the overlap very much require that the throat of the boot where the cuff transitions into the forefoot be ‘generous’. By ‘generous’ I mean that the instep has to be much higher than the height of the instep of the average skier’s foot in order to facilitate entry. In addition, the point where the forefoot of the boot rolls up into the cuff has to be much farther forward than the same reference in a street shoe. But the biggest challenge is that the shape and form of the typical boot tongue bears little resemblance to the asymmetrical shape of the instep of the human foot where what I refer to as the ‘dorsal ridge’ angles inward towards the ball of the foot from the crown of the midfoot.

In what turned out to be another disastrous experiment with Dave ‘Mur’ Murray I had used 2 mm thick sheet thermofoam to fabricate a custom tongue pad that was inserted into the Lange tongue body in place of the factory foam padding. The custom tongue was laminated from a number of layers of thermofoam heated and shaped to Mur’s shin and forefoot with each layer bonded to the layer below. The final assembly was ground to shape to reflect the corresponding interior shape of the shell. The fit of the final product was perfect. But Mur said the tongues made the flex of his Langes so stiff he could barely ski.

At first I was puzzled. What happened was totally unexpected.  After researching the biomechanics of the tibial talar joint (commonly referred to as the ‘ankle joint’) I found out why the tongue made Mur’s boots stiff. The ankle joint is gliding hinge, not a fixed hinge like the hinge a door swings on. The implications of a gliding hinge in the ankle are that when the ankle dorsiflexes (the shin moves towards the toes) a reference point on the tibia moves closer to a reference point on the top of the foot. When this happens the centre of force of the shin pressing against the boot cuff suddenly drops down the shin. The effect is like someone kicking your feet out from underneath you. Not good.

Once I understood what was happening I decided to try and make a tongue for Pod’s boots that had 2 components, a shin component and a forefoot component. The 2 components would have a gap between them. They would be joined together with a flexible link. This would hopefully allow the 2 components move towards each other without binding and causing the centre of force on the cuff to move downward. Now all I had to do was figure out how to make the new boot-fitting tongue.

…… to be continued.

PUTTING THE BOOT TO THE EUROPEANS: DYNAFIT/LANGE SHOOTOUT

As soon as the 1979-80 World Cup season ended Podborski came to Whistler to test boots for the 1980-81 season. In this session Steve compared the Dynafit World Cup boot he used in the last season to a new Dynafit model and a Lange XLR.

In the photo below Steve and I are on Whistler Mountain where we did the testing in April. Some young potential World Cup stars have joined us. Steve is in the white jacket. I am in the blue vest kneeling down making adjustments to his boots. Steve’s brother, Craig, came along to help out. Craig is standing behind Steve wearing a red vest. If you look closely you will that Steve’s left foot is bare.

Pod Lange 1

Pod Lange 2

Pod Lange 5

We spent two days testing boots.  For the tests I had only made some very basic modifications to the new boots. Based on the results of these tests Steve made the decision to switch to Lange from Dynafit, a bold move since no World Cup Downhill racer had ever won on Lange.

After the tests Steve took a break and made arrangement to get a stock of  Lange parts from the factory so I could make up several pair of race boots when he came back to Whistler in June. Steve had very small feet back then – US Men’s size 6. For these tests we used a pair of boots I had assembled for DeeDee (Diana) Haight. Podborski was also one of the lightest racers in the World Cup Downhill circuit, something that was considered a disadvantage when it can to gliding.

In next post I will show the in-boot technology I invented that enable Pod to ‘Walk on Water’ metaphorically speaking.

……. to be continued.

MAC MEETS POD: THE MACPOD CONNECTION

By 1979 things were going so well with the BC Ski Team that Glen Wurtele (the coach) asked me to accompany the team to the Pontiac Cup finals and the Spring Series in Quebec.  The Spring Series are especially important for provincial teams because it gives junior racers a chance to compete against National Ski Team and US Ski Team racers. But spring is also a time when warm weather can bring out the worst in ski boots as racers’ feet swell. Because of the importance of these races, most provincial teams brought extra coaches along. But in his typical ‘take the enemy by surprise’ fashion, Wurtele brought a boot technician. Little was he to know that this bold move would set the stage for a successful Canadian assault on the European Juggernaut of World Cup racing, the World Cup Downhill title.

Although I was getting good results with BC Ski Team racers, most of what I was doing, aside from ramp angle, cuff canting and forward lean cuff adjustments, was what I considered band aid boot work. Where the boot allowed, I was starting to do foot alignment. My challenge was that the construction of most boots didn’t allow for significant modification. But in those days any modification was usually an improvement over a stock product.

After the Pontiac Cup finals at Mont St Marie the team moved on to Sutton, Quebec for the Spring Series.  The opening race was a GS. The men and women  were running the same course. As usual, DeeDee (Diana) Haight was blowing her competition away. She was even beating a lot of the men when the times were compared. For the first run of the men’s GS I was standing about half way down the course at a position beside some National Team coaches. When an National Team racer in a white downhill suit came zooming past me I was taken by how good this guy was skiing. I knew right then and there he could win World Cup races. I turned to one of the coaches and asked, “Who was that racer that just went down the course?” “Podborski“, the coach replied. I had to meet this Podborski. I asked Wurtele to introduce me. He agreed and gave me a quick introduction during lunch. After the second run of the men’s GS, Pod and I retreated to the base lodge to discuss my ideas on ski boots. I rambled on for what seemed like hours. Most would have thought me possessed or perhaps more than a bit eccentric. But after I finished my spiel Podborski calmly said, “When can I come out to Whistler to work with you?” I replied, “As soon as you can get there”. It was game on.

A few weeks later Pod arrived in Whistler. He was skiing on the Austrian Dynafit boot. In those days, it was the most successful boot on the downhill circuit. But it was bloody awful to work on. The large cuff hinge made altering the cuff cant to align with the racer’s leg, something I considered essential, impossible. During the day Pod and I worked on his Dynafits. At night we listened to his favourite group, Steely Dan……..at concert level volume. Working with Pod was a new experience for me. I likened our working relationship to my favourite race car team, Roger Penske and Mark Donahue where results sprung from a collaboration of the crew chief (Penske) who tuned the race car based on input from the driver (Donahue).

I did the best I could with Pod’s Dynafits. As an exceptionally talented skier with the right foot structure (his foot was US men’s size 6 and what was I referred to as ‘stiff’), he could ski in gum boots and probably be competitive. Still, I wasn’t satisfied that the Dynafit allowed me to make the modifications necessary to enable him ski to his full potential. Pod had an OK 1979-1980 season culminating in a bronze medal run in the downhill at the 1980 Winter Olympics in Lake Placid. Seeing a photo of him airborne with his skis oriented on their outside edges convinced me that he needed to change boots for the next season. Besides, I had a new idea that I wanted to try.