Alpine Ski Technique posts

THE SKIER’S MANIFESTO: REBOOT OR DELETE?

Thank you for all who have commented. I listen and I hear you.

I started this blog as a manifesto for skiers to interact and contribute to the betterment of this great sport. I view knowledge as dynamic. Positions on issues should change in response to new and better information. Without this process learning cannot happen.

A significant challenge to making the Manifesto serve this purpose is that it has been difficult for me to know the nature of the information my readers are seeking and whether my posts are providing this information or even resonating with my readers. When put up a post I need to get feedback, suggestions and yes, criticism. If you don’t agree with my position on an issue please tell me. As a critical thinker (self-critical) I always entertain the posssibility that my position on issue is wrong. At the very least  my explanations may not be clear. If this is the case, I need to know.

If you want me to post on a certain subject, please let me know. Without this information I could be wasting my time.

The uncertainty as to the nature of the information my readers are seeking or subjects that will be found in search engines has resulted in post threads that are disjointed as expressed by the comment below from a follower:

While the blog might be improved by some minor rearranging of the sequence of blogs, the important thing is that the information is in there. You have, in fact, suggested sequences for the practical application of several principles, boot fitting for example.

An easy way for me to address this issue is to repost existing posts in a sequence that will group them together according to the subject. After I respost the older post I can edit it in response to comments. So instead of deleting the blog I am proposing culling some posts and reposting and collating existing posts. But I can’t do it without your input and especially your suggestions.

I believe a good starting point is a discussion of how our hard-wired mechanism for walking applies to skiing and especially what is called steering. Does everyone agree? If not please suggest a subject.

 

CHANGES COMING T0 THE MANIFESTO

In a few days, my blog will start to include advertisements. The reason for this is that I have decided to take a break and not renew my subscription for the premium plan that eliminates advertisements. The blog will continue to exist. At some point I may renew my subscription to the  premium plan.

The most important posts I have ever published are the series on The Mechanics Patform Angle and The Future of the Ski Boot Parts 1 and 2. For reasons that aren’t clear to me the ski industry has never done a comprehensive analysis of the forces acting between the outside ski and snow that create a platform that skiers can stand and balance on. Instead a simplistic and incomplete explanation was put forth that viewed balance in terms of opposing vertical forces missing the most important forces, horizontal forces into the hill parallel to the base of the outside ski and multi-plane torques. Unfortunately this seriously flawed explanation gained wide acceptance.

The ski industry also failed to recognize that FIT equates with DYSFUNCTION especially impaired neuromuscular function. I went into detail in this in Part 2 of The Future of the Ski Boot.

The forces associated with The Mechanics Patform Angle are not simple. They are all described in my posts for those willing to invest the time and effort to gain an understanding. But there is no shortcut. Either you understand all aspects or you understand nothing.

Skiing can and should be as easy and intuitive as walking. That it isn’t is the failure of the ski industry,not the failure of the skier.

WHAT SHOULD A SKI BOOT DO?

After Steve Podborski won the 1981-82 World Cup Downhill title using a revolutionary dorsal fit technology I developed for his ski boots in June of 1980, he proposed that we become partners in a venture to develop a new ski boot that would do for every skier what the dorsal fit system had done for him. In exchange for my creative efforts, Podborski would fund the venture up to a point after which we would try to raise funds from investors for the project.

If I accepted Podborski’s proposal (which I eventually did), I knew the we faced significant hurdles. After giving the proposal a lot of thought, I accepted Steve’s offer. Steve and I became partners in a company called MACPOD Enterprises Ltd. While I had identified some of the pieces of the puzzle, I didn’t yet know the answer to the question what a ski boot should do. But I knew that when the time came to raise money I would need to provide investors with convincing evidence that I knew the answer to this question.

Podborski’s success lent credibility to the project. But his credibility was based on his subjective assessment supported by his race results. To be credible, a ski boot design based on principles of science would need to be supported with data from actual skiing maneuvers that could generate meaningful, quantifiable metrics for such things as balance and ski control. When the metrics were compared to the same metrics from data captured from the same skiers using conventional ski boots, they would need to unequivocally demonstrate superior performance of the MACPOD ski boot. I had to come up with a format that would satisfy potential investors that the new ski boot MACPOD would develop would be at least as good, if not better, than the system Podborski used to win the 1981-81 World Cup Downhill title. Whatever format I came up with had to be capable of allowing investors who skied to ski in it.

In 1992, MACPOD raised money from investors to fund the first phase of the venture. The pressure was on.

The single variable assessment protocol

The factor that convinced Podborski of the merits of my dorsal fit system was the comparison test he did against identical Lange boot shells fit with conventional Lange liners.

After rupturing his ACL testing skis at the end of July in 1980 Steve went to France 2 weeks before the opening downhill race of the 1980-81 World Cup season at Val d’isere to be with the team to support them. He had not planned on skiing, let alone racing, because he had been told by his doctors he was out of commission for the 1980-81 World Cup Downhill season. But Podborski had brought 2 pair of identical Lange boot shells to France with him just in case. One pair had the untested dorsal fit system with only the upper cuff of a Lange liner mounted on the boot shaft. The other pair had conventional Lange liners.  The only difference between the boots was the fit system; the classic single variable assessment protocol.

The graphic below from my US Patent shows a conventional tongue format (20) in FIG 3 (prior art) compared to my dorsal fit system (30) in FIG 5. The shin component (31) is like a conventional tongue.

On a whim, Podborski decided to see if he could ski in the boots with the dorsal fit system. He was amazed to find that he could ski well with little pain in his partially healed, reconstructed ACL. But when he tried to ski in the boots with the conventional liner he could barely ski.  I found this interesting because the impetus for the new fit system was my hypothesis that dorsal loading of the bones of the midfoot might reduce strain on the knee by dampening decompression of the arches resulting from perturbations in ground reaction force due to asperities and undulating terrain. A conventional liner could not be used because it would have interfered with the interface of the lower shell overlap closure on the upper surface of the dorsal fit system required to apply force to it. Fig 9 below from the patent shows how the overlap of the shell applies force to the upper surface of the dorsal fit system. The buckle closures allow the force, which should be minimal, to be regulated.

The ability to compare the dorsal fit system against a conventional liner system on the same day and in same conditions made the superiority of the dorsal fit system apparent. The unprecedented improvement in performance with no run-in period or special training program strongly suggested that the improvement resulted from reducing factors in conventional ski boots that limit or degrade human performance. This experience caused me to undertake a critical analysis of the functional requirements of the human system for skiing. This exercise opened the door to the possibility of technologies that would integrate external appendages such as skis and skate blades with the human system, what I later came to term Bio-Integration.

Bio-Engineering

If structures of ski boots, ice skates and cycling shoes can limit or degrade the human performance of the user it also became apparent to me that it might be possible to modify the function of the feet and lower limbs that would make it specific to activities such as skiing, skating or cycling and even potentiate neuromuscular function. I termed this concept Bio-Engineering. I didn’t realize until 1991 that the dorsal fit system used principles of Bio-Engineering.

The graphic below is the pressure image of the right foot of an elite cyclist showing the forces applied by the foot to the sole of the shoe on the pedal spindle at 3 o’clock in the stroke sequence at a low cadence with a moderate to high load on the crank. The cyclist is wearing a conventional rigid sole cycling shoe with no arch supports, wedges or other accessories.

Red is highest force. Dark blue is the lowest force. Forces were recorded with a Tekscan F Scan system fit to the shoe.

The highest force is applied under the ball of the great toe and the great toe and to a lesser extent, the second, third and fourth toes. The dashed line shows the approximate location of the pedal spindle which is the source of resistance/reaction  force. This pressure pattern is typical of elite cyclists. Ideally, the highest force should be applied across the width of the pedal spindle by the heads of all five metatarsals. Note that aside from the high pressure patterns on the ball of the foot and toes 1 through 4 the pattern is diffuse across the heads of metatarsals 2 through 5 and under the heel.


In my next post, I will show a pressure pattern of the same foot in the same position with a technology that Bio Engineers the foot and lower limbs and discuss the significant differences.

SKI BOOT ASSESSMENT PROTOCOL

Step 1 of the synergy 5 Step performance Program described in my last post is a Footbed Check using the Novel Pedar insole pressure analysis system.

Step 3 of the program is the Ski Boot Assessment detailed below. As with the 5 Step performance Program, the Ski Boot Assessment protocol and report were intended to serve as a template to base future programs on. The assessment report was intended to provide clients with information on the effects of their ski boots on their performance and/or as a work order for them to take to a boot-fitter to have any necessary issues identified in the report addressed.  Synergy Sports Performance Consultants Ltd. did not sell products or perform boot modifications.

 



My next post will be called FOOTBEDS: THE GOOD, BAD AND THE UGLY.

 

 

 

 

THE MECHANICS OF BALANCE ON THE OUTSIDE SKI: BALANCE PLATFORM MECHANICS

Turntable rotation generated by the powerful internal rotators of the pelvis (the gluteus medius and minimus) in combination with second rocker mechanics can create a platform under the body of the outside ski and foot that a skier can stand and balance on using the same processes to balance on solid ground. The associated mechanics creates a platform under the body of the outside ski by extending  ground reaction force acting along the portion of the inside edge in contact with the snow, out under the body of the ski.

In order to understand the mechanics, we need to start with a profile through the section of the body of the ski, binding and boot sole under the ball of the foot. The graphic below is a schematic representation of a ski with a 70 mm waist and 100 mm shovel and tail with an arbitrary length of 165 mm. The total stack or stand height from the base of the ski to the surface of the boot that supports the foot is 80 mm. The uppermost portion of the schematic shows the shell sidewalls of a 335 boot in relation to the 70 mm width of the stack. A ski with a 70 mm waist will place the center ball of the foot of skiers with US Men’s 10 to 12 feet close to over the inside edge. The heavy black line at the bottom of the stack shows the projection of the sidecut width beyond the waist.The schematic serves as a base on which to overlay a free body diagram showing the forces acting across the interface of the inside edge with the snow. This is where the rubber meets the road.

There are two possible scenarios in terms of the axis on which the center of pressure W of the skier will act. Unless the foot can sufficiently pronate and especially generate impulse second rocker loading, W will lie on the proximate anatomic center of the foot and transverse center of the body of the ski as shown in the graphic below. In this location, W will create a moment arm due to the offset with the GRF Pivot under the inside edge at the waist. The resulting moment of force will externally rotate the ski and foot under load out of the turn while simultaneously rotating the leg externally.The graphic below shows the second scenario where the center of pressure W lies directly over the GRF Pivot under the inside edge. In this position, W will load the inside edge under the ball of the foot and assist edge grip. But in this configuration, rotating the ski onto its inside edge necessitates overcoming the moment of force created by the moment arm resulting from the offset between the GRF Pivot and GRF acting at the limits of the sidecut. This requires a source of torque that acts to rotate the ski into the turn about the pivot acting at the inside edge at the waist of the ski.An obvious source of torque is to use the leg to apply force to the inner aspect of the shaft of the foot; aka knee angulation. But this will not create a platform under the body of the outside ski. Applying a load to the vertical wall of the shell opposite the ball of the foot will apply torque load to center at the GRF pivot as shown in the graphic below. The moment arm is formed by the point at which the Turntable Torque is applied to the boot sidewall (green arrow) to the center of rotation at the GRF Pivot.

 

The torque applied to the vertical sidewall of the boot shell is the Effort. The sidecut of the ski is the resistance. What effect will this have on the body of the ski under the foot? There is a lot more to this subject that I will begin to expand on in my next post.

THE MECHANICS OF BALANCE ON THE OUTSIDE SKI: GLUTE POWER EDGE CONTROL

The New Year started off on a positive note with a great post on preventing sports injuries by Rick Merriam; Engaging Muscles (1.), a new YouTube video by LaGrandNeve (2.) on the importance of the feet in skiing and the long anticipated delivery of the CARV system.

In his post on preventing sports injuries, Merriam, cuts right to the heart of the matter when he states:

Sadly, most professional athletes don’t even know what it feels like to have muscles pulling at the right time.

Said another way, most professional athletes haven’t experienced what it feels like to perform with more stability throughout their chain.

By chain, Merriam is referring to the biokinetic chain.

My consistent finding over the years has been that most skiers, even racers at the World Cup level, don’t know what a stance founded on a strong, stable biokinetic chain should feel like. Even among those who have skied for decades, many have never experienced it. And the role of muscles is rarely, if ever, mentioned in discussions of ski technique or analysis of technique.

In Corso di sci Check Point 2018 – 03 (2.); Piedi cerca spigolo (Feet looking for corner) Valerio Malfatto states:

Contrary to what is believed in the curves with the skis the feet are very important we see how and why.

At about 1’50” into the video, Malfatta begins to draw a series of sketches. The first sketch appears to show how eversion of the foot puts the outside ski on edge by creating a flow of force into the turn. He appears to acknowledge how the ski and foot can either rotate to the outside of a turn (outside foot/ski inverts) or the inside of a turn (outside foot/ski everts). Then he appears to be showing how pressure applied under the ball of the outside foot rotates the ski onto it’s inside edge. Since I understand very little spoken Italian, it would be helpful if a follower of my blog who speaks Italian could post a comment explaining what Malfatto is saying in his video. My apologies to Malfatto if I have misinterpreted his graphics.

The graphic below is a screen shot from Malfatto’s video that shows how the foot and ski have rotated into the turn by pressure applied under the ball of the outside foot.

Although I have seen examples in that suggest rolling the ankles of the feet into a turn will apply edging forces, Malfatto’s video is the first example I have seen that appears to recognize that the outside foot and ski of a turn will tend to invert (rotate downhill) in the load phase under the force applied by the weight of the skier in the absence of a countering eversion torque.

While elite skiers and racers are usually aware of pressure felt under the ball of  the outside foot, it is difficult to replicate the feel in a static environment. So static exercises are often employed in an attempt to demonstrate what the skier is doing.

At about 5’30” into Malfatto’s video there is a dryland demonstration of the outside foot of a turn being rotated into the turn by contracting the muscles that evert the foot while the inside foot is rotated into the turn by contracting the muscles that invert the foot. There are a number of problems associated with attempting to hold skis on edge by contracting the inverter and everter muscles:

  • The muscles are in concentric contraction; i.e. they are physically shortening.
  • Both muscles are extensors of the ankle; i.e. as they shorten, they will plantarflex the ankle. This will shift the weight of the skier back under the heel, pushing the skier into the back seat.
  • The use of muscles to evert and invert the feet require conscious effort in what is called Executive Control. The processing rate of the brain in this mode is limited to about 60 bits per second compared to that of processing in Automaticity (subconscious control) which is about 11 million bits per second.
  • Both muscles are relatively weak compared to the glutes and soleus which are among the most powerful muscles in the human body.
  • Neither the everters or inverters cross the knee joint.

At the time that I wrote United States Patent 5,265,350 in February of 1992, I described the lack of knowledge of the complex biomechanics of the human muscle-skeletal system as it relates to the interaction of the foot with footwear such as skates and ski boots. In consideration of this, I made a concerted effort to provide as much information as possible to those knowledgeable in the field with the objective of advancing the state of knowledge on the subject. Since the writing of my patent my knowledge has evolved and continues to do so.

The following statements are excerpted from my patent.

The most important source of rotational power with which to apply torque to the footwear is the adductor/rotator muscle groups of the hip joint. In order to optimally link this capability to the footwear, there must be a mechanically stable and competent connection originating at the plantar processes of the foot and extending to the hip joint. Further, the balanced position of the skier’s centre of mass, relative to the ski edge, must be maintained during the application of both turning and edging forces applied to the ski. Monopedal function accommodates both these processes.

As a result of the studies done in 1991 with the research vehicle called the Birdcage, I had come to recognize the importance of a mechanically stable and (physically) competent connection extending from the plantar processes of the foot to the hip joint to facilitate the power of the glutes for balance and edge control.

Yet a further problem relates to the efficient transfer of torque from the lower leg and foot to the footwear. When the leg is rotated inwardly relative to the foot by muscular effort, a torsional load is applied to the foot. Present footwear does not adequately provide support or surfaces on and against which the wearer can transfer biomechanically generated forces such as torque to the footwear. Alternatively, the footwear presents sources of resistance which interfere with the movements necessary to initiate such transfer. It is desirable to provide for appropriate movement and such sources of resistance in order to increase the efficiency of this torque transfer and, in so doing, enhance the turning response of the ski.

Precise coupling of the foot to the footwear is possible because the foot, in weight bearing states, but especially in monopedal function, becomes structurally competent to exert forces in the horizontal plane relative to the sole of the footwear at the points of a triangle formed by the posterior aspect and oblique posterior angles of the heel, the head of the first metatarsal and the head of the fifth metatarsal. In terms of transferring horizontal torsional and vertical forces relative to the sole of the footwear, these points of the triangle become the principal points of contact with the bearing surfaces of the footwear.

A control point in the form of a counter set medial to the head of the first metatarsal is used in order to restrain the first metatarsal against medial movement, such as would occur when internal torsional force is applied to the foot.

In skiing, the mechanics of monopedal function provide a down force acting predominantly through the ball of the foot (which is normally almost centred directly over the ski edge). In concert with transverse (into the turn) torque (pronation) arising from weight bearing on the medial aspect of the foot which torque is stabilized by the obligatory internal rotation of the tibia, the combination of these forces results in control of the edge angle of the ski purely as a result of achieving a position of monopedal stance on the outside foot of the turn.

The edge angle can be either increased or decreased in monopedal function by increasing or decreasing the pressure made to bear on the medial aspect of the foot (turntable rotation) through the main contact points at the heel and ball of the foot via the mechanism of pronation. As medial pressure increases (by glute torque), horizontal torque (relative to the ski) increases through an obligatory increase in the intensity of internal rotation of the tibia. Thus, increasing medial pressure on the plantar aspect of the foot tends to render the edge-set more stable. The ski edge-set will not be lost until either the state of balance is broken or the skier relinquishes the state of monopedal function on the outside ski.

The skiers demonstrating the use of the feet to apply edging forces to the skis at 5’30” in the LaGrandNeve video (2.) clearly show the skiers engaging the second rocker by impulse loading the outside foot and ski and then rotating the outside leg into the turn as they exit the fall line and enter the load phase.

The graphic below shows the device I designed and constructed to train skiers and racers in the movement and muscle patterns required to enable the power of the glutes to be engaged to establish a balance platform under the outside ski and control edge angle as described in my post THE MECHANICS OF BALANCE ON THE OUTSIDE SKI: CLOSED CHAIN OUTSIDE LEG ROTATION. Two forces acting together are required to to create the mechanics that rotate the outside ski on it’s inside edge into the turn.

  1. The center of the weight applied by must be under the ball of the foot and,
  2. Rotational force must be applied to the medial (inner) aspect of the ball of the foot in what I described as Rocker TurnTable Rotation (4.).

If the center of the weight of the body W lies on the anatomical center axis of the foot (under the heel), it will act to oppose turntable rotation applied to the foot by the glutes.

In my next post, I hope to have data from CARV showing the loading pattern that enables the use of Glute Power for edge control.


  1. https://www.engagingmuscles.com/2018/01/01/prevent-injuries/
  2. https://youtu.be/aAJSqzcxrS0
  3. https://wp.me/p3vZhu-2cC
  4. https://wp.me/p3vZhu-2bb

THE SHOCKING TRUTH ABOUT POWER STRAPS REVISITED

Since I started this blog with my first post, A CINDERELLA STORY: THE ‘MYTH’ OF THE PERFECT FIT (1.) on 2013-05-11, THE SHOCKING TRUTH ABOUT POWER STRAPS (2.) is by far the most widely viewed post. This is significant because the content of this post challenges premises that are widely embraced and cited as knowledge that is fundamental to skiing.

The greatest enemy of knowledge is not ignorance; it is the illusion of knowledge.

                                                                                    – attributed to Stephen Hawking

Widely accepted false beliefs can negate incentives to pursue the acquisition of knowledge necessary to understand complex issues that fall outside the limits of established paradigms. A prime example being the ability to balance perfectly on the outside ski.

Observing great skiers like Marc Giardelli or Ingemar and more recently, Mikaela Shiffrin, Lindsey Vonn and Marcel Hirscher balance perfectly on their outside ski suggests it is possible. But uninformed observation in itself does not impart, let alone lead to, an understanding of the associated mechanics, biomechanics and physics of perfect balance on the outside ski as it equates with neuromuscular mediated dynamic balance of triplanar torques acting across the joints of the ankle/foot complex, knee and hip. The intrinsic need of those who regarded as authorities on ski technique to provide plausible explanations for the actions of elite skiers led to the fabrication of terms such as knee angulation that served to create an illusion of knowledge of the mechanism of balance on the outside ski. Knee angulation also provided an effective mechanism with which to demonstrate the mechanics of edge hold.

To raise new questions, new possibilities, to regard old problems from a new angle, requires creative imagination and marks real advance in science.

                                                                                                                          – Albert Einstein

While knee angulation provides a plausible explanation for a mechanism with which to rotate a ski onto it’s edge, it does not explain the mechanism of perfect balance on the outside ski in accordance with Newton’s Laws and the principles of functional anatomy. Solving this mystery required raising new possibilities and creating a new paradigm; one that looked at the function of the human lower limbs from a new perspective with new possibilities.

It took me from 1980 to 1990 to discover how the mechanism of balance on the outside ski works. Trying to impart an understanding of this mechanism to others has presented significant challenges because the illusion of knowledge within the ranks of the ski industry has resulted in a hardened mental model that makes the real mechanism all but invisible. The resulting information bias causes people to seek information that supports what they believe while filtering out information that conflicts with what they believe; i.e.

I don’t need new information on how to balance perfectly on my outside ski because I have been doing this for years and I don’t need to know anything more.

But the reality is, that with rare exception, while elite skiers and even World Cup racers may think they can balance on their outside ski they have no way of recognizing the correct feeling, let alone confirming that they are actually doing what they think they are doing.

I have designed and fabricated a device with which to train skiers/racers to create a platform under their outside ski on which to stand and balance perfectly on. The device can be used to capture what I call a skier’s personal Balance Signature using technologies like CARV. More on this in my next post.


  1. https://wp.me/p3vZhu-p
  2. https://wp.me/p3vZhu-UB