Ski Equipment posts

THE ORIGINS OF KNEE ANGULATION

A recent post on the Foot Collective Facebook page titled, Are you stable on 1 leg?, advises that if  you stand on one leg and look like the top row of pictures in the graphic below (red X), you have a foot & hip that are dysfunctional. This test is best done barefoot on a hard, flat, level surface.

Graphic with permission of Correct Toes

The lower photo (green checkmark) shows the alignment of a leg that is torsionally balanced (stiffened) in the ankle and knee joints. The foot and knee cap align straight ahead and square with the pelvis while the alignment of the knee with the foot, leg and thigh is substantially linear. If you can move to single limb support from two feet, easily achieve this alignment with minimal effort, sustain it for 30 seconds or more, and achieve similar alignment on both left and right legs, you probably have good stability in single limb support.

If you look like the upper photo (red x), it indicates dysfunction and especially a lack of torsional stability in the support limb. The problem is usually caused by constrictive, supportive, cushioned footwear and/or arch supports that, over time, deform feet and weaken the arches. Ski boots are one of the worst offenders in this regard.

If you and when you can achieve good stability in single limb support, you are ready to test the effect of footwear, especially your ski boots. Start by putting on your day to day footwear. Then do the same test on the same surface with each pair of shoes. Work your way up to your ski boots. Adjust the closures of your ski boots to the tension you normally set for skiing. If you are not able to quickly and easily assume the stable position shown in the lower photo (green checkmark), then you know that cause  is the footwear. You can then test the effects of insoles, including ski boot footbeds by removing them from the footwear, placing them on the test surface and moving to single leg support. While not perfect, these tests will help determine the cause of single support limb instability.

In skiing, an unstable outside support leg is characteristics of most skiers and even racers at the World Cup level. It is typically caused by ski boots interfering with the physiological processes that fascially tension the arches and forefoot that create the triplanar torsional stability of the ankle and knee joints of the biokinetic chain necessary to set up a platform under the outside ski to stand and balance on. But instead of addressing the underlying cause, the ski industry invented the term, knee angulation. Knee angulation is indicative of unbalanced torques acting about the uphill edges of the skis, especially the outside ski. When unbalanced torques are present about the edges of a skis or skis, unbalanced torques will also be present across the joints of the lower limb; not a good thing.

The alignment of the knee illustrated in the lower image (green checkmark) is seem as skier or racer enters the fall or rise line with outside leg extended, confirms the existence of a platform under the outside foot on which the skier or racer is balancing on with dynamic balance of torques across the joints of the ankle foot complex and knee. See my post MIKAELA SHIFFRIN AND THE SIDECUT FACTOR – http://wp.me/p3vZhu-1Uu

There is an abundance of information on programs to correct foot deformities,  muscle weakness and imbalances on web sites, YouTube and FaceBook groups such as The Foot Collective, Correct Toes, Feet Freex and the Evidence Based Fitness Academy – EBFA (Dr. Emily Splichal).

The Foot Collective web site has a series of posts on An Introduction to Feet and Footwear (1.) as well as a series of Foot-Casts (2.)

Meantime, a post on a web site called Rewire Me (3.) has an interview with Dr. Emily Splichal called No Shoes Allowed in which she discusses the importance of sensory information entering the body and the need to be able to process this information and handle the load and impact. Dr. Splichal suggests starting the process by getting the body and foot accustomed to sensory information without shoes acting as a barrier.

An excellent free paper with great graphics is The foot core system: a new paradigm for understanding intrinsic foot muscle function (4.)


  1. http://www.thefootcollective.com/an-introduction-to-feet-and-footwear/
  2. http://www.thefootcollective.com/footcast/
  3. https://www.rewireme.com/roses-blog/shoes-allowed/
  4. http://bjsm.bmj.com/content/49/5/290.full#xref-ref-39-1

THE MECHANICS OF BALANCE + BIOMECHANICS ON THE OUTSIDE SKI: WHERE IS GROUND?

This is a revised version of a post I published on February 28, 2017.

It was my intent to discuss the key move in the First Step to Balance on the Outside Ski; Impulse Loading of the Forefoot. However, it has become apparent that it is necessary to preface this subject with a discussion on the source of ground in relation to the outside foot in order to impart an appreciation of why a mechanism is required to extend ground from the running edges of the ski in order to create a platform for a skier to stand and balance on when the outside ski is on its inside edge.

In typical discussions of ski technique and the mechanics, biomechanics and physics of skiing, the prevailing mental model assumes that a skier is in balance (see REVISION TO FEATURE POST: CLARIFICATION OF DEFINITION OF SKIER BALANCE) if they are able to stand upright and exercise a degree of control over their skis. In balance studies performed in gait labs, ground reaction force in the form of stable surface under the entire area of the foot or feet for subjects to stand balance on is assumed. There is no basis to assume this is the case when a ski is on edge because the source of ground is on the wrong side of the platform underfoot.

Mental Models

Mental models are a form of cognitive blindness. Once people assume they know something, they not only don’t question what they believe, they filter out information that conflicts with their mental model. And they typically fail to see the real issue even when it is in plain sight.

A man should look for what is, and not for what he thinks should be.

                                                                                                                 –  Albert Einstein

The Skier Balance Paradox

Even though I quickly became a competent skier soon after I started skiing,  I struggled to hold an edge on firm pistes and especially glare ice. It was disconcerting to see elite skiers hold an edge on ice with minimal effort while making controlled turns. When I sought the advice of the experts, they claimed that holding an edge on ice was matter of sharp edges and/or driving the knees into the hill. When I protested that after trying both and found it harder to hold an edge, the experts claimed that the ability of some skiers to do what I couldn’t was due to superior technique. They were just better skiers. No further explanation was needed.

The inability of experts to explain why a small number of skiers seemed able to balance on their outside ski and hold an edge even on ice provided me with the impetus to look critically at this issue with the objective of formulating an explanation based on principles of applied science.

The only plausible explanation for the ability of a skier to be able to stand and balance on their outside ski when it is on its inside edge is that some source ground (reaction force) must be present under ski that they are using to stand and balance on. Hence, the question, Where is the Ground?

On very hard pistes, ground as a source of reaction force, is limited to the running portion of the inside edge of the outside ski and the small portion of the base adjacent the edge with the edge and base supported on a small shelf cut into the surface of the snow/

In Figure 2.11 on page 26 of his book, Ultimate Skiing, LeMaster explains how the sidecut of a ski creates a smaller radius turn as the edge angle increases.

In Figure 2.12 on the following page, LeMaster shows misaligned applied (green arrow) and ground reaction (purple arrow) forces creating an unbalanced moment of force (yellow counter-clockwise rotation arrow) that  rotates the ski down hill (out of the turn). LeMaster goes on to state that as the skier edges the ski more, the ski bites better. But he fails to offer an explanation as to how the skier can edge a ski more against an unbalanced moment of force acting to reduce the edge angle.

The mechanism that generates a moment of force that opposes the moment force shown by LeMaster in Figure 2.12 and has the effect of extending ground (reaction force) acting along the running length of the edge of the ski  is the subject of this series of posts.

Edge Angle Sidecut FXs

A simple way to acquire an appreciation for the location of ground relative to the outside ski on edge is to make a simple model out of flexible piece of sheet plastic material a few mm thick.

The photo below shows a model I made from a piece of sheet plastic about 8 inches long. The upper portion of the plastic piece has a shorter sidecut with less depth than the sidecut in lower portion of the piece of plastic piece. Both the model and sketches that follow are for illustrative purposes to demonstrate the effects of sidecut geometry on edge angle and a source of ground. Although the basic principles are the same, it is not intended that they be viewed as an accurate representation of actual ski geometries  The symmetrical geometry is for the benefit of the simplifying what is already a complex issue.

sidecut-1

There is a relationship between the depth and length of a sidecut in that the greater the ratio of the depth to the length of a sidecut, the lower will be the edge angle it forms with the surface in relation to the camber radius. In the sketch below, the upper rectangular ski shape will maintain a vertical relationship with a surface regardless of the camber radius.

There is also a relationship between the edge angle a ski with sidecut will form with a uniform surface and the radius of the camber with the edge angle formed with a uniform surface. The edge angle will increase (become more vertical) with a decrease in the radius of the camber. This explains why GS skis that are longer and have less sidecut depth than SL skis can attain much higher edge angles.

side-cut-factor

The photo below shows how the aspect of the model I made with the smallest sidecut ratio forms a steep angle with a uniform surface when bent to sufficient camber radius to allow the sidecut to become compliant with a uniform surface.

sidecut-2

When viewed from the rear of the model, the location of ground in relation to the structure of a ski with sidecut and camber should become readily apparent.

The graphic below shows what a photo taken at a low enough vantage point to the snow would capture looking straight on at a ski carving a turn with its edge compliant with the surface of the snow. This may seem foreign, even extreme to some. But when the edge of a ski is compliant with a uniform surface, the curve of the sidecut becomes linear.

The left image below depicts the schematic model of the ski shown in the second graphic with the camber angle sufficient to make the edge in contact with the uniform surface compliant with it. The angled line represents the surface of the snow. The schematic model of the ski represents the proximate end profile associated with a high load GS turn. A photograph in Figure 1.18 on page 17 of the Skier’s Edge  shows a similar profile in Hermann Maier’s outside (left) ski which is at a very high edge angle.

The graphic on the right shows some penetration of the running surface of the edge of the ski in conjunction with the forces commonly shown in the prevailing mental model that are used to explain how forces acting on the outside are balanced.

 

side-cut-angle

The reality is of the applied forces acting on the ski are shown in the vertical profiles in the graphic below as captured by digitized force plate data. Once the foot is loaded on a surface there is what is called a Center of Pressure as shown by the peaks in all 3 graphs. But when the foot is in compliance with a uniform surface, some pressure is expressed by the entire contact surface of the foot. So, the point application of applied force in opposition to a point application of GRF as depicted in the right hand graphic above is a physical impossibility.

Screen Shot 2015-12-20 at 9.59.06 PM

Viewing a transverse vertical profile of a ski on edge from the perspective of ground as a source of GRF for a skier to stand and balance on puts the issue of skier balance in a whole new, albeit unfamiliar, perspective. But it is a reality that must be dealt with in order to engage in realistic narratives on the subject. Overly simplistic explanations of skier balance attributed to a basic alignment of opposing forces do not serve to advance the sport of skiing as a credible science.

I concur with LeMaster’s position that the platform angle a ski forms with resultant and GR forces must be at 90 degrees or slightly less in order for the edges to grip. In my next post, I’ll start to introduce mechanical principles that explain how this can be accomplished.

It is the ability of racers like Mikaela Shiffrin to stand and balance on their outside that enables them to consistently dominate World Cup competition.

THE MECHANICS OF BALANCE ON THE OUTSIDE SKI: FIRST STEP

In this post, I am going to begin the first of what I expect to be a series of posts on the Two Step Process to Balance on the Outside Ski.

Prelude

Before I start, I am going to caution the reader that they should not expect that the ability to learn and engage the processes responsible for balance on the outside ski to be easy to understand or quick to learn.  Many obstacles stand in the way of the ability to balance on the outside ski. As Benno Nigg’s experiments in the early ’90s at the Human Performance Laboratory at the University of Calgary demonstrated, the human body is highly adaptable. If a person puts their feet in footwear that prevents natural barefoot function, the body will find a best case work around compromise.

This is what happens to skiers when they put their feet in ski boots. As the Polish study showed, over time, the body will adapt. But adaptation always comes at a price.  Some skiers may adapt to constraints of a ski boot to the point where they are considered expert skiers by the prevailing standards. But they typically reach a point where they can no longer advance. Given same ability, the least compromised skiers become the best.

The problem faced by skiers who wish to learn balance on their outside ski (foot) is that the ingrained motor patterns their brain has created as a work around to address the limitations caused by their ski boots can be exceedingly difficult to erase. A skier will typically make some progress only to have their brain revert to motor patterns that have worked in the past when it senses danger. When this happens, the odds are great that even the most athletically gifted skier may have to relearn skiing to some extent. I have seen many graphic examples of this pattern over the past several years in skiers and racers I have worked with.

WARNING: The Mechanics of Balance on the Outside Ski is Not Simple

About the simplest way I can describe the mechanics is that the First Step involves a heel to 1st MPJ rocker loading mechanism while and the Second Step involves an intertia-driven turntable, over-centre mechanism. The mechanics is unified sequence of events. The reason I have broken it two steps is to make it easy to understand the critical nature of the first part of the sequence.

More than 25 years ago, I tried to make the First Step simple and easy to understand with the model I fabricated shown in the photo below and that graphic illustration that follows that shows how the Achilles tendon tensions the Plantar Aponeurosis (aka the Plantar Fascia) and enables foot to pelvic core sequencing. Note the annotation in graphic to Late Stance and (SR) Ski Stance Zone.

In my demonsrations, I  would drop the model on a table from a height of a few inches.  The rotation of the leg of the model would be quickly arrested by simulated isometric contraction of the Achiles. The model and the demonstration failed to garner attention or interest because the importance of the forefoot to foot function was not on the radar screen. Instead, the focus was on the hindfoot and addressing the known looseness of the forefoot associated with the mid stance phase of gait. A late stance phase was not yet part of the gait cycle narrative. The importance of late stance and fascial tensioning of the forefoot to foot function and foot to core sequencing has only recently been recognized.

sr-tripod-demo

Plantar Apo Dynamics

First Step

The First Step is to tension the biokinetic chain that extends from the MPJs of the foot to the pelvis. The timing of this event, which is critical, will be discussed in a later post.

The key move is the loading of the outside foot. This should happen in the top of the turn as the fall line is approached. This is the point where a skier should become the tallest in relation to the snow. At the end of a turn (in the bottom) is where a skier should be lowest.

It is not possible to replicate the loading move except when skiing because of the dynamic nature of the 3-dimensional forces associated with ski maneuvers. But the forefoot loading move that creates fascial tension the forefoot is essentially the same move we make when we move forward on the stance foot in walking in preparation to take a step. Once the foot has adapted to the ground, forward rotation of the shank (ankle flexion) is arrested by isometric contraction of the calf muscle. At this point, further forward movement of the torso occurs through knee extension in what amounts to a heel to ball of the foot rocker mechanism; i.e. a forward and downward action that applies force to the ground to prime the energy return foot spring in preparation to propel the body forward.
One way to get a feel for this mechanism is to stand sideways across the bottom of a stair and place one foot on the first tread about a whole foot length ahead of the foot on the floor. The knee of the leg on the floor should have slight bend so the calf muscle is in isometric contraction (SR Stance). The angle of the shank of the foot on the tread should be a little less than 90 degrees in terms of dorsiflexion. From this base position, the torso is projected forward in order to achieve a position of balance over the foot on the first tread. This is roughly what the loading move should feel like in skiing that is made as the fall line is approached. Once a feel for this has been acquired I can discuss how this integrates with rotation of the leg.
It is important to not have the ankle flexed for the above exercise because the ski boot limits ankle flexion. At the start of the transition at the end of a turn, the weight will be under the heel of the inside (uphill) foot. It is also important that the calf muscle of the foot on the stair tread go into isometric contraction so that further forward movement of the torso occurs through knee extension.
In a ski turn, the forefoot loading move is one of a quick heel to 1st MPJ forward rocker knee extension pulse that loads the ball of the foot (1st MPJ). Loading of the 1st MPJ (ball of the foot) is caused by forward movement of the torso (CoM), not plantarflexion. This loading move is made in the top of a turn as the fall line (aka rise line) is approached. The window in which to make this move is narrow and the time required  to complete the move, brief.
If you watch video of Shiffrin slowed to 0.25 normal speed or step the video in frame-by-frame, you will clearly see her make this loading pulse which usually involves a lifting of the fore-body of the old outside ski due to swing leg reaction force.
In my next post, I will discuss Step Two.

 

 

 

 

 

 

 

 

 

 

 

WHY YOUNG TALENTED SKI RACERS FAIL AND EVENTUALLY QUIT RACING

The impetus for the subject of this post came from interest in my post FEATURE POST: MIKAELA SHIFFRIN: THE POWER OF SHEAR FORCE and an article (1.) in the  February 14, 2017 edition of Ski Racing by sports psychologist, Dr. Jim Taylor.

Taylor’s article, aimed at U14 and younger ski racers, points out that this is the age where the foundations are laid which often determine how well a racer does and especially how long they will remain in ski racing. Taylor cites statistics that show that qualifying for Topolino or the Whistler Cup (international competitions for 13-15 year olds) isn’t highly predictive of success even five years later. Specifically, only 25% of those who qualified for those race series later earned a spot on the USST. Moreover, 35% were off the elite ski racing radar within four years; some before their 18th birthday. The problem, that is the focus of Taylor’s article, is that parents enter what he calls the “too” zone, where the parents of kids, who are 11 years old or younger, have become “too” important to the parents who have become “too” invested in how their kids do (or don’t do).

The question I have is what events preceded parents getting to the “too” zone? I have seen more than one situation where a child who started ski racing at a very young age and who was considered to be a child ski racing prodigy, had a promising racing career unravel soon after reaching their teens. Why? What, changes happened that could have caused such a tectonic shift?

Let’s go back to beginning when a racer first showed promise. Many racers demonstrate prowess when they are only 4 or 5 years old. Often, one or both parents are elite skiers and one or both may have raced. In such a situation a young racer would have had an excellent role model that would have helped them  become comfortable by following one or both of their parents down the ski hill. But there are also other important factors in a young racer’s favour:

  • They are usually light weight.
  • They are usually short in stature.
  • Their muscles and skeleton are not yet fully developed.
  • Their feet are usually small.
  • They may lack fear.

A significant factor is that young racers often learn to ski in their mother’s ski boots or boots that would be considered too big for their feet if they were older. The implications? Young racers acquire a kinesthetic sense of how to stand in their boots in what I call the SR (stretch relfex) Stance (3. to 10.). As a consequence, they acquire dynamic stability that provides superior edge and ski control while enabling the myotatic stretch reflex balance response.

The authors of a Polish study on skier balance (2.) cite three types of postural reactions to external forces that disturb equilibrium and can cause the body to lose balance can be observed.

  1. The first reaction is the myotatic stretch reflex, which appears in response to changes in the position of the ankle joints, and is recorded in the triceps surae muscles. This is the earliest mechanism, which increases the activity of the muscles surrounding a joint that is subject to destabilization. Spinal  reflex triggered by the myotatic stretch reflex response causes the muscle to contract resulting in the stiffening of the surrounding joints as a response to the stimulus that has disturbed the balance. For example, changes in the angle of the joints of the lower limbs are followed by a reflexive (fascial) tensioning of adjacent muscles. The subsequent release of the reaction prevents excessive mobility of the joints and stabilises the posture once again.
  2. The next reflex in the process of balancing is the balance-correcting response, which is evoked in response to a strongly destabilising stimulus. This reactive response has a multi-muscle range, and occurs almost simultaneously in the muscles of the lower limbs, torso and neck, while the mechanisms that initiate the reaction are centrally coordinated.
  3. The last of the three types of muscular reaction is the balance-stabilising response. In a situation of a sudden loss of balance, a myotatic stretch reflex first occurs and is then is followed by a balance correcting response, which prevents or attempts to prevent a fall.

I call these balance responses green (postural reaction 1), orange (postural reaction 2) and red (postural reaction 3).

As young racers enter their teens, a number of significant changes have occurred.

  1. They are much heavier.
  2. They have grown in height
  3. Their muscles and skeleton are more developed.
  4. Their feet have grown larger and are more defined.

It is about this time in what is appearing to be a child’s promising racing career, that parents turn to the experts in a well intended effort to maximize their child’s chances of success. One of the key things parents often do is to get race boots for their child and have them customized with footbeds, form-fit liners and increasingly, heat molded shells. The process typically involves what is called race fit wherein ski boots are downsized to the smallest possible shell that the feet can be squeezed into. Custom footbeds or orthotics are considered an essential integral component of race fit because they prevent the foot from spreading and elongating. But this actually interferes with or even prevents the fascial tensioning process that enables dynamic stability and the myotatic reflex associated with the ultra high speed spinal reflex balance response (11).

No longer able to use the myotatic reflex (Green = Normal) balance response, the CNS shifts to Level 2 (Orange = Caution) or even Level 3 (Red = DANGER).

What happens next? The young racer starts to become intimidated by courses and conditions they were previously comfortable with. When this happens, their brain senses imminent danger of serious injury or worse and resorts to what I call the Survival Technique. Survival becomes the priority of the CNS at the expense of speed. Racers start losing ground to lesser racers. Not understanding the cause, parents and coaches can start pushing the child in an effort to get results. The more the child tries, the worse things get. When this happens, frustration sets in. Eventually, the child no longer wants to race. Defeated by their boots, the child eventually quits ski racing and takes up some other sport.

Unfortunately, this story is all “too” common. This is also one of the “toos”.


  1. What Young Ski Racers Need – http://www.drjimtaylor.com/4.0/young-ski-racers-need-dont-need/
  2. 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.
  3. THE SR STANCE: SURFACE EFFECTS,
  4. THE SR STANCE AND TOTAL BODY CORE INTEGRATION
  5. SR STANCE: ROUNDING THE BACK AND SHOULDERS
  6. THE SR STANCE: AFFECT OF JOINT ANGLES ON COM
  7. LEARN THE SR STANCE IN 3 EASY STEPS
  8. SR: ACHILLES-ARCH TENSION
  9. SR STANCE BASICS: ECCENTRIC MUSCLE POWER AND THE STRETCH REFLEX
  10. I-C-E: SR
  11. INNATE FLOW BALANCE

FEATURE POST – THE PURPOSE OF THE SKI BOOT

After the skier, the most important piece of equipment in the skier/ski equipment system is the ski boot.

The conventional ski boot has the biggest influence on who rises to the top technically. Those who are able to connect with the snow through their feet so as to enable the use of their natural  mechanisms of balance are unlikely to lose the resulting kinaesthetic association. When these skiers try on a new boot, they usually know within seconds whether it will work for them or not without even having to go on snow. But for nine out of ten never-evers, the initial skiing experience involves such a severe disconnect from familiar sensations, especially a compromise of balance so unsettling that their first day on skis is also their last day.

It is for this very reason that the consensus of the previously cited authorities is that a ski boot should be adapted to the functional requirements of the user and not the other way around. It is particularly important that the ski boot not incur functional compromises on the part of the user.

A properly designed ski boot should enable the user to utilize mechanisms of ski control that are complimentary to and consistent with, their innate mechanisms of balance.

THE PURPOSE OF THE SKI BOOT, was originally published on February 9, 2016. The entire post can be viewed at  – http://wp.me/p3vZhu-1lX

 

RX FOR SORE KNEES? LOW FAT

The recent article by Jackson Hogen, A (Slight) Swing Back to Sanity What We Learned at the SIA – http://www.realskiers.com/NEWSLETTERS/sanity.htm), has implications for where I am going with Whistler Ski Pro, Matt. Hogen’s article prompted me to delay my post on the problems with ski boots and add my views that resonate with his.

In his article,  Hogen relates what he saw at the annual ski show in Denver, Colorado as a welcome trend; new ski models for next season will be less than 85 mm underfoot. After reaching widths that could best be described as grossly obese, skis have gone on a low fat diet. Next season, slim is in. Fat is no longer where it’s at, if it ever really was. Why is this trend important and why does it matter?

Like Hogen, I have witnessed the effect of wide skis on technique and it is not good. Hogen expresses the view that once skiers are on boards so broad they can’t comfortably tip them to a high edge angle, the chances of them ever acquiring this foundational skill are virtually nil. I agree. But the issue is more than just high edge angles. It is the ability to apply forces with the foot at turn initiation that rotate or tip the new outside ski onto its inside edge, period. It’s not just skis, boots are equally to blame for the demise of technical skills. In my post, FAILURE TO CARVE  (https://skimoves.me/2016/01/17/failure-to-carve/), I reported on the feature article, To Bend a Ski, in January 2016 Ski Magazine. In the article, PSIA instructors estimated that 9 out of 10 skiers don’t carve their turns. From what I have witnessed on the slopes of Whistler-Blackcomb, these past few seasons, that number is probably more like 1 in 100 and includes a lot of ski pros.

Hogen also commented that most skiers remain unaware that a wide ski on hard snow poses inherently higher risks of knee discomfort and increases the odds of a serious knee injury. In the fall of 2014, Kim Hewson, MD, and I coined the term Fat Ski Syndrome. When Dr. Hewson warned about the stress on the knee caused by fat skis in the November 2014 post, FAT SKI SYNDROME (https://skimoves.me/2014/11/26/fat-ski-syndrome/), he and I were lone voices calling out in the ski world about the potential dangers of fat skis on hard pistes. Now Hogen has chimed in.

The big question is why are most skiers unaware of the inherently higher risks of knee discomfort and increased odds of serious knee injury associated with the use wide skis on hard snow? Perhaps, because no one is telling them? It is hard to find even innocuous products today without encountering warnings on the package about the potential for the product to cause injury, no matter how slight. This is true of even toothpicks and cotton swabs. Skiing and especially ski equipment, seems to be operating in a parallel universe or perhaps a product liability vacuum where the more radical a product, the more ski magazines and ski enthusiasts welcome it as cutting-edge innovation. The only apparent upper limit to the width of fats seemed to be the width between a skiers feet. Risk? What’s that?

The problem is that when those who endorse or promote a product, don’t disclose what should be, or at the very least, what ought to be, an obvious risk like potentially injurious torque on the foot and leg, from skis over a certain width underfoot, the consumer reasonably assumes there are no risks. For the same reason, when those who endorse or promote products like ski boots that have been criticized by independent scientists such as Dr. Stussi, Dr. Pfieffer, Dr Schaff and others, as not founded on principles of anatomy and that loading the ankle sends the stress of skiing up the leg to the rather delicate knee, and those who endorse or promote products, fail to respond to, let alone address these issues,  the consumer reasonably assumes that such products are supported by appropriate science and that there are no significant risks associated with their use.

Hogen ends his article by stating that the reinvestment in the Frontside and Technical categories inspires hope that Americans will rediscover the joys of riding a narrower ski, such as speed control, trajectory management, balance and timing, more succinctly summarized as “skill.” Unfortunately, I tend to agree with Hogen’s statement that once skiers learn a coping mechanism; one that does an end run around sound foundational technical skills, the odds of a skier acquiring such skills in the future is virtually nil.

In working with skiers like Matt, Morgan and racer X, they often have video documentation, notes and records of equipment dating back years. In the case of racer X, I have been provided with copies of hundreds of videos dating back more than 10 years. These have enabled me to study the effect of problematic equipment that precipitated problematic coaching. I was even able to clearly see evidence of a back injury on the racer’s technique. A series of adverse changes over a number of years derailed a promising career to the point where the racer wanted to quit. As Matt recognized, talented athletes are able to fake it and look like the real deal. Race results tell a different story. They can’t be faked.

As I will illustrate with Matt, fixing a skier’s boots is one thing. Erasing the skiing hard drive in the brain and reprogramming and rebooting it with a technique of not just sound, but superior technical skills, is a long, slow process; one that is seldom a straight line. It is unlikely that the average skier has the motivation to pursue such an arduous journey. This being the case, ski technique will continue its downhill descent in spite of any low fat ski diet.

 

THE KNEE INJURY MECHANISM PARADOX

In response to a feature article, ‘Busted knees and broken legs’, that ran recently in one of Whistler’s weekly newsmagazines, I wrote the letter to the editor that follows below.

As seems typical of articles on the subject of knee injuries, the take home message to the reader is that most knee injuries are caused by skier error.  Skiers fall improperly or try to pull themselves forward from a sitting back position. This creates what is called a drawer shift mechanism that pulls the femur back against the tibia at the knee joint rupturing the ACL. While this mechanism is definitely a factor, as Tone Bere of the Oslo Sports Trauma Research Center noted, knee injuries do occur before a fall or without a racer falling after a knee injury is sustained. When a knee injury does occur before a fall, the knee injury invariably causes the fall. This was also noted in the paper I cited in my post GS AND KNEE INJURIES – CONNECTING THE DOTS – https://skimoves.me/2014/05/29/gs-and-knee-inju…necting-the-dots/

Articles such as the one that appeared in the Whistler newsmagazine, also infer that progress has been made in equipment and that skiing is much safer than it was decades ago. This position is contradicted by studies such as Bere’s that found that 1 in 3 WC racers are injured each year. What I have never seen mentioned in any consumer article on ski injuries, is the fact that not only has the modern plastic ski boot never undergone any product safety testing intended to determine the effect on the consumer that I am aware of, but that plastic boot was cited by a number of preeminent authorities in the Shoe in Sport, published in 1987, as being unphysiologic and not designed along anatomical principles.

In the Shoe in Sport, Dr. E. Stussi,  Member of GOTS – Chief of Biomechanical Laboratory ETH, Zurich, Switzerland, commented,

The increasing stiffness of the flexion joint of the boot decreases the ability of the ankle to compensate for the load and places the entire load on the knee. Improvements in the load acting on the ankle make it biomechanically very likely that the problems arising in the rather delicate knee joint will increase.

Dr. med. H.W. Bar, Orthopedics-Sportsmedicine, member of GOTS, Murnau, West Germany, commented,

Investigations by Pfeiffer have shown that the foot maintains some spontaneous mobility in the ski boot. Thus the total immobilization by foam injection or compression by tight buckles is unphysiologic. Only in the case of major congenital or post traumatic deformities should foam injection with elastic plastic materials be used to provide a satisfactory fixation of the foot in the boot.

In effect, the comments of experts in the field such as Dr. E. Stussi, Dr. med. H.W. Bar, Professor  Dr. M. Pfeiffer, were putting the industry on notice that design of the plastic ski boot was problematic.

Seth Masia provides an excellent overview of the ‘anything goes so long as it sells’, marketing approach of the ’70s in his article,  Almost Hits, Mostly Misses, Skiing Heritage 2005 – Google books

A copy of The Shoe in Sport was given to me in 1988 by two German radiologists who were both keen skiers. They were aware of the deficiencies of the conventional boot and had witnessed the injuries. They heard that I was working on a new ski boot design and offered their assistance in designing a boot based on principles of functional anatomy. As the University of Ottawa papers noted, technologies did not exist prior to 1997 that enabled the study of the effects of a ski boot on a user during actual ski maneuvers.  In going forward with the ski boot project in 1991, I was aware of the issues raised in Shoe in Sport. Given that I was starting from a clean sheet of paper so to speak,  if I could not overcome the problems and produce a design based on principles of functional anatomy, one that would be supported and even endorsed by accredited scientists, I could not go forward. I had to get it right. Otherwise, there was no point in proceeding.

The problem for the industry is that I not only succeeded, but the Birdcage studies identified key markers of ski control and balance that can easily be put into algorithm that can assess sound ski technique and be applied to teaching softwares that guide skier learning. In the last 5 years, the introduction of small motion and force sensors has exploded. Used in conjunction with a smartphone app, technologies are now possible that will not only capture and interpret the exchange of forces between the foot of a user and the snow, but act in the capacity of a black box or flight recorder in acquiring a digital record of all events associated with an injury. I foresaw this possibility back in 1991.

As my letter to the editor says…………………..

THE TRUTH IS OUT THERE

In response to the cover feature Pique ran Jan. 21 I wanted to share that in 2013, PhD candidate, Tone Bere of the Oslo Sports Trauma Research Center, asked in Mechanisms of injuries in World Cup alpine skiing” (March 2013), why one out of every three elite alpine skiers is injured during the five month ski season.

Bere’s research found that ACL injuries that occur before a fall, or without falling, develop rapidly due to high skiing speeds and that there is no single solution that will prevent them.

This is due to the presence of phantom torques on the outside leg of a turn that can bend and rotate the leg and shear off the ACL far faster than current binding technologies can detect, let alone react to.

The predisposition of a skier to knee sprains is exacerbated by the fact that tightly-fitted rigid plastic ski boots transfer the forces of skiing up the leg to the knee. The tighter, more precise the fit, the greater the transfer of forces from the ski to the knee.

Prior to the widespread acceptance of the new rigid, plastic ski boot in the early ’70s, knee injuries in skiing were rare. Broken legs occupied centre stage. The introduction of the safety release binding changed that. But the jubilation from the dramatic decline in broken legs had barely subsided when a worse problem began to emerge — severe knee sprains, especially to the ACL.

Contrary to what many believe, there has never been support in sound principles of science for the idea of clamping the foot and leg in what amounts to an orthopedic splint and then attaching a large lever to the boot and applying stress to it.

When the authoritative Shoe In Sport was published in 1987, preeminent experts raised red flags about the effect of the new ski boots on knee injuries. Dr. M. Pfeiffer of Institute for the Athletic Science spoke from the literal epicenter of the ski world at the University of Salzburg when he said, “The ski boot and its shaft must be adapted to the technical skill of the skier, and the technical skills of the skier must be adapted to the preexisting biomechanical functions of the leg and the foot.”

His comments were intended to spur the development of a ski boot designed along anatomical principles, a goal that remains to be achieved even today.

Meantime, Dr. E. Stussi, member of GOTS, chief of Biomechanical Laboratory ETH stated, “Improvements in the load acting on the ankle (meaning a tighter fitting boot) make it very likely that the problems arising in the rather delicate knee joint will increase.” In other words, Dr. Stussi stated that if the industry kept improving the fit of ski boots, knee injuries would increase.

But the industry kept right on improving the fit of the ski boot and knee injuries increased exactly as Dr. Stussi had predicted. Rather than heed the warnings of experts like Dr Stussi and Dr. Pfeiffer, the industry represented the perfect fit, as the Holy Grail with the apparent end objective of transferring 100 per cent of the potentially injurious forces of skiing to the knee,

In 1991, at the request of Canada’s most successful alpine skier, Steve Podborski, I agreed to try and develop a new ski boot. But I agreed on the condition that we would do the prudent and responsible thing, engage scientists with the appropriate expertise to provide oversight and guidance.

My mission was to develop a ski boot that made skiing easier, but more important, made skiing safer. Podborski had competed and won in 1980 on some of the world’s most difficult downhill courses mere months after reconstructive knee surgery using an innovative in-boot technology I had invented. It reduced the stress on his knee to the point where he could compete and win whereas that was impossible with a conventional boot. I knew I was headed in the right direction.

But I wanted accredited experts to confirm that I was. Our company, spent close to $140,000 on studies intended to prove or disprove my theory. The studies proved my theory to be correct.

In 1995, I was nominated for the gold medal in the categories of applied science and engineering in the B.C. Science and Engineering Awards by the industrial technology advisor to the National Research Council of Canada. In order to go forward, a nomination must garner support from a candidate’s peers in the field. In his letter of support, Dr. Robert Colborne, assistant Professor of Anatomy at the University of Saskatchewan, an expert in the human lower limbs, said the following.

“Recent considerations of safety in skiing highlight the importance of dissipating ground reaction forces through the joints of the foot and ankle, which are multi-axial and able to absorb significant energy without sustaining injury.

“Mr. MacPhail’s design enables the musculature of the lower limb to absorb these forces before they are directed into the ligaments of the knee, thus protecting this relatively stiff tissues from injury.”

In his letter of support, Alex Sochaniwsky, P. Eng., the biomedical engineer who designed the research vehicle, wrote the software (where none existed) and conducted the studies said,

The design and development strategies used by David MacPhail are very holistic in nature, placing the human system as the central and most critical component in the biomechanical system. His intent is to maximize human performance and efficiency, while foremost preserving the well-being and safety of the users and minimizing biomechanical compromises.

That is where I drew a line in the snow in 1991, “foremost preserving the well-being and safety of the users.”

I am still waiting for others to join me.

David MacPhail