Skier Stance

WHY STANCE TRAINING IS ESSENTIAL

When readers click on my blog address at skimoves.me, analytics give me a hierarchy of the countries with the most views and the most popular posts in ascending order. This helps me identify which content resonates most strongly with viewers and which content draws a blank.

As I write this post, the top five countries are the US followed by Croatia, the United Kingdom, Slovakia and France.

The most viewed post today is THE SHOCKING TRUTH ABOUT POWER STRAPS; far and away the most popular post I have published to date. But the most important posts by far that I have ever written, A DEVICE TO DETERMINE OPTIMAL PERSONAL RAMP ANGLE and STANCE MUSCLE TENSIONING SEQUENCE EXERCISE barely sputtered in comparison. This strongly suggests that far from just some small gaps in the knowledge base skiing is founded on, massive craters exist.

Arguably the most important aspect of skiing is a strong stance. Any variance in the fore-aft angle of  the plane of support under the feet and the plane of the base of the ski has significant impact on stance. Yet these subjects are barely blips on the Doppler Radar of the ski industry.

Since I started the dynamic ramp angle assessment project a few weeks ago I have found that when asked to do so, it is rare for a skier of any ability to be able to assume a strong ski stance in an off the ski hill environment. Even when a skier  skis with a relatively strong stance, they seem to lack a sense of what a strong stance feels like. Because of this, they lack the ability to consciously replicate a strong stance. If asked to do so, they would be unable to coach a skier in the sequence of events that I described in my last post

In the dynamic ramp angle assessment project, I  have also observed that skiers with with a boot/binding ramp angle greater than 2.8 degrees appear to have become accustomed to the associated unstable, dysfunctional feeling and identify with it as ‘normal’. Before I can test them, I have to spend time coaching them into the correct stance because it feels unnatural to them.

When I go back and forth between a strong functional stance on a flat, hard level surface to a stance on the dynamic ramp angle device set to an angle of 4 degrees, I can get close to the same angles of ankle, knee and hip. But when I do, I feel strong tension, stiffness and even pain in my mid to lower back which is  common in some skiers and even racers.

Based on results to date with the dynamic ramp angle device, it appears as if strong skiers ski best with ramp angles close to zero. But depending on their sense of balance and athletic ability, they may have a wide range in which they sense little difference on the effect of ramp angle until they approach the upper limit of stability. While they may be able to ski well with a ramp angle close to the maximum limit of stability, ramp angles much above 1.2 to 1.5 degrees may not offer any benefits. This can only be tested on skis where balance is tested by dynamic forces which cannot be replicated in a static setting.

Issues affecting skier stance were discussed in detail in my post, THE SHOCKING TRUTH ABOUT POWER STRAPS. Here are the excerpts I posted from the chapter on The Ski Boot in the book, The Shoe in Sport (1989), published in German in 1987 as Der Schuh Im Sport– ISNB 0-8151-7814-X

“If flexion resistance stays the same over the entire range of flexion of the ski boot, the resulting flexion on the tibia will be decreased. With respect to the safety of the knee, however, this is a very poor solution. 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”. – Biomechanical Considerations of the Ski Boot (Alpine) – Dr. E. Stussi,  Member of GOTS – Chief of Biomechanical Laboratory ETH, Zurich, Switzerland

“The shaft of the boot should provide the leg with good support, but not with great resistance for about two thirds of the possible arc, i.e., (14 degrees) 20 to 22 degrees. Up to that point, the normal, physiologic function of the ankle should not be impeded”.

“Previous misconceptions concerning its role in absorbing energy must be replaced by the realization that shaft pressure generates impulses affecting the motion patterns of the upper body, which in turn profoundly affect acceleration and balance.

“When the lateral stability of the shaft (the leg) is properly maintained, the forces acting in the sagittal direction should not be merely passive but should be the result of active muscle participation and tonic muscular tension. If muscular function is inhibited in the ankle area, greater loads will be placed on the knee”. – Kinematics of the Foot in the Ski Boot – Professor  Dr. M. Pfeiffer – Institute for the Athletic Science, University of Salzburg, Salzburg, Austria

It has been over 40 years since international authorities on sports science and safety raised red flags concerning the adverse effects of ski boots design and construction on skier stance, balance and the potential to cause or contribute to injury. It is time that their concerns were taken seriously and acted on. Research on stance and the effect of such things as zeppa and delta ramp angles is urgently needed.

 

ISOMETRIC STANCE MUSCLE TENSIONING SEQUENCE

Tensegrity

Tens(ion) + (Int)egrity 

The optimal ramp angle, as determined by the dynamic ramp device, is based on a stance predicated on the principles of Biotensegrity.

Fascial continuity suggests that the myofascia acts like an adjustable tensegrity around the skeleton – a continuous inward pulling tensional network like the elastics, with the bones acting like the struts in the tensegrity model, pushing out against the restricting ‘rubber bands: Tom Myers, Anatomy Trains (1.)

A ski stance based on the principles of bio-tensegrity must be learned and rehearsed in a step-by-step process. It is neither natural or intuitive although elite skiers and racers such as Shiffrin and Hirscher appear to have acquired the elements of Biotensegrity. Assuming a group of racers of equal athletic ability, the odds will favour those whose stance is based on Biotensegrity.

In a ski stance based on bio-tensegrity, tension in the arches of the feet extends to from the balls of the feet to the palms of the hands holding the poles.

  1. Start by standing barefoot on a hard flat floor or surface in a controlled environment such as your home. Where possible, use the same surface and place to rehearse the stance. If you have constructed a dynamic ramp assessment device, use this with the top plate set to level.
  2. Stand upright at attention. You should feel most of the weight under your  heels and less weight across the balls of your feet. This is normal. The fore-aft weight distribution is actually 50-50 heel to forefoot. But because the weight of the body is spread across the balls of the feet and along the outer aspect behind the small toes, more weight is sensed under the heels. Stand so your weight is distributed equally between both feet.
  3. Relax your hamstrings (in your thighs) and let your torso drop towards the floor.  Your knees will move forward as they flex and your ankles will dorsiflex. Your ankles should stop dorsiflexing on their own when the front of your knee caps are aligned approximately over the balls of your feet. This is the point where the tension in your soleus (calf muscle) peaks with the tension in plantar ligament of your arches. You should feel about the same pressure under the balls of your feet as you feel under your heels. But it should feel as if the circle of pressure under your heels has gotten bigger and your feet are more connected or integrated with the floor. I call this ‘rooted’ because it should feel as if your feet have sunk into the floor.
  4. While keeping your upper body erect, move slightly forward in the hips. You will quickly reach a point where you start to become unstable and feel as if you would fall forward onto your face if you moved farther forward in the hips. When you get to this point your big toes should press down on the floor on their own to try stabilize you. This is the forward limit of stability.
  5. Now move rearward in the hips until you start to feel the same instability. This is the rearmost limit of stability.
  6. Now bend forward from the waist. Do not curl your back. Bend from the hip sockets for the thigh bone (femur). This movement is actually thigh flexion. Lift your thigh to get the right feeling. As you bend forward from the waist, your buttocks will move rearward and upward as your ankles and knees straighten.  Reach forward with your arms as if you were going to hug a large barrel in front of you. Make sure the palms of your hands are facing each other with fingers curled and pointing towards each other.
  7. Find the place where your arms and head feel neutral to your spine. As your arms come into position you should feel your abdominal core and muscles in your back acquire tension. Slings Isometric stance
  8. Experiment by moving forward and rearward in the pelvis. As you move forward in the pelvis the pressure should increase under the balls of your feet. But you should not feel unstable. If anything, you should feel stronger and more stable. You should feel as if the weight of your head and shoulders is pressing your feet down into the floor.
  9. Increase the bend at your waist while keeping the pressure on the balls of your feet and heels until the top of your head is down by your knees. You should still feel very strong and stable in the feet. This is the lowermost limit of waist flexion.

Once you have acquired a kinesthetic sense of the bio-integrity of foot to hand tension, a sense of stability while pulsing the torso vertically up and down over the feet confirms a state of bio-tensegrity.

The photo below is of simple model I designed and constructed in 1993 to illustrate the basic concept of bottom up Biotensegrity and how the degree of passive tension in the plantar ligament of the arches of the feet and the vertical biokinetic chain is driven by the compression from weight of COM stacked over the foot.

The graphic below shows the continuum of tension from the balls of the feet to the opposite shoulders through the mechanism of the oblique posterior sling.

In my next post I will discuss what I term the NABOSO Effect.


  1. https://www.anatomytrains.com/fascia/tensegrity/

A FIVE STEP SKIER PERFORMANCE PROGRAM

Almost 40 years ago to the day, the head of the Whistler Pro Patrol, whose boots I had worked on, introduced me to Nancy Greene in the Roundhouse restaurant on top of Whistler Mountain. The rest is, as they say, history. Nancy asked me if I would work on her ski boots. She was so impressed by the results of my work that she approached the National Ski Team to make arrangements for me to work with some of Canada’s best racers.

Recently, while going through some archived files, I found copies of Nancy’s communication with the Program Director of the National Ski Team, Andrzej Kozbial. When Nancy approached me about working with our National Team, I stressed to her that I did not see any potential arrangement with the team as a job opportunity but instead as a vehicle where I could gain further experience and knowledge while providing a crucial service to the team and furthering the sport of skiing.

The graphic below is an excerpt copied from Nancy’s first letter of April 26, 1978 to the National Ski Team Program Director.

At the time that I wrote my US Patent 5,265,350 in early 1992, the intent and purpose of the detailed and lengthy specification was to provide a repository of the knowledge I had acquired to date to serve as a legacy for skiers and skiing to help advance the sport. While this information was in support of the inventions disclosed in the patent, the majority of the information was not subject to protection under the terms of the patent. The information was open access to the world. This was my intent.

In spring of 2000, I formed a company with 2 partners for the 2000-2001 ski season called Synergy Sports Performance Consultants Ltd. The objective of the venture was to gain further experience and knowledge and create a model that could be used as a template for future skier performance programs.

The following series of graphics are from Power Point presentations synergy made to ski schools.

The following graphic is the poster that described the synergy 5 Step Performance Program.

5 Step Performance Program description

The synergy Analysis Program looks at how your body interfaces with your ski equipment; primarily your footbeds and boots because this is the connection to your equipment and through it to the snow.

Synergy offers the program as a package made up of 5 components. They can either be taken as the complete package [recommended], several components or steps at once, or one component at time. Synergy recommends that you begin at step 1 and follow the sequence in numerical order. But the order can be arranged however you wish to suit your needs. The choice is yours.

1.Biomechanical Assessment

Good foot function is the key to control. That’s why the first thing we thing we assess is your biomechanical function. What that means is that we look at how well your foot and lower limb works. The examination is done by a podiatrist who looks at how your foot functions and how the lower limbs all connect.  Then we see how effectively your feet interface with the ground by putting you on insoles that read the pressures under your feet. We coach you through some balance movements while we watch how your foot functions while our computer records the results

2. Footbed Assessment

Footbeds can have a positive, neutral or negative effect on the function of your feet.

That’s why the next thing we check is how your foot interfaces with your footbed or orthotic.  We make sure that it allows your foot to function as well as it should without one.  And if your foot needs some assistance for optimal function we make sure the footbed is helping your foot do what it needs to do.

3. Ski Boot Assessment

Now that your foot is functioning optimally we make sure your ski boot lets it keep functioning. We conduct a thorough examination of your boot and provide you with a report that tells you how your boot is affecting your performance. Most important, we tell you what has to be done to fix the problem.

4. Kinesthetic Training

Skiing is about making the right moves. Kinesthetic Training is next. It teaches you how to tell when your body is making those moves. What is Kinesthetic Training? In simple terms it means to train your body to associate a feeling or sense with the right movements made at the right time. It is feeling and bringing about an awareness so you know when you are doing it right because we have taken you there and you have felt it. A picture may be worth a thousand words, but in skiing a feeling is worth a thousand pictures. We bring you to understand what you should feel in your foot at the start of the turn and then what it feels like to settle and balance onto the foot that drives the ski. By acquiring this sense you become more aware of how to allow your foot to transfer energy directly to the edge of the ski by using the body the way it was designed to be used. Remember, your body was not made to be a lever.

5. On-Hill Data Collection

This is where everything comes together. We move to the ski hill for this part of the package. We meet up top on Whistler or Blackcomb Mountain. We put our pressure insoles in your ski boots.  A pair of cables from the insoles goes up your ski pants where it connects to the data box [a kind of mini computer] we attached to your waistband.  Then we go out for a run on moderate, groomed terrain.  We record data in three takes in medium radius turns at a speed you are most comfortable with. While this is happening we videotape your skiing. Then we head into the lodge and synchronize the video with your foot pressure data. When this is done we watch your foot function in your boots on the computer screen on one side while we study your ski video on the other side of the screen. This way we confirm that your foot is functioning optimally as confirmed by analyzing your movement patterns and the timing of your skills.

My next post will be on the synergy Boot Assessment program.

 

BEYOND BIOMECHANICS BY DR. EMILY SPLICHAL

The following post appeared on the Evidence Based Fitness Academy (EBFA) fitness blog on February 6, 2018 under the title Beyond Biomechanics | Addressing Foot Pain with Sensory Stimulation (1.).

I have reproduced the post with the kind permission of Dr. Emily Splichal under the title Beyond Biomechanics by Dr. Emily Splichal because her emphasis on the role of sensory stimulation of the plantar foot on foot, lower limb and function of the entire body has both direct application to and implications for, skiing.

I have a theory on what I call The NABOSO Effect that explains how I think NABOSO insoles improve dynamic stability in the biokinetic chain that I will discuss in a future post. I have been testing NABOSO 1.0 and 1.5 for months.


Beyond Biomechanics | Addressing Foot Pain with Sensory Stimulation – by Dr. Emily Splichal

I want you to picture a human foot.   Now picture a person standing barefoot, and then walking barefoot.   Do you see the foot striking the ground and flexing under impact, only to re-stabilize and push off just a few milliseconds later?

Often times when we think of human movement we can’t help but to be drawn to the thought of joints moving and muscles contracting.   Or in the case of foot function we are quick to consider the mechanics of flat feet, high arches, pronation and supination.   However when we delve deeper into the science of human movement there is more than meets the eye.

The Two Sides of Foot Function

When I teach on behalf of EBFA Global or speak to my patients I always emphasize that there are two sides to foot function (and dysfunction) – biomechanical and neuromuscular.    Now both play an important role in foot function which means that both must be appreciated – however to solely treat foot pain with just one belief system in mind is inherently flawed.

In most Podiatric Medical Schools we are taught foot function and foot pathology solely from a biomechanical perspective.

This means that every patient is tested for foot mobility and told to stand statically to determine arch height and foot type.   Based on this foot-focused biomechanical assessment and foot classification system the patient’s cause of injury and treatment protocol is determined.   Some of the favorite treatment recommendations include motion-controlled footwear and custom-posted orthotic both of which are prescribed with the hopes of controlling foot-focused biomechanics and thereby reducing their foot pain.

Beyond Biomechanics

The other side of foot function is one that is driven from a neuromuscular perspective and integrates the science of sensory stimulation and fascial systems.   In the case of neuromuscular function every patient would be assessed for sensitivity of plantar mechanoceptors as well as co-activation patterns between the foot and the core.  The role of minimal footwear, myofascial releasing, breathing patterns and compensation patterns more proximal would all be considered.

So which is more appropriate?  Well it depends.   In certain cases there will be a stronger argument towards a more biomechanical influence and in others it is more sensory.  This means it really is a marriage between the two approaches that provides the greatest patient outcome.

Sensory Stimulation in Foot Pain

My practice and Podiatry career is built around bringing an awareness to the important role sensory stimulation has on foot function and foot pain.

With every step we take impact forces are entering the foot as vibration.  This vibrational noise stimulates unique mechanoceptors on the bottom of the foot and is used to coordinate the loading of impact forces through coordinated contractions of the intrinsic (small) muscles of the bottom of the foot.   This co-contraction leads to a stiffening or strengthening response of the foot.

Researchers such as Nigg et al. and Robbins et al. have demonstrated a direct relationship between sensory stimulation of the plantar foot and intrinsic muscle strength concluding that one is necessary for the other.   This means that if our footwear or orthotics disconnect us from sensory stimulation – as in the case of cushioned footwear – this can actually weaken our foot making us susceptible to plantar fasciitis, Achilles tendinitis and stress fractures.

Beyond Vibration Stimulation

Vibration stimulation is an extremely important sensory stimulation that enters our foot however it isn’t the only stimulation.   Another important stimulation is the ability for our foot to determine texture and if a surface is rough or smooth.   This information is used to help maintain dynamic balance (think walking on ice).

Enter the merkel disk mechanoceptors.   These superficial sensory nerves are used to determine what’s called 2 point discrimination which is translated to roughness or the texture of a surface.  Surface texture and insole texture is one of the most studied aspects of foot stimulation and posture or gait.  From decreased medial lateral sway in patients with Parkinson’s or MS to reduced prefrontal cortical activity in atheltes post-concusion the applications are promising!

One area that hasn’t been focused on for sensory stimulation and foot function is foot pain.  I am here to change the awareness around this concept and share the powerful application of sensory stimulation and foot pain.

As we mentioned earlier sensory stimulation of the foot leads to a contraction of the intrinsic muscles of the foot.   Intrinsic muscle contraction is not only a criticial step in the damping of impact forces but has also been shown to increase the medial arch and build co-activation contractions in the core.

 The Evolution of Textured Insoles

In October 2017 Naboso Technology launched the first-ever commercially available textured insole!   Naboso Technology essentially brought the science of touch and years of textured insole research to the market place giving new hope to people with foot pain.

Available in two strengths – Naboso 1.0 (1mm texture) and Naboso 1.5 (1.5mm texture) Naboso Insoles are designed to be worn without socks (or at the most very thin socks).  They fit into all footwear, are freely movable in all planes of motion and are only 3mm thick.

FROM THE GROUND UP

Are you barefoot strong?


Learn more about the power of texture! – http://www.nabosostechnology.com

  1. https://barefootstrongblog.com/2018/02/06/beyond-biomechanics-addressing-foot-pain-with-sensory-stimulation/

 

HIRSCHER AND SHIFFRIN WIN BY CROSSING THE LINE

When a World Cup racer wins a GS by a commanding margin, it’s a sure sign they’ve crossed the line and the gravity of the situation is significant. But I’m not talking about  breaking any rules. Instead, I’m referring to Hirscher and Shiffrin mobilizing the force of gravity by jumping across the rise line above the gate and/or minimizing pressure while rotating their skis across the rise line towards the gate so the edges of their outside ski progressively engage and lock up as they extend and incline closing the kinetic chain. Knee extension, in combination with ankle extension, uses the momentum of COM in conjunction with the force of gravity to progressively engage and apply force to the outside ski.

Reilly McGlashan has an excellent YouTube analysis of Marcel Hirscher using this technique in the 2017 Alta Badia GS (1.) The technique Hirscher and now Mikaela Shiffrin are using relates directly to the second rocker/internal rotation, impulse loading mechanism I described in a series of posts. The text below is excerpted from a comment I posted on McGlashan’s YouTube video analysis of Hirscher.

Hirscher progressively engages his edges, especially on his outside ski then hooks a tight arc close to the gate to establish his line. Once he has established his line, he no longer needs his outside ski. He gets off it in milliseconds and uses the rebound energy to project forward with only enough pressure on his uphill (new outside) ski to influence his trajectory of inertia so his COM enters the rise line at a low angle of intersection. He gets rebound energy from the loading  of his outside ski and from what amounts to a plyometric release of muscle tension from the biokinetic chain of muscles extending from the balls of his outside foot to his pelvis. The energy is created by the vertical drop from above the gate to below the gate similar to jumping off a box, landing and then making a plyometric rebound. Hirscher is skiing the optimal way and it shows on the clock and leader board.

Replicating the mechanism in a static environment is not possible because there is no inertia. But a device I have designed and constructed enables the mechanism to be rehearsed with the same feeling as in skiing.

The key is loading the forebody of the outside ski with a shovel down position as the leg is rotating the ski into the turn. This sets up the second rocker impulse loading mechanism that tips the ski onto its inside edge. Extending the knee and ankle uses momentum to exert a force on the snow with the ski.

The photo below shows the training mechanism head on. The white horizontal arms represent the sidecut of the ski. The platform under the foot can be adjusted transversely to change the sensitivity. Vertical plates set beside the ball of the foot and on the outer corner and behind the heel transfer turntable rotation torque to the ski created by rotating the leg internally with the glutes. The platform will only tilt under impulse loading if the second rocker can engage. Few skiers can use this mechanism because their ski boots do not accommodate second rocker biomechanics.

The link below is to a video that shows the effect of extending the knee and ankle while moving the hips forward and over the support foot (monopedal function). The stack height and minimum profile width of are FIS 93 mm/63 mm. Rotation in itself will not cause the device to tip onto its inside edge if centre of pressure is on the anatomic centre of the foot (through the centre of the heel and ball of the second toe).

Dr. Emily Splichal’s recent webinar on the Science of Sensory Sequencing and Afferent Stimulation (2.) is relevant to motor control and cognitive development associated with high performance skiing. Pay careful attention to Dr. Splichal’s discussion of the role of mechanoceptors and the fact there are none on the inner (medial) aspect of the arches of the feet which is why footbeds or anything that impinges on the inner arch is a bad thing. I will discuss the implications of Dr. Splichal’s webinar in a future post.

In my next post, I will provide detailed information on the training device.


  1. https://youtu.be/OxqEp7LS_24
  2. https://www.youtube.com/watch?v=2qPnrQ85uec&feature=youtu.be

 

 

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

THE MECHANICS OF EDGE CHANGE

Comments made by followers of my blog suggest that significant confusion exists 0n the meaning of terms and representations of mechanics, biomechanics and physics used in typical explanations of ski technique and ski mechanics. In particular, there appears to be confusion between pressure and the representation of point forces.

Pressure is a physical force applied to an object that is distributed over the surface of the object.

Center of Pressure or COP is the point center of ground reaction force opposing a corresponding center of applied force acting on a object supported on the ground or a stable surface that acts in the capacity of ground in terms of providing a source of reaction force.

Torque or Moment of Force results from an offset between the centers of opposing physical forces acting on either side of an object.  This offset results in a torque or moment arm that tends ti create rotation about a center. When one force has a greater magnitude than the other force, rotation of the object will occur around the point of rotation.

Why typical balance explanations of skier balance are wrong

Balance in skiing is often depicted as a simple alignment of opposing point forces, usually a resultant force R acting in opposition to a snow reaction force S. The mechanics that make the edges of a ski grip are often shown as a simple alignment of opposing forces acting a single point on the edge. Explanations of this nature are physically impossible. What the authorities in skiing seem to conveniently be ignoring is the fact that pressure is applied by the snow along the entire running surface of the edge in contact with the the snow while an opposing area of pressure applied by the weight of the skier is acting on the body of the ski with an offset between the two centers of pressure. The authorities in skiing also seem to conveniently ignore what is arguably the key even in establishing a platform under the outside ski for the skier to stand and balance on, edge change.

Mikaela Shiffrin’s Get Over It drill on the Burke Mountain YouTube site makes a good segue to an explanation of the Mechanics of Edge change in the my next post – https://youtu.be/Bh7KF49GzOc

Bridget Currier is the model every skier should aspire to. She perfectly executes what I call the skimove. The skimove engages the external forces at ski-flat/edge-change to drive multi-plane torques acting about her outside ski into the turn while setting up a solid platform under her outside foot for her to stand on. Magnificent! This video should have at least a million views.

My comment from 2 years ago

Note carefully Currier’s stance in balance on her new outside ski, in particular, the angle of her torso with the snow. This is key to loading the ball of her outside foot.

Note carefully Shiffrin’s comment to move forward onto her new ski and how she used to think the movement was a lateral (sideways) move.

Most important of all – Patient Initiation. The reason? Shiffrin and Currier, don’t tip their outside ski on edge. They rock it on edge with a rocker impulse loading mechanism. The sequence is Rock, Roll n’ Rotate then Rotate the outside leg.