Ted Ligety

TRENDS IN WORLD CUP EQUIPMENT AND SKI TECHNIQUE

An interesting trend is emerging in World Cup Alpine competition. The movement pattern of some male racers is starting to resemble that of Ted Ligety while the movement pattern of some female racers is starting to resemble that of Mikaela Shiffrin. More interesting, Shiffrin has been struggling in the early races.  I’ll speculate later on why I think  Shiffrin is struggling.

In terms of the current trend in ski technique, it is not so much a case of Ligety and Shiffrin defining a new technique but more a case of them getting it right. By getting it right, I mean that they are skiing a technique that uses the innate, hard-wired processes of the human body, in particular, the basic movement pattern of alternating single-limb support made possible by the ability to develop a tensioned forefoot on the outside ski (DOT 4).

One aspect of this technique is the transfer of the load W to the proximate centre of the head of the first metatarsal where it acts in opposition to the point centre of Ground Reaction Force (COP) at the inside edge of the portion of the outside ski underfoot. The vector of the opposing force is perpendicular to the transverse aspect of the ski (DOT 7). This alignment of opposing forces is only possible when the proximate centre of the head of the first metatarsal is substantially aligned over the inside edge of the outside ski. The only way the centre of W can be aligned with the proximate centre of the head of the first metatarsal is through load transfer induced pronation at ski flat between edge change.

Due to the influence of Ligety and Shiffrin, World Cup ski technique is trending in a positive direction, as are skis. But the design of ski boots and modifications made to them continue to gather momentum in a direction that is antagonistic to load transfer-induced pronation.

“When the foot attempts to pronate inside the ski boot, it is often the case that the ankle bone will come to bear against the inner surface of the boot shell. When contact of this nature occurs, pain and other related complications usually result. Since the consensus of those skilled in the art of ski boot design and modification is that pronation or the rolling inward of the foot is detrimental, and, thus, undesirable, provision is not made to allow for such movement. Rather, the structure of the footwear is intended to resist or even prevent it.

“Thus, the problem with existing footwear arises due to the dynamic nature of the architecture of the foot. When the wearer is standing with the weight equally distributed between left and right feet so that the centre of mass of the wearer is manifesting itself in the centre between the feet, the architecture of the wearer’s foot assumes a specific configuration. As the wearer begins to shift his weight towards one foot so that the other foot bears proportionately less weight, the wearer’s centre of mass moves over the medial aspect of the weighted foot so as to assume a position of balance. In order for this movement of the wearer’s centre of mass to occur, the architecture of the weighted foot must undergo a progressive re-alignment. Existing footwear does not adequately anticipate this re-alignment of the architecture of the foot and thus such footwear inhibits the wearer’s ability to assume a balanced position.” – BACKGROUND OF THE INVENTION – US Patent No. 5,265.350 – MacPhail, November 30, 1993

A large camp in the ski industry appears to be of the position that the leg should ideally function as a lever with which to place and hold a ski on edge and apply forces to it. In this paradigm, the foot is viewed as a useless appendage, one that serves no purpose and only complicates the process of achieving a firm connection of the leg with the ski.

The relationship between equipment and technique is fragile at best. In the chicken and egg scenario, equipment enables sound technique. At the same time, equipment can disable sound technique once it has been established. The effect of equipment tends to become exacerbated in competition where races are won or lost by hundredths of a second. Here, seemingly minor changes can have major impacts on racer performance as reflected in results, which brings me to speculate on why Shiffrin is struggling.

It seems inconceivable that Shiffrin has lost her edge in competition. A more likely explanation is that she is literally not able to find her edge due to a change in some aspect of her equipment. Shiffrin comes across as intelligent, focused and disciplined. But like most racers today, she probably has minimal influence or control over her equipment, which is increasingly left to the experts. Indeed, the F.I.S. advises in their 2014-2015 rules document (http://www.artech-ski.com/fis/FIS-Alpine-Ski-Equipment-Rules-2014-2015.pdf), that, “Boot fitting for racers should be done by professionals, as there are many factors that play in to deciding on the correct fit.” I concur with the position of the F.I.S. that here are many factors at play in a ski boot. But the central issue is the affect of these factors on the physiologic function of the user. But this is an issue that does not seem to be appreciated within the ski industry in general, let alone by the F.I.S..

Instead, the prevailing mentality appears to be that solid technique can overcome equipment issues. This being the case, it is probable that her coaches, and even Shiffrin herself, may believe that correcting her current issues is a matter of making adjustments to her technique. But this is like saying that a skilled Formula One driver can win with an improperly tuned racecar. In order to maximize skier potential, the skier/ski equipment components need to be optimized as a system. They are not mutually exclusive. Yet, I have seen no evidence to date that this critical issue is even recognized. In ski racing, relative skier performance, not optimal skier performance, prevails. Here, luck appears to be the main factor in terms of skier/equipment synergy.

The following elements, which will be the subject of future posts, are characteristic of a sound ski technique.

  • A transition phase between at the end of a turn to initiate load transfer to the inside (new) ski.
  • Rotation of ski into the new turn initiated by load transfer to the inside leg while the ski is still on its inside edge.
  • Extension to create load transfer and move COM forward so as to align Resultant, Centre of Load W and Ground Reaction Forces.
  • One hundred percent of the load expressed on the new outside foot and ski at ski flat between edge-change.
  • Coordinated ankle, knee, hip flexion at ski flat to initiate load transfer induced pronation
  • External forces engaged at edge change to drive the torques into the turn and set up a cantilevered platform (DOT 4) of contiguous GRF to support the superincumbent body of the skier and provide reaction force for postural responses.
  • The use of the inside leg as a strut with which to brace the pelvis so it can be oriented to assist in the alignment of R emanating from COM through the proximate centre of the head of the first metatarsal.
  • Phased, multi-plane torques into the turn.
  • Whole leg internal rotation from the pelvis coordinated with edge change.
  • Achilles induced plantar aponeurosis tensioning (tension in the sole of the outside foot).

It is the synergy of these things that allows a skier to engage the process of innate flow balance (DOT 13) with its hyper-speed subconscious information bit processing rate.

“When I ski, it’s like a song. I can hear the rhythm in my head, and when I start to ski that rhythm and I start to really link my turns together, all of a sudden there’s so much flow and power that I just can’t help but feel amazing.”

—Mikaela Shiffrin

I believe that some factor in Shiffrin’s equipment is causing her to make conscious corrections on course. Unless this issue is accurately identified and corrected and soon, she will find it increasingly difficult to ski with innate flow balance.

THE IDEAL SKIER’S FOOT AND LEG

Do you have the ideal shape foot and leg for ski boots? Let’s find out.

Not long after I starting working on ski boots, I began to notice that the best skiers, those who made high performance skiing look easy, seemed to be able to ski in boots right out of the box that usually required major modifications for most skiers just to get their feet into. This small group of elite skiers consistently had very specific foot characteristics, especially the shape of their feet and legs. Although there were some exceptions, the feet of elite male skiers tended to be US size 8 or 9. Podborksi’s foot was a US men’s size 6. The feet of elite female skiers tended to be the equivalent of US men’s size 5 or 6 with some feet as small as size 4. As I worked on the boots of more National Ski Team racers I soon developed a reputation for being able to describe how a racer skied by studying their feet. On one occasion I was with a group of racers in the waiting area of a steak house. Unseen by me, Dave Murray came into the room. He snuck up on me while I was on my knees on the floor studying a racer’s foot. Dave put his bare foot in my face so to speak. Without looking up and without missing a beat I said, “What are you doing here Dave?”

The image below shows the characteristics I have identified as common to racers like Ligety, Shiffrin, Vonn and other World Cup racers. The characteristics of their feet and legs enables them to create the mechanics and biomechanics within the ski boot necessary for them to engage the external forces to drive their outside ski into a turn. Depending on a number of factors, including luck, racer’s with these foot characteristics can often ski in a boot right out of the box with minimal or no modifications. Modifications take their skiing to another whole level.  I believe that young racers such as Shiffrin make the connection with the right feel early in their career. Once a racer, or any sensitive skier, connects with the right feel, especially at an early age, they know as soon as they take a run in a new ski boot whether it will work for them. This group of skiers has the ‘magic touch’.

 

Screen Shot 2014-03-25 at 5.53.08 PM

 

Here’s what the right shape of leg looks like in the cuff of a ski boot. I align the cuff so the leg is centred in the cuff when the skier is standing on two feet in the boot shells with the feet hip width under the pelvis. Note the amount of space on either side of the shin. This is critical for reasons I will explain in a future post.

IMG_3607

 

In my next post I will show what problematic foot and leg shapes look like and the challenges presented in creating a functional environment in a ski boot.

 

SORRY TED, YOUR TECHNIQUE ISN’T NEW

While the NY Times video, Ligety on GS, made a good effort to explain Ligety’s superior GS technique, the Times suggested that Ligety’s technique is unique. The technique, which involves a transition phase between turns, is not, in itself, unique. What makes Ligety’s style unique is the geometry and physical characteristics of the new skis that facilitate the high edge angles he uses. The Times also failed to mention that most skiers can’t do what Ligety, Shiffirin Vonn and many other elite skiers have done since day one; use the external forces acting on them to advantage instead of fighting them. The issue isn’t a lack of natural ability. The issue is an inability to stand on one foot in a ski boot and especially to allow the foot to pronate. Unless one has a pathological condition that precludes this, anyone can easily do it. It’s what we do every time we take a step when we walk barefoot or even in most shoes. It’s standing on one foot in ski boot that’s critical to a technique that harnesses external forces. And it is the very thing that the rigid plastic ski boot and a whole industry associated with skiing is trying to prevent.

The Times description of the differences between Ligety and his competitors (foes) perfectly describes the differences between Ligety’s technique that uses the external forces to advantage and the technique of his foes that attempts to fight the external forces, a losing battle if there ever was one.

“The trace of his (Ligety’s) path is smoother than that of his foes, who ski in somewhat violent fits and starts, making adjustments that spray snow.”

Ligety’s foes are forced to ski in violent fits and starts and to make adjustments that spray snow because the forces acting across their outside ski (and by default, across the joints of their foot and leg) are unbalanced. Because of this, the edge angle and forces acting on their skis and their base of support are constantly changing. Because the edge angle and forces acting on the ski are constantly changing, a corresponding series of small adjustments by the racer are required. This is especially true of the forces acting across the knee which manifest themselves as into and out of the turn oscillations. This is easily seen in HD video. In effect, the technique of Ligety’s foes amounts to a series of linked recoveries in which the most acrobatic racer prevails.

Here is an excerpt from an article that Joan Rostad pieced together from a series of posts I made on the EpicSki forum. The article describes the essential elements of the techniques of Ligety and Shiffrin.

Skiing Biomechanics Explained By David MacPhail Posted 9/21/09 • Last updated 4/26/11 • 3,272 views

Table of Contents

  1. Introduction
  2. Part I. The Secret of Effortless Skiing
  3. Part II. Four Key Biomechanical Principles
  4. Post Script

Introduction

David MacPhail was the innovative engineer who created the “MacPod” prototype boot in partnership with “Crazy Canuck” Canadian downhill champion Steve Podborski as an ergonomic advancement in ski boot technology. The MacPod “birdcage” design, which was applauded by scientists in the human performance community, was met with utter indifference by boot manufacturers who never gave it any serious consideration.

Part I. The Secret of Effortless Skiing

If you understand the following principles and rules you will understand the secret of effortless skiing. More importantly, you will be able to teach it to others, and someday there may be enough people with this understanding to influence the ski industry to produce equipment designed primarily for good biomechanics instead of good looks.

1. Basic physics
Newton’s Law says, “A body in motion in one direction will tend to stay in motion in that direction unless acted upon by an outside force.” In skiing, gravity is always trying to pull us down to the center of the earth. The low friction base of the skis sliding on snow facilitates a shear force component of gravity that acts parallel to the fall line. You acquire inertia due to the acceleration. The turn effort creates centrifugal force, which wants to eject the skier off the tangent of the arc. The only thing stopping the forces from pulling you downhill is the internal force expressed in the outside leg against a ground reaction force (GRF), assuming balance exists.

2. Balance
By my definition, balance is equal and opposite vertical forces aligned in opposition along the same force path with one net external force and one net internal force.

3. Skiers are naturally one-footed

Skiing involves more than just standing in place. We are moving from one limb (outside leg) to another. This basic form of locomotion is one of alternating single limb support, the same as walking. It wasn’t until I connected the movements of walking to those of skiing that I was able to perform and coordinate the movements with ease.

When we walk and when we ski we have a stance foot and a swing foot. When you lift your foot to take a step the movement comes from the inertia of the movement of your center of gravity (CoG), but support from the new stance foot makes the movement possible. If you look at a skier in the middle of a turn the inside leg exaggerates the characteristics of the swing leg in walking. When walking, as you swing the unloaded leg forward, this foot naturally inverts. This is the same movement of release of the old stance foot in skiing. Even when constrained by the ski boot the foot will always try to invert when unloaded.

Similarly, as you shift weight to your new stance foot in walking, so do you shift the weight in skiing: the weight first goes to the outside of the foot, and additional weight tips the foot to the inside, which helps to engage the inside edge of the outside ski. The foot’s anatomy is such that it must adapt to the transverse aspect first before it can fully accept the weight of the body. The lateral arch must make contact first and cause the foot to roll into pronation (i.e., evert) in order to tension the arches in the correct sequence.

In the last third of the turn, CoG is behind the uphill or swing foot. So the initial active weighting will be on the heel. If the skier initiates movement down the hill by relaxing the support or stance leg while starting to extend on the swing leg, the force will start to drive the foot into eversion. The new stance foot needs to fully adapt to the supporting surface in order to generate a dynamically rigid base of support for CoG. Then the skier has to simultaneously extend both legs to get CoG up and over the ankle of the swing foot in order to unequivocally make it the new stance foot. It is important to note that the extension is gravity-assisted.

4. Extension drives pronation
Because (at the end of the turn) the uphill or swing leg is flexed in relation to the support or stance leg, we have an opportunity to extend away from the inertia of CoG–which is being pulled down the hill and down towards the center of the earth. It is important to understand that this is a lateral extension that moves our hips and core towards the center of the next turn, without up motion. We need this extensor effort to create the force in the foot against GRF to drive the outside foot into a pronated, stance position.

This critical moment is sort of a twist on the line of the song New York, New York: “If you don’t make it here you won’t make it anywhere.” If you don’t drive the force in your foot to the ball of the big toe, it will be on the wrong side of the inside edge of the ski at its waist. This will create a situation where you will be using the boot cuff to indirectly transfer power to the ski, and doing so will cause a disruption to the balance system feedback and interfere with effectively skiing from the bottom of the foot.

If you do not drive the force in your foot to the ball of the big toe, as soon as the external forces begin to build, the pronated position of your foot will reverse into supination and your foot will revert back to the adaptive state. Please be clear on this because the end result justifies the effort of extension. Try and visualize what is happening during extension of the swing leg. Your body is pivoting about the uphill or lateral aspect of the foot as CoG moves downhill and over the ski. You have to press with enough force to cause the foot to rotate faster. Additionally, elevating the inside hip greatly assists both rotation around the foot and loading the foot. In this scenario, both internal and external mechanics are pulling the stance foot into eversion and holding the edge. The whole lower limb is turning into the hill.

5. External forces can reinforce stability
By simply positioning CoG over the line of force where the ball of the foot is acting within the sidecut of the ski (think of it as literally a line extending from the point the flare of the ski starts to the point where it stops), the forces acting on the skier will reinforce the stability of the base of support even as the forces grow in magnitude. In other words, external forces that would normally disrupt the skier’s balance will have the complete opposite effect in this configuration.

If the skier is using the inner (uphill side) of the boot cuff to hold the ski on edge then the action of the skier is opposing a force that is trying to rotate the stance foot into inversion away from the slope of the hill, which compromises her hold on the edge.

If you get bumped around, you can absorb and fill the surface gaps by letting the ground push toward you on convex surfaces and letting your leg push toward the ground on concave surfaces. The body will do this reflexively if the forces are balanced and the soleus muscle is in eccentric contraction. You don’t even have to think about it. The only thing you have to do is keep CoG in the right place. (This assumes your equipment will actually allow you to do this.)


Part II. Four Key Biomechanical Principles

1. The pelvis always rotates about the ankle of the stance foot.

In the first photo Norm Kreutz is rotating his pelvis towards the outside of the turn about the ankle of his stance foot. This is driving the inside or swing leg in the opposite direction, i.e., into the hill.

In the second photo Norm is relaxing the stance leg and extending the swing leg. This transfers the support of CoG to that leg making it the new stance leg. This action transfers the point that the pelvis is rotating about to the ankle of the (new) stance foot. As Norm extends his legs the pelvis will draw his feet in the opposite direction that it was moving in the first photo. It is kind of like a power assisted rotary move. For this reason Norm does not want to plant his pole until after the extension has begun. This helps stabilize the position of his CoG to ensure rotation occurs in his femurs.

The interesting thing is that this all happens on its own as part of the kinetic flow which should also flow in the direction that starts when the stance leg changes. Once you get the movement pattern right there is nothing to think about aside from deciding when to start a new turn.

Norm Kreutz 1
2. Kinetic Flow
If there is one area where there seems to be general agreement it is that edging and pivoting occur as a unit movement pattern and not as a series of separate events spliced together. This is why the timing and sequence of the initial move to start a turn is important.

Every turn has a start/end movement sequence that is consistently towards the inside of the turn just as there is a consistent flow in walking. Kick starting the flow is always contrived. This is why the first turn is the most difficult.

The movement that sets up the direction of the flow starts in the feet. At the completion of a turn the flow is to the inside of the turn. To turn in the opposite direction requires that the kinetic flow of the joints of the body be reversed. The outside foot will be in pronation and the inside foot will tend to pronate. In other words the inside foot is already primed to flow to the inside of the new turn.

When Maier relaxes his outside foot (first photo of the turn) his pelvis starts to unwind. This lets CoG drift behind his inside foot. Now CoG is behind his new stance foot and the foot is supported on its lateral or outer border. It is in the same position as it is at heel strike in the adaptive phase of walking.

Herman Maier
If you look at the movement of his upper body as he comes out of the fall line you will note that it seems to be coming at you (like a 3D movie) as opposed to going across the hill. If you were standing opposite the gate looking across the hill this would be more readily seen. As his CoG begins to move downhill Maier extends on his (new) outside foot. The foot is initially on its outer aspect but is tending to pronate. Applying force to the foot in combination with the movement of CoG starts the movement of the foot and leg in the direction of pronation. As CoG crosses over his skis his body will become erect with the slope of the hill. In effect, he is ‘standing up’.

Remember, his inside femur was previously moving in a direction in relation to its position with the pelvis that was consistent with supination of the foot (i.e. as the swing leg in walking). The movement of the femur is in opposition to the joint movement of the foot (supination vs. pronation). Maier has to change the relationship of the pelvis to match the flow of the feet.

3. The pelvis always rotates into the stance foot whether in walking or skiing.
As he extends on the new inside foot the tension of the rotator muscles in the pelvis unwinds the legs and aligns them with the pelvis, turning the legs into the fall line. As the turning progresses Maier applies rotational effort simultaneously to both legs to pivot the legs across the pelvis so that the inside hip leads the outside hip. In effect Maier creates the natural flow of the pelvis that takes place when one steps R foot – L foot, etc. At the same time he uses the extension movement to bring CoG up and ahead of the ankle of his new outside foot. By this movement Maier synchronizes the flow of the legs to match the kinetic flow of the joints of the outside foot (foot everted, leg turning into the turn, pelvis turned into the outside leg or towards the outside of the turn). Once he has synchronized the flow he exaggerates the rotation of the pelvis to reinforce the pronation of the outside foot as he relaxes onto the outside foot and stretches the muscles in eccentric contraction.

4. The flow of the feet is reinforced by the pelvis.
Unless one has a reasonable knowledge of biomechanics the effect of the rotation of the pelvis on edging usually makes no sense because it seems to have nothing to do with the mechanics of the feet. The effect of this movement is that it shortens the muscles that drive the foot into pronation. This not only applies edging force to the ski, it also torques (twists) the ski about its long axis. This is why Maier’s ski bites positively at the shovel. If you compare him to lesser skiers you will typically see skiffs of snow being thrown up off the edges instead of flowing along the ski. This is caused by the percussion of the ski as it oscillates about its edge (into the hill – away from the hill). This is due to insufficient loading of the shovel.

Post Script

Although it is common to speak of kinetic flow starting in the feet, science has proven that the movement really originates out of the pelvic floor, hips, and the abdomen. These muscles will fire first in a functionally fit individual. They do this because they are required not only for stability but also to initiate the pelvic rotation. I think this is why lifting and tilting the pelvis as an exercise is so effective. – Ric Blevins


Compiled and edited by Joan Rostad, September 2006

Here’s the link to the original EpicSki article – http://www.epicski.com/a/skiing-biomechanics-explained-by-david-macphail

MEMO TO TED LIGETY

Dear Ted,

I watched On Giant Slalom: Ted Ligety – Video – NYTimes.com – http://www.nytimes.com/video/sports/olympics/100000002705225/on-giant-slalom-ted-ligety.html

It was really great watching and listening to you explain your technique. But I have a few comments. Right after the comparison of you and Bode Miller there is an excellent graphic that shows how you begin to stand on your new uphill ski while it is still on its uphill edge.  At -01.35 in the video you say, “I go from the apex. I’m  pushing as hard as I can (on the left ski)”. Ahhh, I don’t think so Ted. Unless I am missing something, you were extending on your right leg long before the graphic appeared on your left boot. So how could you be pushing? Before that, your left leg was extended with the muscles in eccentric contraction. That means you were resisting, not pushing. In the next frames you describe how you step on the new (right) ski while it is still on the edge it was currently on in that turn (ergo its uphill edge). Wow! Now I am getting excited. Dam straight Ted! You go on to talk about how your ski rolls from the uphill edge to the downhill edge and how you are getting on the new ski before you actually switch. I don’t think this is quite right Ted. You are in a transition phase from the old turn to the new turn. And just when I thought you and the New York Times had it figured out a graphic popped up showing pressure in the centre of the foot. Darn! Ted, how can a ski be driven into a turn when the force (OK, pressure) applied by your foot is on the outside aspect of the inside edge of a turn? It can’t. I fixed the graphic and posted it below.

Ligety

Thanks Ted, Now go win some gold. In the meantime, I’ll fill in the blanks, connect the dots and get back to you. Good Luck!

Best Wishes,

David

PS: I think it’s great that the NY Times says you are the only one who skis this way. I guess they haven’t heard of Mikaela Shiffrin. I’d appreciate it if you could tell them about her. She is destined to be the next World Cup superstar. Thanks.