World Cup Racing posts

WEIRATHER SWITCHES TO HEAD

This is a quick post to comment on a gutsy move by Tina Weirather; one that probably caught most off guard after her very successful 2016-17 World Cup season and especially just before the upcoming Olympics.

I believe Weirather’s timing is impeccable.  Said Weirather;

……….I’ve spent a long time thinking about all these steps. I asked myself a lot of questions and balanced the risks as well as all the potential advantages and disadvantages. The most important questions were: “How can I be most successful, how can I ski the fastest, how can I evolve the most?” The answers got clearer and clearer with every day I tested, every conversation I had, and the more I listened to my gut.

The tests went really well……………”

When I worked with Provincial and Canadian Team racers, I always made boot changes as soon as possible after the competitive season ended. The changes were done in a structured, systematic manner involving one-on-one testing where changes were made to one boot at a time and then compared to the unchanged boot. Only when the changes were proven better when compared to the unchanged boot were changes made to the other boot. In setting up new boots, it was standard practice to swap the liners from the current boots into the new shells to confirm they were properly set up and do one-one-one testing that compared the new shells with the liners from the previous boots to the previous shell/liner combination.

Always have an Escape Route

Even with a lot of testing that resulted in new boots that appeared to be an improvement, I always recommended that racers keep their old boots intact and with them during training right up until racing started. If last minute doubts arose, the best practice was to revert to the old proven setup. Recall Shiffrin’s disastrous start to the 2014-15 World Cup season after changes were made to her boots in the fall of 2014. Fortunately, Shiffrin was able to revert to her old boots, train in Italy over Christmas and get back on track in the New Year. Many racers are not so fortunate.

It was my policy to not make changes to a racer’s ski boots should during the competitive season unless there was no other option. Making an equipment change now, such as Weirather has done, provides a big window in which to make adjustments in technique and fine tune equipment before the start of competition.

A Formula (One) for Success Team

Weirather impressed me when she said;

It took a while, but I’m now 100% convinced I’ve found my dream team: HEAD (new) Tech: Reini Berbig (new) Coach: Charly Pichler (new) Dryland training: Micha Eder / @rotorteam Sports therapist: Fabienne Frommelt Team: Swiss Ski WC 1 Manager: Christopher Holzknecht (new).

I have long maintained that in order to succeed, ski racers need to adopt the Formula One model where the racer drives the skis and a whole team works together to support the racer.

In important ways, I believe Tina Weirather is the role model for World Cup ski racers.

 

COMMENTS ON SUPER PETRA VLHOVA

As time permits, I analyze the movement and loading patterns of elite skiers such as Mikaela Shiffrin, Lindsey Vonn, Ted Ligety, Tessa Worley and others. Occasionally, a source sends me video of these racers training.

I have identified a specific movement and loading sequence pattern that I use to analyze technique. This requires decent quality video and specific camera angles. In a future post, I will describe the process, the key metrics I look for and what they indicate.

Up until I saw the video of Vlhova, that is the subject of my post, SUPER PETRA VLHOVA’S EXPLOSIVE IMPULSE LOADING IN ASPEN SLALOM, I rated her as one of the better technical racers on the World Cup circuit. But I did not consider Vlhova to be in the same class as a Shiffrin or a Worley.

When someone posted a link on FaceBook to Vlhova’s winning run in the Aspen slalom, I was stunned by what I saw in first few gates. This was not the same Vlhova I had analyzed earlier in the season. Vlhova has definitely changed and it is for the better.

SUPER PETRA VLHOVA’S EXPLOSIVE IMPULSE LOADING IN ASPEN SLALOM

I am blown away by the explosive impulse loading of her outside ski that Petra Vlhova displayed in winning today’s World Cup Slalom in Aspen, Colorado. Vlhova’s powerful impulse loading made other racers, including Shiffrin, look like they were in slow motion in comparison. There are several videos of Vlhova in action on YouTube already.

For those who don’t know how to change video speed and definition in YouTube, the screen shot below shows the range of speed options available from 0.25 to 1.5 times Normal. To select the speed option, click on the gear that says HD then select Speed. I usually watch race videos in several speeds, including pulse frame stepping using the space bar on my keyboard.

Vlhova’s rapid and explosive loading of her outside forefoot at edge change literally supercharges the small nerves in her feet and the muscles in her foot to pelvic core in a way that transforms her into a literal super racer.

Petra; on it – all over it.

Here’s a short video clip in reduced speed of Super Petra in action. In one word; WOW!

Bravo Petra Vlhova! You made my day.

 

A RACE WINNING FORMULA? THERE ISN’T ONE

An article in the April 7, 2015 edition of Ski Racing makes a shocking admission, There’s no set formula or timetable for ski racing success.  According to author, Jim Taylor, it doesn’t matter how talented a racer is, how fit they are or how hard they work, there is no guarantee they will ever succeed. Taylor concedes:

And, the really bad news is that those results that you devote so much time and effort to  achieving may never materialize – that is the inherent risk of giving your heart and soul to ski racing.

While it is shocking that no formula exists for ski racing success, it should come as no surprise. Raw talent is only one aspect of a ski racing winning formula. Like any competitive program, ski racing  doesn’t exist to develop raw talent. It exists to determine who the best overall ski racer is, all things considered. And with rare exceptions, ski coaching doesn’t exist to create a synergy of the components that make up a winning ski racer/equipment formula. Coaching is more like a filter where training and running gates ultimately determines which racer has the strongest combination of  factors needed to win. In this respect, coaches are more like talent scouts than developers of raw talent.

The process is simple. Run racers down a course and see who’s the fastest. It is the shortest and most economical path to the podium. The problem with an unsophisticated approach like this is that the best athlete doesn’t necessarily win. The winner is usually the least compromised athlete. In this format, there is no incentive to develop raw talent.

Although athletic ability is important, athletic ability in itself, it is not enough. Ski equipment, but especially the ski boot, can make or break a ski racer by enabling or disabling performance potential. Even if a ski racer finds the right combination early in their career, history has demonstrated that seemingly insignificant changes can quickly relegate an emerging champion to oblivion.

Have trust. Despite the lack of any formula, Taylor advises racers to have trust and “believe in every aspect of your ski racing including your natural ability, effort, coach, equipment, and program.” Why? With no guarantee of success, there is no good reason any ski racer would do this. It is not that a winning formula in ski racing is not possible. It is. And it is relatively simple. It involves the coordination and integration of the various factors.

Where to start?

The human system with an emphasis on movement science and the application Newton’s Third Law, “For every action, there is an equal and opposite reaction”.

A strong stance and the ability to move precisely from one ski to another is the foundation of a successful ski racing winning formula.  On firm pistes, it involves the ability of a racer to balance external torques and precisely align the resultant force R and the load W (R-W) emanating from COM on the same force vector  in opposition to SRF in two bisecting planes; the saggital plane (front to back) and frontal plane (across the body). The point centre cross-hair where the opposing forces align is called the centre of pressure (COP). Without the ability to create and maintain a precise alignment of the forces of R-W and SFR, athletic prowess and strength and conditioning are irrelevant.

In a series of future posts, I will describe the conditions under which opposing torques can be balanced in 3 planes.

 

WINNING BY A FOOT

Numerous studies have attempted to find a correlation between foot size and height. I believe there is a reasonable correlation between foot size and height if stature is considered. Ski racers tend to have moderate body masses. When I worked on racer’s boots, most female racers had a US ladies size 7 foot (US men’s 6). Male racers tended to have a US  8 or 9 foot size. Ski boot makers usually make prototypes in a US men’s size 9 then scale the shell up or down to create other sizes.

Lange recently introduced a size 4 US men’s race shell. Perhaps it is more accurate to state that Lange reintroduced a size 4 race shell.  After I learned how to read the shell mold codes forty years ago, I knew that Lange made size 4 shells. However, they only sold them in softer children’s boots in North America. The XLR Race boot was only sold in Japan. After I got the Canadian distributor to bring in a supply of size 4 XLR Race boots, I was inundated with calls from all over Canada from female racers with small feet who heard that a size 4 XLR was available.

In my experience, I was usually able to estimate the size of a racer’s foot by looking at their stature and height. Here is a list of 6 top World Cup racers in order of height.

Ted Ligety 1.80 m
Lindsey Vonn 1.78 m
Marcel Hirscher 1.73 m
Tina Maze 1.72 m
Mikaela Shiffrin 1.70 m
Anna Fenninger 1.66 m

Based on Lindsey Vonn’s stature, I estimate that she has bigger feet than both Tina Maze and Mikaela Shiffrin who are very close to the same height. Vonn is  close to the height of Ted Ligety. I estimate that she has at least a US ladies Size 8 to 8.5 while Ted Ligety’s foot is in the order of a US men’s 9. Anna Fenninger is 1.66 m and small boned. She probably has small feet, smaller than Shiffrin who probably has a size 7 ladies (6 men’s). Anna Fenninger’s foot will be no bigger than a size 6 ladies (US men’s size 5). Marcel Hirscher at 1.73 m probably has a size 7.5 to 8 US men’s foot.

With a ski that is 65 mm in Minimum Profile Width who has the winning feet? Ted Ligety and Lindsey Vonn.

REVELATIONS FROM THE FIS GS SKI RULING

The controversy that surfaced in 2011 over the FIS decision to increase turn radius on GS skis revealed a lot about what the various authorities in skiing knew and, especially, what they didn’t know, about the mechanics, biomechanics and physics of skiing. Some critics of the ruling took the position that the reduced sidecuts would actually increase the risk of injury. An article in Ski Racing called, Black Diamond: The Deaf Ears Of The FIS, reviewed the various positions on the matter. And while some critics of the FIS ruling had very strong opinions, no one seemed able to put forth a position based on sound principles of science. In what had to be the height of irony, Guenter Hujara, director of the men’s World Cup was reported to have said, The facts are the facts. If you want safety this is a step you have to take.

Since 1977, I have been stressing the importance of the feet in skiing as the transmission path for forces transferred from the skier’s centre of mass to the snow. Knowledge of the forces acting between the soles of the feet and the snow surface is the arbiter of knowledge as a whole in skiing.  At last, a World Cup official was finally talking about taking a step. But my elation was short-lived. Hujara was talking about new regulations for GS skis, not my long hoped for new regulations for ski boots.

Two statements pertaining to injury mechanisms and ski safety were telling; Scientists at the University of Salzburg determined through a subjective study of 63 experts that the main risk factor was the “system ski, binding, plate, boot,” and By their own (FIS) admission, boots are too complex, and plates are, too. I say, ‘wait a moment’. The common denominator in the ski system/skier interface with the potential to cause injury, especially knee injury, is moments of force (torques). To be more specific, an unbalanced inversion moment of force present across the inside edge of the outside ski and the associated joints of the ankle-complex. By association, an unbalanced external (out of the turn) vertical axial moment of force acting on the tibia that tends to rotate it out of the turn against a well-stabilized femur or, worse, a femur that is being rotated into the turn by the powerful hip rotators. Between the tibia and femur lies the knee; a fragile joint with only ligaments holding the two bones in proximity to each other.

Mechanisms of Anterior Cruciate Ligament Injury in World Cup Alpine Skiing  (The American Journal of Sports Medicine, Vol. XX, No. X DOI: 10.1177/0363546511405147), states, under Background,

There is limited insight into the mechanisms of anterior cruciate ligament injuries in alpine skiing, particularly among professional ski racers.

My US Patent No.  5,459,949 published on or about November 29, 1994, goes into great detail about the importance of positioning the foot within in the ski boot and especially positioning the ball of the foot in relation to the inside edge of the outside ski of a turn so as to facilitate the setting up of moments of force (torques) into the turn with which to oppose externally generated torques out of the turn and the avoidance of mechanical relationships that result in unbalanced torques, It can be debated whether the presence of an unbalanced external vertical axial moment of force causes or contributes to an injury. But there is no debate that an unbalanced external vertical axial moment of force is a predisposing factor to injury.

 

Here are some excerpts from the subject patent that discuss moments of force acting about the inside edge of the ski with my notes and emphasis (bold) added. Due to the relatively short moment arm, aligning applied and ground (snow) reaction forces in opposition to each other or even creating an alignment where the applied force is on the inside turn aspect of the inside edge of the outside ski is not, in itself, sufficient to engage the external forces that drive a ski into a turn. It is merely a prerequisite. The factors that multiply moments of force once an over-centre mechanism is initiated are much complex than a simple misalignment of opposing applied and snow reaction forces.

SOLE ADJUSTMENT

While the adjustment of medial forefoot counter 2201 enables the foot 2001 of the user to be correctly aligned on rigid base 2100 yet another problem has arisen. The alignment of the head of the first metatarsal of the foot 2001 of the user has been altered in relation to the appliance affixed to the sole of the footwear, in this instance, a snow ski, in comparison with the alignment of the appliance in relation to the head of the first metatarsal as shown in FIG. 63.

Alignment of the center of the head of the first metatarsal is an important factor influencing physiological mechanisms which balance pronation/supination moments acting transversely across inside edge of appliances such as snow skis. The contact point of such an appliance with the surface on which it is acting can act as a fulcrum and, in so acting, establish a moment arm pivot in situations where the ground reaction force and the force applied by the user are not acting linearly in opposition to each other. In monopedal stance (pronated) the weight of the body acts substantially through the center of the head of the first metatarsal.

It is important, in activities such as snow skiing, that means be provided to allow the center of the head of the first metatarsal to be positioned so that the force applied by the user can be aligned in opposition to the ground reaction force when the snow ski is placed on its inside edge. If opposing ground reaction and applied forces can not be aligned, a moment arm will be created with the effect that the force applied by the user will tend to rotate the foot in the direction of either supination or pronation.

The location of the inside edge of (the outside ski) a snow ski tends to favour a supination moment arm since the ski edge generally lies medial of the center of the head of the second metatarsal. If the force applied by the user is sufficient in the presence of a moment arm to rotate the foot in the direction of either supination or pronation, the long axis of the tibia will also be caused to rotate through an intrinsic mechanism within the tarsus of the foot.

The means to adjust the transverse position of the foot in relation to the inside edge of a snow ski while maintaining the means to independently adjust the position of the foot on the longitudinal axis of the sole of the footwear is important and advantageous to the user and is thus an object of the present invention. FIG. 70 shows substantially the same view as FIG. 69 except that the ground reaction force FR and the force applied by the user F are shown substantially as they would be when the user is in monopedal stance (pronated) with the foot correctly positioned in relation to the inside edge of a snow ski affixed to sole 2101.

FIG. 71 shows substantially the same view as FIG. 70 except that the snow ski shown affixed to sole 2101 is wider on its medial aspect in comparison to the snow ski affixed to sole 2101 as shown in FIG. 70. The position of the inside edge of the snow ski in relation to force F applied by the user is such that the ground reaction force FR and the force F applied by the user are not acting linearly in opposition to each other. The transverse offset between the ground reaction force FR and the force F applied by the user creates a moment arm MA which acts lateral of the ski edge with the result that force F applied by the user acting on the moment arm MA will tend to rotate the foot in the direction of supination when the ski is placed on its inside edge.

Fig 70-72

FIG. 72 shows substantially the same view as FIG. 71 except that sole 2101 has been shifted laterally in relation to rigid base 2100 so that the ground reaction force FR and the force F applied by the user are now acting linearly in opposition to each other with the result that the moment arm MA as shown in FIG. 71 facilitates a countering muscularly generated torque from internal rotation of the leg at the pelvis.


The link to US Patent No.  5,459,949 is:

http://patft.uspto.gov/netacgi/nph-Parser Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=5,459,949.PN.&OS=PN/5,459,949&RS=PN/5,459,949

PUTTING THE BOOT TO THE EUROPEANS: A NEW DIRECTION

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

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

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

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

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

…… to be continued.