world cup racing

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.

 

GIRARDELLI AND STENMARK DEMONSTRATE BALANCE ON THE OUTSIDE SKI

In my last post, I discussed the movements elite Ski Pros make to balance on their outside ski.  I used Big White Ski Pro, Josh Foster as an example and reproduced his key comments from his YouTube video, Strong Platform.

Since Foster was skiing on moderate terrain, his speed is the equivalent of slomotion in comparison to typical World Cup speeds. For this post I am providing a video clip of Marc Girardelli and Ingemar Stenmark from the 1987 World Championship SL in Crans Montana, Switzerland. The video will allow you to compare the movements that create balance on the outside ski at race speeds to Foster’s movements at recreational speeds. I added reduced speed clips at the end to allow the rapid extension movement to be more easily seen.

I don’t believe there is any question that Marc Girardelli and Ingemar Stenmark can actually balance on their outside ski, especially in view of Girardelli’s statement: –

Once you can balance perfectly on the outside ski, everything else follows.

Note that the movement occurs above the gate as Girardelli and Stenmark approach the rise line and it mainly involves a rapid extension of the knee. According the predominant view, as articulated in the mental model of ski teaching and coaching, a quick extension is an unweighting movement. If this were true, why would the best skiers in the world unweight their outside ski above the gate?

What Foster, Girardelli, Stenmark, Shiffrin, Hirscher and all the best skiers in the world are really doing is loading and engaging a dual rocker system by applying a high impulse load to their outside foot at ski flat between edge change. Without knowledge of the associated mechanics, biomechanics and physics, no amount of observation will provide insights as to what is really happening. This is why 30 years after the World Championships at Crans Montana, what racers like Shiffrin, Ligety, Hirscher and other World Cup greats are doing remains a deep, dark mystery.

In my next post, I will introduce you to the Rockers.

 

 

 

BEEN THERE, DONE THAT

Thirty-five years ago, I was doing most, if not all of the things that are promoted today as the state-of-the-art in ski boot modifications; custom footbeds, cants, varus wedges, valgus wedges,  heel lifts, ankle padding, heel cups, foam liners, alignment, etc. You name it, I did them all. But I discarded most of them just as fast as I tried them. Why? Because, with few exceptions, I was working on the boots of World Cup racers or elite ski pros. Most of the mainstream ideas I tried, did not perform as advertised; they simply did not appear to produce beneficial results

My foray into ski boot modification started after I mentioned to a professional skier friend that I was trying fix my own boots. He asked me if I could help him with his. One thing led to another. Soon I had skiers calling me from all over the area asking me if I would work on their boots. After great success with the boots of my ski pro friend, he introduced me to Canada’s World Cup and Olympic medalist, Nancy Greene Raine.  She immediately asked if I would agree to work on the boots of the racers of Canada’s National Ski Team. In all the years I worked on ski boots I never advertised or solicited work, not once. Every single person whose boots I worked on, came calling on me.

The reason I ended up rejecting most of what is promoted today as state-of-the art is that I was working on the boots of racers who were in the ranks of the top 1% of the world’s best skiers; the best of the best, the top guns of skiing. In those days, the racers I worked with had all cut their skiing teeth in low-cut leather boots.  They not only knew right away whether something I tried worked, they didn’t hesitate to let me know in no uncertain terms when it didn’t.

If I asked, “How did that work out for you Dave?” Mur replied without hesitation, “It sucked”. When it came to choice of boots, they didn’t pull any punches either.  If the boots of the official suppliers didn’t work  for them, they skied in what did and ignored the official supplier team policy.

Crazy Canuck, Dave Murray, lived close to me. He probably spent more at our house than his own. Mur was a willing guinea pig for my boot experiments. But at the same time he was a stern critic. Today’s generation of skiers and ski racers have grown up in the ‘fix the foot in neutral and immobilize it‘ paradigm. Most have never skied in a ski boot without a custom footbed and a form-fitted liner. So they have never known anything different. With rare exceptions like Ligety and Shiffrin, when I watch ski racers today, even World Cup racers, I feel like I am watching athletes trying their best to compensate for an equipment  imposed disability. In the brave new world of ski racing, the least disabled racer prevails instead of the best athlete.

LIGETY’S MOMENT OF TRUTH – STEP 4

In order to be able to develop a dynamically stable base of support on the outside ski of a turn, one that supports the processes that use external forces to drive the ski into the turn, the ski must have a waist that is close to the centre-to-centre dimension ‘X’ between the balls of the great and 2nd toes. In addition, the anatomical centreline of skier’s foot must be aligned with the running centre of the ski. The graphic below shows what it looks like when the foot is correctly positioned on a ski with the appropriate width underfoot. In reality, there is a stack of equipment between the sole of the skier’s foot and the snow surface. F.I.S. rules allow up to 100 mm of stack height between the sole of a racer’s foot and the snow surface. So the graphic below does not reflect reality. The reason I am starting with the skier’s foot directly on the ski top plate is to demonstrate that an applied vertical force acting against an opposing snow reaction force (SRF) is insufficient to explain the edging mechanics that skiers like Ligety and Shiffrin are able to develop. There are other factors at play that I will introduce in future posts.

L foot on ski

US Patent No 5,265,350 – MacPhail: November 30, 1993 – “The prior art refers to the importance of a “neutral sub-talar joint”. The sub-talar joint is a joint with rotational capability which underlies and supports the ankle joint. The sub-talar joint is substantially “neutral” in bipedal function. That is to say that the foot is neither rolled inward or rolled outward. If the foot can be substantially maintained in a neutral position with the arch supported and with a broad area of the inner aspect of the foot well padded, there will exist a good degree of comfort. Such a state of comfort exists because the foot is not able to roll inward (pronate) to a degree where significant mechanical forces can be set up which would allow it to bear against the inner surface of the boot shell. In effect, this means that initiation of the transition from a state of bipedal to a state of monopedal function, is prevented. This transition would normally be precipitated by an attempt to balance on one foot. If the foot is contained in a neutral position, traditional supportive footbeds (arch supports) are quite compatible with the mechanisms and philosophies of the prior art.”

Here is what the inside and outside feet of a skier in a turn look like when  the feet are in neutral.

Neut edge

Since there are offsets or moment arm between CoP and SRF on each foot, the sole of the inside foot of the turn will tend to roll away from the centreline between the feet (ergo, it will tend to evert) while the sole of the outside foot of the turn will tend to roll towards the centreline between the feet (ergo, it will tend to invert).  Under specific conditions the external forces acting on the skier will tend to make the outside foot of the turn rotate into the turn (ergo, it will tend to evert). But, for reasons that will be provided in a future post it is not possible to create conditions under which the external forces acting on the skier will tend to make the inside foot of the turn rotate into the turn. For this reason the force applied to the snow by the skier must be directed to the inside edge of the outside ski of the turn. The inside foot and leg are used to help direct the force to the outside ski. This what Ligety and Shiffrin do so well.

LIGETY’S MOMENT OF TRUTH – STEP 3

In my last post, I said that I would offer an explanation for the historically consistent 67 mm (+ or -)  ski waist dimension of skis. From a mechanical and biomechanical perspective, the innermost inside edge limit of the outside ski of a turn of the human foot is the ball of the great toe. The anatomical centre-line of the human foot runs through the centre of the heel and the centre of the ball of the 2nd toe. Therefor, it follows that if the foot is oriented on the proximate transverse running centre of a ski, the width under the ball of the foot should be in the order of 2 times the centre-to-centre dimension between the balls of the great and 2nd toes. The graphic below shows these relationships with X indicating the centre-to-centre dimension.

1-2 MT centre

It is easy to measure this dimension on your own or someone else’s foot using an out-to-out micrometer (with points) or a protractor. The foot should be weighted when the measurement is taken. Although the balls of the feet (metatarsals) spread in a fan-like manner when the forefoot is weighted, the centre-to-centre dimension between the balls of the great and 2nd toes does not increase significantly. In addition, as foot sizes and widths vary, the variation in the centre-to-centre dimension, X is small, in the order of 1-2 mm per full size. The centre-to-centre dimension between the balls of the great and 2nd toes of  my US Men’s size 12 foot is in the order of 35 mm. My spouses’ US  Ladie’s size 8 foot (US Men’s size 7)  centre-to-centre dimension is in the order of 30 mm. The table below shows an extrapolation of these numbers based in studies of specific foot references for a range of sizes. I am going to do a study that measures dimension X for a cross section of foot sizes, both male and female. As far as I am aware, such data does not exist. Nor, am I aware of any studies or teachings pertaining to the mechanics and biomechanics of skiing where this issue is discussed.

X Dimension

As far back as 1978, I was very much aware of the importance of positioning the ball of the foot as close as possible to the inner sidewall of the boot shell as well as maintaining the normal alignment of the big toe, something the DIN standard toe shape makes extremely difficult. Ideally, the Centre of Pressure should be over or slightly on the inside turn aspect of of the inside edge of the outside ski of a turn. Although edging mechanics that are driven by external forces require more than the aforementioned alignment of the centre-to-centre dimension between the balls of the great and 2nd toes, as the dimension of the waist of the ski becomes increasingly unfavourable a point is reached where edging mechanics driven by external forces are no longer an option.

As far as I know, the current low end of waist width in skis is 63 mm. It is not unusual for female racers to have feet as small as US Men’s size 5 or even 4. The implications are  that a female racer with feet in this size range could need a ski with a waist dimension as small as 54 or 55 mm in order to be competitive. There are significant implications for females with small feet that are skiing on skis with waist dimensions that are significantly in excess of these dimensions. It is worth noting that the design of ski boots is typically based on a US Men’s size 9 foot and then scaled up and down for other sizes.