Lindsey Vonn


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.


Camera angles and the sometimes less than sharp picture quality of  World Cup race coverage can make it difficult to critically analyze ski technique. It doesn’t help that cameras often switch views or gate flags obscure racers just as an important event is occuring. But there were three sections of the January 19, 2015 Cortina d’Ampezzo Super G, won by American, Lindsey Vonn by a convincing 0.85 second margin over second place Austrian, Anna Fenninger, that clearly demonstrated Vonn’s superior technique.

The video clip below compares Vonn to Fenninger in two sequences with a third sequence of Vonn.


In the first sequence, Vonn is ahead of Fenninger by 0.4 seconds as she passes the gate (Vonn –  estimated at 33.8 seconds vs Fenninger – estimated at 34.2 seconds). The most important Event of an effective ski technique is Event 7 (whole leg top down internal rotation). This requires inside ball of the foot to outside heel boot shell force-coupling while maintaining force over the inside edge of the outside ski with the load W on the head of the first metatarsal. The position of a racer at Event 3 (ski flat) and in especially whether Event 4 (load transfer induced pronation) occurs, provides a good indication of what the racer is able to do in the subsequent turn phase. Depending on the alignment of the load W and the resultant force R emanating from COM in relation to the inside edge of the new outside ski, the ski/foot/leg will either rotate into the turn or out of the turn. The sketch below shows the two possible options for the ski lever – DOT 10: SKI LEVERS –

The vertical grey box represents a lift height from the base of the ski to the plane of the boot board of approximately 90 mm in relation to a 65 mm ski width underfoot. The graphics represent a frontal view of the ski/equipment system with approximately  3 degrees of edge angle into a right hand turn as represented in the first video sequence of Vonn and Fenninger.

Ski Lever OptionsClick on the image to enlarge it

If the load W is on the inside turn aspect of the inside edge as shown in the left hand graphic above, a platform of contiguous ground reaction force exists on which to support the racer and engage the external forces to drive the ski into the turn. If the load W is on the outside turn aspect of the inside edge as shown in the right hand graphic, the edge will not grip and the ski will tend to slip away from the turn as the forces acting on the ski build.

The racer has two options with which to resist the loss of edge grip of the outside ski, 1) use what is incorrectly referred to as knee angulation (adduction of the hip in combination with some internal rotation of the whole leg) or, 2) move to the inside ski and increase the inclination into the turn. Neither option is as effective as a platform under the outside ski where the load W is acting on the inside turn aspect of the inside edge. Without a contiguous source of ground reaction force with which to apply force to the ski and generate postural responses to perturbations in GRF, superior strength and conditioning are irrelevant. Precisely carved ski turns are replaced by a series of linked recoveries. Survival instincts and acrobatics, not skill and superior technique, prevail.

In the first sequence, as Vonn comes around the gate, she rotates her outside leg and ski across her trajectory, loads and locks the inside edge and  neatly cuts off the turn. That her outside ski does not appear to oscillate in the high load phase of the turn suggests that she has successfully executed Events 4 through 7. As Fenninger comes around the same gate, she appears to be carving a clean turn on her outside ski. But this is an illusion. If you watch carefully, you will see that she appears to have much more weight on her inside ski than Vonn. Fenniger appears to be using her outside ski to steady her position on her inside ski.

The next sequence is even more telling. The fluidity with which Vonn moves from one turn to the next attests to the continuity of the coordinated lower limb muscle activity across the bridge of her pelvis. This is also evident in the last sequence of Vonn. By comparison, Fenninger makes a move from the old turn to the new turn that is both awkward and disruptive of the processes of balance as it pertains to neural flow. The hallmark of the world’s best skiers has always been that they maintain and control pressure on the outside ski from the start of a turn to the finish. – DOT 13: INNATE FLOW BALANCE –‎

The question is whether the move to the inside ski is a part of a deliberate technique or a reflex action arising from a loss of edge grip on the outside ski. Since others appear to be using a similar move it seems to have become an established technique as evidenced by Germany’s Felix Neureuther in the short clip below from the recent men’s slalom in Wengen. The tight timing of slalom is one thing. Super-G is another whole matter.


In my mind the issue is not who the best ski racer is but rather whether all racers are realizing their full human performance potential, especially as it pertains to the physiological processes that defend against injury. If racer A is at 95% of their maximum potential and racer B is at 80%,  is the best athlete winning? I don’t think so. In formula one racing, the combination of the best driver and the best race car consistently win. In ski racing it should also be the combination of the best racer and the best equipment tuned to the racer, that consistently wins. I have not seen evidence that this model is part of the current paradigm. The question is why not?




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.



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.



I hadn’t intended to discuss ski injuries at this point. But in preparing the visuals for my last post, NEUTRAL? ANYTHING BUT, my mind kept running through the horrific, gut wrenching crash of Lindsey Vonn in the women’s downhill in February 2013. This post segues to an issue that is central to my efforts, skier safety.

When I did a research project in 1991 with a company called MACPOD (Steve Podborski and I) on the mechanics, biomechanics and physics of skiing,  I was fortunate to have worked with some exceptionally talented scientists. One such scientist was Alex Sochaniwskyj, P. Eng. Alex is a biomedical engineer. At the time that we started our project I specifically requested that we ask Alex if he would work with me. He was working as a consultant at the Hugh MacMillan Rehabilitation Centre in Toronto. When Alex was approached he left his position to work on our research project. Alex’s impression of me, as expressed in his letter in support of my nomination for a science award in 1995, is as follows:

“The design and development strategies used by David MacPhail are very holistic in nature, placing the human as the central and most critical component in a biomechanical system. His intent is to maximize human performance and efficiency, while foremost preserving the well-being and safety of users (emphasis added) and minimizing biomechanical compromises.” – Alex Sochaniwskyj, P. Eng.

In an ideal world, there would be no injuries in sports. Although some injuries are unavoidable, I believe that every effort should be made to keep the number as close to zero as possible.

The official explanation of the events of Lindsey Vonn’s crash was that she came off the jump off line, tried to correct, could not hold her line, crashed and injured her knee. Other than Vonn appearing to come off the jump off line, I disagree with the events. What I saw after much frame by frame study is that Vonn landed with her right extended and angulated in anticipation of beginning a correction when her skis made contact with snow. She appears to have landed with her right ski on edge. Landing jumps on anything other than in a straight line on a pitch incurs risk because the feet and legs have limited ability to dissipate the energy of impact. Landing on one foot multiplies the risk. If this post helps even one skier avoid injury it will be worth my effort.

Here is a short clip of Vonn’s crash in slow motion with a number of stop action frames at critical events.


Here are a series of still images.

In the first image below Vonn appears to be caught back and trying to get over her skis. Her left arm is up. Her right arm appears to be directed across to the left as if she is trying to make a left turn. The angle of her right leg appears to be angulated in the direction of a left turn.

Vonn 1

In this image it appears as if Vonn’s right knee has moved towards her left knee. Her right ski has acquired more edge. I think it probable that her knee was injured in this frame.

Vonn 2

In this image it appears that Vonn has lost support of her right leg

Vonn 3

In this image Vonn’s right leg is giving way.

Vonn 4

This image is hard for me look at. The angle of her right leg is brutal. It was after this frame that she tumbled forward. I believe she fell because her knee was injured and did not injure her knee in the forward fall as some claim.

Vonn 5

I hope that I never see anything like this again.