Biomechanics

WHY TRYING TO COPY HIRSCHER AND SHIFFRIN’S MOVES DOESN’T WORK

There appears to be a widely held perception within the ski industry, even among coaches and trainers at the World Cup level, that skiing like Hirscher and Shiffrin is simply a matter of observing and then copying their movements. There also appears to be a widely held perception that strength training and training on BOSU balls, wobble boards, slack lines and thick foam pads will transfer to improved balance on skis.

In a recent article, Nailing the Coffin Shut on Instability Training Ideas (1.), trainer, Bob Alejo, cites 59 papers on the topic of instability training in support of his position that not only are the assumptions about instability training improving balance in a specific activity incorrect, instability training may actually have a negative effect on performance.

As far back as 1980, I had found that an immediate improvement in skier performance after ski boot modifications was a reliable indicator that the modifications were positive. Sometimes this was evident in the first few turns. I had also found that equipment modifications or equipment changes that had a negative effect did not become obvious right away. I didn’t understand the reason for the immediate and sometimes dramatic improvement in skier performance following ski boot modifications. But I suspected it had something to do with improved skier balance.

By 1990, I had hypothesized that elite skiers are able to create a dynamically stable foundation under their outside ski and foot in a turn to balance on by rotating the edged ski against resistance from the sidecut and that this has the effect of extending ground reaction force from the snow out under the body of the ski. But even after the Birdcage studies of 1991 validated my theory, I still didn’t fully understand the reason for the dramatic improvement in skier performance in the Birdcage tests or following modifications made to conventional ski boots. Strain gauges fit to the Birdcage showed forces and the sequence of loading. But the strain gauges could not measure the magnitude of the forces.

It was Dr Emily Splichal’s (2.) that answered my question when she said;

It doesn’t matter how physically strong you are. Without a foundation of stability, you are weak. With a foundation of stability, you are stronger and faster than anyone.

In his article, Nailing the Coffin Shut on Instability Training Ideas (1.), Alejo supports Dr. Splichal’s position:

The predominant theme of the training data analysis under unstable conditions is the striking reduction in force and, subsequently, power. It would be of no surprise then that the speed of motion, as well as the range of motion, were negatively affected under unstable conditions, as cited in the literature.

Reduced Force Outputs Result in Less Power

Essentially, even though both groups improved in some instances, the stable surfaces group outperformed the unstable group in all categories. So much so that it led the authors to conclude that the results of their study affirmed—what was a criticism then and now is fact—that unstable training does not allow for enough loading to create strength and data.

Simply put, athletes can handle heavier weight under stable conditions versus unstable conditions.

Dynamic Stability is critical for a skier or skater to assume a strong position from which to generate force while maintaining control and initiate precise movement from. A key marker of dynamic stability in ice skating and skiing is the magnitude of impulse force, especially peak force.

Impulse

Impulse is a large force applied for a short duration of time. Peak force is the highest force applied during an impulse force.

If superior dynamic stability is the reason for the dominance of racers like Hirscher and Shiffrin then pressure data obtained during skiing should show higher impulse and peak forces than generated their competition. While the technology to measure these forces is readily available I don’t have access to this data even if it does exist. So I’ll use data generated from hockey skate study I was involved in 2012 that compared data captured from competitive skaters performing in their own skates to skates I had modified using principles from my patents and modifications described in this blog.

The first step was to capture baseline data from the test subjects own ice skates (OS). The bar graph below shows the peak force in Newtons applied by each of the four test subjects. Peak force has a very short duration.

Subjects 1 and 3 applied a peak force of approximately 800 Newtons. A pound is 4.45 Newtons. So 800 Newtons is approximately 180 lbs.

Test subjects #1 and #3 are almost identical. But test subject #1 has a very slim edge over test subject #3.

Test subject #2 is 3rd in ranking while test subject #4 is last.

Assuming this was a study of competitive skier test subject #1 appears to have a stability advantage over the other skiers. This would translate into quicker more precise turns (hairpin turns) and less time on their edges.

In my next post I will show what happened when the same test subjects used the skates I prepared.


  1. Nailing the Coffin Shut on Instability Training Ideas – https://simplifaster.com/articles/instability-training/

 

THE HIRSCHER/SHIFFRIN HAIRPIN TURN EXPLAINED

The topics of interest in recent views of my blog combined with comments on online forums on ski technique where nebulous terms such as pressure and tipping are an integral part of the narrative, have highlighted the need for a uniform frame of reference as a basis for meaningful discussions of ski technique as well as for the analysis and accurate identification of factors that explain the superior technique of racers like Marcel Hirscher and Mikaela Shiffrin. Simply trying to emulate the moves of the great skiers without re-creating the equipment factors that enable superior performance is not a productive exercise.

I touched on some of the factors that enable Marcel Hirscher and Mikaela Shiffrin to dominate their competition in my posts WHY SHIFFRIN AND HIRSCHER ARE DOMINATING (1.) and WHY HIRSCHER AND SHIFFRIN CAN CROSS THE LINE (2.). Over the coming weeks, I will post on the factors that I believe explain the ability of Hirscher and Shiffrin to make rapid, abbreviated hairpin turns even on the steep pitches of a course using what I call the problem-solving matrix jigsaw puzzle format. In contrast to the linear step-by-step progression problem-solving format, the matrix jigsaw puzzle format lays out information relevant to a situation in a grid format much like a jigsaw puzzle.  Known factors are assembled where there is a fit with the interfaces and arranged in relation to other components until a solution begins to emerge much like a coherent picture begins to emerge in a jigsaw puzzle as the pieces are correctly assembled. As the picture becomes more clear, tentative connections between the known segments are hypothesized to try and extrapolate the big picture. As the process progresses, less certain or flawed information is discarded and replaced with more certain information

A lot of critical information on the neurobiomechanics and even the mechanics and physics of skiing is either missing, misapplied or misunderstood in the narrative of ski equipment and technique.

Biomechanics of Sports Shoes

A valuable reference on neurobiomechanics and the future of sports shoes is the technical text, Biomechanics of Sports Shoes by Benno M. Nigg. Used in conjunction with the chapter on the Ski Boot in the medical text, The Shoe in Sport, valuable insights can be gleaned on the mechanics, neurobiomechanics and physics of skiing.

Nigg’s book can be ordered at NiggShoeBook@kin.ucalgary.ca. The following chapters in particular contain information relevant to skiing:

3. Functional Biomechanics of the Lower Extremities (pp 79 to 123) – contains essential information on the human ankle joint complex, tibial rotation movement coupling and foot torsion.

4. Sensory System of the Lower Extremities (pp 243 to 253) – contains essential information on the sensory system responsible for balance and precise movement, both of which are key to effective skiing.

In order to advance skiing as a science, a mutual objective must be getting the right answer as opposed to a need to be right.

The wisdom of Albert Einstein is appropriate.

A man should look for what is, and not for what he thinks should be.

To raise new questions, new possibilities, to regard old problems from a new angle, requires creative imagination and marks real advance in science.

We cannot solve our problems with the same thinking we used when we created them.

If you can’t explain it simply, you don’t understand it well enough.

In my next post, I will start laying out the functional principles that I currently believe explain the factors that enable the superior performance of racers like Marcel Hirscher and Mikaela Shiffrin and their ability to rapidly redirect their line and maximally accelerate by making rapid, abbreviated, hairpin turns.


  1. https://wp.me/p3vZhu-2q3
  2. https://wp.me/p3vZhu-2qo

SCHEDULE OF POSTS

The link below will take you to a page with a link to a PDF of all 298 posts I have made since my first post of May 11, 2013.

https://wp.me/P3vZhu-2sM

The schedule lists posts in the order of newest (Jul 10, 2018) to oldest (May 11, 2013). The image below shows what the schedule looks like. The date and time of the post and the views and likes are listed below the title of each post.

 

The top 10 posts to date are shown in the graphic below.

I am in the process of reviewing and analyzing post subjects based on ranking with the objective of better directing my efforts to my readers. If there are any subjects you would like addressed please post them in the comments section.

 

WHAT’S YOUR PQ? [PERFORMANCE QUOTIENT]

After my disastrous experience in 1977 with the mythical Perfect Fit with Crazy Canuck, Dave Murray (.1); one that transformed Mur from a World Cup racer to a struggling beginner, my work on ski boots became focussed on removing instead of adding material and making room to allow a skier’s foot to assume its natural configuration in the shell of the ski boot. As I improved the accommodation of a skiers’ neurobiomechanical functional requirements in the ski boot, skier performance improved in lockstep. I was merely reducing the structures of the boot that interfered with performance to enable a skier/racer to use the performance they already had.

Fit: The Antithesis of Human Function

Fit, by it’s definition of joining or causing to join together two or more elements so as to form a whole, is the antithesis (def: the direct opposite) of enabling the function of the human foot and lower limbs as one of the most dynamic organs in the human body. Fitting a ski boot to the foot and leg of a skier, especially a racer, equates with imposing a disability on them (2.). Although I didn’t realize it until I read The Shoe in Sport and learned of the barefoot studies done at the Human Performance Laboratory at the University of Calgary, my work on ski boots had transitioned from Fitting (disabling), by adding materials to liners to fill voids between the foot and leg and shell wall, to UnFitting (abling) by removing materials from liners and expanding and grinding boot shells so as to accommodate the neurobiomechanical functional requirements of the foot and leg of a skier.

But the big breakthrough for me came when Steve Podborksi won the 1981-81 World Cup Downhill title using the dorsal constraint system (Dorthotic) I developed and later patented. The Lange boot shells the device was used in had the least constraint of any ski boot I had ever worked with. The instantaneous quantum leap in Steve’s performance compared to the same shell using a conventional liner raised the question of how could a skier’s maximum performance be achieved and was there a way to compare to a skier’s performance in different ski boot/liner configurations to an optimal reference standard?

A reliable indicator that my un-fitting was trending in the right direction was that skiers consistently found that skiing became easier. For racers, coaches would typically report that the racer was skiing better. Improved race results served as further confirmation of my efforts. But these indicators were subjective. I wanted a way to not just measure performance with quantifiable metrics generated from data specific to the activity, I wanted to be able to compare the same metrics to a reference or baseline standard that represented the optimal performance of a skier or racer at a given moment in time. Without a way to measure and compare performance there is no way of knowing how a ski boot is affecting a skier or racer and especially no way of knowing how close they are to skiing at their maximum level of performance. I wanted to develop a skier Performance Quotient or PQ.

Definition of Quotient

  • Mathematics: – a result obtained by dividing one quantity by another.
  • a degree or amount of a specified quality or characteristic.

A skier Performance Quotient would capture baseline metrics from a skier’s performance in a ski boot that provides the optimal functional environment for the foot and lower limbs to the skier’s peformance in different ski boots including a skier’s current ski boot. The ski boot that provides the optimal functional environment for the foot and lower limbs would be designated as 100%. If the same metrics captured in a different ski boot were 78% of the reference standard, the skier’s PQ in the ski boot would represent a PQ of 78% against a possible 100% or 78/100.

Raising the bar of skier/racer function with body work and/or conditioning will raise the PQ. But it cannot close the PQ gap created by the performance limitations of the interference with neurobiomechanical function caused by their ski boot. Nor can trying harder or training more intensely overcome the limitations of a ski boot. Assuming 2 ski racers of equal athletic ability and mental strength, the racer with the ski boot that enables a higher PQ will dominate in competition. The only way to improve a skier’s PQ when it is less than 100% is to improve the functional environment of the ski boot.

In current ski boot design process, manufacturing and aesthetic considerations override skier functional requirements. An innovative approach to the design of the ski boot is needed. This is the subject of my next post.


  1. IN THE BEGINNING: HOW I GOT STARTED IN SKI BOOT MODIFICATIONS, May 12, 2013 – https://wp.me/p3vZhu-y
  2. LESS REALLY IS MORE, May 13, 2013 – https://wp.me/p3vZhu-N

 

SKI BOOTS: WHY LESS IS MORE

At the time I filed an application for my second patent in April of 1989 , I had some ideas of what a ski boot should do for the user from what I had learned from the dorsal containment system I was granted a patent for in 1983. But I was still a long way from being able to answer the question.

A watershed moment came for me in 1990 when I read a medical textbook published in 1989 called The Shoe in Sport on what is referred to in the text as ‘the shoe problem’.

The Shoe in Sport, supported by the Orthopedic/Traumatologic Society for Sports Medicine, was originally published in German in 1987 as Der Schuh im Sport. The textbook is a compilation of the collective efforts of 44 international experts, including Professor Peter Cavanagh, Director of the Center for Locomotion Studies at Penn State University, biomechanics experts from the Biomechanical Laboratories at ETH Zurich and the University of Calgary, Professor Dr. M. Pfeiffer of the Institute for Athletic Sciences at the University of Salzburg, Dr. A. Vogel of the Ski Research Syndicate, Dr. W. Hauser and P. Schaff of the Technical Surveillance Association Munich and many other experts in orthopedic and sportsmedicine on  ‘the shoe problem’.

The buyers of athletic shoes are always looking for the “ideal shoe”. They encounter a bewildering variety of options and are largely dependent for information on the more or less aggressive sales pitches that directed at all athletes in all possible ways. (1.)

This volume should assist in defining the role and the contributions of science in the further development of the athletic shoe and in the recognizing of the contributions made by the various research groups, who are all interested in the problems of the athletic shoe. (1.)

Dazzled by the fancy names, the buyers believe that they can match the athletic performance of the champion who wears “that shoe,” or after whom the shoe is named. The choice is not made easier by the plethora of promises and a roster of specific advantages, most of which the merchant cannot even explain. (2.)

When The Shoe in Sport was first published in 1987, the field of biomechanics was in its infancy as was the associated terminology. This created an opportunity for a new marketing narrative of techno buzzwords. Since the consumer had no way to understand, let alone assess, the validity of any claims,  the only limits to claims made for performance was the imagination of the marketers. Consumers were increasingly bombarded with features that far from recognising the human foot as a masterpiece of engineering and a work of art as espoused by Leonardo da Vinci, suggested the human foot is seriously flawed and in need of support even for mundane day-to-day activities. These marketing messages distract attention away from the real problem, the design and construction of shoes and their negative effect on the function of the user; the modern ski boot being one of the worst examples.

The Shoe Problem

For this reason, the “shoe problem”as it exists in the various fields of athletic endeavour, will be studied with respect to the biomechanical, medical , and technical aspects of shoemaking. The findings (criteria) should enable the interested reader to distinguish between hucksterism and humbug on the one side and the scientifically sound improvements in the athletic shoe on the other. (1.)

Form follows Human Function

The Shoe in Sport focusses on the medical orthopedic criteria in offering guidelines for the design of shoes for specific athletic activities including skiing and ice skating.

Less attention will be paid to the technical and material aspects of the running surface and shoe, and more to the medical and orthopedic criteria for the (design of) athletic shoe. For this reason, the “shoe problem”as it exists in the various fields of athletic endeavour, will be studied with respect to the biomechanical, medical , and technical aspects of shoemaking. 

This volume should assist in defining the role and the contributions of science in the further development of the athletic shoe and in the recognizing of the contributions made by the various research groups, who are all interested in the problems of the athletic shoe.

Barefoot as the Reference Standard

Research done at the Human Performance Laboratory at the University of Calgary found that optimal human performance is produced with the unshod foot and that human performance is compromised by the degree of interference; the greater the interference caused by any structure appended to the foot, the greater the compromise of performance. This is true even for a thin sock.

The authors of The Shoe in Sport ask:

Is there really a need for shoes? The examples of athletes like Zola Budd and Abebe Bikila suggest in a technologic environment the evolution of the athletic shoe parallels the decline of our organs of locomotion. (1.)

The Future of the Ski Boot

The shoe affects the athlete’s performance and serves to support the foot as a tool, as a shock absorber, and as a launching pad. Giving serious consideration to our organs of locomotion opens up an enormous area of activity to the athletic shoe industry. (1.)

This is especially true of the ski boot. The questions that needs to be asked is how does the structure of the ski boot affect the human performance of skier and what is the minimal combination of structure that will enable maximum skier performance.

Few forms of athletics place as high demands on the footwear used in their performance as alpine skiing. It (the ski boot) functions as a connecting link between the binding and the body and performs a series of difficult complex tasks. (3.)

Before the question of what structure of a ski boot will maximize skier performance can be answered, the functional mode of the human system in the complex physical environment associated with skiing must be known. The first and most important and fundamantal component of this question is explaining the mechanism by which the human system is able to achieve a state of balance on the outside ski characterized by neuromuscular control of torques in all 3 planes across the joints of the lower limb and pelvis.


  1. Introduction by Dr. med. B. Segesser, Prof. Dr. med. W. Pforringer
  2. 2. Specific Running Injuries and Complaints Related to Excessive Loads – Medical Criteria of the Running Shoe by Dr. med. N. L. Becker – Orthopedic Surgeon
  3. Ski-Specific Injuries and Overload Problems – Orthopedic Design of the Ski Boot –  Dr. med. H.W. Bar, Orthopedics-Sportsmedicine, member of GOTS, Murnau, West Germany

WHY HIRSCHER AND SHIFFRIN CAN CROSS THE LINE

There has been a huge surge in interest in my post HIRSCHER AND SHIFFRIN WIN BY CROSSING THE LINE.

The reason Hirscher and Shiffrin can ski this way is that they have the ability to cross the rise line and establish balance on their outside foot and leg in milliseconds. This enables them to make what amounts to a hairpin turn. They are on and off their edges like a flat stone skipping off the water. The reason they can do what few other racers can is because their boot setup supports the requisite neurobiomechanics. I discuss this in my last post WHY HIRSCHER AND SHIFFRIN ARE DOMINATING.

(NEURAL) BIO (MECHANICAL) ENGINEERING: DOES IT WORK?

The proof of a performance concept lies in the data. If neural bio mechanical engineering can improve human performance in a specific application such as skiing, skating or cycling then it should be possible to demonstrate meaningful performance improvement with quantifiable metrics generated from data captured from the actual activity. In the case of cycling, meaningful improvement would be shown by an increase in metrics such as peak force transferred to the pedal spindle that cannot be explained by other factors. In order to attribute any change in performance, whether positive or negative, to neural bio mechanical engineering the effect must be immediate, reversible and reproducible. In the case of the improvement seen with Podborski’s performance using ski boots fit with the dorsal fit system, reverting to identical boot shells fit with a conventional liner reversed the improvement in performance.

Where possible, standard protocols should be used and testing performed by experts in the field. In the case of the cycling shoe Tekscan F Scan data comparison, my only involvement was to analyze the human lower limb requirements for cycling and generate the design and specification for the device that produced the neural bio mechanical engineering effect. I played no role in designing the test protocol or conducting the tests. I was not even an observer.

So how did the neural bio mechanical engineering system work in the application to cycling?

Performance Metrics

There are numerous metrics that can be used to assess and compare performance. The subject test was limited to pressure analysis using the Tekscan F Scan system.

In the graphic below the upper image outlined in red is the F Scan pressure image of an elite cyclist captured at 3 o’clock in the crank cycle at moderate to high load using their own conventional cycling shoe. The F Scan pressure image outlined in green below the first image is of the same cyclist using the device that bio engineered the foot and lower limb.

Results

There are a number of significant differences between the forces applied with the same cyclist with the conventional cycling shoe and the bio-engineering. In the 2 F Scan images, the contact area of the application of force across the heads of the metatarsals over the pedal spindle with bio-engineering is much greater and the force much higher than the force applied to the heads of the metatarsals in the conventional shoe.

The two significant, quantifiable (measurable) metrics that relate directly to cycling performance are: Peak Force and Anterior-Posterior (forward-backward) Excursion of the Center of Force.

Peak Force

The peak (maximum) force with the device that bio-engineered the foot and lower limb was 140% of the peak force applied with the conventional cycling shoe.

Anterior-Posterior (fore-aft) Force Excursion

This is the range of forward-backward movement of center of force through the crank cycle.

The graphic below shows the tracking of center of force forward and backward in the pedal stroke. Notice how straight the force tracks in the lower image with bio engineering compared to the upper image captured from the conventional cycling shoe.

The ability to move the center of force forward and backward, not just down and, more important, substantially aligned with the crank rotation is both more consistent and efficient than the excursion tracking with the conventional shoe. The bio engineering device improved excursion by 175% in rearward tracking force (long bars) and 200% in forward tracking force (over the top) as shown by the short bars below the images.

In my next post I will discuss how I designed a ski boot from the snow up using principles of neural bio-mechanical engineering.