IMPLICATIONS OF THE UNIVERSITY OF OTTAWA PRESSURE STUDIES


The two University of Ottawa pressure studies used different groups of ski instructors with different qualifications for each study. One study used three highly skilled ski instructors (C.S.I.A. Level VI). The other study, the one presented at the Proceedings of the XVI International Symposium on Biomechanics in Sports (1998), used six internationally certified Canadian ski instructors. The pressure patterns seen in the two groups had some important differences.

“Of interest however is the short distance travelled by the cop during most of the turns.” (made by the six internationally certified Canadian ski instructors)

In the three C.S.I.A. Level IV instructors, the centre of pressure (COP) traveled from the head of the first metatarsal to the medial part of the heel as they made their way through a turn whereas COP in the six internationally certified Canadian ski instructors moved from the head of the first metatarsal at the beginning of all turns, except Giant Slalom turns, and progressively migrated towards the medial aspect of the longitudinal arch near the end of the turns. In all turns made by the internationally certified Canadian ski instructors, except GS turns, COP barely moved back from its position under the head of the first metatarsal.

It was only in the Giant Slalom turns for the internationally certified instructors that COP traveled from the head of the first metatarsal to the medial part of the heel in the last part of the turn. In no case did the pressure data find that COP was at the heel at the initiation of a turn for either group of instructors. While the studies might have inferred that high pressure COP was either under the head of the first metatarsal or the under the heel, but not both at the same time, this was not the case. When there is a well defined area of high pressure COP under the head of the first metatarsal or the medial part of the heel, there will always a secondary well defined area area of high, but lesser pressure COP, under the opposite area. The difference is in the degree or pressure differential between the two areas of high pressure COP.

When there is high pressure COP under the heel, there will be a poorly defined area of low pressure under the center of the forefoot as shown in the graphic below. The red circle over the heel with the black dot represents COP. COP creates a weak ‘sense’ of force along the center of the ski, in addition to a well defined sense of force acting perpendicular to center of the base of the ski. But a secondary area of a lesser high pressure COP cannot exist under the head of the first metatarsal in this configuration.

Heel

High pressure COP under the head of the first metatarsal is dependent on a secondary area of lesser high pressure COP under the heel as shown in the graphic below.

1st 2

COM can only be guestimated when there is high pressure COP on the heel. But COM must be aligned with COP on the same axis and close to, but behind, COP when there is high pressure COP is on the head of the first metatarsal. The higher the pressure on the first metatarsal COP, the closer COM is to it. As I will explain in my next post, the position of COM creates high pressure COP; stance regulates the position of COM in relation to the outside foot of a turn. Therefor, stance creates high pressure COP. The ability to create these two areas of high pressure COP and control and especially manage the pressure differential between these two areas of high pressure COP, has long been the secret of the world’s greatest skiers. It is the ability to generate the combination of high pressure COPs on the head of the first metatarsal and heel and especially to manage the pressure differential between these two COPs, that seems to have eluded researchers. As I intend to explain in the next post, the small fore/aft movement in COP seen between the head of the first metatarsal and the medial arch, as turns progressed, is indicative of the degree of effectiveness of the management of the pressure differential by the skier between the high pressure COP on the head of the first metatarsal and high pressure COP on the heel. Increasing or decreasing pressure on one COP will result in a corresponding opposite change in pressure on the other COP.

“Historically, it has been quite complicated to perform biomechanics research on alpine skiing on-site. This fact is so because of the environment where the sport is practised which does not lend itself well to biomechanical measures using traditional equipment.”

Did I hear Birdcage? The researchers are correct when they say, “it has been quite complicated to perform biomechanics research on alpine skiing on-site”. Up until I designed the Birdcage 7 years earlier, in 1991, with Alex Sochaniwskyj, a brilliant biomedical engineer, it had been complicated to study biomechanics of alpine skiing during actual ski maneuvers. Sochaniwskyj not only contributed to the design of the Birdcage research vehicle, but also wrote the software and assembled the instrumentation package where none existed. For the studies done on Whistler’s summer glacier, Toshiba loaned Alex a prototype of a battery powered portable computer they were developing. This was in a day when the only computers commercially available were monsters that filled whole rooms or in kit form. The difference between Sochaniwskyj and I and the researchers who had to wait seven years for technologies to emerge before they could follow in our ‘footsteps’, was that we knew precisely what pressure patterns we were looking for in the feet of Olympic and World Cup Champions and neophyte skiers. And we knew what the pressure patterns meant before we did our studies. If we had been wrong, and we weren’t wrong, our very specific sensor placement would have recorded nothing of interest. Guess what we were studying?

Birdcage Sensors

In my next post I will talk about what the two high pressure COPs mean.

Wishing you all the best for the holiday season

 

 

6 comments

  1. How relevant is this now? The study was done and then published in 1998.

    Ski design has changed rapidly since then, and so has the technique used by CSIA level IV’s.

    I fail to see how valuable a study done 18 years ago, with 3-6 test subjects is. Is there a link somewhere to both the papers? Has further study occurred since 1998 on this subject? Surely we can’t still be basing our bio-mechanical principals on a 6 man test performed 18 years ago?

    1. Seriously? The University of Ottawa studies didn’t even investigate or comment on biomechanical principles. They looked objectively for pressures under the foot and reported what they found. The principles I am espousing are sound, thoroughly proven and eminently defendable. If you disagree with something I say, go ahead, hit me with your best shot. But don’t waste my time by offering uninformed opinions.

      You insult any person of reasonable intelligence by attempting to ply the tired old prescripted con that implies that the fundamental laws of the universe are in a constant state of flux. How about submitting a position on the mechanics, biomechanics and physics behind the technique promoted by the CSIA with 1) detailed explanations based on sound principles of science and, 2) studies that validated the theory of the CSIA, that can be defended against severe scrutiny. Better still, go back to square one and produce the studies and principles that support the concept of clamping the foot and leg into what amounts to an orthopedic splint that severely compromises the defences against injury and then attach a large lever to the splint and apply high forces to the foot and leg.

      1. Wow. Way to encourage people to get involved.

        I simply asked if the study was still relevant.

        I can understand that you believe all of what you say to be true, I simply asked whether more study was done, and if the validity of the study was still relevant given that it’s 18 years old. But I can see that you’re not really open to any kind of questions, and seem to believe that everything is a personal attack on yourself.

        As a “person of reasonable intelligence” I don’t feel insulted by asking my questions, however as a member of the skiing community and someone looking for further information, I am.

        Your response is rude, un professional, and disheartening for anyone looking to ask questions, or for further clarification. Perhaps you should should look more into developing you own social skills, and trying to help grow a fledgling sport than berating others looking to try and expand their knowledge. Good work.

        So I ask again, how relevant is the study, as it’s 18 years old? Was further study completed? Perhaps using a more modern technique instead? Does Hirscher still do the same as Stenmark did?

        As I’m not certain (because of course I’m an idiot and not a reasonably intelligent person it seems), but surely when technique changes, so does the area in which we might want to pressure the foot, however I am NOT a physicist, an engineer or a biologist, and so I am seeking some guidance. That’s all. Please reply in a courteous manner, in order for me to be able to understand.

        Regards.

      2. First of all, I apologize. A standard response from a certain camp in the ski industry to any study I post is to attempt to discredit it by claiming it is outdated, it was not done by the ski industry (which would have ensured it was biased) the researchers (no matter how qualified) were incompetent because “I say so”.

        To your question, “Is the study relevant today?” Absolutely.

        A bit of background on how I got here today is appropriate. I started skiing in 1970 and quickly skied at an expert level on green and blue runs until the following year when I changed from leather boots to the new all plastic boot. My first day on the new boots on a picture perfect ski day was one of the most terrifying experiences of my life. When I started looking for answers, no one could offer anything more than try another boot. I tried more than one. None worked. Being a problem-solver, the approach that was obvious to me was to study the expert skiers. That is when I began to notice that being fit was not necessary to be an expert. After I started working on my own boots, expert skiers started asking me to work on their boots. This is how it went. In 1978, was approached by Nancy Green Raine and asked to work with National Team racers. After I helped Steve Podborski win the WC Downhill title using a new in-boot technology I invented he asked me in 1983, “Can you do what you did for me for every skier?” That was a very tall order. But I said, “I will try”.

        By 1985, I was starting to understand how the world’s best skiers were able to balance on their outside ski. By balance, I mean balance the forces across the inside edge. By 1988, I was certain I had it figured out. But when the company Podborski and I formed called MACPOD raised investor money to try and design a new boot, I dug in my heels and refused to go forward on my ‘unproven theory’. No matter how good my theory sounded, to me it was so much fluff until I saw hard data. The problem was that there was no commercial technology available to get the data. So I found two bright scientist who designed and built technology that still isn’t available today. Then I stood back and let the scientists design the study protocol to test my theory and do the studies. The resulting data proved my theory and showed what I am about to describe. The model behind my theory made it possible to apply what amounts to a formula to ski technique and the design of ski equipment. There was very keen interest from a small number of passionate people in the ranks of the ski industry. But aside from that, the interest was zero. I started this blog so I can put what I found out there for the world to use how they see fit. My reward? I have connected with some amazing people who are bringing, or at least trying to bring, skiing out of the dark ages. If my efforts help even one person who is struggling to ski at their potential but who has not found answers, succeed, that is more than enough reward for me.

        I forgot to mention the most important point. I never became involved in the quest to solve the issues in skiing to make money. It would have been nice. But I was never distracted by that goal. Ponzi schemes are far easier way to accomplish that objective with a tiny fraction of the work of the route I have taken.

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