Biomechanics ofTipping

[skijim13]

My understanding is that any rotary movements in PMTS is the result of lateral tipping movements at the ankle, there is no leg pointing or steering. The action of inversion and eversion occurs at the ankle joint of the foot. The action of inversion at the ankle joint enables tipping of the inside foot to the LTE. The process of inversion of the inside foot helps to move the CM into the new turn and increase edge engagement and angles. I focus on tipping my foot to start this movement, but I do feel that the boots are rigid and does limit my ankle movement somewhat. I got into a discussion on another site about tipping and most did not agree it happens at the ankles.

My response " I edge by focusing on my foot and ankle at the base of the kinetic chain. Since everything is connected together tipping the foot will cause the knee to also tip and move. A force acting on the foot will travel up through the kinetic chain move to the leg, thight and even to the hip. However by focusing on the foot you have much better fine control over you edge angles that at your knees. Next time you are on the slope with your boots no more than hip width apart, and you want to turn to the right only focus on the right foot, tip the foot the the little toe edge at the same time lighten the foot while flexing the right leg as you start to turn. Keep tipping and flexing that foot and leg while gently allowing the outside leg to lenghten stay balanced on the outside leg, you will make a nice turn to the right".

His response
"I have actually tried that several times, in fact, and it doesn't make any difference in a turn. I can see where some skiers might think that they are turning with their ankles but, in reality, they are actually turning with their knees because their ankle is laterally immobilized by their boots. When somebody can show me how they edge their skis by moving their ankles without moving their knees, I will be a believer. Until then, not so much"

[milesb]

I suppose it's a phase many of us go through. You will soon tire of explaining this stuff to people like that. Good descriptions, btw.

[Max_501]

My mental model is to ski from my feet rather than the ankles. I want to use the smallest muscles possible for fine tuning edging and balance.

[blackthorn]

The PMTS Direct Parallel - Instructor Manual explains the biomechanics in a very clear and understandable way and is well worth reading if one wishes to gain a deeper understanding.

[skijim13]

I agree the instructor manual is very useful for learning PMTS in a more detailed manner.

[BigE]

His response shows a profound ignorance with respect to the operation of balance. I suspect that the stubborn instructor has other issues which preclude him from using his feet and ankles to initiate changes in balance.

[DougD]

His response shows a profound ignorance with respect to the operation of balance.

Indeed. I wonder if he can reliably stand on one foot while brushing teeth, combing hair, putting on a sock, tying a shoe, etc. I've done this daily for ~30 years. It develops balance and teaches you that it begins with tiny movements within the foot. Large movements above the ankles are only needed for emergency recoveries after things have gone wrong.

I suspect that the stubborn instructor has other issues which preclude him from using his feet and ankles to initiate changes in balance.

Very probable, either physical, psychological or both.

My mental model is to ski from my feet rather than the ankles. I want to use the smallest muscles possible for fine tuning edging and balance.

+ 1,000

When carving on boilerplate or ice, for example, a gentle flexion or relaxation of the stance foot is all that's needed (or wanted) to maintain optimum edging. Gross knee movements, even a too-sudden ankle tip, almost always lose the ski.

[BigE]

Yes, it all begins at the foot. Even walking necessitates that the foot first adapts to the weight which it is about to bear. This is true if the foot is in a ski boot or bare or receiving an arbitrary amount of support.

It sounds very much like our stubborn instructor would suggest that walking begins at the hip, by swinging the leg. Walking begins by shifting weight and balancing on the stance leg. Balancing begins at the foot, as the foot adapts to the terrain to provide a base of support. After the foot adapts to the terrain, the ankle makes the first balancing movements, which propagate up the kinetic chain. Only then, can the "free leg" be swung, and on heel strike, when weight shifts again, the sequence is repeated: foot adapts to terrain, ankle begins to make balance movements.

Is there any wonder why the calf muscles are so very very strong?

Now it is true that skiing is not walking, but balance is balance. The mechanics of balance do not change.

[skijim13]

I agree balance is key to good skiing, I spend a great deal of time working on improving my balance. Anyone who would like to make great improvements on your skiing should work on the balance drills in the Expert II book. Billy Asad, makes a great yoga DVD for ski training that is also helpful. You will find the opening skiing moves funny, I feel like writing him and tell him to follow PMTS.

[Max_501]

I got into a discussion on another site about tipping and most did not agree it happens at the ankles.

These posts explain why some skiers may not feel much, if any, movement in the boot:

viewtopic.php?f=1&t=3709#p37955

viewtopic.php?f=1&t=2116&start=30#p20658

[skijim13]

Max, thanks for the reference I know I can tip inside my boot due to the custom work done at the Harb shop. Never crossed my mind about the rigid footbeds.

[DougD]

Max,

I've read pretty much every post on this forum, but you have an uncanny knack for finding the real gems. I'll be working with Diana on new liners and perhaps new footbeds before next season's Short Turns Camp. The posts you linked really help me understand what she'll be trying to achieve... and how to leverage it to improve my skiing.

Thx

[skijim13]

Doug, if you are going to the short turn camp in January, Lorie and I will be there.

[DougD]

Jim,

Would be great to camp together, but I'm signed up for Short Turns 1 in November. Trying to get a head start on you guys!

[François]

The interesting thing is that even when wearing antique racing boots that do not allow my ankles much mobility, I still ski by deliberately tipping my feet/skis as if my ankles were free to move. I don't drive the tipping with my knees. I deliberately try to tip the bottoms of my feet/skis, just as I would if I were in bare feet. Come to think of it, I've been doing that for a long, long time. I have tried the "move your knees from side to side", and when I do that, not only is it hard on the knees, it (knee driving) seems to interrupt the flow, and puts a snag in things, like the jerk you feel when you swing too high on a swing set. Makes sense that it would seem so, since you're basically starting in the middle of a chain instead of at the end.