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Movement During a Turn - Page 3

post #61 of 64

I don’t disagree with your own post - I’m just describing single foot actions where you are describing two-footed interaction. With two-footed interaction we have way more options than from a single foot. I’m simply trying to describe the fundamentals of lateral balance when starting with Zero momentum across our skis.

The diagram below describes the idea better than words alone.

Attachment 1966

In Fig-1 the Lamp has two ‘legs’ both in contact with the surface. The green lines show that the CM (red dot) is well within the Base-of-Support on both sides.

In Fig-2 the lamp base has articulated (at the yellow dot) such that pressure is removed from leg A. You could also say that pressure was increased at leg B. Either way the remaining green line shows the only Base-of-Support left (under leg B). The yellow line shows just how far to the left side the CM is relative to the remaining Base-of-Support - causing the lamp to topple. It mimics a skier retracting one leg on a straight run.

Fig-3 is essentially the same situation as Fig-2 but with the legs removed and only the ‘flat’ of the Base remaining against the surface - very much like a ski. Our tilted Base-of-Support still causes imbalance which causes the lamp’s CM to move left. So long as the base continues to articulate, the lamp will continue to fall over.

If the base hinge locks up at the point depicted in Fig-3 then Fig-4 comes into play. Because the CM has not yet moved beyond the left edge of the base (green line on side A) the lamp will stop falling over (unless it has sufficient toppling momentum for the CM to continue past the green line by side ‘A’). The flat base is very much like a ski if our skier is truely balanced over the middle of the ski. This is obviously an exaggeration to make things clear but the idea is the same.

Of course in a normal two-footed skiing situation (with pre-existing lateral momentum) we many more options at guding the progress of our CM as it migrates past our skis.

Normally our CM is somewhere between our skis while moving rather than balanced to perfection over one ski or the other. The ‘lamp scenario’ (skiing directly down the fall-line on one ski, perfectly balanced) is a peculiar, but informative situation - I don’t mean to imply it’s a common occurrence though I imagine it might become apparent on very fat ski.

As to Lateral balance with respect to F/A balance I think it’s important to recognize the ongoing cyclical transformation between the two as we ski a series of linked turns. Any given lateral movement of the upper body across the skis while the skis are traversing results in some given F/A position of the upper body in relation to the feet by the time a skier gets to turn apex. I think it highly relevant to T-Square’s question, especially as applied to short radius turns.

post #62 of 64

My Beach-ball example is about the application of Guiding efforts rather than any specific mechanism of guidance. Certainly manipulating our BoS would do it as I just described in the post above. A skier moves down the slope propelled by gravity as the beach-ball does. Whether 'guidance' comes from within or without makes no difference - it remains an issue of guiding pre-existing, ongoing momentum. How we guide that momentum (BoS changes, pushing, pulling, etc) makes no difference - it is still guidance in one form or another.

I’m unaware of any ‘resolution’ on where a turn begins or ends. Was there a meeting to the Intergalactic Council on Beginnings and Endings that I missed…?

When you arbitrarily choose ‘CM Release’ as such a point you’re still choosing a preferential point in the ongoing sequence. True, it may have Special Characteristics you wish elevate with distinction - but there are many such points in a turn sequence with unique and distinct characteristics. So far as I can tell, my statements above have no content that could be construed as ‘red herring’ material as each was a direct analogy for ‘guidance of existing motion’ - the idea I was describing.

Also, my reference to …TkPzTkPz… as an ongoing sequence is again a direct analogy for the ongoing nature of biomechanical movements made to guide our existing momentum down the slope. At any given moment we may deliberately hinder the current speed/direction of our Mass or we may deliberately enhance the current speed/direction of our Mass. However we choose to do it, I view it as guidance.

Analogy (when properly targeted) is meant to provide the reader with situations familiar to the reader that are similar to what is proposed rather than to provide perfectly identical scenarios. Not sure why you’re calling them ‘Red Herrings’ :. My analogies were specific to the points I was making and therefore not irrelevant (generally the basis for calling something a red-herring tactic) and not to distract from anything you or others have presented. (But I think it's cool that you may have read up on that list of fallacies I mentioned elsewhere!)

Your statement that “Skiing in a perfect state of balance is the goal.” Is something I’ve been pondering mathematically of late. Nothing definitive on that front yet . As you and I have had ongoing differences of opinion in this area, I say no worries - we’ll just have to continue to agree to disagree.

BigE, I too prefer to teach from selected points in the ongoing process where major events are easily discernable by students - and to teach the series of movements that occur between one point and some subsequent point. All I’m saying above is that I feel quite free to select whatever beginning and ending points I choose as appropriate for the topic of the day. I think the description of skiing as an ongoing cycle of movements fits quite well with how I teach.

Again - no intent on my part to detract from nor decry the perspectives preferred by others! Simply presenting a perspective that works well in my own skiing and works extremely well for me in the teaching of skiing to others.

post #63 of 64
Originally Posted by michaelA View Post
The diagram below describes the idea better than words alone...
Hmm...I don't understand how that applies to the human body or skiing? What was the point again?
post #64 of 64

I think we'll have to agree to disagree.

How we choose to guide the body is the crux of the biscuit -- it's what we teach.

Certain ways are better than others. The better ways align themselves with positive and not negative movement patterns.

From a pattern matching/mathematical perspective you are correct, it makes no difference where you start in the sequence. However, when you isolate and repeat one complete string in the sequence, you'll get different biomechanical effects. Imagine walking:

1) move the foot into position
2) move the body into position
3) repeat

This characterization clearly produces a movement pattern that maintains balance.

Now, reverse the order of events:

1) move the body into position
2) move the foot into position.
3) repeat

This categorization does not describe a movement pattern that recovers balance -- the movement of the foot is recovering from the loss of balance that the initial movement of the body created.

The issue of assigning arbitrary points to where a turn begins or ends produces substative changes in performance. This is why I call the the sequences 'red herrings' -- on the outside, it appears that it is valid to create arbitray begin/end points, but in reality, they do not support the same biomechanical movement patterns. Hence, the argument based on general sequence matching is a "red-herring". That it was created in support of your point is not an issue - an argument based on mathematical sequences cannot support any point, since it fails to address biomechanics. You may assert that the biomechanical movement patterns are the same, but they are not -- the walking thought experiment shows that.

Which is why I cannot re-define the end or completion of a turn as anything other than "stop deflecting the CM" -- other starting points will not produce the movement patterns that I want. I can see no good reason to modify this definition. In fact, redefining terms to suit an agenda has been frowned upon here. A glossary was attempted, but sadly no one could agree on even the first definition. In my view of the world, this does not make for "richness" of instruction, it makes for confusion. Of course, I will focus on parts of the turn, but the meanings of the terms being used will never be redefined.

FYI: the CSIA see it this way too, so at least up here, there are clear definitions of the phases of the turn -- completion being a critical moment in every turn, and defined the same way ALWAYS. Ask any CSIA instructor, and they'll tell you the same thing. Having a common framework goes a long way to maintain clarity.

That being said, I never speak of this framework during lessons. The eyes would glaze over. Of course, there are key elements of it that pop up, but teaching the framework is not the goal -- these are students, not teachers.

The mantra that describes the basic parallel turn as taught up here: Flex, flatten, pivot and extend. Note very well that the initial word is flex, which stops deflection of the CM -- turn completion is where this sequence begins.

I'm sure epic does not state that a turn can begin anywhere.
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