Skeletal Support

PMTS Forum

Postby h.harb » Mon Sep 17, 2007 3:29 pm

?Stacked?, conveys a static position, (like piling bricks on top of each other) and doesn?t convey how to approach any benefits it ?should? communicate. Joints and bones should remain properly aligned, even when moving from one turning alignment to the next. I don?t ever think of myself as stacked. I?m never in a position long enough, and stacking refers to bones on top of each other, rather than the constant activity of tendons, ligaments and muscles making adjustments to maintain a balanced state. Now that would be Co-contraction.

Notice in PMTS, we use words and definitions that describe movement: Counterbalancing, Counteracting, and Tipping.

Co contraction is not a PMTS invention, it is however a description of skiing initiated by movements at the bottom of the kinetic chain and that originate in PMTS literature; therefore it can?t possibly be right, right?

Co contraction doesn?t connote static positions, it means: constant movement of antagonistic, yet cooperative muscle groups, to stabilize joints, and keep mass above the moving joint, in balance. I know, that's not complicated enough for ski instructors to understand!

It is very hard to describe movement in the fore/aft balance relationship, (compared to lateral balance) because fore/aft balance requires management of numerous joints with many muscle groups, originating at different joints. Once your mass moves too far from the balance point over a joint, co-contraction of that joint halts. The muscles have to readjust to an out of balance situation and relocate the mass above the joint to regain in alignment, where co-contraction can manage balance. Stacking doesn?t address these situations.
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Postby Heluva Skier » Mon Sep 17, 2007 3:34 pm

Harald,
Correct me if I am wrong but I always thought that "stacked" as defined by ski instruction meant a term that meant a body position that lacked any sort of counterbalancing and counteracting movements (straight skeletal alignment with the stance leg) and following the skis? I have grown think of it as a negative term to describe a skiing stance or position because it doesn't seem to fit with what really goes on in the dynamic ski turn (dynamic being the key word there).
Later
GREG
I Ski.

All-Mountain: A common descriptive term for boots or skis that are designed to perform equally poorly under a variety of conditions and over many different types of terrain.

aka. HeluvaSkier
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Postby h.harb » Mon Sep 17, 2007 4:16 pm

I guess there are more definitions or meanings out there then the one understood in the ski instruction (Epic) community.

In ski coaching, that?s where I hear it, it means piling or aligning the bones in an orderly way to accept forces efficiently.

I still think this is a limited definition, but not quit as limited as the definition you offered. Seems like it?s not that easy to interpret, based on all the definitions out there? That?s why I prefer to use known, accepted, biomechanical and kinesthetic definitions.

PSIA has so many confusing terms that mean anything and everything to instructors, so they can weasel out of their own contradictions. I wrote PMTS and my books with terminology that was consistent with the scientific community, so as to not have to rely on these back door exits.
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Postby BigE » Tue Sep 18, 2007 10:34 am

Ken wrote:
"...keep your hips over your feet"

This is commonly misinterpreted in TTS to mean to keep the hips above the feet laterally--side-to-side. This, of course, prevents any edge angle except that of the slope. Keeping the hips laterally over the feet makes skid-steering easier, tho.


The misinterpretation is correct on all counts. Especially if you think about adding Heluva's alignment to the mix.

The other misinterpretation, which I am surprised that no one has mentioned, is what happens (or actually doesn't happen) at transition -- flexion. People are so worried that they'll be "in the back seat" because their hips are no longer over their feet, that they will not flex.

The direction does imply a stasis, however it can convey a number of things, based on context. If I recall that posting, it was intended as a "home base" position where the lack of tension in the hips (relative to the virtual arm-chair) can be taken as an internal cue or indicator of being "in balance"/'aligned" or using "skeletal support".

Going further, if one can balance their *relatively* relaxed hips atop a sliding platform, you can be sure that their knees and ankles will be quite stable. I strongly suggest that those joints would be co-contracted in this scenario. (*relative to the virtual arm-chair)

Going still further, there is nothing suggesting that taken in the correct context, "keep hips over feet" denies counterbalance or counteraction. In fact, when you are carving turns those two essentials help keep "hips over feet" to manage turn forces.

Please note, flexion to release/recentering/extension is not being addressed in the words "keep hips over feet". I presonally see nothing in those words that is in conflict with PMTS in the way it was intended[\b].

Thanks


[b]
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Postby h.harb » Tue Sep 18, 2007 11:42 am

I know the fed just cut interest rates by 50 bases points, but what's more important skiing or your portfolio?

Big E wrote:

The other misinterpretation, which I am surprised that no one has mentioned, is what happens (or actually doesn't happen) at transition -- flexion. People are so worried that they'll be "in the back seat" because their hips are no longer over their feet, that they will not flex.



We have extensively addressed this issue of ?why we don?t flex?, on this forum. I remember my comments, in an answer to a question by John Botti,

My response was along these lines, ?there will be a time when you get back, or feel back in flexing. The crux is, what you do to regain a centered (fore/aft) position??

Max and Bolter are right about where to stand on the foot to feel your position and your efficient fore/aft range. Just forward of the arch and just back of the arch. It doesn't make for a very efficient movement series, if flexing results in a back of the calf pressured save, on the back of the boot. This position requires too much effort to re-center.
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Postby BigE » Tue Sep 18, 2007 12:37 pm

Sorry Harald, I was just referring to this particular thread topic. You're right, there are many references to flexion and recentering elsewhere.
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Postby h.harb » Tue Sep 18, 2007 12:56 pm

It?s more than likely we have not answered all the questions about flexing and the consequence of dropping the hips. I think there are some valid concerns that as instructors, we should keep in mind.

Dropping the hips into a low position, in the release and through transition requires considerable energy from the previous turn so it can be managed in a way that suspends the skier.

If this isn?t happening, I think skiers should be reluctant to flex themselves into a rearward position. In these cases skiers should flex with fore/aft balance, using forward lean of the torso and strong boot retraction, when necessary. There is nothing wrong with this type of transition for almost all skiing situations.
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Postby h.harb » Tue Sep 18, 2007 2:05 pm

I went to Epic to view some of the posts by Skidude's. I heard about Bolter?s exit. Too bad for Epic, he?s one of the few reasonable evaluators of skiing there.

Skidude on the other hand is way off base with his theory of acceleration at the end of turns to release. There is acceleration, yes, (but only of the skis) but there is no net gain in speed or acceleration for the skier. If this is supposed to all happen by using the tail of the ski, all that would do, if it were true (which it isn't), is put the skier out of balance and that's not the intent of a WC racer.

He's guessing, using a poor arguement and using an incorrect concept. Once you again, regain the center of the ski for the next turn, you neutralize any acceleration even gained by the ski's supposed energy, being used to squirt forward (if it existed).

I can't believe anyone would advocate that this type of movement is intended or trained by WC skiers. This activity is also terrible for releasing and transitioning. It forces the racer to stay on the wrong line, and without the ability to decrease the ski's angles for the transition.

In any study using measurement instruments I am aware of (this was discussed once before) there is very little useful energy from a ski?s rebound, in skiing anyway.

Skidude, is misusing terms like energy and acceleration. He?s probably trying to explain what he understands as ground reaction and the effects of momentum on a skier.

Skiers carry and are influenced much more by momentum, then by acceleration. He is confusing momentum with acceleration and energy. He interchanges them and they are not the same.

Just as leg steering is not the same as; legs following the tipping actions of the skis. It?s too bad threads get railroaded by people who have very little understanding of physics.

Bolter, you are correct and you don?t have to come by your correctness, by association or identification with PMTS. What Skidude talks about isn?t even logical outside the context of skiing.
Last edited by h.harb on Wed Sep 19, 2007 11:48 am, edited 2 times in total.
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Postby Bolter » Wed Sep 19, 2007 5:45 am

Harold,
Thank you. Your achievements in the form of books, videos, PMTS forum, Harb Ski Systems, Carvers, Coaching success, Demo Team, and a long list of on snow accomplishments firmly place you as one of the authorities of skiing. I am grateful to say the least for your generous contributions on this forum. Nowhere else can I find your level of skiing knowledge. It goes without saying but I will- I look forward to all of your posts and use them as a template to test and compare just about everything I know about skiing, in particular WC Tech.
In large part due to you, I look forward to this coming season (more than usual, which is a lot), bringing the opportunities to apply new-found insight and a fresh outlook. Like icansee the carvers are getting me ready to go. Thanks JR

I hope to contribute to this forum in a productive manner.
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Postby h.harb » Wed Sep 19, 2007 11:46 am

Thank you and we are pleased to have you contribute to the forum and I look forward to your logical approach to how skiing works. Let's not leave out getting on snow together sometime.
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