Should vertical CoM movement be minimized in short turns?

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Should vertical CoM movement be minimized in short turns?

Postby theorist » Sat Oct 11, 2014 6:17 pm

I understand that one only needs the tiniest bit of retraction to count as retraction. And that one can adjust the amount of retraction to achieve different effects. Yet at the same time we know that doesn't necessarily mean some amounts of retracting aren't better than others. For instance, Max_501 mentioned, in commenting on one skier's video, that his skiing might be improved by holding the retraction longer. So the duration (and, certainly, timing) of retraction is something that can be optimized. But what about the speed and amount of retraction, which in turn determines the degree of vertical CoM rise? I know there is a positive correlation between slalom times in top WC skiers and vertical motion in their CoM (less vertical motion => shorter times). And to minimize the latter, at the speeds they're moving, they use very strong retraction. Here's a montage of Hirscher using strong retraction minimize hip rise: viewtopic.php?f=1&t=3065

But, as to how this informs recreational PMTS skiing, I'm not sure -- in short turns, is it nearly always best to use sufficient retraction to minimize vertical CoM movement, or are there merely specific skiing situations in which this should be minimized, or is it purely a personal choice on the part of the skier (in determining the character of short turn he/she wishes to make), such that it does not matter how much the hips come up, so long as flex is used to release?

Perhaps it's accurate to say this about short turns: (1) Weaker retraction is perfectly correct; however, aggressive retraction (resulting in the hips coming up as little as possible) represents higher-performance skiing, and allows you to get on your new edges earlier. [With a sufficiently strong and well-timed retraction, it's even possible to get some float with minimal hip rise.] (2) In certain situations (bumps, powder, steeps), strong retraction, to minimize hip rise, is particularly called for. I'll be interested to hear what the PMTS experts have to say on this.

Supporting no. 2, I found this, which is an excerpt from a larger quote about GS, below:
h.harb wrote:In slalom, which is the technique most closely related to recreational skier needs, in most situations, like bumps, steeps and powder, deep bending and flexing is very important, if not compulsory.


In writing the above, I'm thinking of short turns. For longer turns, where there's more time, perhaps there's no longer as clear a relationship between how much your hips come up and performance level -- consider von Grunigen's weighted releases in GS. See also:

h.harb wrote:In GS you have more time between turns so you can afford to let the outside leg get less bend and not immediately absorb all the energy from the arc. If you absorb too quickly in GS, you will begin an arc or turn immediately, as that movement projects your CG into the next arc and on to the new set of edges.

GS skiers have more distance between arcs, so they time the transitions with the release. You will see in a given GS run both methods depending on the course set. You will see bending and flexing releases and you will see some up and over transitions, but still with a bending move, they just avoid the deep bend. In slalom, which is the technique most closely related to recreational skier needs, in most situations, like bumps, steeps and powder, deep bending and flexing is very important, if not compulsory....Quick bending and flexing are slalom skier movements. Some GS movements are still applicable for the recreational skiers, but less so.


I'll add I searched the forums extensively, and was able to find little specifically on the topic of minimizing vertical CoM motion-- just statements saying that, in PMTS, we want to move the CoM down the hill, not up from the snow. However, these statements weren't specific enough to say whether, if you flex to release, but your CoM still comes up, you might want to try to flex more. The closest I found to saying you want the absolute minimum vertical CoM movement is this from 2006, but I don't know if it's authoritative:

John Mason wrote: We do flex at transition in PMTS in such a way that looks natural and the CM is traveling the shortest path even in terms of vertical motion.

Also, to forestall any misunderstanding of my question: (1) I understand we adjust the movements to control the CoM, we don't adjust the CoM to control the movements. The movements are primary, the CoM is merely a reference for what the movements are doing. (2) I understand the most important thing is that there be retraction -- any amount of retraction. This question uses that as a starting point to ask, as a refinement, if it matters how much there is.
Last edited by theorist on Sat Oct 11, 2014 8:57 pm, edited 2 times in total.
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Re: Should vertical CoM movement be minimized in short turns

Postby Max_501 » Sat Oct 11, 2014 8:49 pm

theorist wrote:I'll add I searched the forums extensively, and was able to find little specifically on the topic of minimizing vertical CoM motion...


Because we talk about movements rather than outcomes. When it comes to flexing to release you need what you need for the given turn, no more, no less. See the Essentials flexing chapter and DVD for more info.
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Re: Should vertical CoM movement be minimized in short turns

Postby theorist » Sat Oct 11, 2014 9:01 pm

Max_501 wrote:
theorist wrote:I'll add I searched the forums extensively, and was able to find little specifically on the topic of minimizing vertical CoM motion...

Because we talk about movements rather than outcomes. When it comes to flexing to release you need what you need for the given turn, no more, no less. See the Essentials flexing chapter and DVD for more info.

Thanks, I will review those tomorrow.
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Re: Should vertical CoM movement be minimized in short turns

Postby skijim13 » Mon Oct 13, 2014 3:57 am

Theorist, another great source of information is the chalk talks from many of Haralds camps you can find on Jays website (skiersynergy.com). I do remember in his free skiing DVD he says for very quick turns you should release and use some retraction, you can see it in the video with his hips dropping down. I know in my short turns that are quick I still have a small amount of up movement that I need to remove, been working on it all of the end of last season.
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Re: Should vertical CoM movement be minimized in short turns

Postby h.harb » Tue Oct 14, 2014 8:55 am

Flexing vs extension has always (and never deviated from it) been one of the Primary (Movements) tenants of PMTS Skiing, right from the "Anyone Can be an expert Skier" series.
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Re: Should vertical CoM movement be minimized in short turns

Postby milesb » Tue Oct 14, 2014 2:55 pm

The value of flexing deeply in short turns is that it allows the skier to get early high edge angles while staying in balance. Because the skier is typically going slower in short turns than long turns, there are less forces available to balance against. A skier that attempts to get high edge angles early in a turn without deep flexing will usually end up on their inside ski halfway through the turn.
This is where the slant board is a great teaching tool. Because there are no forces, ALL the balance must come from flexing and CB/CA.
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Re: Should vertical CoM movement be minimized in short turns

Postby emakarios » Tue Oct 14, 2014 4:54 pm

My PMTS coaches have taught me that there are two questions to ask in assessing a ski movement: 1. How does the ski perform? 2. How is the skier's balance affected? The question of how much retraction or flexing to release a turn goes back to "just the right amount".
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Re: Should vertical CoM movement be minimized in short turns

Postby h.harb » Fri Oct 17, 2014 5:35 pm

That's right Ebbie, how much flexing, depends on your needs for absorbing energy and transitioning.

For those that don't or can't flex to release, there is always the question. Like the chicken and the egg, what comes first? Do you have to start with flexing to be able to flex, do you have to have tipping angles first and how high in the arc does the tipping need to engage the skis to be able to flex to release. PSIA guys can't flex to release, that's why they extend. If you begin a turn with steering or twisting, you end up with no choice but to extend to push out of the turn. That's why they all do it. It's not because it's elegant or efficient, it's because they created a weak technique that demands you use poor movements to get down the hill.
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Re: Should vertical CoM movement be minimized in short turns

Postby blackthorn » Sat Oct 18, 2014 12:19 pm

So I take it then then that what Theorist says is essentially correct. :?: I guess "weak" flexion vs "aggressive" flexion will include components of timing, speed, range etcetc to get it right in terms of desired outcome.
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Re: Should vertical CoM movement be minimized in short turns

Postby Max_501 » Sat Oct 18, 2014 1:46 pm

blackthorn wrote:I guess "weak" flexion vs "aggressive" flexion will include components of timing, speed, range etcetc to get it right in terms of desired outcome.


Once you master the full range of movements it should be evident how much you need for a given turn. While learning we suggest exaggerating the movements.

As I said above...

Max_501 wrote:When it comes to flexing to release you need what you need for the given turn, no more, no less. See the Essentials flexing chapter and DVD for more info.


And Harald reiterated...

h.harb wrote:That's right Ebbie, how much flexing, depends on your needs for absorbing energy and transitioning.
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Re: Should vertical CoM movement be minimized in short turns

Postby blackthorn » Sat Oct 18, 2014 3:05 pm

Yes indeed.
But I would also like to be able to understand what I am doing and put it into words. It helps me, and it helps me explain/debate with friends, many of whom "bat for the other team." And they "demand" detailed justifications!
Aging gapers in their midsixties are apt to do this after a day on the slopes.
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Re: Should vertical CoM movement be minimized in short turns

Postby HeluvaSkier » Sat Oct 18, 2014 3:19 pm

blackthorn wrote:Yes indeed.
But I would also like to be able to understand what I am doing and put it into words.


Get video. Post it for movement analysis. Accept the feedback. Implement the feedback. Get video. Post it for movement analysis. Accept the feedback. Implement the feedback. Get video. Post it for movement analysis. Accept the feedback. Implement the feedback. Get video. Post it for movement analysis. Accept the feedback. Implement the feedback. Get video. Post it for movement analysis. Accept the feedback. Implement the feedback. Get video. Post it for movement analysis. Accept the feedback. Implement the feedback. Get video. Post it for movement analysis. Accept the feedback. Implement the feedback. Get video. Post it for movement analysis. Accept the feedback. Implement the feedback.

Repeat until you ski better than Harald.
Discipline is the refining fire by which talent becomes ability.

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Re: Should vertical CoM movement be minimized in short turns

Postby h.harb » Sat Oct 18, 2014 3:35 pm

I'm trying to ski better then the Harald I know all the time. And it takes me sometimes 2 seasons to create a new movement pattern.
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Re: Should vertical CoM movement be minimized in short turns

Postby Max_501 » Sat Oct 18, 2014 4:27 pm

blackthorn wrote:But I would also like to be able to understand what I am doing and put it into words.


To help put it into words:

PMTS Instructor Manual

Anyone Can Be an Expert Skier 1

Anyone Can Be an Expert Skier 2

Essentials of Skiing
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Re: Should vertical CoM movement be minimized in short turns

Postby blackthorn » Sat Oct 18, 2014 5:28 pm

Point taken guys!!!
I do have the books and DVDs, and starting to get some of the eVideos. And I am practising. :)
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