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Bullet Proof Short Turns - PMTS - Video - Page 23

post #661 of 1165
Quote:
Originally Posted by BigE View Post
Can't you generate that anticipated position by pulling the new inside ski back hard, and not counteracting while tipping and counterbalancing?
Here is the link to ligety again for those trying to follow this thread
http://ronlemaster.com/images/2005-2...l-1a-flat.html

I'm a little confused by your comments. I feel that he is anticipated in frames 1 and 2. He is anticipated BEFORE starting the new turn. When he does his retraction release in frame 2, he is still anticipated, but I would expect the wound up tension in his body to twist his lower body once airborne.

Interestingly, pulling back his old inside foot MIGHT add a bit to the anticipatory tension. However, once he's airborne, he is unwinding out of anticipation..
post #662 of 1165
BigE (or someone),

Can you elaborate or further define/clarify this movement pattern you're laying out ...I don't follow what you're getting at.

Why does pulling one foot back result in the opposing hip moving forward? What are you pulling the foot back with, what supports this movement? Why do we seem to be pulling things back now? ...shouldn't we be moving forward?
post #663 of 1165
BTS, I think you are correct. I was looking just at frames 2 and 3 and overlooked the unwinding. Good stuff. Makes more sense.

cgeib, from the viewpoint that every action requires and equal but opposite reaction, if you pull the new inside foot back while unweighted ( eg. the downhill leg in frame 2) the other side must move forward, which will give you that pivot you see.

The feet being pulled back under the body is a requirement to recenter in the position that Ligety finds himself. In fact, if you feel your skis jumping forwards and out from under you, you too would pull them back. It's just a way to stay balanced/centered over the skis at transition.

As I said, this was an attempt to exercise my limited understanding of the PMTS movements -- I guess my PMTS goggles are still pretty hazy.
post #664 of 1165
Quote:
Originally Posted by BigE View Post
Translation: pulling the inside ski back will move the uphill hip and shoulder forwards, rotating the upper body into the turn. Note that the rotational axis is between the feet. Not performing a counteracting movement means applying insufficient counter, so that the tipping movement does not result an edge lock. The counterbalance assists tipping to assert the carve after the pivot( angulation via rotation of the femur in the hip socket).
This is where I get so confused.

If we watch Max's video, there are only two segments of the video that exhibit actual carved turns out of the ten or more total segments. There is no "edge lock" in 80% of those bulletproof short turn video segments, and the only turns where there is edge lock are not short ones.

Why do some of you keep talking about carving when there's very little of it shown in the video?
post #665 of 1165
Quote:
Originally Posted by BigE View Post
The feet being pulled back under the body is a requirement to recenter in the position that Ligety finds himself. In fact, if you feel your skis jumping forwards and out from under you, you too would pull them back. It's just a way to stay balanced/centered over the skis at transition.
How about flexing the ankles forward to move the COM over the skis? There is more than one way to skin a cat...
post #666 of 1165
Quote:
Originally Posted by Rick View Post
Hey, Hobbit, it's been a while. Hope you had a good season. Check out this article: it should give you a start on understanding what I'm talking about.
http://modernskiracing.com/balance.php

And here's a photo I pulled out of the article for quick reference. Perhaps it will provide you a quick answer, without having to comprehend all the information I share in that article.

http://ronlemaster.com/images/2003-2...e-width-A.html

If Hermann were to relax both legs at this moment his CM would not follow the path of the blue arrow, as many people believe. It would actually follow the path of the green arrow, and slam into the snow.
Hi Rick, I had a great season but I had my ups and downs as well.

I read through your article and I am not sure I can agree with your analysis. I don’t claim to have any authority in the subject, I wish PhysicsMan would be here for us but here it goes.

Your picture closely matches the Figure 2.8 on page 12 in the Ron LeMaster’s book “The Skier’s Edge”. Ron correctly mentions that he avoids the discussion on the nature of the centrifugal force which some mention does not exist. The centrifugal force might be OK for the analysis of the static equilibrium. The simple explanations on the high school physics level on why centrifugal force actually does not exist may be found for example at http://phun.physics.virginia.edu/top...ntrifugal.html .

It is easier to analyze the dynamic system behavior based on analysis of the real forces applied to the object (in this case skier’s body). When the object moves on the circular trajectory, due to the nature of the mass and inertia, there must be a force applied to the body in the direction of the center of the circle – this is centripetal force. Without such force the body would be moving on the straight line trajectory. The well known formula for the centripetal force is:

Fcp = mv2/r

If the skier in the picture you presented would flex their legs the COM would move diagonally (in the direction of the legs flex. This means that the radius from the COM to the center ob the turn increases and the centripetal force decreases. Due to the inertia and the momentum the skiers body possess the skier would not sit on the snow as you claim but would start moving over the skis in the direction of the new turn. This is of course very simplified explanation and I don’t take into account extra acceleration caused by the change in the centripetal force.

The reason I mention all this is that someone in the previous posts in this thread said that flexing alone would make you sit on the snow and you must be turning your feet (I’d say secretly without admitting it ). This does not match my experience and as Max mentioned all we do is flex the outside foot. Depending on the flexing speed the results may be quite dramatic and there is no active (muscle induced) feet turning whatsoever.
post #667 of 1165
I have a question for everyone who is taking about what WC skiers "plan" to do while running gates. Do you really think that they think about any of the moves they make? I think I would argue that they don't think about any of it at all. I think they simpy REACT based on years of training. How much thinking can you do in the .7 of a second you have per gate in SL? If that's the case, most of the above discussion is moot.
post #668 of 1165
One more note Rick,

The nature of the ILE turn is identical and is caused by reduction in the centripetal force the only difference is that COM moves up and around the ski edge as a pendulum but the radius from COM to the center of the turn increases.
post #669 of 1165

correction

Correction:

I think there was a mistake in my reasoning and I'd like to try to fix it.

No matter what, you flex the outside leg (OLR) or extend the inside leg (ILE) the radius increases. The required centripetal force to stay in balance and continue the circular motion increases much more due to the velocity increase compared to the component reduction due to the radius increase. Since the centripetal force is provided by the snow reaction and basically stays the same we would "loose the balance" to the outside of the turn. The conclusion is still the same -- we would move out of the current turn into the new turn instead of sitting down on the snow.
post #670 of 1165
Well if we're gonna talk physics now..

Quote:
Originally Posted by Hobbit View Post
Your picture closely matches the Figure 2.8 on page 12 in the Ron LeMaster’s book “The Skier’s Edge”. Ron correctly mentions that he avoids the discussion on the nature of the centrifugal force which some mention does not exist.
Actually, that is not quite what LeMaster says, to be clear, he says this:

"We will not quibble here about the nature of centrifugal force, which some argue is not a true force. For our purposes it is quite acceptable to consider it one."

The entire LeMaster book is expressed in terms of centrifugal, not centripetal force, regardless of what the academically correct way of considering the laws of physics are. (shrug).

Quote:
If the skier in the picture you presented would flex their legs the COM would move diagonally (in the direction of the legs flex.
Yes. Well if your CoM moves in that direction then somehow the core of the skier's body will have to fill the space where their boots are before flexing. What you really want is for the CoM to follow the blue arrow not the yellow one:
http://ronlemaster.com/images/2003-2...e-width-A.html

If your CoM follows the blue arrow then you will cross-over. If it follows the yellow arrow, you will end up blocked by your own body parts and fall into the snow. Something has to nudge your CoM in the direction of the blue arrow to teeter the balance point enough to send your CoM over your feet to the other side. That is where ILE comes in. There may be other ways to tip the balance to the outside besides using ILE. Perhaps you can share the PMTS approach. But the raw physics require some additional input to avoid falling in the snow.

Another way to think about it, and I'll even refer to centripetal forces........imagine if you were skiing along, balanced on your outside ski in a turn and you hit a patch of nasty nice and lost the edging. What happens? The Centripetal force you mentioned is reduced. The radius of the circle is increased. The skier falls down on the inside. UNLESS they save themselves by standing on the inside ski and use that leg to regain balance by pushing down.

Quote:
The reason I mention all this is that someone in the previous posts in this thread said that flexing alone would make you sit on the snow and you must be turning your feet
Two issues there. Rick mentioned turning the feet to get out of the backseat. That was not particularly to avoid falling in the snow. When you perform a pivot and then establish edging, this automatically positions your CoM more forward from what it was before the pivot. So Rick was trying to say that when Ligity went into the transition his hips were way back behind his knees and boots. But by pivoting his skis and engaging the edges, that instantly transformed him into a more centered place relative to his skis and all the forces at play. I don't think Rick meant to say that this is the kind of move that is used all the time, but in a high energy retraction turn like ligity was doing there, its easy for the skis to jet forward, and using pivot entry for the turn overcomes that aft balance problem by the time you are at the apex again.

The movement Rick has referred to related to the falling in the snow has to do with using ILE in addition to OLR at transition.

ILE = Inside Leg Extension
OLR = Outside Leg Release
post #671 of 1165
Quote:
Originally Posted by Hobbit View Post
Since the centripetal force is provided by the snow reaction and basically stays the same we would "loose the balance" to the outside of the turn. The conclusion is still the same -- we would move out of the current turn into the new turn instead of sitting down on the snow.
The problem with MOST ALL of you guys here is that soon as you start to analyze something you all jump into the race course at 50mph.

I will now kill the above theory. A given skier is turning at 4mph. Still think the above will work? The "sitting down on the snow" statement as originally stated could still very well be accurate.

There is a point (with some given speed) where the ideas above mentioned by Hobbit(this post and a few of the previous ones) would explain things. The question now is with what move....and at what speed.
post #672 of 1165
I'll agree with Lonnie here in regards to the notion that WC skiers don't have the time to "think" about what they are supposed to be doing during a WC race. Those movement patterns have to be ingrained over the course of years of proper intensive training. I think that is one reason that good bump skiing is so difficult to grasp. You seldom have time to think about what you are supposed to be doing in difficult bumps. If you don't have the fundamentals down to the point where they are second nature, then it's always going to be a struggle.
post #673 of 1165
Quote:
Originally Posted by Lonnie View Post
How about flexing the ankles forward to move the COM over the skis? There is more than one way to skin a cat...
It can be done, but it's sort of slow don't you think? It's far quicker to move the feet than lever the upper body forwards.
post #674 of 1165
UL,

I made a disclaimer that I am no expert. You see, I was not even able to make it through the first explanation attempt, and I am not saying that my second one is correct for sure. This is more in line of the question from the Dave Letterman's show "Will it float?” .
I am just trying to reconcile my common sense with my experiences. I would definitely agree with your point that on the low speed the centripetal force is negligible. Actually this is one of the factors contributing to maneuvers and demo runs on the very low speed being in the domain of high expertise. It demands much higher balance skills.

On the other hand, the question is -- will I end up sitting on the snow when skiing with my average non-WC class speed and flexing the outside leg without twisting my feet or will this move help me get into the new turn. Will the skiers shown in the book or in the picture presented by Rick end up sitting on the snow while skiing at the speed shown and collapsing their feet? My experience tells the second scenario is a case, but I may be mistaken.
post #675 of 1165
To get to the snow, you need to flex BOTH legs. Flexing ONLY the outside leg just removes part of your base of support, not the entire base. The inside leg remains supportive.
post #676 of 1165
Quote:
Originally Posted by BigE View Post
It can be done, but it's sort of slow don't you think? It's far quicker to move the feet than lever the upper body forwards.
I'd counter that I'd want to flex the ankles because they are closer to the snow and small movements there related to bigger movements to were the COM ends up. It's starting at the snow and working up as opposed to movements that start in the hips/waist and move down (and isn't the kinetic chain HH's idea?) But then I'd say "Does it matter?" I don't really care HOW you get back to neutral, just that you DO get back to neutral. These are only two of many, many ways to be centered. If you've got a way and it works for you and it's easier for you, got for it.

See, come to think of it, this is my whole problem with a strict adhesion to any particular system. All you you pmts guys think that just because it come out of HH's mouth means it's gospel. HH says do it this way, that's the best and ONLY way to do things. No. I sure these things work, but why in the world would you want to limit yourself to just those movements? I just don't get it. Why not open your eyes and not limit yourselves? Afraid of getting banned from realskiers?

I mean the philosophical question is this, What's the difference in a coach that says "Get back to neutral. Here are the ways you can do it and the pros and cons of each. I want to pick the way that works best for you and a given skiing situation you are in at the moment." vs "Get back to neutral and this is the best way and the only way I want you to do it." Which would you rather learn from?
post #677 of 1165
Quote:
Originally Posted by Lonnie View Post
See, come to think of it, this is my whole problem with a strict adhersion to any particular system. All you you pmts guys think that just because it come out of HH's mouth means it's gosple. HH says do it this way, that's the best and ONLY way to do things. No. I sure these things work, but why in the world would you want to limit yourself to just those movements? I just don't get it.
Hey! Don't do that! Many of us here are merely trying to fully understand the gospel according to Harald. I have a slight understanding about how that stuff works, but it is by no means comprehensive.

FWIW, I'd prefer not to have to get into the situation where I need to pull back the feet - I view it as corrective medicine. Consequently, I find the notion of "pull the feet back and continue to do so throughout the turn" to be a bit to much, although I can see how this directive would help the back seated skier.

As far as pulling the feet back being the ONLY way to recenter, I think not. There's a bunch. I like to use poling to assist in the recentering process. HH says that's a no-no. Gurshman says it's the best.

To me, gait mechanics is truly top shelf.

Re PMTS. I think that a lot of what has gone into PMTS deals with the utilization of the inside leg. Instead of being a useless appendage, just coming along for the ride, PMTS promotes the use of the inside leg as a key point of focus. Demanding that the Kinetic Chain is activated to transmit the movements from the inside leg sets up a useful functional tension within the body.

That is very clever.

It is also in harmony with notions of "ride ski and guide ski" to which everyone has been exposed. Now, one can disagree with the teaching progression, but the emphasis that "this is the one way to ski" ensures that the student does not get confused and allow extraneous movements to occur.

For example: rotary. As I understand the use of the term in PMTS it refers to rotary force added by use of the upper body. PMTS admits to no rotation other than those afforded and controlled by the basic movements.

It has also been suggested that PMTS is all about carving. Well, yes, that is a primary focus. Why? because while carving you can add no external rotary forces.

Someone posted that they like to show the entire range of rotation. From zero to pivot slips in their teaching. Well, PMTS movements promote getting to zero rotary in such a way that rotation is later allowed to occur. Not added, but allowed. So, the conclusion that I've come to is that the movements of PMTS do allow for the entire range of rotary to be displayed, using a functional tension throughout the body, that differs from that of "adding" rotation by forcibly twisting.

Now look here. If you think I've "drunk the Koolaid" because I've taken the time to understand this much about it, well that's your choice. As I've said, it's a very clever approach, and is IMO worth taking a good look into.
post #678 of 1165
Lonnie, the simple answer is which ever system/coach works best for me.
post #679 of 1165
Quote:
Originally Posted by BigE View Post
It has also been suggested that PMTS is all about carving. Well, yes, that is a primary focus. Why? because while carving you can add no external rotary forces.

Someone posted that they like to show the entire range of rotation. From zero to pivot slips in their teaching. Well, PMTS movements promote getting to zero rotary in such a way that rotation is later allowed to occur. Not added, but allowed. So, the conclusion that I've come to is that the movements of PMTS do allow for the entire range of rotary to be displayed, using a functional tension throughout the body, that differs from that of "adding" rotation by forcibly twisting.
Let me see if I can shed some light here. In my personal skiing there was (and sometimes still is) the appearance of rotation toward the turn with my torso. People have always said I rotated to start the turn, (with the upper body) but I disagreed. I find the rotation to be a result of what I'm doing at the feet and failing to have (or worry about really) a strong enough core to "counter enough". I refer to it as "resultant rotation". Seems to me it's the same basic theory that's noted above.

As I understand the PMTS view (but Harald has been quite clear that I don't), if you rotate (legs) to make the turn it's wrong. If rotation in the legs shows up because all your other moves are correct and it happens as a result of you staying in balance you are OK.
post #680 of 1165
BTS, thanks for jumping in to help explain this stuff. Thumbs up to your entire post. Completely accurate, very well done.

Hobbit, read BTS's post closely,,, along with my article again,,, attempt to grasp what UL is trying to tell you and how it relates to what BTS and I are saying,,, open your mind to the possibility we may know what we're talking about,,, and you just might be able to get a solid handle on this subject.

It's like those 3d pictures that a first glance look like nothing more than a formless collage of discombobulated color. You stare and stare, but just can't see the picture. Then all of a sudden you blur your eyes just right and, WOW, the image jumps out at you clear as day.

Once that happens with this stuff, once you come to understand what's really happening beneath skiing's veil of movement clutter, all the technical mumbo jumbo you hear spewing from various knowledgeable mouths starts to make sense, and can be self expanded on in multiple ways.
post #681 of 1165
Quote:
Originally Posted by JRN View Post
Lonnie, the simple answer is which ever system/coach works best for me.
EXACTLY!!! This is why I'll never say that another way to do things is "Wrong". I'm simply not that arrogant. There might be an alternative way to do things, and here are the pro/cons of the two (or more) methods. Use what works for you. This puts the "choice" in the hands of the student, and I think that's one of the most empowering thing a teacher can do for a student. But that doesn't mean that approach is for everyone. Some people don't want a choice, they want "a way". That's cool with me to....

And to take us back in this thread, this was the whole point of the "teaching cues", tangent that I went off on about 100-200 posts back. The reason I REALLY like that teaching method/style is it allows me to use multiple methods/tactics with multiple students in the same lesson. I'm telling my students how I want them to ski, but not necessarily not how to do it.
post #682 of 1165
Quote:
Originally Posted by BigE View Post
To get to the snow, you need to flex BOTH legs. Flexing ONLY the outside leg just removes part of your base of support, not the entire base. The inside leg remains supportive.
Exactly. Now, BigE, tell us (Hobbit) what will happen next.

Hobbit, add this to your reading list.
post #683 of 1165
Quote:
Originally Posted by BigE View Post

FWIW, I'd prefer not to have to get into the situation where I need to pull back the feet - I view it as corrective medicine. Consequently, I find the notion of "pull the feet back and continue to do so throughout the turn" to be a bit to much, although I can see how this directive would help the back seated skier.
Try to think of this as why it may be required for the PMTS skier. It may help if y'all read my post again in this thread as to "what joint takes you where". (no "joint jokes" please)

If you "crouch" to release, the knee joint seems to be the joint that sees the most action. We see it in Max's demo. Pulling the feet back would increase the flex (hopefully) in the ankle joint and move the CM further forward with respect to the new position of the feet. Sitting here in the chair I can also feel core muscles when I pull my feet under me. (OH MAN.....I'm beginning to sound like Barnes). Pulling back the feet will re-center the skier. PMTS guys here....do a reality check on me if this doesn't make sense.

The problem with trying to equate this to the 4 pic shot of Ligety is the SKIS have been released in pic 2 as the upper body heads for the next gate. Pulling your feet back at that point would be worthless. His only action, and I bet thought at that point, would be to redirect the skis to his new intended path which is PAST the gate he is headed for and hope the edges hold. As cgeib said, "Turn the feet". The torso does one thing....the legs another.
post #684 of 1165
I think it's time for a balance dynamics test. Study up, folks, it's coming soon.
post #685 of 1165
Quote:
Originally Posted by Rick View Post
Once that happens with this stuff, once you come to understand what's really happening beneath skiing's veil of movement clutter, all the technical mumbo jumbo you hear spewing from various knowledgeable mouths starts to make sense, and can be self expanded on in multiple ways.

We should "sticky" this somewhere. Its rather brilliant.
post #686 of 1165
You can tell there's not much skiing going.....
post #687 of 1165
Quote:
Originally Posted by Uncle Louie View Post
I will now kill the above theory. A given skier is turning at 4mph. Still think the above will work? The "sitting down on the snow" statement as originally stated could still very well be accurate.

There is a point (with some given speed) where the ideas above mentioned by Hobbit(this post and a few of the previous ones) would explain things. The question now is with what move....and at what speed.
Well, a skier at 4mph is going to be much closer to being in static balance than a skier moving at 50mph, because his edge angles will be flatter and his body will be more upright. If he relaxes his outside leg, his balance will return to his inside leg much more quickly, and the forces levering him over into the new turn will be miniscule, so its unlikely he'll be unable to avoid sitting down in the snow.

I think the PMTS super-phantom turn works at slow speeds because it involves relaxing the outside leg AND tipping that ski. If the turn forces themselves are not sufficient to pull the new stance ski flat or onto its new edge, the tipping motion will do it. As always, those forces not available from the turn the skier has to generate themselves.
post #688 of 1165
Yes Simon, in terms of PMTS, I think you are on to something related to the phantom move, kinetic chain and tipping.
post #689 of 1165
Since the inside leg remains supportive it resists gravity.

Since you do not move your balance point to the inside ski, the centrifugal force (inertia of the CM) carries you across the skis.

Far enough yet Rick?
post #690 of 1165
Quote:
Originally Posted by Uncle Louie View Post
Let me see if I can shed some light here. In my personal skiing there was (and sometimes still is) the appearance of rotation toward the turn with my torso. People have always said I rotated to start the turn, (with the upper body) but I disagreed. I find the rotation to be a result of what I'm doing at the feet and failing to have (or worry about really) a strong enough core to "counter enough". I refer to it as "resultant rotation". Seems to me it's the same basic theory that's noted above.

As I understand the PMTS view (but Harald has been quite clear that I don't), if you rotate (legs) to make the turn it's wrong. If rotation in the legs shows up because all your other moves are correct and it happens as a result of you staying in balance you are OK.
That's my understanding too.

As for a strong enough core to counter enough, I think that everyone has enough to do that. IMO, it's really a matter of coordination the counteracting movements with the tipping at the feet.
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