How does PMTS generate rotary turns like at the top of Mogul

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How does PMTS generate rotary turns like at the top of Mogul

Postby John Mason » Fri Apr 02, 2004 12:14 pm

PMTS is thought by many to be for learning carving. Yet, in Eric and Rob's Ski the Whole Mountain book, they use PMTS for all types of sking. They even describe using the Phantom Move to position the body in hop turns for landing correctly.

In what ways or how does the Phantom Move allow rotation effects tighter than the turn radius of the skis.

In my own experience I can leave the stance ski flat and phantom move with my other leg and do a hockey stop with no external leg steering. All active inputs are with the free foot. Obviously external stance leg steering is occuring but it is as a reslut of the free ski actions.

How is this effect best explained to people that have never experienced it. Is it inside leg steering combined with the phantom move? I don't see that myself as my skis are remaning parallel.

In our own PMTS all mountain camp training and in HH's books, you teter at the top of the mogul, then phantom move down the face of the mogul. This makes you pivot in place at the top of the mogul. So, this is happening without stance leg steering inputs, but obviously rotational movements in the stance leg are being generated.

Opinions please?
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Postby piggyslayer » Fri Apr 02, 2004 12:33 pm

Here is my opinion.
I can spin 360 turns on my skis until I get dizzy. I do not use phantom or leg steering or explicit body rotation, rather small fore-aft adjustments to do that. When skis are flat on the snow they will turn, even spin without much explicit turning applied to them.

Ski positioned flat on the snow and perpendicular to the fall line is not a stable position (in terms of underlying physics). Ski wants to turn what it needs is only a small kick (any ?catalyzer? will do). Facing you upper body forward (making it square after last turn) on the top of the bump, planting a pole and using it (even mentally) for support into next turn, in my case moving my head :D (Jeff knows what I am talking here), hey just willing your body to turn if you have any ?jedi? powers will do the trick.

Just my opinion, so please correct it if I am wrong.
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Postby piggyslayer » Fri Apr 02, 2004 12:43 pm

John
You have wrote somewhere that if phantom tipping is applied with ankles closed you feel a strong rotary turning sensation on the other foot.
I do not feel that (maybe is because I am the piggyslayer). I do feel a strong lateral )and only lateral) sensation on the other foot.

Am I the only one who does not feel that rotary aspect of phantom!!!
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Postby Jeff Markham » Sat Apr 03, 2004 10:03 am

In http://realskiers.com/pmtsforum/viewtopic.php?t=162&start=0&sid=c44a445e25043e526972a246107913c4,
Tommy said:

Jeff, if the outside ski would turn only due to its sidecut, assuming that a "purely" sidecut generated turn results in a pure carved turn, it would be very difficult for most recreational skiers to make any short radius turns. Even a 4 m radius turn on 170cm skis would demand the ski to be bent almost 10cm, which takes considerable force (and technique!).

As far as I can see, to keep linked turns within a narrow corridor, say less than 5m wide, there has to be some fair amount of "pivoting" of the new outside ski involved. The question is how this pivoting occurs.

In the instructor manual, pages Int-10, Int-11, there is a few paragraphs on rotation:

"In the strictest context, rotary movements do occur in PMTS skiers. The difference is that the PMTS rotary actions are a consequence of lateral tipping movements at the ankle"
...
"The legs react to tipping by rotating along their length from the hip joint"

My current understanding of all this is that in order to do "non-pure-carving" turns with PMTS, the outside ski must pivot to some extent, and this pivoting is generated by the leg rotation caused by the tipping input of the free foot.

Tommy, you are correct. The PMTS Instructor Manual does say this. It also says:

The resulting rotary response is reactive and more easily controlled than an active initiating rotary movement that imparts large momentum to the body and skis.

So, I stand corrected in my earlier assertion that the tipping-induced rotary response has no impact on the stance ski (although I still can't feel it).

However, I'll stand by my earlier assertion that this resultant rotary response doesn't significantly contribute to PMTS turning, whether in a "pure" carved turn or a "non-pure-carving" turn. I certainly don't think that this response is strong enough to cause the ski to pivot. Strong statement: If the skis are pivoted, then I don't think that PMTS techniques alone are being used. Also, I'm still curious whether upper body countering (what Tejado-Flores calls 'dynamic anticipation') "cancels out" the resultant rotary response.

My understanding is that, in PMTS, turning is caused by the ski bending (mainly influenced by the sidecut), not by any pivoting action. Harald consistently and strongly decries active rotary or pivoting movements. IMHO, the Instructor Manual's comments regarding "rotary movements do occur" is an admission that technically this response occurs, but this admission is a long way from suggesting that it is anything other than a faint result of PMTS technique. In other words, I believe that Harald is just trying to be utterly honest when he says that does occur, but is certainly not saying that it is a "hidden" (or significant) component of PMTS technique.

Like the rest of us, I'll have to wait for Harald's comments.

As far as linking turns in a narrow corridor, I did this drill at the B-S A-M camp and AFAIK was not pivoting. At least, I hope not. :shock: However, I wasn't necessarily "purely" carving them. So, maybe the question is: If a short turn is not "purely" carved, does it follow that it has to be pivoted? In my opinion, this does not necessarily follow.

As a side note, all of these discussions are making me do more research and reconsider my PMTS conceptions. As Harald has written, we become our own instructors.
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try this

Postby John Mason » Sat Apr 03, 2004 10:30 am

and it's not even April fool

Try flexing the stance leg some while you do it on a floor you slicked up with butter. There is no rotary force that I feel either without some flex of that stance leg.

And if you fall while doing this, I disavow everything I just said. (Harold's little twist excersice platform would be a safer way to try this out.


Or, is the pivot turn more a reaction of the lower body wanting to come around to match the upper body in a turn like at the top of the mogul?
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Postby piggyslayer » Sat Apr 03, 2004 2:22 pm

Or, is the pivot turn more a reaction of the lower body wanting to come around to match the upper body in a turn like at the top of the mogul?


I like this explanation more.
It does not take a lot to spin around/rotate when skis are flat.

My wife will not let me butter the floor
But I do not feel any rotary sensation with my stance leg fully flexed. I feel lateral sensation on my stance foot (fully flexed) when tipping the free foot. The femur rotates all right, but this is between knee and hip, not between knee and ski!

Harald WE NEED YOU HERE!
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Postby piggyslayer » Sat Apr 03, 2004 4:38 pm

Guys I GOT IT!
I think we sort of are all correct.
Here it goes:
John I agree when you tip you free foot, the stance foot (when fully flexed) wants to turn (to the inside).
Now try the same experiment, but this time let the hip follow the tipping action. That is, let the hip move sideways (like in sitting on the bench).
This time the stance leg is also affected, the femur in the stance leg rotates as before, but this time the action on the foot is completely lateral.

I could not reproduce before what you have been describing since I always "stretch" my hip when I tip.
My understanding of correct PMTS movement is to use tipping action of free foot to initiate moving you hip to the inside of new turn.
If the turn is done this way there is no pivoting/rotary force applied to the stance foot.

I truly believe that well executed short turns are achieved without any pivoting/rotation and involve both tipping and ?stretching? the hip.

Am I not supposed to move my hip on the top of the bump?
Can someone explain?
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lets explore what your saying a bit

Postby John Mason » Sat Apr 03, 2004 4:59 pm

You say the hip moves sideways. Not sure what direction you mean.

When I stand in the doorway and tip my free foot (left foot) that has the result of moving my knee left. This makes the hip want to rotate left as well. This hip rotation makes the right leg also want to rotate left to recenter itself in the hip. It's all connected.

Tip the foot, knee moves inside the turn, hip rotates, external leg rotates to keep up with the hip.

Is there a way to tip the foot and not have the knees seperate? Now I know the hip and femurs can be rotated independently, I'm just describing where "neutral" is as that is where the body tries to keep things. As you move out of neutral by any action, such as tipping the free foot, the whole kinetic chain tries to go back to neutral from that action. Tipping the foot makes the neutrality of the kenetic chain go out of balance.

Now one way to counter this out of balance kinetic chain is to let your body go the way of your tipping foot which will make the external foot laterally match the motion of the tipping foot. In this case, the rotation effect does not happen. Matched lateral tipping occurs with an infintesimal lead by the inside foot. (Its all connected so it acts like one motion). This is what happens in a phantom move carved turn. Its the edging of the shaped skies that create the turning motions.

But standing mostly straight and tipping the inside foot not allowing the lateral motion, the hip rotation will make the external leg want to come around. When I'm on a flat stance leg and want to come around in a pivot stop via the phantom move, I just lift my free leg's tail and tip it and I go right around. The more I tip the more and faster I turn. I'm way inside the turning radius of the skis. You can see HH do that in his video and it's almost done in 2 or 3 feet. I'm not letting myself, in this case move my cm cross over my skis as I'm basically straight up.

Or - is it inside leg steering doing this type of turn. If it is then it's subtle because my skis stay parallel. The knees come apart though as a result of the tipping which means I either have to fall to that side or the femurs will rotate to cancel the pressure. One or the other has to happen when the kenetic chain is knocded out of kilter by tipping the free foot.

I'll try the butter test. If I don't get back here to report my results, I've probably fallen and died.
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Postby Jeff Markham » Sat Apr 03, 2004 5:37 pm

I tried the "butter test" in the shower with a little shampoo on the floor of the tub. Extending my arms to opposite walls for balance, I tipped my right foot almost 90 degrees to the right. I was flexing as much as I could. To the degree possible (i.e., without falling on my can), I allowed my hips to move laterally to the right.

I could not detect a rotary/twisting force on my left foot.

However, my feet are very clean now. :D
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Postby piggyslayer » Sat Apr 03, 2004 10:41 pm

Jeff,
I am saying that allowing hip to move laterally (tip with left foot, hip moves left) eliminates any rotary effect.
And since this is the way we use tipping when sking, there is no rotary effect applied to skis. (short turn or long, I do not care).

Now, if you repeat the shower test tomorrow, resist any movement on the part of hips (try to keep your hips directly above your feet). Flex legs to the max and tip one foot. The other will want to turn. Actually a simpler way to see it (without butter or shampoo) is to do the tipping action with 2 footed stance (weight on both feet) and unweight even lift the other leg slightly when tipping. ie. if you tip left foot lift the right foot a little bit.
You will see it rotating. You will also see the right knee tracking inward - which indicates the rotary force applied to the foot as well.

This movement is not what I do when skiing, and (I believe) not what HH does on skis. However, it explains why John and others are so worked up about discovering rotary element to PMTS.

It may be usefull in bumps. I do not know, have to try it first.
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Yes - I think you may be explaining it correctly

Postby John Mason » Sun Apr 04, 2004 12:23 am

That matches my experience. If you resist the lateral tipping you get rotary. Of course, you wouldn't normally do this in a carve, but in a hop turn or on top of a mogul you get rotary when you tip before the lateral tipping occurs.

I think you have a very good paraphrase of what I've been trying to explain were my observations.

I'll be at Nubs Nob skiing Monday and Tuesday - anyone wanna do some turns? (it's up by petosky michigan) I'll be with my brother in law. It'll be his first day ever skiing - so it should be interesting.
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Postby piggyslayer » Sun Apr 04, 2004 6:45 am

Cool names:
    lateral tipping - tip to create lateral movement applied to knee and hip. Causes lateral movement of the hip.
    rotary tipping - tip to rotate the knee outward, hips stay above the feet and resist lateral movement


I think the biomechanics of this is quite interesting: the stance leg wants to replicate the tipping leg knee position if legs are fully flexed.
In lateral case this causes lateral stance foot angulation.
In rotary case, the tipping leg knee rotates outward, the stance leg knee replicates the movement rotating inward and this applies rotary pressure to the stance foot.

Interesting, I never understood this biomechanical phenomena before.
I still do not agree that this (rotary tipping) is the way to shorten radius of turns.
I can be persuaded that this is the move on top of the bump or in hop turn.
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Postby tommy » Sun Apr 04, 2004 8:10 am

Guys,

great discussion, and fun too! I'm just waiting for the next "experiment": maybe pouring olive oil on the livingroom floor....?! ;-)

Jeff wrote:

So, maybe the question is: If a short turn is not "purely" carved, does it follow that it has to be pivoted?


WIth the above question you've really pinpointed something that's a key question for my understanding of PMTS! If I can get a firm answer on that question, I will rest my case and be happy; then I've found the Nirvana of Skiing! ;-)

My current position is that in a non-purely-carved-turn there has to be some amount of pivoting or rotation occuring, which causes the skis, or at least the aft part of the skis, to skid. like a rallye car's tail.

So, as soon as I get "the definitive answers" to two questions:

- does a non-pure-carved turn have any rotation/pivoting involved ?
- if yes, then how's that rotation/pivoting created using PMTS ?

I'm happy!

Cheers,
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Shortening turns

Postby John Mason » Sun Apr 04, 2004 11:45 am

words again

In a carve you pressure the ski more to make it curve more. You can do this by making all your weight be on that ski if it wasn't already or tip more which generates more force and bends ths ski more.

But the pivot turn by phantom move is a different beast.

I guess that's the point of the thread, how in PMTS is the best way to approach a pivot turn. Is it simply uncoiling the lower body to match the upper body and you face the direction you want to go? On the top of a mogul, it seems to be more than that as the phantom move gets your body in the position to take the force of the new direction. So maybe the pivot portion of that turn is mostly upper/lower body uncoiling. Is there any rotary component to the phantom move itself?

Jeff has said he feels pressure on the stance leg femur in the door excersize to rotate when flexed and tipping but not in the stance foot. If there is preasure to rotate on the stance femur than there would be pressure on the foot to go neutral in relation to the femur. Everything is connected. The farther away in the kenetic chain from the tipping you go, the pressure would be less as our ligiments and joints all have flexibility and streching abilty. But the body likes to be neutral and when anything is streched or there is pressure to return to neutral.

In the pivot on top of a mogul, this pressure is probably both. You phantom move the inside leg to go the new direction. This adds an inside leg steering component that hasn't been raised yet. Also, with the pole plant, your upper body is now facing down the fall line and the skis want to unwind into the new direction as they are flattened. Everyone would agree that these two things - unwinding the lower body to match the position of the upper body, and the inside leg pointing the new direction while doing the phantom move (inside leg steering) wil make the body quite out of neutral and it will respond by doing an immediate pivot without activily thinking or doing stance leg steering.

Active stance leg steering as in "point that big toe edge the new direction" tends to lead most people to a wedged entry where they have to then focus on getting that inside leg out of the way. It's more natural to just focus on the free leg movement and let the stance leg come around on its own. No wedge entry that way, no crossing of the tips, automatically parallel skiing results. The other issue with active stance leg steering is that for many people when you think point that stance leg big toe edge into the new turn, that will tend to make you put your weight on that stance ski. Putting your weight on a ski tends to make most people go in that stance ski direction which at the beginning of the turn is actually back up the hill. The phantom move, on the other hand, the weight on the stance ski comes from relaxing the old stance ski as a result weight transfers to the new stance ski. This also keeps your body continuing down the fall line and angles the skeleton in a better alignment to take the upcoming turn's building forces.

So maybe my doorway test is "nada". If there is a slight rotary effect, then it's by far overcome by the phantom move combined with inside leg steering and the body wanting to unwind after the pole plant.

I have avoided bringing up inside leg steering into the equation because of a history of misunderstanding of PMTS being all inside leg steering which it is not. You tip to turn in PMTS most of the time. But, obviously, in the top of mogul pivot turn described in the PMTS books, there is more than tip to turn going on.

Thoughts?
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Postby milesb » Sun Apr 04, 2004 12:44 pm

John , here is a thought: understand how alot of good skiers use steering before making statements about it (hint-both legs are working....) Just as you and many of us get miffed when hearing people bring up myths about PMTS. Just forget about talking about steering, it's not important to the PMTS progression other than Harb says don't do it! Let it go.
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