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# Pivot point under foot

Although perhaps intuitively clear what pivot point under foot is, it is not obvious what a technical definition should be.

Well you have a moving system so it is not obvious.

In a pivot slip the reference is the straight line that the foot moves, and then it is quite obvious that we (should) have pivoting around the location of the foot.

If you take the same line and push you heels out so that the tips follow the line the ski has rotated around the tips so the pivot point is around the tip.

Fine so far, but what if you actually turn also. Say that you turn so that the end of the tail follows the same same line. Now the skis has pivoted around the tail, but likely this is one of the cases you would say that the pivoting is around the foot.

Or if we take the previous example a bit further and push the heels out at the same time so that instead of the tails following the straight line the feet are following the straight line.

Hmm, now the skis have rotated around the same point as in the first pivot slip example, but clearly this is not a case you would describe as pivot point under the foot.

Thoughts?

I'm not yet understanding what you're describing.  Let me see if I've got it right.  Is this what you are talking about?

1.  Imagine a narrow corridor about as wide as the skis are long, running straight down a slope.  There are two edges to the corridor, left and right.

2.  Pivot slip down the corridor.  The pivot point is under the feet.

3.  Slip down the corridor again, this time keeping the tips on the left edge of the corridor, but allow the tails to move downward farther until skis are pointing uphill.  The pivot point is the tips.

4.  Slip down the corridor again, this time keeping the tails on the right edge of the corridor, but allow the tips to move downward farther until both skis are pointing downhill.  The pivot point is the tails.

5.  Not sure about the last one.....

... and not sure about the point you are making ??

Might be my lack of coffee intake so far this morning, but I don't follow this Jamt.

Seems example 1 would use ILS and example 2 would use counter rotation, but it also seems you say the same inputs are applied. Yes/No?

Well the point is that it is stated quite often here that a good turn has the pivot point under the foot and not closer to the tips. My examples show that it is not as simple as that since both heel push turn and a pure pivot slip can have the same ski pivot.

So jamt, did I get my descriptions right?

Quote:
Originally Posted by Jamt

Well the point is that it is stated quite often here that a good turn has the pivot point under the foot and not closer to the tips. My examples show that it is not as simple as that since both heel push turn and a pure pivot slip can have the same ski pivot.

I'm not sure what a good turn is .  I think in general I would want the pivot point fairly close to my foot.  There are situations where I might want the pivot point to be closer to my tips.  Sometimes my "Plan C" involves a rapid pivot move off of my tails and I'm happy to do it .  Whether a move in skiing is good or not so good depends on intent.

I tend to think that a heel push moves the pivot point forward on the ski.

Yes you do know what a good turn is, tpj.

Making a rule about how to get it is not going to work.

But we can make a rule about how to get a bad turn, as long as we remember there are exception to every rule.

Some of the ski ballet people may be able to pivot around the tail, but other than that this not very useful for skiing.

Let's get the semantics down first. To start, let's consider the path of travel of the skis to be a straight line. If the tips turn off that line and the tails stay on it, the pivot point is the tail. If the tips stay on the line and the tails turn off, then the pivot point is the tips. If the tips and tails turn off the line an equal amount, then the pivot point is under foot. That's not exactly accurate because the center of the foot is usually not exactly under the center of the ski.

There should be general agreement that pivoting around the tips (aka pushing the heels out) is not an efficient method for turning. Let's theoretically analyze a Ron Lemaster style sequential photo of a recreational skier in a simple skidded parallel turn. At each snapshot the skiers boots are tracing a turn arc. From one snapshot to the next, the skiers tips and tails are rotating positions relative to the previous snapshot with the boots at the pivot point. There are three basic approaches to get this to happen. The skier can be rotating their feet. To the extent that skis edges are partially engaged during the skid, the sidecut will cause turning to happen. Finally, the skier can be utilizing a combination of the first two methods.

There are some who will argue that any rotation of the feet during a turn is inefficient. I would not argue strongly against that ("waiststeering" is a legitimately arguable point here, but it's a small point). There are some who would argue that rotation of the feet should never occur during any turn. I would argue that not having this as an option limits one's versatility and safety. The PSIA theory is that a blending of steering and edging appropriate to intent is required for effective skiing.

There are some who posit that this is an essential point in the topic of "dead end" approaches to teaching beginners. I would argue that the legions of pro athletes who started with an element of foot steering in what was taught to them from the beginning belies this point. It is a legitimate discussion to argue which approach is more effective, but there is no scientific data to back up claims either way. I've taught lessons using both approaches and found each to have its own pros and cons.

When you look at all of the pivoting that occurs in world cup skiing, this ought to be a moot point. I have seen the explanation that this is lower body unwinding vs foot steering. I won't argue this point because these arguments typically go nowhere. It doesn't really matter what people say is going on because both "sides" agree on what the end result is. If both sides teach to achieve the same result and get there, who cares? When each side claims "my approach works and your's doesn't" it is time to walk away from the discussion.

Quote:
Originally Posted by Jamt

Although perhaps intuitively clear what pivot point under foot is, it is not obvious what a technical definition should be.

Well you have a moving system so it is not obvious.

In a pivot slip the reference is the straight line that the foot moves, and then it is quite obvious that we (should) have pivoting around the location of the foot.

If you take the same line and push you heels out so that the tips follow the line the ski has rotated around the tips so the pivot point is around the tip.

Fine so far, but what if you actually turn also. Say that you turn so that the end of the tail follows the same same line. Now the skis has pivoted around the tail, but likely this is one of the cases you would say that the pivoting is around the foot.

Or if we take the previous example a bit further and push the heels out at the same time so that instead of the tails following the straight line the feet are following the straight line.

Hmm, now the skis have rotated around the same point as in the first pivot slip example, but clearly this is not a case you would describe as pivot point under the foot.

Thoughts?

I dont really follow this either  - but intiuitivley I think you are suggesting where is the pivot point really when "we have a ski that is turned about the foot, while moving in arc"....is the pivot point under foot?

Assuming my understanding is correct - the answer is simple really.

Pivoting is a skill, executed by the skier (active or passive dont matter).  Hence when we talk about pivoting it is within the context of the skiers moving "Frame of Reference".

If you look at it again using the the skiers "FoR" you will see (in good skiers anyway), the pivot pt is indeed underfoot.

jamt, i don't understand what you're saying either.

You also said in that closed thread:

Quote:

Originally Posted by Jamt

However, skiing with ILS/Femur rotation or whatever you want to call it is also very similar to skiing with ski manipulation that involves counter. Hence the turns we are discussing might not be so different after all, the biggest difference is where the focus is.

Since you cannot maintain a twisting torque, what most people are doing when they think they are twisting the femurs is probably they they are pressuring the feet sideways close to the balls, but what is this if not manipulation of fore-aft, edging and relative pressure between left and right? Different focus, almost the same output.

If as in a proper pivot slip, the skis are pivoting under the feet, where is the problem?  Even if it's true what you're saying on a micro level, the macro is the skis pivot under the feet.

These are more pivoting about the tips than under the feet. They would be a fail for pivot slips. Certainly by Bob anyway. Cgeib you concur?

For one thing the slip isn't continuous, there's an extension/upunweighting for each one.

Second, pivot is not under the foot.

http://youtu.be/8BRO6zKU7Jg

yep those are pivot slip fails.

I would like to know how anyone thinks it is possible to pivot around a pivot point under the feet, while the skis are edged?

In this video example, they are not maintaining flat during the pivot, they are edged.   if the ski is edged, the front half of the ski can't be moved towards the inside, it can only be torqued against the snow with rotary input from the legs.

Turning real turns involves edged skis.  That is one reason pivot slips have limited utility IMHO.  They are interesting for exploring femur mobility and other things, but not as a basis for a real world turn where the edged ski does not really even allow the ski to be pivoted.

If you think about it, in a real world turn with edged and weighted skis, only a heel push is really even possible in terms of manual manipulation, though it can be combined with self-steering properties of the skis.

Quote:
Originally Posted by borntoski683

yep those are pivot slip fails.

I would like to know how anyone thinks it is possible to pivot around a pivot point under the feet, while the skis are edged?

In this video example, they are not maintaining flat during the pivot, they are edged.   if the ski is edged, the front half of the ski can't be moved towards the inside, it can only be torqued against the snow with rotary input from the legs.

Turning real turns involves edged skis.  That is one reason pivot slips have limited utility IMHO.  They are interesting for exploring femur mobility and other things, but not as a basis for a real world turn where the edged ski does not really even allow the ski to be pivoted.

If you think about it, in a real world turn with edged and weighted skis, only a heel push is really even possible in terms of manual manipulation, though it can be combined with self-steering properties of the skis.

Bts, you can't have it just one way. You can't say that skis are self steering, pivoting under the foot, by putting them on edge and then claim that the same thing is impossible by actively twitsing the foot. Makes no sense. If self steering works, then twisting works.

How is it possible?

You are moving.

It is nigh impossible when not moving to pivot edged skis under the foot, granted.

While moving, it is done all the time. To explain it would require paragraphs I can't do now. Easier to show on snow.

So gentlemen perhaps rather than detail the difference, we might explore the similarities. Like BTS I see edge purchase having a huge influence on the ability to twist the skis freely. But I feel the effect of twisting the ski while the edge is engaged has been largely overlooked. It's not about pressure being applied through the bottom of the ski , or our feet. It's about applying it to the side of the ski and feet. It comes down to where the snow is relative to the ski. If it is out to the side of the ski, the force vector that would create that pressure would naturally need to follow where the snow is relative to the ski. So edge angle becomes a very important when it comes to how we create that pressure. Consequently, Rotary skills and flexing / extending of our legs just cannot be viewed as always having the same effect on pressure along that edge platform.

My take is that ILS offers a way to regulate pressure along the entire length of that edge platform without the need to move either the BoS, or the core away from the fore / aft balance axis. Yes some fore / aft stance adjustments must naturally occur as the tips dip below the feet and the rise back up to level of the feet but I question if that means levering is always the best option.
I believe we all can agree that these things occur and our differences come down to how much we use either option (lever / steer) to create and manage pressure.

Knowing different systems embrace different places along this spectrum, at best we here at Epic cannot expect any more consensus than we see in that larger ski world.
The title of this thread concerns where a ski would pivot and again I feel we would all agree that the rotational axis would be where our incidental fore / aft balance would be. Flexing and extending any joint would move that balance point. Levering thus becomes one major way to adjust that fore / aft balance but I question why anyone would suggest it is the only way. Nor is it fair to suggest rotary will always force the skis to pivot. That simply isn't true.
Edited by justanotherskipro - 11/14/13 at 11:37am

real quick before I run out the door....

Quote:

Originally Posted by Tog

Bts, you can't have it just one way. You can't say that skis are self steering, pivoting under the foot, by putting them on edge and then claim that the same thing is impossible by actively twitsing the foot. Makes no sense. If self steering works, then twisting works.

How is it possible?

You are moving.

It is nigh impossible when not moving to pivot edged skis under the foot, granted.

While moving, it is done all the time. To explain it would require paragraphs I can't do now. Easier to show on snow.

Ah but interesting.   If you are moving then the tail can move faster than the tip, causing rotation...  That is self steering!

No muscles needed.

That is nothing like what happens in pivot slips

Forget pivot slips, yes the skis are at critical edge angle, aka "flat". (They are not flat to the slope)  Does not make the excercise useless.

So how could you tell visually whether someone is using "self steering" of the skis or steering the skis themselves?

Quote:
Originally Posted by justanotherskipro

So gentlemen perhaps rather than detail the difference, we might explore the similarities. Like BTS I see edge purchase having a huge influence on the ability to twist the skis freely. But I feel the effect of twisting the ski while the edge is engaged has been largely overlooked. It's not about pressure being applied through the bottom of the ski , or our feet. It's about applying it to the side of the ski and feet. It comes down to where the snow is relative to the ski. If it is out to the side of the ski, the force vector that would create that pressure would naturally need to follow where the snow is relative to the ski. So edge angle becomes a very important when it comes to how we create that pressure. Consequently, Rotary skills and flexing / extending of our legs just cannot be viewed as always having the same effect on pressure along that edge platform.

My take is that ILS offers a way to regulate pressure along the entire length of that edge platform without the need to move either the BoS, or the core away from the fore / aft balance axis. Yes some fore / aft stance adjustments must naturally occur as the tips dip below the feet and the rise back up to level of the feet but I question if that means levering is always the best option.
I believe we all can agree that these things occur and our differences come down to how much we use either option (lever / steer) to create and manage pressure.

Knowing different systems embrace different places along this spectrum, at best we here at Epic cannot expect any more consensus than we see in that larger ski world.
The title of this thread concerns where a ski would pivot and again I feel we would all agree that the rotational axis would be where our incidental fore / aft balance would be. Flexing and extending any joint would move that balance point. Levering thus becomes one major way to adjust that fore / aft balance but I question why anyone would suggest it is the only way. Nor is it fair to suggest rotary will always force the skis to pivot. That simply isn't true.

JASP, I too find it very interesting to explore similiarities.  To apply sideways pressure along the edge at a fore position is possible in at least two ways, either you are fore and/ or you twist the femurs in the socket to produce this sideways force.

The fore is the manipulation I mentioned before but lets look at the other option, to twist the femurs in the socket.

This will create some sideways pressure and will engage the shovels, but it cannot be done with arbitrary force persistenly throughout the turn because every action has a reaction, and in this case this action will cause the upper body to act in the other direction. In one system this is called counter acting, and I cannot see why it should be so different from ILS to cause the huge amount of debate that has been going on. There are differences in timing etc but on an overall scale a good skier from one system will not be that different from a good skier in another system.

Semantics to a large degree I suppose, but personally I like to talk about pivoting, ILS etc in transition, unweighted. When the edges are engaged I think it is better to talk about counter, fore-aft and edge angles.

Quote:
Originally Posted by Tog

So how could you tell visually whether someone is using "self steering" of the skis or steering the skis themselves?

There would be more counter in the latter case. But I am of the opinion that a skilled skier uses more self steering, but he may not know it! It is quite sub-conscious in a good experienced skier. It just happens.

Jamt, if there was just one pivot point your idea of a counter rotary reaction of the upper body would occur but with two hips acting as pivot points a rotational twisting of the upper body doesn't need to happen.
Quote:
Originally Posted by Jamt
Quote:
Originally Posted by Tog

So how could you tell visually whether someone is using "self steering" of the skis or steering the skis themselves?

There would be more counter in the latter case. But I am of the opinion that a skilled skier uses more self steering, but he may not know it! It is quite sub-conscious in a good experienced skier. It just happens.

Theoretically perhaps more counter, but in practice due to people rotating their bodies with it, you get less I think. Maybe others can put their experience in, but I don't think there's a lot of excessive counter issues one sees.

Not sure I even buy the more counter in theory. What, from an opposite reaction? From oversteering?

Quote:
Originally Posted by justanotherskipro

Jamt, if there was just one pivot point your idea of a counter rotary reaction of the upper body would occur but with two hips acting as pivot points a rotational twisting of the upper body doesn't need to happen.

I believe it does: http://www.epicski.com/t/114527/physics-and-ski-technique#post_1499608

Quote:
Originally Posted by Tog

Theoretically perhaps more counter, but in practice due to people rotating their bodies with it, you get less I think. Maybe others can put their experience in, but I don't think there's a lot of excessive counter issues one sees.

Not sure I even buy the more counter in theory. What, from an opposite reaction? From oversteering?

Opposite reaction. Of course if the skis are flat this opposite reaction is very small since the legs are much lighter than the upper body.

Quote:
Originally Posted by Jamt

Quote:
Originally Posted by justanotherskipro

Jamt, if there was just one pivot point your idea of a counter rotary reaction of the upper body would occur but with two hips acting as pivot points a rotational twisting of the upper body doesn't need to happen.
I believe it does: http://www.epicski.com/t/114527/physics-and-ski-technique#post_1499608

And...?

Jamt, seems in practice the counter can be totally over run by something as simple as the outside arm swinging forward.

Cgeib accuses me of that all the time.

Well, Tog, I have video so I am going with 'fact' vs accusation

As to the and...

1)
I agree with Jamt that the counter rotation can occur in situations, but I think more often then not it doesn't have to is my experience.

2)
This horse has been beaten so much I don't see the point in swinging any more
Quote:
Originally Posted by "Tog"

Forget pivot slips, yes the skis are at critical edge angle, aka "flat". (They are not flat to the slope)  Does not make the excercise useless.

So how could you tell visually whether someone is using "self steering" of the skis or steering the skis themselves?

If someone is developing a lot of counter then self steering can still be at work, a lot of skiers are using it even if they think not. But the skis have to be tipped. The video above of fail pivot slips are using huge amounts of it.

It's also possible to self steer without developing any counter, it's an interesting discovery session to isolate self steering effects of skis and explore what they can do while avoiding any and all foot twisting. But in real world skiing, some counter can be introduced, allowing upper/lower separation. But it does not require such active foot twisting that pivot slips encourage. Also my opinion is that when skiing on outside dominant skis, that ILS loses some of inside leg as a stability point. In my view real world counter in a ski turn happens mostly around the outside hip joint and the outside ski is used as anchor point to counter-rotate the pelvis out into counter as the skis self steer inwards.

Real counter is a very small amount. Look at BB's animation and the grey pelvis only tips up and down a small amount while the legs are turning a ton. The leg independence is not really the counter though I know everyone has come to think of it that way. Rather counter action happens using muscles up and down the side of your body to basically manipulate that small grey bar in BB's animation, the feet can turn underneath that, pushing and pulling against that counteraction, and using the outside ski as anchor point.

When you see classic pivot slips, there is no self steering really. The skis are pretty much flat and its pretty much all about twisting those femurs with virtually no anchor point. A pure pivot if you will, as opposed to a smeared turn like the video above where edge engagement and ski steering are resulting in nearly pivot slips but not quite. Because they are edged they require self steering to do its magic and that requires a bit of forward motion that a pivot slip doesn't have. That's why you see them moving from side to side making actual turn shapes, albeit very tight.

While looking for self steering, look for edge engagement, steeriness, some forward motion, and actually probably not huge steering angles because large steering angles and edge angle tend to have opposite effect, self straightening. Counter and femur rotation optional, but if you see super isolated ILS femurs then maybe they are twisting more, but I doubt you will see that with edge engagement.

Quote:
Originally Posted by "Jamt"

JASP, I too find it very interesting to explore similiarities.  To apply sideways pressure along the edge at a fore position is possible in at least two ways, either you are fore and/ or you twist the femurs in the socket to produce this sideways force.
The fore is the manipulation I mentioned before but lets look at the other option, to twist the femurs in the socket.
This will create some sideways pressure and will engage the shovels, but it cannot be done with arbitrary force persistenly throughout the turn because every action has a reaction, and in this case this action will cause the upper body to act in the other direction. In one system this is called counter acting, and I cannot see why it should be so different from ILS to cause the huge amount of debate that has been going on. There are differences in timing etc but on an overall scale a good skier from one system will not be that different from a good skier in another system.
Semantics to a large degree I suppose, but personally I like to talk about pivoting, ILS etc in transition, unweighted. When the edges are engaged I think it is better to talk about counter, fore-aft and edge angles.

JASP and jamt great points. I actually do endorse a very small amount of femur rotary maybe that will shock some of you. But not for pivoting the skis. For one thing you want to twist your feet to keep up with the self steering so that the ski doesn't have to push your whole passive leg. So at a simplistic level turn the leg just at the right amount so that you don't feel those torques acting on the leg. Further to that you can apply even a tad more as JASP suggested to kind of help self steering do its job, but again without actually pivoting the ski, just very light pressure, not enough to cause counter either or move something away and not be sustainable. Its more like just enough to sense you are not blocking self steering. Like following someone in a dark room and touching their shoulder to keep up without actually pushing them.

Also if you create too much lateral pressure in the side of the front, I feel you can twist the tail out of engagement into wash out.

It's generally more effective to manipulate fore-aft pressures to manipulate self steering effects a bit and/or tip more.

Quote:
Originally Posted by "Jamt"

There would be more counter in the latter case. But I am of the opinion that a skilled skier uses more self steering, but he may not know it! It is quite sub-conscious in a good experienced skier. It just happens.

Exactly, a lot of people are getting more of it then they realize.

I'd like to pose another question, why the obsession over pivoting the ski around the foot point? Aside from dreadful thoughts about heel pushing, if the pivot point is the tip or the tail or in between what is so bad after all?

I'm just posing the question to hear some well thought out reasons for why a pivot under the foot would be superior to a pivot under the shovel, for example. Certainly if you are trying to do it by twisting your feet then a tail wash out would probably be bad. But if it comes from self steering on engaged edges, then I suggest it may not be under the foot and may not be a problem. So why is pivoting under the foot such a goal?

Edited by borntoski683 - 11/14/13 at 4:56pm
Actually Tog the Whistler training thread has some valuable a/b visual comparisons. The narrative helps guide our attention to what is moving.

Which Whistler videos?

http://www.epicski.com/t/119377/whister-ski-school-development-sessions

with these videos? :

http://www.wbsss.com/training/a_and_d_videos/

That's like 5 hrs of video, any specific ones?

Quote:
I'd like to pose another question, why the obsession over pivoting the ski around the foot point? Aside from dreadful thoughts about heel pushing, if the pivot point is the tip or the tail or in between what is so bad after all? - bts683

It's just the definition of steering, no obsession. It's like saying, why the obsession with self steering? What's so bad.... I mean a little counter??

Guiding the tips. Not pushing the tails out

With steering, you can reduce skiing to the most simple phrase:

"Left tip left to go left, right tip right to go right"

Also, ILS is "Independent Leg Steering"

Edited by Tog - 11/14/13 at 6:06pm

Where the pivot point is depends on where the foot is with respect to the center of mass.

If the foot is directly below the COM, not in front of it nor behind it, then the pivot point will be under the foot should you so desire to turn the foot manually.

Having that foot under your COM (taking momentum into account) is a good thing in most cases.

I'd think that the location of the foot relative to the body is what matters because it determines how all kinds of things are going to work in the turn.  It's not the pivot point itself that matters so much; although the two are directly dependent on each other.  The pivot point is a symptom.

It can be or not.

What if you are way forward pressing into the front of the boots but your feet are under com - you will pivot off the tips.

One could sit way back and still pivot under the feet. You'd have to do it in the phase where your feet are light

In moguls one is often pivoting while way back before you catch up to your feet. Granted skis often have the fronts off the snow to pivot easier, but it's done.

Actually, the ability to selectively access any skill is why a centered stance makes sense. It is the difference between Compensatory moves, (or as some would call them recovery moves), verse anticipatory moves where we ski into the future in such a way that the outcome expresses our planned intent.
Levering, too tall, too croutched, leaning to a dominant side, are all stances we might visit temporarily but would not prescribe to our students and staff. But we will certainly see them out on the hill. The limitations those stances impose make that selective access much more difficult to attain. That in as short of an answer is why we teach centered stances that would allow the ski to turn under the foot, not the tip / tail.
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