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# Momentum and initiation

Some turns generate lots of momentum; other turns generate less.

How do you see the role of momentum in initiating turns?
How does this affect your instruction?

Please define momentum as you use it in this case. The definition of momentum is Mass times Velocity (MV).  The only way you increase momentum is to increase speed.

Do you actually mean centrifugal force?  Or are you talking about something else?
By momentum I mean a moving body's tendency to continue moving in a straight line at whatever speed it's currently going.

So the faster you go, and the more mass you are carrying, the more tendency your body has to continue in a straight direction.
I suppose that when we are turning on skis we experience this as centrifugal force.  No physicist here, sorry.

When you're turning, you resist the body's tendency to move straight down the hill - you use your skis to make yourself turn.
When you "release" the old turn, it's your built-up momentum that drives your body forward into the new turn.  Thus initiation.

But sometimes we have lots of momentum to send us forward, and sometimes (wedge turns, no speed, no pitch) we have little momentum.
Just wondering how instructors deal with this issue.
LF,

Would you agree that momentum is more noticeable the more the path of the skis differs from the path of the body?
Yes - also more noticeable at speed, and more noticeable with more pitch, and with shorter turns.  But maybe the turn radius makes it more noticeable than the other factors  ...  since release sends you in a very different direction.
How about this concept: momentum causes release? The release should not send you in a different direction. Release should occur as a result of a continuation of movements.
Momentum doesn't cause a release, only our movements to release the forces in a turn do. Though we can and should utilize our momentum to assist us in moving from tun to turn. If we stay in our turn and make no movement to release, we will simply continue in our turn until gravity over powers our momentum and we slide to a stop. We need to make a movement(s) to flatten our skis and/or reduce the pressure by flexing the outside leg. More than one way to accomplish this, which is another topic.

LF, even in a wedge turn we need to have a release of the outside ski's edge in the snow. I teach releasing the outside ski's edge to beginners as well. IMO all turns have enough gravity and momentum working on us to have it work for us. Release the outside ski edge (flatten the ski) in a wedge turn and the body will move in the direction of the new turn. No need to push it there or make big directional movements. As the speed increases, flexion and extension, pressure control, becomes even more important if we are to harness the forces to work for us. Better to collaborate with the forces than try to overpower them, or as Arcmeister used to say "we should never cause to happen what we can allow to happen". Or something like that.
A very good topic, LiquidFeet--and a good continuation of a popular theme from other current threads. Thanks!

First, we should make sure we're getting our definitions straight.

Quote:
By momentum I mean a moving body's tendency to continue moving in a straight line at whatever speed it's currently going.

So the faster you go, and the more mass you are carrying, the more tendency your body has to continue in a straight direction.
I suppose that when we are turning on skis we experience this as centrifugal force.  No physicist here, sorry.

While it may be nit-picking, what you are describing here is actually not momentum, but inertia. Inertia is a function of mass--the more mass, the more inertia. It is defined as a body's tendency to resist changes in motion (to "accelerate"). In other words, it is inertia that is the tendency of a body at rest to remain at rest, a body in motion to remain in constant, straight-line motion until acted on by an external force (anything that pushes or pulls on it). This is Newton's First Law of Motion, also known as the "Law of Inertia." Heavier things have more inertia than light things (it's harder to push a ship than a canoe away from a dock). Inertia is independent of motion--you have just as much inertia standing still as moving fast. It is true that the "the more mass you are carrying, the more tendency your body has to continue in a straight direction." It is NOT true that "the faster you go,...the more tendency your body has to continue in a straight direction."

Momentum is the term that describes the "quantity of motion" of a moving body. As T-Square suggests, it is a function of inertia (or mass) AND velocity (speed and direction). No matter how massive, if a body is not moving, it has no momentum (velocity is zero). It is not "harder" to change the motion of a body moving faster (it has the same amount of inertia)--but there is a lot more "motion" (momentum) to change!

So...skiing can be distilled down to the simple act of "managing momentum." The more we slow down in turns, the more momentum we lose. When we change direction (turn), it requires force (because direction, and thus velocity, and thus momentum, changes)--whether we lose or gain speed or not. In transitions, when we stop turning (stop changing direction) and carry our speed out of one turn and smoothly into the next, it does not need to involve force or effort. In other words, if we have managed our momentum optimally through the previous turn, we can release our effort and simply allow our momentum to continue where we need to go, through the transition, across the paths of our skis (which have their own inertia and momentum, in a different direction) and into the new turn.

And that, I believe, is the heart of the matter of your original post--the "role of momentum in initiating turns." If we can manage the momentum of our body (CM) and our feet/skis optimally, such that, as one turn ends, both are going in the needed directions and optimal speeds (both have the "right" momentum), we can release all of the forces applying to both and simply allow their momentum to carry them through the transition.

To me, this describes the optimal "default" scenario--the "perfect turn"--with movements that I can, and will, change as needed in any "real" situation where I've either failed to manage the momentum(s) optimally, or need to change the path or speed of my feet or body in the transition, for any reason. In other words, in the real world of constantly varying situations and "imperfect" movements, I may rarely be able to take advantage of this "perfect," effortless transition. I may often need to generate force (exert effort) in the transition to get my body or feet moving in the required directions. I may need to actively flex or extend one leg or the other in an active weight transfer, forcefully flex or extend ankles, knees, hips, or arms to adjust my fore-aft balance, or twist my feet and legs to redirect my skis. All of these movements are important options, and good skiing requires becoming skillful at them. But none are what I would call "default movements" that I should look to do in all turns.

---

RicB--you wrote, "Momentum doesn't cause a release, only our movements to release the forces in a turn do." While you are correct that "movements to release the forces" are certainly required for a release, please consider that momentum describes movement! And that is the whole point--if the momentum is "right," then we don't need to make any other movements or efforts to cause a release, or continue through a transition. If the movement is already happening, inertia will keep it going, and I can relax and just enjoy the ride for a moment! If my previous turn ends "perfectly"--with my body and my skis in the right places and going the right directions and speeds--then I really do not need to do any of the many things instructors tend to emphasize to get the new turn started. While that "perfection" may rarely happen in real skiing, it should not stop this concept from being the "ideal," the "default" technique of great turns.

These thoughts place a lot of significance on the efforts and movements we make throughout turns, especially in the finishing portion, where we literally finish directing our momentum. In other words, the only time I should have to "do something" (exert some muscular effort) to start a new turn is when I've either made an error in the previous turn, or suddenly changed my mind about how I want the next turn to happen. Show me a move that is needed to start a new turn, and I'll show you a move that should have happened already in the last turn!

Best regards,
Bob

Would you guys agree that flex to release maintains more momentum into the next turn than extend to release?

Newtonian laws are at the heart of this discussion but I wonder if we really want to go there. Yes without any external forces acting on a moving body, it will continue to move along a linear path. Perhaps instead of even discussing momentum, it would be better to suggest that if we remove the external forces causing the turn (change in direction of travel) we would return to moving along a straight path. Said another way, each phase of a ski turn includes a sum of forces acting to accelerate us and thus change our direction of travel (we turn). Releasing the skis (disengaging the edges) changes the mix of these forces and we simply stop turning (changing our direction of travel). It's also important to understand that speed is irrelevent to this return to linear motion. It occurs immediately when we eliminate the turning forces that are occuring as a function of the ski snow interactions. Where speed and momentum come into play is in how quickly the forces that would cause a new turn would begin having the effect of accelerating you in a new direction. This is more a discussion about decaying orbits though and I wonder how far we want to really want to delve into that subject. Especially without adding all the supporting evidence that so many here find boring. For those looking for information on that level, I'd suggest Vagners book as a starting point and if that's not detailed enough, there are several University studies available. Ask a local race coach for a copy of their association's coaching journal and I'm sure you will find more than enough links to these sort of works. BTW reading all of those studies is a great cure for insomnia.

Obviously, we can introduce lateral acceleration by re-establishing edge purchase and changing the mix of forces I mentioned. It's also worth noting that we can do this to continue turning the same direction as before, or we can begin turning the other direction. So IMO, the whole discussion of momentum needs to be seen through the filter of you carrying it through the transition rather than it carrying you through the transition. Reducing, or eliminating extraneous braking movements and eliminating, or reducing unnecessary body movements (movements that move you away from your intended direction of travel), allows you to carry more directionally relevent speed and momentum through the transition. This is the principle idea behind the slow line fast concept Bob has been talking about for so many years.

So how do I package this to a student? I don't unless they're an engineer type who insists on discussing the math and science. Even then I try to save the mental gymnastics for lunch, or an evening clinic since the math usually requires a pencil and a lot of paper. On the hill, I tend to focus more on setting up situations where they will experience the sensation of moving through the transition with a minimum amount of braking. I do this at all levels with the notable exception of when we're working on a closing radius braking finish. Which is still needed at times, just not all the time.

P.S. Nice post Bob! I didn't mean to be redundant here, I was editing my post when you added yours. Ski well my friends,
JASP
Edited by justanotherskipro - 3/14/10 at 11:40am
Quote:
Originally Posted by TomB

Would you guys agree that flex to release maintains more momentum into the next turn than extend to release?

Good question, TomB. While there is surely a kernel of truth to what you suggest, I'm going to answer it with "no," for a couple of reasons.

First and foremost, it's important to realize that the "release" that occurs in these types of turns results from tipping movements--specifically, the crossing of the paths of the CM and feet. It is NOT caused by either "flexing" OR "extending," and is completely independent of these movements. Although the release tipping action may be accompanied by either "flexing" or "extending" (or neither), the causal relationship implied by "flex TO release" or "extend TO release" simply does not exist. If you happened to scratch an itch at the same time as the edge released, you would not say, "I scratched an itch to release," would you? At best, we should discuss the relative advantages of "flexiing WHILE releasing," vs. "extending WHILE releasing."

Second, "flexing" and "extending" while releasing are better viewed as a continuum of movement options during the transition, rather than as two distinctly different techniques. Both can be done subtly or intensely, smoothly or abruptly. And, of course, there's the option in the middle of the continuum of doing neither. It is certainly good to practice both ends of the spectrum, as well as the middle, in order to develop our full range of technical options and versatility. One is not inherently or universally better than the other.

Finally, there are many factors that come into play that determine which option--and how much (where on the continuum)--is appropriate for any given turn. This is where versatility, adaptability, skill, and "touch" trump "dogma" every time! How fast are you going? How tight is your turn radius? How far across the hill are you trying to get in the transition? How quick is your turn tempo (slalom--a turn a second, GS--two or three seconds per turn, or longer)? How steep is the hill? Does the transition occur over a bump or a rise, or does the terrain drop away from you as you release your edges?

One very simple analogy that comes to mind is playing catch with a ball. How much "loft" should you give the ball when you toss it to the other guy? How high should you throw it? The answer, of course, "depends." It depends on how fast you throw the ball. It depends on how far away from the catcher you are. Like skiing, this too is a case of "managing momentum"--you have to adjust the trajectory each time before you release, weighing a number of factors. In many ways, skiing is just our feet "playing catch" with our bodies--moving into position, catching and redirecting the body, then releasing and moving into position (through the transition) to do it again in the next turn. The speed and direction of the body--that is, its momentum--at the moment of release are critical. We spend the time leading up to that moment precisely controlling and guiding the body's momentum, so we can release it in the new direction and get ready to make the next turn. If we manage everything right in the previous turn, the transition and the initiation of the next turn are effortless!

And that optimal direction (momentum) has three dimensions: fore-aft, left-right, AND up-down. Whether, and how much, to "flex" or "extend" is entirely driven by the up-down component of the "ideal direction" for the body's momentum for each turn. Flex too much (or too soon), and you'll literally throw yourself into the ground. Extend too much, and you may not come down for a while, or in the right place--delaying the edge engagement ("the catch") for the new turn, or throwing yourself completely off your line.

Manage the momentum! In great turns, great skiers accomplish this with continuous, smooth guiding movements throughout the turn. Unfortunately, most skiers fail miserably at it, employing gross and sudden exertions with staccato stop-and-go effects, instead of smooth, sustained movements. It is exceedingly rare to see skiers who truly "flow" (carry their momentum!) through their transitions as a rule.

But it's a worthy target!

Best regards,
Bob

I'm glad we all agree that something needs to happen to move from one turn to the next. How big a something or when we time this something is really the point to be discussed.
Quote:
Originally Posted by TomB

Would you guys agree that flex to release maintains more momentum into the next turn than extend to release?

No I would not agree with this. But you must realize it's a tricky question. Because momentum includes velocity and velocity includes direction, the shape of the turn is important. A straighter turn conserves more momentum! You may be thinking that flex to release may be more efficient, but being more efficient does not necessarily change the turn shape or the speed (the two controllable pieces of momentum). You may also be thinking that flex to release produces a rounder or more carved turn. This is not necessarily true and we've already noted that straighter turns conserve more momentum. This may be mind boggling because we know that carving and round turns are keys to success in racing, but it should be too surprising, because in racing you can make turns too round or too carved.

How you release and where you release are choices. Flex to release may be a mental cue that causes multiple movements that result in a rounder turn and higher conservation of velocity. But skilled skiers can initiate turns with either extension or flex movements. Skilled skiers can also make choices to conserve momentum or create changes in momentum. A high G turn has a lot of change in momentum and can also be a lot of fun. To answer one of LF's original questions, I like to have a lot of fun in my lessons.
Quote:
Originally Posted by TomB

Would you guys agree that flex to release maintains more momentum into the next turn than extend to release?

Quote:
Originally Posted by therusty

But you must realize it's a tricky question. Because momentum includes velocity and velocity includes direction, the shape of the turn is important.

It's not a tricky question at all.  Assuming the same shape / speed / radius / terrain etc etc flexing to release should be faster, and more likely to conserve momentum.  When flexing and releasing the body is allowed to seek the fall line.  When extending the CM heads away from the fall line (up though even for only a brief period).  Given that down the fall line is the fastest line, flex and release should send the CM that direction sooner......therefore faster.

The argument could be made though that you may be able to accelerate off the tail of the ski if you did in fact extend,  but if you are centered in both turns a release will be faster.
It is very simple.  Any force, or any component of any force, acting on you that goes against your current real-time velocity direction (direction of motion) reduces the magnitude of your momentum; any force, or any component of any force, that pushes in the direction of your current direction of motion adds momentum, any force completely perpendicular to your current direction of motion has no effect on the magnitude of your momentum.
Quote:
Originally Posted by Uncle Louie

It's not a tricky question at all.
...Given that down the fall line is the fastest line, flex and release should send the CM that direction sooner......therefore faster.

UL,

The problem with physics is that it is precise. "Sending the CM that direction" is a change in direction and that means a change in momentum. Speed is different than velocity. Yes I'm being picky, but that is the tricky part I was talking about,
Quote:
Originally Posted by Bob Barnes

Quote:

First and foremost, it's important to realize that the "release" that occurs in these types of turns results from tipping movements--specifically, the crossing of the paths of the CM and feet. It is NOT caused by either "flexing" OR "extending," and is completely independent of these movements. Although the release tipping action may be accompanied by either "flexing" or "extending" (or neither), the causal relationship implied by "flex TO release" or "extend TO release" simply does not exist. If you happened to scratch an itch at the same time as the edge released, you would not say, "I scratched an itch to release," would you? At best, we should discuss the relative advantages of "flexiing WHILE releasing," vs. "extending WHILE releasing."

I don't have much recent experience with extending to release, so I'll accept your statement about it and add my suspicion that it contributes to the staccato stop-and-go turns you mention.

Your statement is completely wrong for flexing to initiate the turn.  The root of your fallacy is considering the skier as a rigid body.  Flexing gently is a relaxation of the muscles in the lower body.  This briefly decouples the lower body upon which the contact forces at the snow act from the upper body where the bulk of the skier's mass resides.  This decoupling, i.e. breaking of the rigid body assumption, is how releases are initiated via flexing.  In a more aggressive retraction turn, the skier actively contributes to this momentary decoupling.
Quote:
Manage the momentum! In great turns, great skiers accomplish this with continuous, smooth guiding movements throughout the turn. Unfortunately, most skiers fail miserably at it, employing gross and sudden exertions with staccato stop-and-go effects, instead of smooth, sustained movements. It is exceedingly rare to see skiers who truly "flow" (carry their momentum!) through their transitions as a rule.

Agreed, it is unfortunate given how easy it is to accomplish this "flow" and how much more rewarding ones turns become with it.
I think we all see the merits of the dual paths model where the feet and the body move smoothly and without interruption along their seperate paths. It's not as easy to take this concept and bring it into the real world without mentioning how we should move to conserve the maximum amount of speed and momentum.
The feet moving faster than the body suggests a bit of a crack the whip movement quality. But how do we get the feet to move so fast in the first place? Is it simply a matter of not letting the skis skid, or is there a moment where we actively accelerate the feet? I suspect this moment occurs when the feet are uphill and must begin catching the body. As this occurs does the body lose some momentum because we played crack the whip to accelerate the feet? If not, what force accelerates them without also accelerating the body at the same rate? Like Ric pointed out there has to be some active body movements and internal motive forces at work for us to produce more foot speed and a relatively lower body speed.

Quote:
Originally Posted by therusty

UL,

The problem with physics is that is precise. "Sending the CM that direction" is a change in direction and that means a change in momentum. Speed is different than velocity. Yes I'm being picky, but that is the tricky part I was talking about,

Yep, and I wasn't talking about an internal movement as in WE SEND the CM.....I was talking about where it was "allowed to go" as a result of the release.  I agree that a release will allow the CM to travel in a new direction, and it should be one that would change our momentum.

If a change in direction means a change in momentum wouldn't you agree that if the "new direction" (of the CM) is moving in a direction where one would normally accelerate it would be easier to increase or maintain momentum then if we moved the CM in a direction other than that direction?  Ghost's post below mine explains it rather clearly.
AH, "allowed to go". That's exactly what I was hinting at in my first post. We all know this stuff. It's the semantics that gets tricky.
Quote:

These thoughts place a lot of significance on the efforts and movements we make throughout turns,
especially in the finishing portion, where we literally finish directing our momentum.

In an across the hill series of turns, like in B. Barnes "Dynamic parallel turns" picture, we are literally
changing the direction of our CoM almost a full 180 degress across the hill.
On a clock, with the fall line going from 12 to 6, this puts the end of going one way at 3 o'clock
in a right hand turn or positions 8 and 16 in Bob's diagrams.
The forces to change the CoM's direction are maximum at or just past the apex of the turn.
I am thinking that while the direction changes at 3 o'clock, I am still having to "finish" dealing with the presures from the turn past that point.
How far past is based upon your speed and the steepness of the slope.  Let's say this is at 4 o'clock (or 9 in Bob's).
So at this point I have stopped the going left across the slope and the dealing with the forces required to do that.
Now I can start managing the going right across the slope and get set up to turn to the left.
At 4 o'clock (Bob's 9) I can start the efforts and movements required to direct my CoM towards it's future point in the apex of the next turn.
Careful? it's the CoMs apex and not the skis apex?  Ditto, I can steer the skis to where they need to go.

For me, that moves the whole turn thought process about 70 degrees sooner around the turn.
Instead of finishing the turn at 6 o'clock and doing whatever I have to do to perform the next turn and direct me and my skis where they should go,
I have to be thinking and acting much sooner and looking out further.
Instead of thinking where my skis will turn, I have to think about where I want my CoM to finish going across the hill.
It takes my thinking of an apex to apex turn to a different level.

OK, so here I am at 4 o'clock and I need to "release" to initiate the process of getting ready for the next turn. This "release" is really "I can stop pressing against the snow to change my direction from going left to going right cause I'm already going right and if I don't ease off on it now I'm going to have to make a much bigger and quicker adjustment later so I can get my skis on the other side of me to be able to stop going right and get me going left again."
If I time it just right, I can let the forces of the turn do the work of moving my CoM to the other side of my skis.
Or is it the skis to the other side of the CoM?

Doesn't "release" mean releasing the CoM to allow it to move downhill and across our direction of travel?

I'm trying for an ILE type turn.  This then means that my outside leg stays long, right?
Then with any inclination at all, the best I can hope for if I extend my inside leg is an up and over arc with my left foot as the center of the arc (right hand turn of course).
By my thinking, this causes a slower movement of the CoM down the hill/across my line of movement.
An OLR type turn means I am flexing the outside leg to allow the movement of the CoM down the hill and across my direction of travel.
This seems more direct and therefore enables a faster transition and therefore a faster/tighter turn.
In either case, the flex or extend released my CoM didn't they?  And if I allowed my CoM to move downhill and across my direction of travel, without any tipping effort won't the skis eventually change edges?

Or does "release" mean releasing the angle my skis are to the snow because they are headed in the direction they need to be to get on the other side for the next turn?  If I don't flex or extend my legs, I can only tip (or untip in this case) my skis with ankle, knee and hip angulation or somehow reduce my inclination.  Again, without flexing and extending the legs, I suspect this would be a long drawn out process ending with an uphill stop.

OK, so it's a skill blending of edging, pressure and rotary steering but which came first, the chicken (Flex/extend) or the egg (tipping)?
Seems to me like the chicken came first.
What ya think?

Seems like there is a case building to say that the transition is not the focus area, that the point just after the apex is where it all begins and should be the focal point.

Good post, Snowhawk, summed up, I would think, by these lines:
Quote:
For me, that moves the whole turn thought process about 70 degrees sooner around the turn.
Instead of finishing the turn at 6 o'clock and doing whatever I have to do to perform the next turn and direct me and my skis where they should go,
I have to be thinking and acting much sooner and looking out further.

What you describe here is exactly the point! The skis, through their interaction with the snow, apply force to the body (CM), which causes the direction change (turn). Once that redirection is accomplished, we "release" the force, allowing the body's momentum to continue unimpeded for a moment, as we move the feet into position to "catch" and then redirect the body into the next turn. It's a game of continuous, flowing, cyclical motion--not of "stop and go." And you are right--the key is to have the skis and the body moving as needed, each with the optimal momentum (direction and speed), at the end of the turn. So the movements required to make this happen must, obviously, take place in the control and completion phase of the turn you're finishing--it's too late if you try begin these movements at the beginning of the new turn. Unfortunately, since few skiers do this accurately, they cannot merely "release" the forces to start at turn, and must instead create a great deal of force and exertion to get things moving in the right direction AFTER the old turn ends. The result is an abrupt, not-smooth, not effortless transition.

You suggest that the "release" is where you can "stop pressing against the snow to change my direction." Yes! However, it may be more applicable to think of it as the moment the snow stops pressing against you.Sure, it's the same thing--equal and opposite reactions and all that--but the point of that interaction between yourself and the snow is that it is the very force that causes the direction change we call "turning." The snow pushes me; I accelerate (turn). Just as you'd be more likely, when explaining how to throw a ball, to describe it as your hand pushing against the ball, rather than the ball pushing against your hand, I suggest that thinking of the pressure resulting from the snow pushing against you, rather than you against the snow, paints a clearer image of what's happening--and of what we need to "do." Do you try to hit the ball with a golf club--or do you try to hit the club with the ball? Both are accurate descriptions. But one more clearly describes the intent--and the job of the athlete.

Either way, it's a good description.

Regarding your "chicken and egg" question, I suggest that you really can't separate these things, and shouldn't think of them as sequential events. As I described previously, at the moment of release, it's imperative that the body (CM) be traveling with exactly the right direction and speed (momentum), and that the direction of the momentum involves three dimensions--fore-aft, lateral, and vertical. Whether (and how much and when) to flex or extend as we release the forces of the turn is entirely determined--in every unique transition--by the specific and unique needs of that transition. Leading up to the release (in other words, as we complete the previous turn), we steer and guide the body's momentum in all three dimensions, simultaneously,

Indeed, to the point of the original post, it is only when we have finished the turn optimally--with the body (and the feet) ending the turn with the optimal momentum, that we can release the forces and "carry the momentum out of the turn, and into the next." Anything less, and we'll have to exert some effort (produce some force) as we start the new turn, in order to change the momentum.

Best regards,
Bob

Quote:
Originally Posted by Bob Barnes

The skis, through their interaction with the snow, apply force to the body (CM), which causes the direction change (turn). Once that redirection is accomplished, we "release" the force, allowing the body's momentum to continue unimpeded for a moment, as we move the feet into position to "catch" and then redirect the body into the next turn. It's a game of continuous, flowing, cyclical motion--not of "stop and go."   .....   Indeed, to the point of the original post, it is only when we have finished the turn optimally--with the body (and the feet) ending the turn with the optimal momentum, that we can release the forces and "carry the momentum out of the turn, and into the next.

What about when we are instructing never-ever-skiers who are slowly making their way down a nearly flat bit of snow, centered over their skis in a wedge?  Momentum = mass x velocity, so not much velocity means not much momentum to continue unimpeded into the next turn once the release is accomplished.  When guiding these skiers to initiate a new turn, do instructors find it useful to instruct them differently than when instructing intermediates skiing parallel on a moderate slope, who therefore have more momentum to release?

Does a first-lesson skier often get the kind of "optimum momentum" you are describing?
Quote:
Originally Posted by Snowhawk

I'm trying for an ILE type turn.  This then means that my outside leg stays long, right?

Not necessarily, Snowhawk.  ILE simply means pressure transfer is initiated with an extension of the old inside leg.  It doesn't distinguish how much extension of that old inside leg is executed.  At the minimal end of the ILE execution spectrum, you won't even see the extension happen, and the old outside leg will have to flex as the CM crosses over.  At the maximal end of the ILE execution spectrum, the old inside leg will extend to full functional length before reaching edge angle neutral, the old outside leg will indeed remain long, and a large lifting of the CM will happen as it crosses over the skis.  Any variation of extension/flexion with in those two extremes are options a skier has to employ.

BTW, OLR without accompanied flexion of the old inside leg will also show a rise of the CM as it crosses from one side of the skis to the other.  OLR and retraction are not the same thing.  OLR and ILE can look very similar in how much the CM rises as it crosses the skis.
Thanks guys, I now get a week at the Beaver and surrounding areas to play with these things but unfortuantely off the grid.  May do Keystone Monday so here's to ya Bob!
Liquid feet,
The slow skiers still have momentum and carrying it into the new turn occurs the same way just very slowly. In fact, I think it's hard for better skiers to slow down and develop this disciplined patience. Moving at 1/8 mph and producing a turn at that speed isn't that hard but most skiers start adding edge, or steering because they lack the patience to allow the turns to occur that slowly. The usual result is they can't keep the skis gliding so they step or push the ski around. It's almost counter intuitive to suggest accuracy at speed begins with accuracy without speed.
Quote (LiquidFeet, post #23):

When guiding these skiers to initiate a new turn, do instructors find it useful to instruct them differently than when instructing intermediates skiing parallel on a moderate slope, who therefore have more momentum to release?

Does a first-lesson skier often get the kind of "optimum momentum" you are describing?

Another great topic for discussion, LiquidFeet!

It's the principle of the thing!

You're right, of course, that at lower speed, there is less momentum. Yet to echo JASP, there is still some momentum, and it can still be carried out of one turn and into the next, or not. There is still a moment of "neutral" (the inflection point, where one turn ends and the next turn begins) in all linked, offensive (gliding, not braking) turns, regardless of speed. And at that point, the paths of the feet (balance point) and the Center of Mass cross. (As an aside, it's important to note that even with a wide stance and pressure on both feet, there is still a single "balance point" where the "line of action" through the CM intersects the snow surface. This point may move about within the larger, stable platform of a novice skier in a two-footed stance, but its path will remain outside the path of the CM in any turn--until the skier loses balance and falls over.) At low speeds, those two paths never diverge very much, as the skier does not incline (lean) far into the turn for balance. Yet they still cross in the transition, and that crossing can still result either from continuation of the momentum at the end of the turn, or from active, muscular exertion to accelerate (redirect) the CM, or the skis, or both. Even for a beginner, the "perfect turn" begins with a release of the force from the snow--not from the exertion of muscular effort.

So no, in essence, I do not find it necessary to teach beginners anything fundamentally different from what I would teach intermediate or advanced skiers. Certainly, many characteristics of the movements will differ--range and intensity will vary with speed, steepness, turn size, and confidence, while accuracy, consistency, and balance will improve with skill level and experience. But the fundamental principles can be (and should be) the same for all offensive turns. It is critical for instructors to understand and recognize this difference between principles (fundamental, essential, underlying truths, irrespective of speed or skill level) and characteristics (superficial attributes varying primarily with speed and skill level). Beginners' turns and experts' turns can look very different, yet still embody the identical principles of great turns. Or they can look superficially the same (both "parallel," for example), while living on opposite ends of the spectrum of technique and intent.

Also certainly, the offensive mindset ("GO! Factor") that is the prerequisite intent of great turns at any level, can be quite fragile for beginners. Sometimes even the slightest speed, pitch, or distraction is all it takes for beginners to become defensive--wanting to slow down now! Defensive intent dictates defensive technique--for anyone. Only when intent turns defensive will the principles of technique become fundamentally different from the principles we're discussing here. But that change of intent is not uncommon--and we must not ignore it (Sometimes, you gotta' teach people to brake. Just don't call it "turning"!)

Again, a great key to discovering these movements through the transition is understanding, exploring, and experiencing the moment of "neutral"--and the movements and sensations that precede and follow it. Being the moment the two paths cross, and the moment you are not turning either direction, there is no inclination, no g-force, and released edges. It is the single moment in basic, offensive turns where the characteristics (not just the principles) of edge angle, rotary, and pressure control can look and feel the same, regardless of speed and turn size. And, at any speed or skill level, if you finish a turn in "neutral," you've had to make the correct movements to guide the direction and speed of your feet and CM to make your transition flow effortlessly into the new turn. This is true by definition--"neutral" is the moment the new turn starts; therefore, it describes a "position," or attitude, from which the least possible amount of movement is needed to start a turn. Therefore, if you've finished your previous turn in "neutral," you have literally already done everything you need to do to start the new turn, and every movement necessary is already in motion. Effort is superfluous (at best) at that point, and momentum will carry you into the new turn.

Yes! Beginners can get this (and they'll love it as much as anyone else when they do). Or...you could just teach them shortcuts to mediocrity, focusing on a few superficial characteristics of high-speed, high-level skiing (like "parallel," high edge angle, "pure-carved arcs," "early" weight transfer, and such), while sacrificing the principles of great skiing (like "independent leg action," "positive movements" [movements in the direction of the turn], edge release, offensive intent, shaping turns, and balance.) It has always been a precept of good teaching that what we teach beginners should transfer seamlessly through their subsequent development, never needing to be "untaught" or fundamentally changed.

I like to say that we do not teach "beginner skiing"--we introduce beginners to the skiing of experts! That takes integrity on the part of the instructor, as well as deep understanding of principles vs. characteristics. It takes watching World Cup racers, for example, and distilling what is fundamental, essential, "default technique" from what is individual "style," situational exception, and movements that result from (and are only appropriate at) the speeds they are going. It takes recognizing that much of what they do is either because they are going so fast, or actually error or compensations for error (they are, after all, pushing their considerable limits to the max, and even the best in the world have only made their best turn once!). Beginners certainly won't look at all like World Cup racers to the untrained eye, but they can work on the same fundamental principles.

Best regards,
Bob

Good Post Bob!
Conservation of momentum would state that mometum is conserved in all cases unless acted on by a nonconservative force. Example: Friction. But because we are talking about a surface like snow that has such a negligible coeffiicient of static and kinetic friction, momentum would be same at one point as it is in the next if moving in a straight line. Of course, turns will make conservation of momentum irrelevent, but nonconservative forces are the only forces that change momentum in conservative or even nonconservative conditions.
Actually the transition is where we are in the near flat zone, just like the beginners. Carrying momentum through this zone takes patience and discipline. While a beginner may not leave this near flat zone, IMO too many skiers never take the time to work on accurate movements in this zone. Without that accuracy their transitions suffer and IMO it's why they can't carry momentum from one turn to the next.
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