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Cross Under

Thought I'd throw this up, to give people an idea of what cross under is.  It's a very fun transition, that provides a sensation very unique from Cross Over and Cross Through

In Cross over, the body takes a pendulum, rainbow path of travel across the skis.  This is a natural occurrence that will always take place if the legs are not flexed as the body moves across the skis.

Bear with me, I've had trouble before posing multiple images in a single post, so I'm going to do this presentation in multiple posts

In cross through the body takes a straight line path of travel across the skis.  This is accomplished by flexing both legs as the body moves over the feet and into the new turn.

But Cross Under is different.  In Cross Under the feet cross underneath the body to facilitate the transition into the new turn.

So how does it work?  Imagine you're making a turn.  Your Center of Mass is aligned with the ground reactionary force, so you're in balance, which allows those forces to push your body through the turn.

But if you situate your Center of Mass such that is not in line with the forces, but rather is above that force line, then only your skis and feet will be propelled through the turn.  Your body will be left behind, and your skis will cut beneath it and cross to the opposite side of your CM.

The sensation comparison is just like that.  In Cross Over and Cross through you get a very clear feeling of your body cross over the top of your skis, from one side of them to the other.  In Cross Under you get a distinct sensation of your feet and skis cutting aggressively and dynamically beneath you, from one side of your body to the other.

http://www.yourskicoach.com/glossary/SkiGlossary/Cross_Over_Under_Through.html

Is this correct?

Cross over - vaulting over, no flexing through transition

Cross through - moving your upper body laterally from one side to the other, flexing through transition

Cross under - letting your legs cross back and forth under your body, flexing through transition

T

Quote:
Originally Posted by tdk6

Is this correct?

Cross over - vaulting over, no flexing through transition

Cross through - moving your upper body laterally from one side to the other, flexing through transition

Cross under - letting your legs cross back and forth under your body, flexing through transition

T

Yep, spot on.

so cross under is what you get when you develop big angles: your CM cannot be inline due to the angulation required.

p.s. i think you have the CM too low in the photos above - the body's mass cannot equal the leg's mass so the CM cannot be in the middle - i take it it's just for making a point... i like that point though: at big angles if you don't flex to release at the right time, you will get inclination into the new turn, as the hip is pushed over....?

cross under = short swing.

cross over = everything else

Quote:
Originally Posted by razie

so cross under is what you get when you develop big angles: your CM cannot be inline due to the angulation required.

p.s. i think you have the CM too low in the photos above - the body's mass cannot equal the leg's mass so the CM cannot be in the middle - i take it it's just for making a point... i like that point though: at big angles if you don't flex to release at the right time, you will get inclination into the new turn, as the hip is pushed over....?

This is the key point you've zeroed in on, Razie.  The angles don't have to be huge, you just have to use more angulation than creating lateral balance requires.  That's what I'm doing in the cross under picture, by means of the knee angulation I'm using.  Knee angulations in more intense than hip angulation.  It moves the CM back towards the feet more.  If I'd hip angulated there, my CM would have dropped down onto the force line, and the skis/feet would not have bee free to cut under my body.

Anytime you see skiers doing this dynamic looking cross under turns, such as the ones JF Beaulieu loves to make, watch for the quick injection of knee angulation at the end of the turn.  That's all there is to it, looks flamboyant, but the mechanics of it are pretty simple.

As far as the location of my CM in the picture, yep, you're right.  My wife added the graphics, I think she was trying to keep me modest.

Quote:
Originally Posted by borntoski683

cross under = short swing.

cross over = everything else

Sure, you can go that route.  Many do.  I find it useful to add cross through.

you are conflating two different things.

Quote:
Originally Posted by borntoski683

you are conflating two different things.

Not sure how you figure that, BTS.  Seems just the opposite. You're conflating two of my categories into one.

its very common for people to conflate things related to the "cross under" idea which is not a very good idea in any case.  the two things being conflated are:

1 - the act of changing the relationship of the CoM to the BoS, from one set of edges to the other set of edges.

2 - the act of of the CoM taking a shorter line then the skis and the skis crossing from right side to left side from turn to turn, how much does the CoM move from side to side with the skis, etc.

Those are two different things.  when you talk about "crossover" you are basically talking about #1.  #2 also happens in crossover in some shade.  if you think, about it in terms of idea #1, the only thing that makes sense to be cross under compared to cross over, is a windshield wiper style short swing where the skis are moved laterally under the CoM from one set of edges to the other set of edges.  Otherwise, the CoM moves across (crossover), and it is irrelevant whether it moves across on an arch or straight through for the sake of comparing to crossing the skis under.  That is the only apples to apples comparison.  And by the way, short swing turns are most effectively done with up extension and unweighting, not retraction.  But retraction or not, is irrelevant to making an apples to apples comparison on point #1 above.

Most people conflate 1 and 2 above, however.  Referring to #2 for seeing crossunder and #1 for seeing crossover.  Your cross over and cross through concepts have more to do with comparing two different ways of doing #1.  But then you try to bring #2 in as the retraction alternative and calling that cross under, but retraction does not neccessarily mean cross under, another common misconception.  If you were referring to 3 different types of cross over I would agree wtih you, but you are conflating cross under and cross over and two different dimenional ideas, one about moving from one set of edges to the other, and the other about the Skis crossing the path of the CoM; which are two different things.

Edited by borntoski683 - 12/30/14 at 10:43pm

Yes, BTS, my drawings showed what you point out here, that both cross over and cross through are characterized by the body moving across the skis, as opposed to in cross under the skis crossing under the body.

But I deem the differences in the nature of how the body comes to cross the skis in Cross Over and Cross Through are significant enough to recognize them separately.   So I do.  The movements, sensations and performance differences between the two are night and day different.  In fact, they're different enough to spark big debates in the land of ski instruction over proper vs improper.  If we lump them all together it makes it so much harder to argue about.

hence they are conflated.

Quote:
Originally Posted by borntoski683

hence they are conflated.

Nope, I dis-conflated them.

i don't see it that way.  past my bedtime...

Quote:

Quote:
Originally Posted by Rick

Thought I'd throw this up, to give people an idea of what cross under is.  It's a very fun transition, that provides a sensation very unique from Cross Over and Cross Through

In Cross over, the body takes a pendulum, rainbow path of travel across the skis.  This is a natural occurrence that will always take place if the legs are not flexed as the body moves across the skis.

Bear with me, I've had trouble before posing multiple images in a single post, so I'm going to do this presentation in multiple posts

Quote:
Originally Posted by Rick

In cross through the body takes a straight line path of travel across the skis.  This is accomplished by flexing both legs as the body moves over the feet and into the new turn.

The third drawing in your series should be

The skis are crossing under you as you cross over them in all cases.

The thrid drawing you posted introduces a new concept: the degree to which the skis seem to be crossing your path, as opposed to the degree which you feel like you're crossing the skis path.  This is subjective and varies along a continuum.  Taking a frame of reference fixed to the hill, you can define cross under as being closer to one end of the spectrum, but it is a spectrum (with a turn at the extreme cross-under end the skis are not affecting your momentum as your weight is completely released).

exactly ghost!

Another way to compare extremes without conflation would be to examine this point you made:

Quote:
The thrid drawing you posted introduces a new concept: the degree to which the skis seem to be crossing your path, as opposed to the degree which you feel like you're crossing the skis path.  This is subjective and varies along a continuum.  Taking a frame of reference fixed to the hill, you can define cross under as being closer to one end of the spectrum, but it is a spectrum (with a turn at the extreme cross-under end the skis are not affecting your momentum as your weight is completely released).

So you could say the CoM moves laterally across a laterally stationary BoS, or you could say the BoS moves underneath a laterally stable CoM, or you could say they move kind of move in the opposite direction and cross each other in some fashion..  Upwards and downwards motions are irrelevant to that discussion.  And I totally agree with you also about there potentially being a spectrum of shades there, not 3 granular modes.  And also a lot of this is in fact very subjective, or hard to interpret, depends so much on the frame of reference.  I don't like to use the term cross-under at all.  In my world I'm always trying to keep my CoM moving down the hill and its nearly always crossing over.  The degree to which my skis zip back across to the other side depends on a lot of factors and if they do that a lot faster then my CoM is moving down the hill, then it will feel kind of like a cross under, but if I do that move without a pivot, then actually it was in fact a crossover.

Meh--we stopped using these terms 7 or 8  years ago...for this reason. Muddies the waters IMO.

zenny

Quote:
Originally Posted by zentune

Meh--we stopped using these terms 7 or 8  years ago...for this reason. Muddies the waters IMO.

zenny

I actually use these terms to bring clarity, and it works quite well in the context in which I use them.  The waters mud up again when the townfolk refuse to declare me king and abide by my every decree.

Edited by Rick - 12/31/14 at 9:37am

To what BTS and Ghost have said.  Yes, the feet are not stationary in cross over as the body crosses over them.  They too participate in the crossing process a bit.  Just as the body is not completely stationary as the fee/skis pass under it in Cross Under.  It's more a case of which is taking the leading role in making the process of body/feet changing sides occur.    When you try each of them the distinctly  different sensations you experience makes it very clear which (body or feet) is leading the charge in each.

It's important to recognize and understand Cross Under, because no transition type is faster.  When you need to get the new turn going yesterday, Cross Under is the transition to use.  And BTS is right, it's generally a pivot transition.  Without the pivot it can easily leave you floundering in the back seat as the ski rocket out from under you and off into the future.

I often use cross under with no pivot.  I seldom find myself floundering.  Maybe that's because I skipped all the lessons where folks learned to pivot.

What I see often on the hill are folks using cross-over with an unweighted pivot.

Quote:
Originally Posted by Ghost

What I see often on the hill are folks using cross-over with an unweighted pivot.

Yep, that's another variation, Ghost.  A more unrefined means of pivoting often called up unweighting, and powered by a flex/extend move in the old outside (downhill) leg.  Generally done by skiers who have yet to develop their skills to a point where they've gained access to other options.

Rick has a point to all this.

The thing is that Cross Under is quite a simple consept to grasp. Your upper body trawels straight down the hill while your skis are crossing back and forth underneath very quickly. Your upper body remains facing straight down the fall line and your feet are flexing through transition and extending out into the turns. Cross Over is also kind of easy to grasp. Insted of keeping your upper body stable and crossing back and forth with your skis underneath your skis become the rigid point of reference and you move your upper body across the path of the skis by extending your old inside leg and vaulting over.

However, these two blend all the time and this is where the Cross Through consept steps in. You can still flex to release and let your CoM get pushed to eather side without vaulting over. Most turns in a SL course are probably CT turns.

On the other hand. Why not call CU and CT simply CU and CO (same thing), and then call CO vaulting or ILE transitions? Wonder if I got it close to as how I was thinking it .

T

Quote:
Originally Posted by Rick

It's important to recognize and understand Cross Under, because no transition type is faster.  When you need to get the new turn going yesterday, Cross Under is the transition to use.  And BTS is right, it's generally a pivot transition.  Without the pivot it can easily leave you floundering in the back seat as the ski rocket out from under you and off into the future.

i would have thought that pivoting puts you back instead... that's in fact how you pivot the easiest right? push them heels/tails out, right? it is what almost everyone is doing and all those are back as well.... I don't see many lifting their tails out of the snow

If you refuse to pivot, like @Ghost insists he does and like I strive to, that in fact would likely mean you are more forward. We prefer to use magic to turn the skis at the top of the turn and rather not look like all the pivoteurs out there... and, while the radius is debatable, from the tracks left behind our skis you can see that the edges like to stay engaged... for the most part.

cheers

Edited by razie - 1/1/15 at 11:54am
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