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Crossunder vs. Crossover

post #1 of 15
Thread Starter 
So as I understand it:

ie when making a left turn - right ski (outside ski) is pressured.

Crossover: Gradually extend the left (inside ski) thus propelling your hips and center of mass diagonally over the skis to the right to begin the next turn and change of edges.

Crossunder: Gradually retract (lighten) the right (outside ski) thus pulling the legs under the center of mass effectively moving the hips and COM over the skis to the right to begin the next turn and change edges.

a. Is this correct?

b. when, which, why?

It seems to me that it produces less up and down motion and helps to train the body to absorb terrain and makes for a smoother turn.
post #2 of 15
you are way over my head! but keep going, I may understand someday.
:-)
post #3 of 15
Thread Starter 
If I'm over your head, then look out below cause if I fall I'm going to land on you!
post #4 of 15
I am eagerly awaiting the experts to chime in here. I have heard it described various ways. Some folks relate it to body mechanics. Some folks look at it as whether you feel as if you are going straight while the skis scoot underneath you versus you crossing over the skis. Some relate it to your body elevation when going through transition. What you describe is close enough to what I've heard that you are probably doing cross over when you think you are and cross under when you think you are.

Personally I think you should practice both types of transitions and mix them up. It is especially fun to start a "cross over" early and suddenly switch to a cross under. Playing with the timing gets interesting results from ski rebound, you can really load up your skis and get them to shoot across into the other turn. You can even get air on a flat slope.
post #5 of 15
I'll bite.

I know that as Ghost said, many people have different definitions of these terms, but the important part (I guess) is to undertand roughly what they mean, and how/when to execute them on the snow.


Cross Over: I tend to think of a cross over as a transition where your CM rises through the transition because you extend your old inside and engage the new turn with the new outside ski. Cross overs are used commonly in GS or speed events for setting up a turn in a steep section or pitch change of the hill/course. It allows the skis to be engaged very easily - but sacrifices moving your CM down the hill ahead of the skis.

Cross Under: A cross under in simple terms is a transition where your old outside leg flexes as you pass through the transition and it also usually involves a redirect of the skis - or if you prefer - forcing the skis onto their new edges. This is usually used on flats, areas of sustained pitch, or where you just need a very fast (forced) edge change.

Cross Through: This is a transition that comes up here every so often and does not involve a rise or collapse of the CM and really allows the skis to carve arc-to-arc through the transition with your CM continuing on it's natural path down the hill. This is probably the most useful and most efficient transition out of the three, as it really does not force the skis or the CM into a behaviour.

I also tend to look at these transitions as difficult to define - but I know them when I see them or perform them.

I guess that is about it... others can probably give a better explanation and more information.

Later

GREG
post #6 of 15
It's kind of like the question, which comes first, the chicken or the egg.

Crossover occurs in virtually every turn because we finish one turn (your left, for example) with the center of mass toward the inside of that turn and must move the COM across the skis toward the inside of the next. There are several mechanisms we can use to make that move. One of them, usually in shorter, more intense turns, produces the sensation of the skis crossing under the skier, and this crossover then is referred to--by some--as a crossunder.

Traditional crossover in a less intense, rounder turn results from the early weight transfer approach to turn initiation characterized by an extension of the old inside ski leg of the last turn as it becomes the new outside leg of the next. The extension pushes the COM across the skis into the new turn. The result may be a "pop up" or a more diagonal move forward and across the skis.

The alternative to the pushing extension is a relaxation/flexing of the old outside ski/new inside ski leg accompanied by a general lengthening of the old inside ski/new outside ski leg. The activity of the new outside leg lengthening is aimed more at maintaining ski/snow contact than at thrusting the COM into the turn. In this approach, the weighting of the new outside leg is more a result of the turn dynamics than the skier's dynamics.

Typically in either of these practices, the COM is taking a path that will be inside that of the skis, but that follows an arc that's somewhat smaller than the arc the skis travel.

In the more intense turns characterized as "crossunders", the COM generally is travelling basically straight down the fall line with little side-to-side deviation and both legs are extending and flexing more in unison and more in a side-to-side manner and at a quicker pace.
post #7 of 15
smj,

I think you basically got it, KB's descritpion is least confusing.

crossunder
Quote:
turns characterized as "crossunders", the COM generally is travelling basically straight down the fall line with little side-to-side deviation and both legs are extending and flexing more in unison and more in a side-to-side manner and at a quicker pace.
Crossover

Quote:
Crossover occurs in virtually every turn because we finish one turn (your left, for example) with the center of mass toward the inside of that turn and must move the COM across the skis toward the inside of the next.

Quote:
smj when making a left turn - right ski (outside ski) is pressured.
Outside ski is load bearing, but you must balance between the skis. Don't add weight or pressure. As you balance between the skis, your load on the outside ski may vary. Very different than pushing, or adding pressure or pressuring the outside ski. Think more of softing the load on the inside ski.

RW
post #8 of 15
Jan 22, 2007

Dear All:

Thanks to SMJ for starting this thread and thanks to all the respondents for their responses. I had asked about crossunder of Bob Barnes for an upcoming podcast. Now armed with this information, in addition to what I now know of the cross under, I will be able to get even more out of his responses.

CharlieP
post #9 of 15
I like Kneale's description as an easy way to understand the concepts. But I believe that crossunder is not limited to straight down the fall line. I think of crossunder turns as when the feet are doing the movement relative to the upper body to get the COM to the inside and crossover turns as where the hips are doing the movement to get the COM to the inside. In other words, when the feet are doing the most deviation from the direction of travel, that's a crossunder turn and when the hips are doing more deviation from the direction of travel than the feet, then that's a cross over turn. What muscles you fire to get the COM to the inside is a tactical choice.

In the last few PSIA clinics that I've taken, the examiners have been passing the message that crossunder needs to be emphasized more as a critical element in high performance skiing (e.g. steeps and moguls).
post #10 of 15
Good to have some definitions that most agree with

Isn't it "modern technique" to aim for the cross under approach? This means that at the transition between two turns our legs are flexed, thus allowing us to reach maximum extension of the legs at the fall line.

I'm pretty sure we're trying to avoid the "pop" that results from cross over technique, where you extend the inside leg in transition - this is old school technique.

comments?
post #11 of 15
Simpler:

Crossover: The movement of the CM over the skis is responsible for the change in orientation between feet and CM. In short, the CM is moving downhill faster than the skis are moving under the body.

Crossunder: the movement of the feet under the Cm is responsible for the change in orietation between feet and CM. In short, the skis are moving faster across the hill than the CM is moving downhill.

Cross through: the speed of movement of the CM downhill is equal to the speed of movement of the skis across hill. Each component contributes equally to the change in orientation of the feet and CM

Relating the movements to a fixed frame of reference solves the problem/confusion presented by relating the movements to the relationship of feet and CM.

What do you think, yay or nay?
post #12 of 15
I'm hoping to do a PSIA ski camp at Sundance in about 11 days' time - I'll be interested to see a) if it comes up and b) how.

Had a great all-day clinic with one of the top instructors at PCMR the other day which made me reconsider quite a few of the concepts in my skiing and how to adapt it. This question (crossover being regarded as old school, and crossunder the current thinking - without actually using those terms) was part of it.

I don't think I've had a day on snow this season when I haven't learned something. I'm loving it (my knee abstained on the vote, though).
post #13 of 15
I think Kneale has hit on the conceptual point that in ALL turns there is a cross over of the CM across the skis/feet.
But when broken down, I agree with BigE, in that it is important to fix a point of reference. I have always used the CM vs feet as my reference point.

In describing this idea ( I view it as one, not two), I relate it to which is being more active- the CM or the legs/feet.

If the CM is moving in a very stable, consistent manner, then it is more likely that the legs/feet are moving more actively, and is therefore performing what most view as a crossunder.

If the legs/feet are moving more consistently than the CM (eg- a long radius turn), then it is usually viewed as a cross over.

Which is used, and when? Now this is the most interesting part of the question!

It has to do with energy management! If you have it- manage it! If you don't have it- create it!

'Having it' justifies stabilizing the CM (core) and allowing the legs/feet to support the direction you wish the CM (core) to go.
'Creating it' means using the CM (core) as a means to generate energy by moving it in a way which can create momentum, which then needs to be managed.

The skis we are using these days generate so much energy, that the idea of managing that energy is becoming more prevalent. But there are still occasions when we need to create a little more...

Use them both, as needed!
post #14 of 15

Within the race community...

...I think there's a feeling, in some camps, that crossunder leads to tipping in while crossover tends not too. In the old days, we used to say you can create edge angles (which is what you're doing with co or cu) by moving the feet out, inclining the body in...or a combination of both. So it's basically whatever you gotta do to create (new) edge angles, and get the cm and momentum in a place where you can then load the new outside ski...
post #15 of 15
Quote:
Originally Posted by vail snopro View Post
Which is used, and when? Now this is the most interesting part of the question!

It has to do with energy management! If you have it- manage it! If you don't have it- create it!

'Having it' justifies stabilizing the CM (core) and allowing the legs/feet to support the direction you wish the CM (core) to go.
'Creating it' means using the CM (core) as a means to generate energy by moving it in a way which can create momentum, which then needs to be managed.
Sept 22, 2007, er March 22, 2007, er Jan 22, 2007

Dear Vail SnoPro:

Hi! Please elaborate.

CharlieP
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