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The mystery transition - Page 3

post #61 of 79
Quote:
Originally Posted by Ghost View Post
If the skier is in perfect balance when the cm is released and nothing changed in the vector picture, Rick would be correct, but something does change.
What does change? Flexing down does not change anything related to the lateral balance picture.

Quote:
The cm is released, but the ski is still tipped. The ski continues going around its turn until something releases the ski.
Which is true regardless of whether the skier flexes down or not, but only if SOMETHING ELSE upsets the balance. What is that something else?
post #62 of 79
Thread Starter 
Ghost and Michael,,, think about this; it's very possible to flex both legs simultaneously, to the point of unweighting, and just end up a lower stance and in the same turn. It's also very possible extend to the point of actually leaving the snow, then landing on the same set of edges, and in the same turn. We simply follow the force line acting on our CM to make it happen when we extend, or allow the forces to do it to us when we flex. To release in an extension move, you have to manually extend out of the force line,,, more straight up in relation to the earth, and out of the direction you're inclinated. This is how we manage whether an extension will be simply an extension, or also a release. I have a drill I teach that requires executing both types within the context of a single turn.

That force line is the string you refer to holding the rock, Ghost. If the centrifugal component of the balance equation were to impose more influence on our CM upon release, it would also do so before release, and we wouldn't actually be in balance during the turn,,, the centrifugal component would drive us over our skis then too. But it doesn't, precisely because we ARE in balance. The combined turn forces of gravity and centrifugal are driving our CM toward our outside foot along that precise force line, and the snow is pushing back in the exact opposite direction.

Balancing on skis is just a matter of lining up the force line to where we want to balance, be it the inside foot, or the outside foot, or anywhere in between. Remove the legs and you remove the snows push back force, and the CM is free to move along the force line acting on it; that line being towards the balance point (normally the outside foot).

Think of it like this; have you ever been skiing along balanced on your outside ski and have that ski lose it's grip on the snow? Say on an icy slope? Did your CM go flying laterally across your skis, or did you find yourself suddenly falling on your inside ski? For most people it's a rhetorical question because they've been there done that enough times to clearly know. Of course, you fall on your inside ski, because your body suddenly starts to drop, and you catch yourself with your inside leg. It's just the body losing is centripetal push back, and following the force line to the balance point on the ground.

Too, look at the video of Bode when he lost his outside ski in the SG last week. Did he fly laterally over his skis when he lost his ski? No, he went to his inside ski, and landed on his inside hip, inside his feet. Again, following the force line.
post #63 of 79
Thread Starter 
Quote:
Originally Posted by borntoski683 View Post
This is a better way of saying it for science heads. Yes. Many non-science-heads would not have understood a statement about angles and relationships. Remember, this is a ski forum. If you need to validate ideas with science I think that's good, but at the end of the day the point is for everyone to learn about skiing better, not debate about how to properly discuss science.

This is my concern, BTS, thanks. The deeper we get into discussing the physics/science, the more heads will start to spin, and technique for doing a smooth/efficient/flowing one foot transition will get lost in the fog for the average reader who's just trying to find out how it's done.
post #64 of 79
Thanks for your efforts Rick. Here's how I see it now.

I will agree that the cm will accelerate in the direction of the forces acting on it, and since we are starting from static equilibrium in the skier's frame of reference, the cm moves up and down along that line joining the cm to the contact point of the ski/snow.

However moving the skier's cm up and down that line changes the radius of the turn the skier's cm is making in plan view. Changing the radius of the turn the skier is making changes the centrifugal acceleration and force. In order to remain in balance, the skier would need to adjust his inclination.

Pure extension or retraction means staying along that line joining cm to contact point without change to inclination (edit: and) would constitute a failure to adjust inclination to stay in balance.

Pure extension means that now centrifugal force is to high and skier goes over skis changing angle of skis on snow in cross-over move.

Retraction means centrifugal force is too low and skier falls in changing angle of skis to make skis carve a too tight turn which self-corrects in classic cross under move.
post #65 of 79
Hey Rick,

I been skimming some of the responses and think some have been swinging in the right direction.

Let me ask this; can skiers that don't close or open their ankle joints do clean turns or make a smooth transition while skiing on one foot?

RW
post #66 of 79
Quote:
Originally Posted by Rick View Post
So here's the question; how do we do it in one foot turns?
Like this.

http://www.youtube.com/watch?v=i9UtlSrwgGA
post #67 of 79
That video is not great to analyze because the turns are too small. I fact I would say the skier never really establishes a state of balance at apex but is always out of balance in such a way to transition the next turn. If the same skier attempted a medium radius turn this would become rather apparent
post #68 of 79
bts,

Good observation.
post #69 of 79
Quote:
Originally Posted by borntoski683 View Post
If the same skier attempted a medium radius turn this would become rather apparent
Rick, Got your camera handy?
post #70 of 79
Thread Starter 
Quote:
Originally Posted by Ron White View Post
Hey Rick,

I been skimming some of the responses and think some have been swinging in the right direction.

Let me ask this; can skiers that don't close or open their ankle joints do clean turns or make a smooth transition while skiing on one foot?

RW
Yes, Ron, there have been some insightful suggestions.

As to you're question, I would say that no ankle flexion articulation at all would make the task more difficult, for sure. Changing edge angle normally requires some ankle flexion involvement, of some degree, even if small. That said, I think there's a lot of latitude in how much you use, and the manner in which it's done. I have footage in which I'm doing one foot turns always fore (predominantly dorsi flexed),,, and always aft (predominantly plantar flexed),,, and moving from fore to aft through the transition (plantar flexing),,, and moving aft to fore also (dorsi flexing). All varieties are fairly smooth transitions, other than the obvious fore/aft adjustment.

What are your thoughts on your question? I think I know you well enough to know you have some good ones.
post #71 of 79
Thread Starter 
Quote:
Originally Posted by Uncle Louie View Post
Rick, Got your camera handy?

Yep, practice up.
post #72 of 79
Hey Rick,

Quote:
What are your thoughts on your question? I think I know you well enough to know you have some good ones.
I ski daily on all terrain available on one foot and at varying speeds including ripping to hone balance and accuracy of movements. Skiing slowly on steep terrain takes more accuracy than at moderate speeds.

If I look at the mechanics, first of skiing (turning) on the inside edge, I extend my leg as I flex my ankle into the inside edge of the tongue of the boot as I ad-duct my femur moving the ski through the arc to keep up with my CM.

Second skiing (turning) on the outside edge, I close my ankle toward the outside edge of the tongue of the boot as I abduct my femur, pushing the ski forward through the arc to keep with my CM. To transition to the inside edge, I first open my ankle joint, stopping the directional force to the ski and as I start to extend my leg, my CM comes in line over the foot, flattening the ski and then I resume the mechanics of turning on the inside edge.

To answer your original question, this transition is possible by a combination of our ability to open and close (in a direction) our ankle joints, extend and flex our legs and apply rotary torque to the ski (through leg rotation) while balancing on a ski. The same mechanics we use in two footed skiing, but used singularly instead of in harmony.

RW
post #73 of 79
Thread Starter 
Here's a video that shows one footed, center balanced, arc to arc, med radius carving. You'll find it at the 5:00 mark. I think I have some aft one footed arc to arc too, but the center balanced is the best to see the transition elements.

post #74 of 79

Nice

Quote:
Originally Posted by Rick View Post
Here's a video that shows one footed, center balanced, arc to arc, med radius carving. You'll find it at the 5:00 mark. I think I have some aft one footed arc to arc too, but the center balanced is the best to see the transition elements.
Rick,

In truth I don't agree with some of your explanations, but your fine demos and drills here would make any good skier proud.

Well done!
post #75 of 79
Quote:
Originally Posted by borntoski683 View Post
That video is not great to analyze because the turns are too small. I fact I would say the skier never really establishes a state of balance at apex but is always out of balance in such a way to transition the next turn. If the same skier attempted a medium radius turn this would become rather apparent
When Rick originally challenged us to define how we can make one footed turns he didn't define any of the criteria for the turns such as short or long radius, carved or skidded, position for the unweighted foot, parallel legs or A-framing, pole use or not, normal two footed stance or not. In the excellent discussions which have followed we all assumed a generic vision of what type of turn to do on one foot. Some may have even envisioned the one foot always on the outside of the turn, changing feet at the transition.

It is interesting that in a real life scenario on the snow, one footed skiing often results in a stance which is unique and different than our normal two footed stance.
As an example, I use one footed drills in upper level skiers to tune their balance and edge control skills. The goal is to ski on one foot in a stance which closely matches a two footed stance, such that at any point in the turn they could put the other foot down and continue without significant change in the turn dynamics.
I start with suggesting a carved traverse to a stop on the downhill leg leaving a clean non skidded track. Most skiers can do this after a few tries with a fairly normal two footed stance except for the slightly raised unweighted foot.
I then have them do the same carved traverse on the uphill leg. This is where the stance usually changes with edging accomplished by uphill inclination on an extended leg supplemented by counter balancing with the unweighted leg, the arms or even by tilting the head.
I then have them traverse on the down hill leg but add Garlands to the equation to create the one footed edge release and change. This is most often done in a metronome fashion with inclination instead of shortening of the inside leg, angulation and leveling. Taking this drill into a completed turn often results in some of the banked turns which Rick demoed so well in his video.
My question is then, what is it about skiing on one ski which can create a fairly common response in one's stance adjustments. Why is it difficult to learn to ski on one foot in a stance such that someone observing would be unaware that it is only one ski involved.
post #76 of 79
Quote:
Originally Posted by gcarlson View Post
When Rick originally challenged us to define how we can make one footed turns he didn't define any of the criteria for the turns such as short or long radius,
No he didn't, but he was trying to discuss specifically how transitions would work as it relates to ILE and OLR concepts. That uber-short radius example from Uncle Louie, though fun, is not great for analyzing this aspect. That's all I was trying to say. Rick did provide some other video of himself which is, IMHO, much better for analyzing transition movements.

You tube actually has quite a lot of video examples of people skiing on one foot. Look for examples where they are not using gross body movements like sticking their arms or legs way out to compensate, and where the turns are medium sized IMHO, if you want to analyze the turn phases and want to find skiers that establish a balanced state during the meat of the turn before then having to upset their balance in order to transition.

Quote:
Some may have even envisioned the one foot always on the outside of the turn, changing feet at the transition.
It was clear to me from Rick's original question that he meant a transition that happens completely on one foot. Some of the dynamics and balance issues will definitely be different if you are transitioning on your inside leg vs your outside leg and I think Rick meant either/or/both, but the key element is that the transition takes place without changing feet during the transition.

Quote:
My question is then, what is it about skiing on one ski which can create a fairly common response in one's stance adjustments. Why is it difficult to learn to ski on one foot in a stance such that someone observing would be unaware that it is only one ski involved.
Most people simply aren't that well balanced or practiced at balancing on one foot. The fact is that if you are doing a turn completely on the inside ski, it does not feel normal at all and will require fairly substantial adjustments to balance, that go outside the normal realm of muscle memory responses for skiers that haven't practiced it. If you do a turn completely on the outside ski, for a lot of skiers this will feel quite normal during the meat of the turn, though they may struggle a bit to initiate the turn and they may struggle a bit on how to transition out of the turn, without doing something that they don't normally do, which may feel to them like an exaggerated movement, even if it looks smooth and normal to an observer.
post #77 of 79
Thread Starter 
Thank you, Joseph.



Gary, great input. I think a discussion of variations and methodologies of teaching one footed skiing is a worthy offshoot topic for this thread. I like the progressions you shared, and have a couple comments.

Quote:
When Rick originally challenged us to define how we can make one footed turns he didn't define any of the criteria for the turns such as short or long radius, carved or skidded, position for the unweighted foot, parallel legs or A-framing, pole use or not, normal two footed stance or not. In the excellent discussions which have followed we all assumed a generic vision of what type of turn to do on one foot.

Yes, different approaches will have different execution requirements. The difference between steered and carved is, of course, significant. The balance skills required are higher with carved,,, the edge angles needed higher,,, and the transition triggers different.


Quote:
Some may have even envisioned the one foot always on the outside of the turn, changing feet at the transition.
Terminology does trip us up sometimes. When I refer to one foot skiing, I mean same foot one foot skiing. I have other terms for one foot with foot changes from turn to turn: outside ski turns,,, inside ski turns,,, inside lift turns,,, outside lift turns. Because language commonality is not the same through all the various microcosms of ski instruction, there exists many terms and ways of describing skills and tasks. As that's not about to change soon, the best we can do is explain more clearly, and ask more pointedly.



Quote:
My question is then, what is it about skiing on one ski which can create a fairly common response in one's stance adjustments. Why is it difficult to learn to ski on one foot in a stance such that someone observing would be unaware that it is only one ski involved.
I think the differences you see erupt will happen most during inside ski turns. Here's a major reason why. In normal 2 footed skiing the inside leg needs to flex as the skis are tipped onto edge, to allow the outside ski to remain in contact with the snow.

This flexing weakens the load bearing capacity of the inside leg. The more we tip, the more it gets flexed, and the weaker it gets. This is a good reason for maintaining dominant pressure/balance on the outside foot/ski during normal 2 feet on the snow skiing.

If we try to replicate that 2 footed stance during inside foot skiing, or one foot skiing, we are requiring weight to be assigned to a flexed and weakened appendage.

Many skiers, if not required otherwise, will naturally gravitate to extending and strengthening that inside leg they're directing all the turning forces to. It's just a lot stronger and more comfortable stance to ski in.

Keeping the inside leg flexed, in traditional 2 foot skiing fashion, will also limit a skiers desire and/or ability to attain higher edge angles during inside foot turns, because the higher the angle gets the weak the inside leg becomes.

I have some stepping stone drills to inside foot skiing that require a touch of the outside ski during the turn. Even as the coach I can feel extra strength required to keep the knee flexed enough to touch the outside ski to the snow, and it limits how far I'm willing to lay it over as I do the drill. There's an "ahhh, that's better" sentiment when the touch aspect of the drill is removed and the leg is allowed to extend.

The other difference in stance inside foot skiing will require is in that amount of angulation used. Simply because the balance point is moved inside requires the use of less angulation to achieve balance on that foot. This is especially true when the both skis are left attached to the feet. The lifted ski acts as a ballast that reduces the angulation need. If a ski is taken off during one foot skiing, much of that ballast is removed, and the need for angulation increases.

Personally, I don't favor removing a ski when doing or teaching one footed skiing, because it changes the force picture and movement possibilities so much it doesn't provide as close of representation of the balance and movement skills required in real life skiing situations. I may introduce ski removed exercises later, once ski on skills are refined, but the only value I can see in for that skill in real life skiing is preparation for those rare Bode ski loss moments.
post #78 of 79
Quote:
Originally Posted by Rick View Post

I think the differences you see erupt will happen most during inside ski turns. Here's a major reason why. In normal 2 footed skiing the inside leg needs to flex as the skis are tipped onto edge, to allow the outside ski to remain in contact with the snow.

This flexing weakens the load bearing capacity of the inside leg. The more we tip, the more it gets flexed, and the weaker it gets. This is a good reason for maintaining dominant pressure/balance on the outside foot/ski during normal 2 feet on the snow skiing.
Rick,
Thanks for your excellent insight, analysis and response. I agree and think that this example of anatomical advantages and disadvantages harks to our advice to our students to "stack your skeleton."
post #79 of 79

My interpretation

Quote:
Originally Posted by gcarlson View Post
Rick,
Thanks for your excellent insight, analysis and response. I agree and think that this example of anatomical advantages and disadvantages harks to our advice to our students to "stack your skeleton."
Stand tall?
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