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Independent Leg Steering

post #1 of 18
Thread Starter 
Independent Leg Steering (ILS) has been mentioned a number of times in one of the currently active technical threads. So here's an opportunity to talk about this technique.

What is ILS? Do you use it? When is it useful to you, and on what terrain? What does it accomplish? Where did the term originate?
post #2 of 18
Hey Bob, got a minute? She's playing your song .

.ma
post #3 of 18
Quote:
Originally Posted by LiquidFeet View Post
Independent Leg Steering (ILS) has been mentioned a number of times in one of the currently active technical threads. So here's an opportunity to talk about this technique.

What is ILS? Do you use it? When is it useful to you, and on what terrain? What does it accomplish? Where did the term originate?
There is abit of a debate raging elsewheres on long wordy answers vs. short ones and target audiences....so as an experiment I try my best to give you the short and sweet.


ILS = Independent Leg Steering.

ILS is really just the outcome of proper pivoting. It is not a technique in itself. But rather just one component of a full technique. Most systems around the world use it. It is used in all turns except arc to arc (pure carving).

What it accomplishes is really two fold. First, it helps create a steering angle, which assists with tightening our turns.

Second the way it is done...ie 2 legs pivoting "independently" in their respective hip sockets is really a key point. The term "independent" does not refer to different rates of rotation, as is commonly beleived. Rather the independent refers to the independent axis of rotation that each leg is on.

Having these 2 inpendent "axis of rotations" working under our upper bodies act to stabilise the upper the body. This is good thing...and hence why ILS is the prefered method of developing steering angle when arc to arc is not possible.

Sorry...so much for short.
post #4 of 18
Take two sheets of paper and place them on the floor. Stand on the papers one foot on each distance between feet about what is normal when you walk.

Now using your feet and legs point both feet to the right, point both feet to the left. Point your toes toward each other point your toes away from each other. Shift your balance toward your heels and notice how the pivot point of the twisting of the feet moves to the heel along with your balance. Move your balance to the ball of the foot and see how the pivot point of the twisting feet moves forward. Turn the feet slowly back and forth turn the feet quickly back and forth. Turn the feet in the same direction but at different rates so that the feet end up pointing away from each other or toward each other.

You have just experienced independent leg steering. Now when you get some snow try all the above with skis on and moving forward over the snow surface. Please report back.

fom
post #5 of 18
HuskyMatureMan,,, nice response. Very simple explanation that covers many leg steering options. And I like that you didn't include rotation in the hip sockets as a manditory element,,, as it is NOT.
post #6 of 18
Quote:
Originally Posted by Rick View Post
HuskyMatureMan,,, nice response. Very simple explanation that covers many leg steering options. And I like that you didn't include rotation in the hip sockets as a manditory element,,, as it is NOT.
How do you have independent leg steering without rotation of the femurs in the hip socket?
post #7 of 18
Quote:
Originally Posted by Skidude72 View Post
There is abit of a debate raging elsewheres on long wordy answers vs. short ones and target audiences....so as an experiment I try my best to give you the short and sweet.


ILS = Independent Leg Steering.

ILS is really just the outcome of proper pivoting. It is not a technique in itself. But rather just one component of a full technique. Most systems around the world use it. It is used in all turns except arc to arc (pure carving).

What it accomplishes is really two fold. First, it helps create a steering angle, which assists with tightening our turns.

Second the way it is done...ie 2 legs pivoting "independently" in their respective hip sockets is really a key point. The term "independent" does not refer to different rates of rotation, as is commonly beleived. Rather the independent refers to the independent axis of rotation that each leg is on.

Having these 2 inpendent "axis of rotations" working under our upper bodies act to stabilise the upper the body. This is good thing...and hence why ILS is the prefered method of developing steering angle when arc to arc is not possible.

Sorry...so much for short.
This is almost exactly as I suspected. ILS is an outcome of proper pivotting. What I dont really get is why we need the word "incependent" since parallel skiing aims at keeping the skis parallel and not let them pivot "independently" in different directions like fatoldman suggested. I believe what you said here above targets that exact issue but Im a bit lost in translations and mechanics.

Anyway, excellent definitions. If we can stick to these definitions for ILS I think we can get somewhere. Why Rick said there is no femour rotation involved "necessarily" could be explained by the fact that during the steering phase if upper and lower body remains static there is no pivot or femour rotation present. The pivot and the femour rotation takes place earlier. Just prior to steering. The pivot and the femour rotation is fore gone by some kind of unweighting (for example) which is fore gone by extention and relese.
post #8 of 18
Quote:
Originally Posted by tdk6 View Post
This is almost exactly as I suspected. ILS is an outcome of proper pivotting. What I dont really get is why we need the word "incependent" since parallel skiing aims at keeping the skis parallel and not let them pivot "independently" in different directions like fatoldman suggested. I believe what you said here above targets that exact issue but Im a bit lost in translations and mechanics..
Well ILS is not only for parallel turns, you use ILS in wedge turns, or stems too...so some of FOM's examples relate to that.

But again the "independent" part has nothing to do with rates of rotation or direction....it is all about the 2 axis. It is the 2 axis which stabilise the upper body. And it is this resulting upper body stability that makes ILS the preferred method of turning the skis in non arc to arc situations.

Quote:
Originally Posted by tdk6 View Post
Anyway, excellent definitions. If we can stick to these definitions for ILS I think we can get somewhere. Why Rick said there is no femour rotation involved "necessarily" could be explained by the fact that during the steering phase if upper and lower body remains static there is no pivot or femour rotation present. The pivot and the femour rotation takes place earlier. Just prior to steering. The pivot and the femour rotation is fore gone by some kind of unweighting (for example) which is fore gone by extention and relese.
Well I am not sure I follow you. But to me the only thing Rick could have been referring to is a throw back to Warren Witheral days of the Atheltic Skier where he talked about "steering an edged ski" by apply a rotorary force to the skis. The action was static of course...no actual movmenent occoured...but the effort would apply tip pressure, just like moving forward on the ski...and this could tighten the arc. This action in my book would be ILS.....however this concept has really gone out of vogue in the skiing community since the introduction of shape skis and I dont really understand how this relates to the examples FOM put forward, where movement is infact happening.
post #9 of 18
I too am interested in how independent leg steering can happen with no movement of the femurs. This discussion is not about foot steering, steering of the skis by pressure manipulation, or waist and upper body torque, but Leg Steering happening independently in both legs simultaneously. I'm guessing it will boil down to how we define ILS.
post #10 of 18
Excellent explanation Dude!

TDK6 if you draw too parallel skis on a piece of paper as you would see them looking down from above, stick a single pin in the middle of the two skis, and rotate the paper about the pin you get rotation of the two skis about a single axis. If you cut each ski out of the paper, stick a pin into each ski and rotate each ski about it's own pin you have ILS.

Of course you are free to apply a translational movement, moving the outside ski forward and in to make the resulting motion indistinguishable form non-independent steering, but you don't have to. The key is that the steering of each ski is a degree of freedom removed from the rotational state of the upper body (and if you desire it from the other ski).
post #11 of 18
Does ILS imply the work of the steering is done by forces applied directly to the ski by the boot as opposed to forces acting at the snow/ski interface controlled by simply rolling the skis onto their edges and biasing fore aft pressure to vary the amount of skid at each end of the ski?

Also, could we please get on with tactics. Where do we need ILS?
post #12 of 18
RicB,
Considering each ski is attached to it's own leg, the only way to get them both to turn (via leg powered steering) is to turn each "independently" with the attached leg.

If both legs/skis turn the same amount, and the skis remain parallel through the entire turn, then hip socket rotation on the femur head that would leave the pelvis and skis pointing in different directions is not needed. In a parallel turn, the legs can work independently to turn their respective ski, without having to do the whole thing independently of the pelvis. In a wedge, if the wedge stays the same size, then also, no femur/hip joint rotation is needed.

The theory is that the two legs working in opposition to support the action of each. The old bar stools explanation. Well, yep, the process of that is very effective. But it doesn't HAVE TO involve femur/hip rotation. It still works if the pelvis goes along for the ride, and changes direction with the legs/feet/skis. As long as it does that, then little hip/femur joint rotation is going on. Yes, some has to happen, as the joint is not frozen, but not to the extent of creating any significant pelvic/feet directional orientation divergence. You CAN cause that divergence to happen, but you DON'T HAVE TO.

And one more thing to throw into this, which actually could be a thread of it's own. It's common belief that you can't steer on one foot. That both feet/skis need to be in contact with the snow for leg steering to be possible. Well,,, I'm here to tell you it's just not true. I can't yet explain the exact science behind why its not true (I have only a theory), I just know that in real life execution it's not. I have video of a turn in which the inside foot is held entirely off the snow, and ultra smooth leg steering is demonstrated from turn entry to turn completion,,, with no pushed or pivoted initiation,,, with no upper body rotary assistance,,, with no femur/hip socket rotation. Perhaps someone here would want to take a shot at how, against popular belief, it's possible.

RicB, you're probably right about the definitions factor. If one considers the "independent" referring to the each leg steering it's assigned ski, then femur/hip rotation is not needed to make it happen. If they reference "independent" to what the legs are doing, independent of what the pelvis is doing, and believe what pelvis and legs are doing (in regards to directional orientation) have to differ for ILS to exist, then that rotation is obviously necessary.

tdk6, keep in mind when trying to comprehend what is being said here: it's my understanding that those folks up in Canada define pivoting a bit differently then many others do. They consider steering to be a form of pivoting. It doesn't have to be that non-pressured redirection thing we see WC racers do at the start of a turn.
post #13 of 18
Just as I thought. It is really about definitions. In my mind if the legs and skis turn the same amount and the pelvis orientation to the feet and skis stays the same them we may have steering of the skis through other forms of leverage, but we don't have independent leg steering. The only way the term independent leg steering makes sense to me is to include femur rotation. Other wise it becomes meaningless as it encompasses so much.

On the both feet needing to be on the snow to steer I agree with you. We can leverage our pelvis and trunk to stabilize this movements and add in mirrored movement on the leg and foot as well.
post #14 of 18
Quote:
Originally Posted by Ghost View Post
Excellent explanation Dude!

TDK6 if you draw too parallel skis on a piece of paper as you would see them looking down from above, stick a single pin in the middle of the two skis, and rotate the paper about the pin you get rotation of the two skis about a single axis. If you cut each ski out of the paper, stick a pin into each ski and rotate each ski about it's own pin you have ILS.

Of course you are free to apply a translational movement, moving the outside ski forward and in to make the resulting motion indistinguishable form non-independent steering, but you don't have to. The key is that the steering of each ski is a degree of freedom removed from the rotational state of the upper body (and if you desire it from the other ski).
Ok, I think I get it but i did not know there were any other kind of proper steering than what is by you guys being called ILS. We allways end up with a little inside ski tip lead and upper body counter if we teach classic parallel skiing.

I have a very good example of where ILS is failing. When you teach beginners to wedge, sometimes they let one ski ride along the edge while the other skidds massively and sometimes as much as 90deg to their headding. This can be a never ending nightmare. The cure is to ski a slope that is more flat so that ILS can be mastered without the need to be defensive (wow, first time I used that word ).
post #15 of 18
Do I use ils? Yes. When do I use it? All the time in all sorts of terrain. Ils is one of the bedrocks of my skiing.

At lower levels/speeds it is a great tool for guiding a skidding ski to point it where you want to go. Also it gives you great control over the amount/rate of skid and where along the length of the ski the pivot point of the skid is.

Ils gives me a variety of transitions from a brushed patient transition to a instant edge change arc to arc transition.

Ils gives me the ability to tip my feet from one side to the other independent of each other and independent of the upper body. This allows me to create the independent edge angles required for railroad track type turns. It also allows me to keep the feet/skis engaged in the last turn while releasing the upper body to move into the new turn.

Ils lets me adjust where along the length of the ski pressure is applied without having to change the centered relationship of my upperbody to my feet.

I could go on but I think what I have said will garner enough comment,

fom
post #16 of 18
tdk6,

Your example of a railed skier is not an example of ils failing. It is an example of: (1) A skier moved onto a too steep slope too soon so that their defensive move away from downhill combined with their trying to force a turn with their upperbodies pulls the outside ski up onto a edge angle that makes it impossible to control. (2) A skier who is very one footed and stand so strongly on their dominate foot that it rotates the hips away from the nondominate foot and keeps the hips far to the inside of the nondominate foot again resulting in the railed outside ski.

Intrestingly, both the above problems can be solved with proper application of ils.

fom
post #17 of 18
Quote:
Originally Posted by fatoldman View Post
tdk6,

Your example of a railed skier is not an example of ils failing. It is an example of: (1) A skier moved onto a too steep slope too soon so that their defensive move away from downhill combined with their trying to force a turn with their upperbodies pulls the outside ski up onto a edge angle that makes it impossible to control. (2) A skier who is very one footed and stand so strongly on their dominate foot that it rotates the hips away from the nondominate foot and keeps the hips far to the inside of the nondominate foot again resulting in the railed outside ski.

Intrestingly, both the above problems can be solved with proper application of ils.

fom
Ok, I see what you mean. ILS is really the skill of proper steering.
post #18 of 18
Quote:
Originally Posted by Rick View Post
If both legs/skis turn the same amount, and the skis remain parallel through the entire turn, then hip socket rotation on the femur head that would leave the pelvis and skis pointing in different directions is not needed. In a parallel turn, the legs can work independently to turn their respective ski, without having to do the whole thing independently of the pelvis.
This is a really good point... I totally agree. I also am wondering about what RicB said..if we aren't actually turning the femur in the hip socket, then by what mechanism are we "steering" the skis? Probably not the mechanism a lot of people seem to think if they are trying to execute something like ILS or similar derivative. I reckon that a femur spinning form of ILE may only be the case if and when a skier is simultaneously developing counter. But if they aren't, then by what mechanism are they steering?
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