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The Rotary "Thing" (again)

post #1 of 107
Thread Starter 
While this has been discussed many times before I continue to find myslelf at a loss on why some people here on Epic (almost exclusively instructors I believe) keep on focusing on "rotary movements." I have no argument that hip rotation is a part of supination which is what you do to tip the new inside ski of a turn. But, SO WHAT!

To focus on this and generalize the concept of hip rotation into "rotary movements" seems to me to have very little value. In the same way that focusing on knee flexion (especially generalized to "flexion movements") or torso rotation (conceivably generalized to rotary movements just like hip rotation) would be of little value.

While there is certainly value in understanding the anatomical movements that are part of a kinetic chain, I believe there is great confusion and misinterpretation brought into play when these anatomical movements are regularly brought up in discussions of integrated ski movements and the old argument that "rotary" is an important part of skiing are made. To take it further into actual instructional situations (although I certainly don't know that the intructors who keep on defending rotary even use that term in their teaching) I would say that there is very little value and generally some harm done when individual, anatomical joint movements "description" are employed.

I do believe that there is an important issue to be understood and discussed and that is when, where, and to what degree skiers should focus on tipping vs. rotation (pivoting) of the ski. I do think this continues to be an area of valid debate (I have voiced my opinion on this subject many times before so I will spare my fellow Bears here). However, to mix in specific joint (anatomical) movements into this discussion is not helpful. As an addendum I would also comment that a confounding issue along with this is the use of the term steering. Again, many people here argue that "steering" is a critical part of high level skiing. The trouble is that for some "steering" may relate to pure tipping (via supination) of the inside ski (described by some as a "rotary" movement much to my chagrin) and for others an actual pivoting or combined tipping and pivoting action of the ski. Bottom line is that when someone says that rotary or steering are an important part of skiing I have great confusion and little idea of what they really mean.

End Rant.
post #2 of 107
[Q]

To focus on this and generalize the concept of hip rotation into "rotary movements" seems to me to have very little value. In the same way that focusing on knee flexion (especially generalized to "flexion movements") or torso rotation (conceivably generalized to rotary movements just like hip rotation) would be of little value.

While there is certainly value in understanding the anatomical movements that are part of a kinetic chain, I believe there is great confusion and misinterpretation brought into play when these anatomical movements are regularly brought up in discussions of integrated ski movements and the old argument that "rotary" is an important part of skiing are made. To take it further into actual instructional situations (although I certainly don't know that the intructors who keep on defending rotary even use that term in their teaching) I would say that there is very little value and generally some harm done when individual, anatomical joint movements "description" are employed.
-------------------------------
I agree with you professor. I am a practitioner and words "rotation, rotary .." etc. do nt hepl skiers trying to learn carving. Most people equate rotary movemnts with pivoting and in many cases it is. If and when the ski is engaged in the arc there is no rotari movement needed.
Greg
post #3 of 107
Quote:
Originally posted by Si:
I have no argument that hip rotation is a part of supination which is what you do to tip the new inside ski of a turn. But, SO WHAT!

Bottom line is that when someone says that rotary or steering are an important part of skiing I have great confusion and little idea of what they really mean.

End Rant.[/QB]
I don't recall anyone mentioning hip rotation in conjunction with supination.

In a car or on skis you can go straight or......you can turn. The mechanisms we use to turn our skis are the steering mechanisms. Rotary movements are one type.

[ July 09, 2003, 12:33 PM: Message edited by: Rusty Guy ]
post #4 of 107
Not every turn needs active steering. But if you want to go beyond just using the ski as a tool to using the whole ski/body system, it's a necessary skill.
post #5 of 107
Thread Starter 
Rusty,

I believe I could find numerous references from previous threads in regards to hip rotation if I looked. But even in a recent post you said:

"What I tried to suggest on previous occasions is that inversion
results in a foot being "toed in", thus, biomechanically one must dial in lateral rotation of the foot in order to tip a ski on edge. This is solely (poor foot pun) the rotary movement to which I refer."

Given that there is extrememly limited rotation of the ankle and knee, where do you think lateral rotation of the foot you refer to comes from?

Secondly I guess I'm surprised about your perplexion about my confusion in regards to steering [img]smile.gif[/img] . First if steering is synonomous with turning the skis (and the skier) than why not just use turning? On the other hand, I think steering is used to refer to some very different things:

Pure tipping of the ski leading to bending of the ski leading to turning.

Tipping combined with pivoting of the ski.

Pure pivoting of the ski.

That's Confusing. It's very difficult to understand which one of these someone is referring to when they talk about steering even though it is usually critical to the point they're trying to make.
post #6 of 107
Quote:
Originally posted by ski coach:
I agree with you professor. I am a practitioner and words "rotation, rotary .." etc. do nt hepl skiers trying to learn carving. Most people equate rotary movemnts with pivoting and in many cases it is. If and when the ski is engaged in the arc there is no rotari movement needed.
Greg[/QB]
I for one am not suggesting use of terminology with students. It is July and we are involved in a different endeavor at a website.

Exploring rotary movements with a student might involve ramping up offensive movements such as turning the tip of the inside ski in the direction of a turn as opposed to ratcheting down negative movements such as pushing out the tails of the skis in a defensive manner.

"Carving" is merely one type of turn. It is wrong, IMHO, to castigate skidding or scarving.
post #7 of 107
Quote:
Originally posted by Si:

Given that there is extrememly limited rotation of the ankle and knee, where do you think lateral rotation of the foot you refer to comes from?

Secondly I guess I'm surprised about your perplexion about my confusion in regards to steering [img]smile.gif[/img] . First if steering is synonomous with turning the skis (and the skier) than why not just use turning? On the other hand, I think steering is used to refer to some very different things:

Pure tipping of the ski leading to bending of the ski leading to turning.

Tipping combined with pivoting of the ski.

Pure pivoting of the ski.

That's Confusing. It's very difficult to understand which one of these someone is referring to when they talk about steering even though it is usually critical to the point they're trying to make.[/QB]
The lateral rotation is the femur in the hip socket or possibly some abduction of the femur or of course a blend. The hips can remain stationary and not rotate.

Concerning terminology you are right on the button. PSIA-RM has adopted tipping,turning,flexion and extension in their "Three Steps to Success" as opposed to PSIA national using edging, rotary, and pressure.

I think turning is a much better term and was confused by the gist of your comment
post #8 of 107
hairsplitters, calm down!



Si, I believe the oversensitivity to "rotary" in technique is the fear that if one emphasizes only rotary, carving becomes somewhat happenstance, because the emphasis is on the rotational component and not the feeling of edge engagement, longitudinal pressure control, or angle variation (through various body movements and combinations thereof)

Only a fool would suggest that rotary movements should be banished.

Only a fool would suggest that rotary movements are the pinnacle of technically advanced skiing.
post #9 of 107
gonzo, Where have you been and a hearty amen.
post #10 of 107
howdy Rusty,

I've been busy wondering how my Lv I exam will go when my secret lover nolo has to recuse herself because of personal involvement with the candidate! heh heh heh...

actually, I've been busy working on many things mtn bike-related, mostly riding and trail building... also my new business that I'll be starting in September, building custom steel mtn bike frames. no more lawyering!

the Lv I comment clearly is a joke, as I have no plans to teach skiing. I would seek such certification in mtn bike instruction if it were available.
post #11 of 107
Thread Starter 
Gonzo,

My sensitivity to rotary comes from the belief that references to integrated ski movements and anatomical joint movements need to be clearly distinquished. From an instruction point of view (whether in discussion or especially on the slope), I believe that reference to anatomical joint movement has little value and can actually cause harm in the sense of confusion (in the case of discussion) or an ineffective focus (for a student on the slopes). As per my original post I am at a loss to be sure I understand what you mean by "rotary."

Rusty,

Hip rotation refers to rotation of the hip joint, that is of the femur within the acetabulum. Lateral rotation is hip rotation - in exactly the same fashion we talk about hip abduction, adduction, and flexion. When you say the hips shouldn't rotate I think you are refering to pelvic rotation.

[ July 09, 2003, 01:40 PM: Message edited by: Si ]
post #12 of 107
Gonz:

...and here I thought nobody noticed my little attempt at humor... [img]graemlins/evilgrin.gif[/img]

Tom / PM

[ July 09, 2003, 01:52 PM: Message edited by: PhysicsMan ]
post #13 of 107
Quote:
Originally posted by Si:
Gonzo, My sensitivity to rotary comes from the belief that references to integrated ski movements and anatomical joint movements need to be clearly distinquished. From an instruction point of view (whether in discussion or especially on the slope), I believe that reference to anatomical joint movement has little value and can actually cause harm in the sense of confusion (in the case of discussion) or an ineffective focus (for a student on the slopes). As per my original post I am at a loss to be sure I understand what you mean by "rotary."
Aaaahhhh. Okay. Now I get your concern.

I agree that anatomic references can be dangerous in ski instruction. I think of several reasons for this: (1) the instructor errs on anatomic information; (2) the student doesn't know anatomy; (3) the student doesn't care about the precise anatomic workings; (4) the student might care about anatomic issues but be unable to reconcile gross conscious movements and the anatomic details of such movements.

I'm a geek on leg biomechanics, as I'm a victim of many knee and ankle injuries. I would love to talk anatomy in the course of receiving coaching from Yoda. He'll do so if/when I ask. But I also know how the excess information cna create mental blocks that get in the way of using known, learned coordinated movements... too self-conscious on anatomic precision, not enough use of feel and learned movement.

When I use the term "rotary" I am referring to a conscious rotary movement at the foot, regardless of where one senses the origin of the foot movement (hip, knee, ankle, torso... doesn't matter). Such movements in themselves are not the apex of technical refinement. They are, as Mark Elling called them, tools for the advanced all-terrain skier's toolbox.
post #14 of 107
gonzo,

Stay strictly on topic or the thread nazis will get you. Any reference to mountainbiking needs to be at the miscellaneous thread under a seperate post. It is after all July and somewhere in some hemisphere this means something to someone.

I will however go on record as saying I am the worlds worst mountainbiker. Worse than 97% on the mountainbikers in the world.
post #15 of 107
Hmmmmm. Just because I don't say the words "rotary" or "rotaion" doesn't mean I don't teach it, and it certainly doesn't mean I don't believe in the concept. (nor is rotary the only COMPONENT of skiing that I focus on.) I triple-dog-dare any of you to stand, right now, with your feet in a ski boot flat on the floor... Now tip that boot up onto its "edge" without using any rotary movements, or falling into the china closet. 10 bucks sez you can't do it. With students I can say any combination of things like "knees to the trees" or "roll your knees up hill" or "roll your ankles in the direction you want to go"... just to name 3 of 1000 ways to get someone to put their skis on edge. I'm not saying "rotate", but that's really what I'm after.

Someone made a good point about the difference between hip and pelvic rotation. Hope you all saw it.

Spag :

[ July 09, 2003, 03:52 PM: Message edited by: Notorious Spag ]
post #16 of 107
Quote:
Originally posted by Rusty Guy:

Stay strictly on topic or the thread nazis will get you. Any reference to mountainbiking needs to be at the miscellaneous thread under a seperate post. It is after all July and somewhere in some hemisphere this means something to someone.
Now, now, if you're not carefull we're all going to think you're a malcontent and a troublemaker.

Gonzo, BTW I made the mistake of showing my boys (ages 8 & 11) the picture in your profile. I thought they'd get a kick out of it. About an hour later they were over in the woods with the neighbors kids nailing boards together between low forks in the trees and getting ready to ride. I guess I better start hunting the insurance cards. [img]smile.gif[/img]

[ July 09, 2003, 03:55 PM: Message edited by: sportscoach13 ]
post #17 of 107
Quote:
Originally posted by Rusty Guy:
Stay strictly on topic or the thread nazis will get you.
.
.Ya, you have zat right.
.
.Ve vill watch you carefully.
.
.You vill get away with nothing.




[ April 15, 2004, 09:37 AM: Message edited by: PhysicsMan ]
post #18 of 107
coach,

remind your sons that Mother Nature gets angry when you use live trees for such stuff!

it's easier if they practice by riding on paint stripes on abandoned/unused parking lots. the focus is the key. if they get elevated too quickly, you're going to see a lot of sprains and potential broken bones! from paint stripes, they can move to elevated curbing (usually about 6" high) and then to other things.

on the other hand you could tell them that the picture was created with PhotoShop!
post #19 of 107
Thread Starter 
Quote:
Originally posted by Notorious Spag:
Hmmmmm. Just because I don't say the words "rotary" or "rotaion" doesn't mean I don't teach it, and it certainly doesn't mean I don't believe in the concept. (nor is rotary the only COMPONENT of skiing that I focus on.) I triple-dog-dare any of you to stand, right now, with your feet in a ski boot flat on the floor... Now tip that boot up onto its "edge" without using any rotary movements, or falling into the china closet. 10 bucks sez you can't do it. With students I can say any combination of things like "knees to the trees" or "roll your knees up hill" or "roll your ankles in the direction you want to go"... just to name 3 of 1000 ways to get someone to put their skis on edge. I'm not saying "rotate", but that's really what I'm after.
Spag :
Spag,

What would you be after for them to rotate? If I said those things I'd be trying to get someone to tip the ski, certainly not rotate. I wouldn't be concerned about what joint they needed to flex, rotate, or abduct (often goes right with the rotation for the hip), I'd leave that for the skier to "implicitly" accomplish. I'd just give them a goal of tipping the ski in a way similar to what I might demonstrate.

What would you tell someone if you were trying to get them to pivot the skis vs. tipping the skis?
post #20 of 107
Si. I maintain that the act of tipping contains a definite amount of rotary. The knee joint does not act as a hinge joint side-to-side... only front-to-back. You cannot tip the skis on their edges without rotating the femurs, unless you just lean the whole body one way or the other. In which case you will just fall. Like or not, tipping, rotating and flexing/extending are not independent of one another. In order to get any desired result from a student, be they a racer or recreational skier, rotary Must be included in the scheme right along with edging and flex/extending.

"Of course that's just my opinion... I could be wrong."
- Dennis Miller -

Spag :

PS. Oh yeah. If I wanted to focus wholly on rotary I would likely pick an exercise like "making bow-ties in the snow with our ski boots" For beginners, I'd have them do this one-footed, feet together (to demonstrate that when the feet are too close together we have a hard time turning the legs from the hip socket. They will tend to try to "fling their upper body), Feet hip-width apart ( to isolate the legs and turn them independent of the torso). And for more advanced I'd have the student maybe take the skis off and sit on the ground. I then would grab the person's boot and tell them to straighten the leg out and try to turn it... not much torque there. THEN to bend the leg at the knee/hip and turn it... Lots more force available for those situations where we get locked into a park'n'ride and need to bail out to miss the tree/kid/mogul/old lady/etc.

There's tons of 'em like Whirly birds, Pivot slips with uppper/lower body separation, Pivot slips with upper body following ski tips (Mannequin turns). An instructor/coach could realistically attack any problem using any of three different skills (rotary, edge, Pressure control) if they were creative enough. But to discount rotary as an important skill is a cop-out. Too much reliance on the equipment to do what you hope it will do every time as opposed to USING the equipment.

[ July 09, 2003, 08:46 PM: Message edited by: Notorious Spag ]
post #21 of 107
Thread Starter 
I don't mean to be antagonistic but you use of "rotary" is exactly what I find so confusing. Of course there is hip rotation with supination, but, like I said before, so what? Then you go on to talk about rotary as a basic skiing skill?

I can't for the life of me see the importance of focusing on hip rotation as an aspect of a skiing movement. It happens automatically (along with him flexion and abduction) when tipping the new inside ski. Hip rotation can be a part of tipping or pivoting a ski but I still don't see where it deserves all this attention. It is only one aspect of a kinetic chain - why not treat all the joint movement involved equally (or better yet just ignore them - my vote).

I will grant you that before I had my hip replaced and I had severely limited hip rotation it helped to understand the role of this joint movement as apart of the skiing movements I wanted to make. Other than understaning pathological situations like this I remain at a loss why you want to focus so much on this particular joint movement.
post #22 of 107
Gonzo SAYS he is not taking his Level I because he doesn't want to teach, but I KNOW it's because he doesn't want me to have to entertain an ethical dilemma. Isn't he the sweetest thang? [img]graemlins/angel.gif[/img]
post #23 of 107
Si,

I'm going to talk out of both sides of my mouth. In the context of the discussion recently at epicski I don't think anyone has attached any special importance to rotary movement.

Having said that, nolo and others have alluded to the fact that there is a groundswell of opinion suggesting the desire to carve has led to an emphasis on movements other than rotary or the term you, and I, and PSIA-RM prefer.....turning. In short we have been trying so hard to put the ski on edge that we don't turn them as well.

I know in my case, ten years ago I made a much better short radius turn, on longer skis. Granted, if we had video of me a decade ago, what I now say was a short radius turn was probably a short swing or wedel with considerable tail displacement. In addition....time has marched on

In the winter issue of TPS Deb Armstrong wrote an article entitled "Turning to Tipping and Back Again....a Process of Rediscovery".

In my personal skiing I worked hard to create a pure carve. In the process I lost dynamic movement, athleticism and the ability to turn my feet.
post #24 of 107
nolo and gonz,

In all honesty you two made my day. I'll lay my head down with a broad smile. You are both a hoot!

[ July 10, 2003, 06:16 AM: Message edited by: Rusty Guy ]
post #25 of 107
This rotary stuff can get confusing because it can be utilized for distinctly different purposes: as a turning force in steered or pivoted turns, as a means to enhance angulation in carved or steered turns, and as a mechanism to create pronation in the outside foot and thus direct pressure to the engaged edge. And to complicate things even more, when used for multiple purposes, such as hip angulation in steered turns and combined knee and hip angulation in carved turns, the rotary applications can act to cancel each other out. No wonder people have trouble understanding it all.

Lets see if I can provide some clarity, but first I'll define the terminology I'll use.
=========
STEERED TURN: A turn in which turn shape is created by twisting the pressured foot/feet. A ski must be pressured to be steered. By definition steering can't occur on a non pressured ski because no direction change will occur from the action. All those who use the term "inside foot steering" are doing so in error if that ski is not substantially pressured as it is twisted. Only in a white pass lean can inside foot steering be legitimately used. I have heard an alternate term, "inside foot guiding " for the twisting of a non pressured inside ski. I like that better.

CARVED TURN: A turn in which turn shape is created solely by the sidecut and bending of the ski. No steering occurs.

SCARVED TURN: Aint no such animal, carving and steering are different species, they can't be mated. Either a turn is steered or it is carved, there is no in-between. Scarving is a term used by some to describe a way to tighten turn radius with minimal tail/tip displacement from the arc path, but the bottom line is displacement does occur in some degree and steering (foot twisting) is the mechanism that creates it and dictates turn shape.
==========

Steering requires rotary movements that act to twist the feet and turn the skis. It requires a rotation of the femurs within the pelvic socket toward the desired direction of travel which acts to twist the feet toward the target. Greg (ski coach) is right when he says in carved turns this type of rotary movement does not exist.

Anytime rotation of ball of the femur within the pelvic joint occurs a countered or rotated (depending on the direction of rotation) relationship between the pelvis and the legs/feet results. In a steered turn that relationship is one of counter, but it is not obvious to the observer because the pelvis remains rather constant in its relation to the world around it and the counter that occurs does so as a result of the twisting of the femurs/feet/skis under it towards the inside.

In carved turns it's a different story. Here rotary movements are made to facilitate balancing or edge application movements, not to directly create turn shape. Any counter or rotated relationships between femur and pelvis occur as the pelvis is rotated about a more stable femur/foot/ski. As such the movement has no influence on turn shape.

In high level carved turns the rotary movements are all about balance. As I've spoke of before, every moment in every turn will have forces of momentum and gravity that produce a resultant R force vector. To achieve efficient balance the skier must move his CM until that R vector emerging from his CM is directed at his outside ski's inside edge. He does that CM manipulation by angulating.

The hip and knee offer little lateral range of motion. Our greatest range of motion in these joint is through fore/aft flexion, so to provide the most angulation benefit from that flexion we must use rotary movements to re-orientate the joint so that flexion has a lateral effect on the location of our CM. For the knee joint rotation (turning pelvis toward the inside of the turn) is required to accomplish that goal, and for the hip counter is required. The more the R vector is out of alignment with the edge angle, the more CM relocation required, the more angulation required, the more rotary required.

In the days of straight skis, momentum forces in carved turns were much smaller than those produced by todays small radius skis so R vector angles were much less inclined at similar edge angles and required less CM movement to the inside of the turn to achieve balance. It often required knee angulation to move CM from the edge angle to the R angle. This put the body in a very weak structural position but the forces were small enough that the stress put on the knee could ussally be tolerated and the forces resisted. Now with forces much higher R angles are much more inclined and knee angulation is seldom needed and we can ski in much stronger sketetally aligned body positions. The necessity for the rotation associated with knee angulation is now a thing of the past for all but the slowest carved turns.

Tomorrow: rotary as a means of pronation creation.

[ July 09, 2003, 10:33 PM: Message edited by: FastMan ]
post #26 of 107
IMHO, many of the differences of opinion about "what is rotary" that have been expressed in this thread boil down to differences in focus about what exactly is being rotated (and relative to what), or around what axis the rotation is occurring. Another difference is whether something actually is being rotated versus a torque is being applied to try to make a particular thing rotate.

Examples:

1) Some people would define "rotary" as rotation of one specific anatomical part relative to another vs. rotation of the ski (around an axis normal to its base and passing through the center of the ski) relative to the body;

2) Some people would define "rotary" as rotation of ANY part of the anatomy in the chain relative to some other part of the anatomy;

3) Rotation of the ski around the previously defined axis vs. rotation of it around a longitudinal axis (ie, what most people would call tipping);

4) Rotation of the ski relative to the body vs. rotation of the ski relative to a fixed coordinate system in the ground;

5) An attempt to rotate a weighted inside ski about the axis of Example #1 vs. the actual rotation one could achieve with an unweighted ski;

5) etc.

Thus, wouldn't much of the discussion in this thread be unnecessary if people would be careful to spell out exactly what type of "rotary" they were talking about, or, even better, have different shorthand names for each movement and these would be part of generally accepted skiing or biomechanics terminology?

In other words, doesn't much of this discussion really come down to just another case of poor definitions, much like in the "inclination & angulation" thread, where everyone is trying to persuade everyone else that their favorite definition of "rotary" is best, when actually separate terms for all the similar but significantly different concepts are needed to hold an intelligent technical discussion?

IMHO, until this is done, people will waste much time continuing to go round and round in similar, never-ending discussion.

Making matters even worse, but once again, exactly like in the angulation-inclination threads, many of the needed terms are highly inter-related, (eg, rotation angle #1 relative to coordinate system #1 is equal to the sum of angles #2 and #3 in a coordinate system #4).

Tom / PM
post #27 of 107
PSIA definition, p. 14, Alpine Tech Manual:

Rotary (or rotational) movements involve turning some part of the body relative to other parts of the body.

Also (p. 15):

Remember that the term "rotary movements" has many different uses in skiing. Rotary movements can be efficient in some ski situations and inefficient in others. Rotary movements can be overused, resulting in stemming, skidding, and over-turning; or they can be underused, resulting in unfinished turns. An appropriate blend of rotary movements with edging and pressure control movements is a highly developed skill that takes time and practice."
post #28 of 107
Thread Starter 
I have no difficulty with Fastman's definition and his differentiation between a rotary joint movement to balance and one to actively twist a ski. But it doesn't solve the problem. Tom/PM hit the nail on the head. This is an analagous issue to the angulation/inclincation definition problem. Nolo's quotes from the PSIA manual perhaps pinpoint some of the roots for this definition problem. It creates such a broad/generic class for the term rotary that I view it as worthless. It then demonstrates its own uselesssness and adds confusion when it talks about blending rotary and edging/pressure movements (therebye contrasting them) even though, by its own defintion edging requires rotary movements. I say discard or ignore it.

To me, there seems to be a very simple bottom line. In order to turn a ski you can combine both tipping and twisting (pivoting) movements. I interpret the Deb Armstrong article (I don't normally receive or read TPS but I happen to have that issue only because I had my one and only ski article published in it) as referring to her rediscovery of actively twisting the ski in addition to actively tipping it. (Although I had to fight through her use of rotary to figure out what she was trying to say and even now I have doubt remaining that I understood all that she was trying to convey). I actually posted a thread on this as, at my level, I can't say that I have seen much need or sense for adding twisting of the ski into the formula for a better "carved" turn. Of course off the groomed there are countless situations where I employ a lot of active twisting.

If we look to the anatomical movements involved in either tipping or twisting of the ski there are rotary joint movements involved in both. Again I say, so what? The most useful situation for such "movement analysis" is in critiquing the effectiveness (or lack thereof) of someone's skiing movements. However, such MA, which describes the "what is happening" for skiing movements is pretty far removed from the "how to" that most people want and need to focus on.
post #29 of 107
Here is a reprint;

Good question, TTF. The short answer is that pivoting that ski you're standing on will involve the upper body in one of three ways. Because of this, it will lack precision. The long answer follows:

Remember that there are five, and only five, basic mechanical ways we can turn our skis.

1. You can get the skis to turn themselves--either by carving (bending into an arc that slices a curve of its own shape), or by being knocked around ("deflected") some other way--hitting a chunk of snow, etc. Since this is something ELSE turning your ski, it doesn't really answer your question about how YOU can turn it.

2. You can turn them with "Rotation." This classic technique involves turning one part of your body first--typically your shoulders, hips, or arms--and then "yanking" the skis around when you slow or stop the rotation of the first part. It's a "one-two" move, and can involve both skis turning at once, or one at a time.

3. You can turn them with "Counter-Rotation." This is doing "The Twist"--rotating the upper and lower body/skis simultaneously in opposite directions. Newton's Third Law of "equal and opposite reactions" is clearly illustrated!

4. You can turn them with a "Blocking Pole Plant." If you reach your arm out to the side and something pushes back on it, it will turn you the same way a wrench turns a nut. Angling the pole forward and planting it firmly causes a brief rotary impulse that can initiate a turn. Reaching a pole out to the side and dragging firmly can also provide some torque to turn the skis, and, while not terribly precise, can actually allow subtle steering of one or both skis.

5. You can turn your legs independently, each using the support/resistance of the other to turn against. I've described it before as how you would move if you stood on two separate barstools, one with each foot, and turned them with your LEGS ONLY. You can, of course, also turn them with counter-rotation, but true "Independent Leg Steering" involves ONLY the legs. It's important to understand the difference. The femurs rotate in the hip sockets, and the pelvis does not move. Nothing above the pelvis is involved in any way whatsoever, when done correctly.

This last mechanism is the way we steer modern skis in modern turns. It is the only one that we can sustain throughout the turn for accurate, continuous guiding. It is precise and powerful, and with it we can pivot either or both skis quickly, slowly, one at a time, or both at the same time.

But we can NOT do it with one foot lifted! As soon as you lift one foot off its barstool, the only way you can turn the other one is with your upper body, through one of the other mechanisms. (Or you could ask someone else to turn it for you, which would be equivalent to the first mechanism.) And we can't do it with a very narrow or closed stance either. With both feet on one barstool, you will once again need the involvement of your upper body to turn it.

Terry Dunne, a Level 1 certified instructor I worked with last season, came up with a great way to remember the basic principles of the Rotary Skill:

The Four R's of Rotary:

Rotation
Counter-Rotation
Wrenching
Right!

You could also add the fifth "R"--"Riding"--to include carving or otherwise deflecting the ski, but again, this is not YOU turning the ski. And, of course, there are many variations and sub-categories of the basic four, and they can combine in a myriad of subtle ways.

But you cannot "steer" that one ski if you lift the other. All you can do is throw it around with your upper body, or try to accomplish a pure carved turn.

I hope this helps!

Best regards,
Bob Barnes
post #30 of 107
Si's response to the material Nolo quoted is almost exactly what I would have written myself. Not only is their attempt at a definition overly broad in some ways, it is obviously incomplete in other important ways.

Specifically, it omits the usage of "rotational movements" to describe angular changes of the skis themselves (relative to anything) or angular changes of the whole body (or parts of it) relative to the ground. IMHO, their definition is about as good as one might get from a dictionary for general usage, and not at the level one would expect from a serious technical manual.

In fact, Rusty's quote of BobB's material (where is he, by the way?) serves to make the shortcoming of their definition even more obvious because Bob is clearly talking about angular movements of the skis and body about a vertical axis and relative to the ground, a situation not covered by the PSIA definition. For brevity, Bob himself does not explicitly state this assumption (which underlies his post), but because of his excellent writing style, it is quite clear what he means. This is not the case when many other people write or speak about this topic, and confusion results.

I notice that Bob also mentions two more widely used meanings for terms in the rotation/rotary family, namely, his items #2 and #3. In keeping with the approach of his post, these are "how-to" usages that unfortunately are only indirectly related to the well-defined geometric usages of these terms (ie, a simple description of the angle of something relative to something else, intentionally defined with no mention of how to accomplish such angular changes.

If I had my druthers, the term, "rotary", would always be used in the exactly same sense that Bob uses it in his second quoted paragraph, ie, "what the skis are doing", specifically, angular changes (about a vert axis) of the skis relative to the ground. Then, "rotary input" would be anything you do to accomplish this, much like Bob's post.

If someone wants to get into the topic more deeply and talk about the specific biomechanics involved, it would obviously be a technical oriented person and they would probably have the motivation to deal with a large number of wordy but precise phrases like, "rotation of the femur in the hip", "rotation of the upper torso relative to the skis", etc.

Personally, I think that usage of "rotary" in the sense of the PSIA definition (and repeated by individuals here) is putting the cart before the horse and isn't focusing on the end, important result - getting the skis and the person to change their angle (around a vert axis) relative to the ground. Note, that in keeping with BobB's preferences, I did not use the word "turn" in the previous sentence.

Tom / PM
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