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Turn Initiation

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MikeS

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I think the "feet up" mantra is a valid one, but like has been mentioned, can't be taken too much in isolation. Some people might interpret a "feet up" approach as a "feet only" approach, which is certainly not the best way to get yourself down the hill. The OP presents a situation where he says he would rather move his CoM (hip bones) down the fall line to initiate a turn. So let me counter with this question. How does one move their CoM down the fall line without first manipulating the ski/snow interface through their feet and legs? The ski/snow interface is our only leverage to enact any change, unless you're going so fast that you can use the airflow, or you're so angulated that you can reach down and push your CoM over with your hand.

So yes, I can have my focus be the CoM. And that's definitely a good place to focus, since it determines a lot of other things. But to make my CoM do something, I first have to do something with my feet and my legs, even if that's not my mental focus. Right?
 

Zentune

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^^^^^Well in a sense yes, because imo (and many others!) of the way our bodies evolved in regards to everyday gait---to include running, jumping, walking, skipping, dancing, etc, to move based upon its interaction with ground reaction forces.

So as an example, during "normal" walking, assuming good alignment, when we touch down to take the next step we strike lightly with the lateral aspect of our heel, the foot rolls medially and the big toe ball and little toe ball make contact simultaneously, the arch collapses, the foot lengthens, the toes spread. Meanwhile during this foot pronation, the leg rotates internally at the ankle and hip, and the shank (lower leg) moves forward, dorsiflexing the ankle. Above that the pelvis then has to begin counter rotate against the internal rotation of the tibia/talus (because your free foot/leg are moving forward to prepare for the following step) and the mass shifts medially and forward as well. It is then that we begin to move toward the supination phase--the arch re-forms as the center of pressure moves over the big toe ball and the foot becomes a rigid lever against which we push off and take our next step, and the leg then begins to externally rotate....

So, when skiing, what the foot does/is told to do/can't do definitely has an up-stream impact, biomechanically, so in that regard if you foot action is off or our out of sync, the rest of the body will then have to make compensatory moves that will have an impact.

It should be said though that theses kinetic chain movements are essentially simultaneous, as opposed to sequential, eg once your foot receives load the rib cage is responsing at the same time. So in that sense it is NOT foot first. Foot first to me means that it is the structure that receives or un-receives the load.

zenny
 
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razie

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So, here’s my question, why not initiate the new turn by moving my COM (top of hip bones) down fall line instead of my feet, or boots or knees or whatever is lower on the kinetic chain?
You could certainly let your hips drag your heels down the hill, but putting the cart before the horse is not always the best way to go down the hill...

The hips do not really stop and go... and neither do the feet. And, they are connected, to boot - so they can't get ahead of each-other much. I figure that the only way to go about it hip-first is to purposefully delay the feet or... push your hips down the hill.

Since the hips flow down the hill anyways, the focus should be on timing the feet properly and stacking it all properly. And, much like in everyday life, we don't start building from the 45th floor down, but from the foundation up... so I will submit that feet-first is important, even if only for a proper kinetic chain activation.
 
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François Pugh

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Multi tasking: Two separate paths: one for the skis, one for you. Control your skis and boots mostly via tipping angle and pressure control so as they take your chosen path down the hill as directed by all the forces acting on them (ski-snow forces and body-boot forces). Control your upper body so it hovers, sometimes ahead, sometimes behind, along it's own separate but related path down the hill via gravity and the forces acting between it and your skis/boots. You body needs to be where you can still control your skis; you need to keep your skis where they can control and be controlled by your body.
 

Don Duran

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We are making all this way more complex than necessary. The entire body participates in our balancing efforts. In a contemporaneous way I would add. A focus on edging shifts focus to the feet but without actions in everything superior to the feet our stance can only change so much. Knee, hip, spine, and arm moves are necessary. So taken too literally the feet first mantra infers a sequential quality of movements up through the body. Meaning the body would be late to the party all the time. Much like walking where the torso is leaning and falling forward as the legs swing forward and back.
 

Zentune

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It would be impossible while in motion in a closed chain situation for the foot/ankle to articulate in ANY fashion without simultaneous movements ("correct" or "incorrect") all over the body upstream , so you are right it is not sequential....nonetheless, the foot/ankle complex is what "perceives" the surface---"the joints act, the muscles react"---a quote by Gary Ward, author of What the Foot.

Basically the point of my previous post :)

zenny
 
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john petersen

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sometimes I ski just like PSIAMAN....

love that vid!


and, I am really lol....

JP
 

Don Duran

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The OP presented a chicken or egg question. My first response was to point out the erroneous nature of that thinking. Thinking we encouraged with catch phrases like feet first. So it's our fault that so many skiers adopt sequential movement patterns that to be blunt screw up their skiing.
 

JESinstr

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sometimes I ski just like PSIAMAN....

love that vid!


and, I am really lol....

JP
And the operative word is.......SOMETIMES!

There are multiple options (techniques, kinetic chain combinations) for entering and exiting circular (centripetal) travel. Some driven by environment (terrain, speed, conditions etc), some driven by desire/fear and most driven by both. As centripetal travel becomes more and more established, the options for continuing it become fewer and fewer.

The "conceptually simple" and "black and white" bottom line to all of this is the understanding that our COM/mass is either traveling in a straight line or in a circle. The revert-to default travel is straight line. Centripetal travel needs to be produced.

Complexity and ability issues reside mostly in the transitions.

Here is a video for your consideration. I prefer that you watch and not listen. Although I do see the point that he is trying to make, I do not subscribe to the author's position that centrifugal force is not real because (IMO) he ignores Frame of Reference.

Anyway, the black ball is your COM. The hoop represents your skis albeit pre shaped and fixed. The lifting of the hoop by the demonstrator represents release (no matter what technique is employed). Notice that when released, the ball (your COM) and hoop (the skis) cross each other. Also note that the transition process (lifting the hoop) is clean and direct...no skidding


 

Don Duran

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Zenny, I am curious about how to apply Ward's saying. The joints move phrase is especially troubling since it suggests the joints move first then the muscles respond. Proactive movements like anticipation get left out of that picture. Said simply there is a lot more going on than that phrase suggests. I know you see that wider view but some here with less experience and knowledge than you could easily be led astray by a too literal interpretation of that phrase.
 

Don Duran

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JESinstr,
Euler's laws take Newton's laws a bit further. Juris Vagners suggest an interesting seperation of discussions about CoM motion (basically Newtonian) and the motion of the feet and skis (basically Eulerian). I am sure some of our PhD level physisists here can explain this in greater detail but it again proves that a lot of important details get left out when we try to take complex concepts and oversimplify them.
 

Zentune

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The OP presented a chicken or egg question. My first response was to point out the erroneous nature of that thinking. Thinking we encouraged with catch phrases like feet first. So it's our fault that so many skiers adopt sequential movement patterns that to be blunt screw up their skiing.

For sure! Just like the "get forward" mantra taken by itself can produce less than desirable results. Although my point I think has been missed, I've sort of changed my thinking/mental model of skiing a bit lately....I'm not sure sequential movements are possible. Any movement by any body part will have an instantaneous global (whole body) effect, that's all I'm saying.

Zenny, I am curious about how to apply Ward's saying. The joints move phrase is especially troubling since it suggests the joints move first then the muscles respond. Proactive movements like anticipation get left out of that picture. Said simply there is a lot more going on than that phrase suggests. I know you see that wider view but some here with less experience and knowledge than you could easily be led astray by a too literal interpretation of that phrase.

People could definitely be lead astray by that, I agree. To keep it super brief, "joints act" refers to the skeletal "acceptance" of a load placed on it, like when the foot pronates in response to a grf----that force transmits instantly and globally, so we are assuming a closed chain scenario here. "Muscles react" in part, is the view that they eccentrically contract to decelerate joint movement and return the joint back the other way (with the help of concentric contractions on the opposing side of the joint). A muscle has to lengthen before it can shorten, and vice-versa to help control joint movement.

Ward asserts that the whole body is ALWAYS in motion, even when standing "still" (foot pressure maps show this), and that a joint is almost never perfectly neutral--neutral is just a snapshot in time, part of a joint's overall RoM. This is somewhat opposed the the "traditional" way of viewing muscles and joints in isolation and is not necessarily a popular view....

zenny
 
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razie

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The OP presented a chicken or egg question. My first response was to point out the erroneous nature of that thinking. Thinking we encouraged with catch phrases like feet first. So it's our fault that so many skiers adopt sequential movement patterns that to be blunt screw up their skiing.

well, to be fair, i think lack of good instruction screws up their skiing ;)

It does raise an interesting question though and I think the answer has to do with the level the skier is at. As we all know, skiing is not a really easy sport to pick up at a high level of proficiency. Sure, some with great balance skills like hockey players etc tend to pick it up quickly and rely on intuition, but good technical skiing is not easy.

Let's skip the bike example and go to motorcycles. You have 6 controls (front/rear brakes, clutch, shifter, throttle, steering) plus the body positioning (pegs, saddle, standing, hanging etc) that you must control simultaneously to take one single turn at a high level (brake front and rear independently, clutch and downshift two gears at the same time, while blipping the throttle to avoid rear skid, correct steering angle, body hanging off) etc. Pretty insane, if you actually think about it.

Skiing by comparison is easy peasy: gravity is constant and all you have is the ski edge angle and body positioning, really. And poles, I guess.

So does anyone think that we can explain a noob about using all those controls and do all those maneuvers at the same time, in the first turn he'll ever make and put him on a WC level race bike? Nope. That'd be nuts. We start easy and introduce one at a time and, in a few years of practice, he/she'll be able to take the "race turn" using all controls simultaneously at some level of proficiency.

Basically... while I agree with you, I simultaneously disagree with you... :eek: it's important to consider the audience and their level of competence. I don't think the level of understanding matters as much as the skill level. Perhaps.

So... just as on bikes we start with steering and handlebars first, then braking, then shifting, then hanging off etc - on skis, I prefer to start with edge angle, then body etc. In reality, like zenny says, all body parts are connected, so some level of lower/upper body coordination is required at all times.

cheers...
 

Don Duran

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We pretty much agree Zenny (except you still haven't accounted for the nature of anticipatory actions) and Razie the caution I mentioned is when we package an idea for a neophyte and inadvertently and unintentionally create dogma in their minds. The larger picture gets lost pretty quickly in that situation. IMO that is clearly visible in the chicken / egg type of question the OP posted.
So what collective advice can we offer that satisfies their curiousity but doesn't violate basic Euler's and Newton's laws of motion or the idea that we all seem to agree about how the whole body participates in a symbiotic way in our balancing efforts?
 
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Zentune

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I would say that anticipatory actions are the response to finding balance in a dynamic situation, but also a response to decelerate joint movement (to protect the joints) and send the body the "other" way, ie, into the new turn....so as an example, from an angulated/countered "position" (terrible descriptor imo) in the "old" turn, wherein the pelvis is laterally shifted left and transversely rotated right, to eventually the opposite "position" in the "new" turn. In a sense like a pendulum, in order to be in motion at all, it passes from one extreme, through a "neutral" phase, and to the other extreme.

All part of total motion dynamic balancing.

zenny
 

Don Duran

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I would add that proactive (strategic) moves change the vector representing the sum of all the forces in play. So they (proactive movements) generally are internally created actions verses reactions to external stimuli. Moving to change the future verses dealing with the past and present. Especially during transitions where we stop turning in one direction and start turning in another. Hope that makes sense...
 

Zentune

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Yup, just like when walking or running...the foot pronates, the leg internally rotates, and the pelvis (and mass) instantly move forward and away from that foot in anticipation of being "caught" again by the "future" foot.

Personally, I would view that as an internal response in regards to the future that is simultaneously initiated by the response to present external stimuli---both being true at the same time, if that makes sense.

zenny
 
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Mendieta

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We pretty much agree Zenny (except you still haven't accounted for the nature of anticipatory actions) and Razie the caution I mentioned is when we package an idea for a neophyte and inadvertently and unintentionally create dogma in their minds. The larger picture gets lost pretty quickly in that situation. IMO that is clearly visible in the chicken / egg type of question the OP posted.
So what collective advice can we offer that satisfies their curiousity but doesn't violate basic Euler's and Newton's laws of motion or the idea that we all seem to agree about how the whole body participates in a symbiotic way in our balancing efforts?

Love the discussion because it is technical, but not empty. And our collective mind only grows with discussion. As a learner, not an instructor, I can perhaps offer some perspective. Don, IMHO you hit it on the head in your first post in this thread, in that we get confused with short, dogmatic statements. And not only we (less advanced skiers) do. Lots of empty discussion goes on around ski technique because of that.

Your level of detail in that post is ideal, IMHO. I think you are all making a point that different parts of the holistic, perfect turn must be learned at a time. And I don't think focusing on that first, with new skiers, is incorrect. I loved side stepping and J turning at the beginning and getting on edge in an easy way, which is the way your trajectory will be centripetal and not linear, towards a tree ;)

But I think the key is to always give the student a little more info and the big picture. So they (we) don't get hang up on empty semantics, but we also understand where things fit in the big picture.
 

Don Duran

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Was out fishing...no luck...
...too many knuckleheads on jet skis...
...good thing I smoked some st louis ribs for dinner.

I'm seeing some congruency in our messages in spite of our organizational differences. Although I gotta say I rarely think about centri-centripital forces while skiing. I wanna go there, then I wanna go to another there, that is more an example of my thoughts as I ski. Remember TMI creates paralysis through analysis. Rehearsing and refining our game (experiential learning) is the slow and steady pathway but ownership only comes from that sort of practice. Which is the good and bad news all at once. Jump on boards once a year and it really makes equaling last years performance a challenge. That's why pros in almost every other sport practice at least once every 72 hours.
 

Don Duran

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But here is the better news go rollerblade a month straight before hitting the slopes.
 
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