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Does this look like an A-Frame to you? - Page 5

post #121 of 167

Discovering why that option serves her so well is where i'm trying to lead Metaphor in his quest to increase his MA skills. So Nord I know it's been years but care to give us your interpretation of the article?

post #122 of 167

What kind of cracks me up in reading through this thread is the obsession with trying to determine whether or not a few degrees off of parallel through the legs constitutes some kind of technical error. In the world of PSIA, perhaps it does because it detracts from the esthetic, similar to gymnastics where unpointed toes or legs a little apart result in point deductions. In racing the only thing that counts is the clock, and while gross departures from more or less parallel leg shafts will cause some biomechanical inefficiencies, I guarantee that at speed in a turn, athletes are not focused on leg shaft alignment. The preoccupation of racers is not a look, but a move. If you go further back up the thread and look closely at the Canadian video that starts out with Cuche and features Grandi and Nyberg, et. al., the primary movement pattern demonstrated by all of these athletes is a positive weight transfer from the old outside ski to the "new" ski (uphill ski) in the transition. They are all keying on establishing a solid platform with all of their body weight up over that new ski before it is rolled on edge and breaks into the fall line. This is particularly noticeable in Cuche, where in some turns his downhill ski is completely off the snow as he shifts his weight onto the new ski. By having established that new platform the outside ski arcs into the fall line fully weighted and the athlete builds more pressure on that ski with the aid of ''centrifugal force" and active extension of the outside leg. Once the ski is engaged the athlete can incline if need be because he has something to stand on, and he can take the resultant high load through a more aligned skeletal structure in the sagittal plane. On steep icy slopes when carrying speed, if the athlete moves his CM inside before having established a platform on the new ski the result is pressure builds late on that ski and usually more abruptly, edge grip is compromised and there is risk of the ski sliding out or experiencing bounce. In the bottom third of the turn from the fall line back to the gate, the outside ski experiences maximum pressure and is fully decambered, but the arcs are short and powerful and the frictional coefficent is high. Consequently, once having established the appropriate exit angle, the athlete wants to get off that ski as quickly as possible and prep for the next turn. The position and angle of the inside knee and leg relative to the outside leg should be wherever it needs to be to help facilitate the smoothest most efficient transfer of weight from the pressured outside ski onto the inside ski. Arguably, if the inside leg is a bit more vertically aligned under the torso relative to the outside leg it may have better biomechanical efficiency in extension as the weight transfer occurs. The point being, it's important not to confuse effect with cause and intention.


Edited by georgert - 6/3/11 at 12:40am
post #123 of 167

Thank you Georgert, I would add that perhaps in the certification process Metaphor is being tasked with showing parallels in his certification reference manuevers. I think he's in CSIA so I may be off target here but in PSIA it's quite common for our level 2 coaches to view the certification test reference maneuvers as final forms where style is as important as function. In many ways these coaches are still refining their fundamental skills and the framework of that learning process certainly includes performing test maneuvers as prescribed in the movement descriptors. Unfortunately, that process gets viewed by them as teaching them to perform final forms and IMO in some way it is exactly that. Is there a little wiggle room based on their unique physiology? Sure but perhaps in that learning process their mentors need to express more often the idea that training for a test defines a specific intent, that intent is simple, we want them to prove they can ski to a set standard. We grade them on doing that but beyond that it's hard to suggest that any testing standard (reference maneuver) is a universally appropriate final form.

 

Especially when it comes to racers and the variations so often present in their technique. Do the fundamental skill pools lose importance in racing? Far from it, if anything they are even more important in race training. Those folks need to rely on their ability to perform turns while on the ragged edge of control. They might invent a recovery move out of necessity but they also have spent a heck of a lot of time developing their fundamental skiing skills. IMO that is why racers can usually express them successfully in a wider variety of situations than a recreational skier who neither owns that same level of developed skills, or is willing to commit the time and effort to develop them to that level.

 

 

BTW Georgert, I really like how you described the efficacy of non parallel shins during a foot to foot weight transfer. I was serching for those words a while back but I doubt I can express that idea any better than you have. I'm hoping other see the adducting of the outside knee during the middle of the turn through that same filter. Sometimes efficacy and efficiency are different objectives and understanding why isn't alway easy. Thank you for the great post, I hope to see more of them in the future.

JASP

post #124 of 167

Good point about most racers, aesthetics and speed. Because speed is the goal, racers need to minimize inside ski skidding which is slow. So the inside ski should be at equal or a greater angle.

 

 


Edited by skiatansky - 6/4/11 at 11:33am
post #125 of 167

Interesting, why would keeping the inside shin more vertical (relative to the outside shin) facilitate less inside ski skidding? 

post #126 of 167



 

Quote:
Originally Posted by justanotherskipro View Post

Interesting, why would keeping the inside shin more vertical (relative to the outside shin) facilitate less inside ski skidding? 


 

Sorry I was not clear. I meant exactly the opposite. Edited my post above to be more specific.
 

 

post #127 of 167

trick question...

...Without pressure the edge angle is largely irrelevent. Although as you begin to perform ILE the more vertical shin is capable of more weight bearing and doesn't put as much lateral load on the knee.

post #128 of 167
Quote:
Originally Posted by justanotherskipro View Post

trick question...

...Without pressure the edge angle is largely irrelevent. Although as you begin to perform ILE the more vertical shin is capable of more weight bearing and doesn't put as much lateral load on the knee.


Shouldn't the forces be directed straight through the soles if you are in balance? It sounds as you are thinking that the little toe edge of the inside leg are getting a sideways force on inside leg extension.

If that is how it's done then that alone should be proof that outside leg flexion is way better.

I don't think your statement above is completely correct thou, so I'm emphasizing that the previous sentence is based on speculation around that very statement.
post #129 of 167

The only time there is no pressure is when the ski is in the air, and I agree, at that point the angle doesn't cause the inside ski to skid - since its not touching the snow. But, if the ski is on the snow there is some pressure, and a ski that is not carving is skidding and a skidding ski is slow.
 

 


Edited by skiatansky - 6/7/11 at 9:15am
post #130 of 167

Ski, the inside ski carving is a falicy based on some pretty faulty assumptions. A carved turn of a smaller radius would require a couple things that don't exist, even in theory. The inside ski is not bearing enough weight to bend it into that tighter arc and without that force bending the inside ski that much, the inside ski's edge angle would have to exceed the outside skis if no skidding was occuring. We're also assuming the skidding inside ski introduces a lot of drag. Without the pressure I already mentioned that is a questionable assumption as well. In fact it introduces an off axis turning force that can compliment the effort to get the outside ski to turn. Finally, we need to be quite clear that pure carved turns are a theoretical idea but even racers don't carve all the time.

post #131 of 167

Racers want to reduce drag as much as possible. That's why they bomb down the hill in skin tight suits on freezing cold days and spend gobs of money on special waxes. Some even cook up a proprietary blends aren't shared even with the closest of friends. Point being that even the smallest cause of drag should be eliminated in an attempt to gain the fastest possible time.

 

Sounds like you believe that the inside ski angle is irrelevant from a speed point of view. I disagree but its a pointless discussion so we'll just have to agree to disagree.

 


Edited by skiatansky - 6/7/11 at 5:31pm
post #132 of 167

We don't have to agree. Nor do you have to agree with the physics that points to the fact, yes fact, that the inside ski can only carve a tighter arc if it is bent more than the outside ski. There are only a few ways you can do that SKI and none include less weight on the inside ski, or an equal, or lesser edge angle. If that were true we would see bow legged, inclined stances from racers all the way down into J5's. We don't and won't because that myth is based on the erroneous assumption that the inside ski can actually carve a clean but tighter arc than the outside ski without the forces it would take to create that tighter turn outcome. Not to mention glide and how the best gliders (fastest) use the lowest edge angle possible, not the highest edge angle possible. Or the fact that racers get on and off their edges quickly because it is slower to remain on that strong edged platform. Too much traction (friction) from the metal edges. Or the fact that racers seek to focus the vast majority of their weight on to the outside ski to keep it from skidding. All of these objectives are far more important than whether or not the inside ski skids a bit. Do we strive to keep that to a minimum? Sure, we just don't and can't eliminate it completely. BTW,  I suspect we actually agree more than we disagree SKI.

post #133 of 167

On a hard surface, when tipping and pressuring a ski that has a given side cut radius, the angle of tipping will determine the bend of the ski, and the amount of pressure needed to produce that bend is not all that much as compared to the turn forces in a high speed turn, leaving plenty of force for the outside ski dominant skiing style.

 

When carving on a hard surface, the relative radius of the carved path of the inside ski as compared to that of the outside ski can and does change continuously during a series of turns and in different parts of the same turn. 

 

Just Say'n.

post #134 of 167

Sounds like there is an assumption being made that the inside ski needs to scribe a tighter arc than the outside ski to be carving - or as close to carving as is possible given the circumstances. Is there no other possibility to consider? The tracks left by a high level racer will often diverge and then converge. Perhaps the angle of the inside ski combined with the inside leg retraction explains how this happens?

 

Is the inside ski in this picture carving? Close enough to be referred to as carving rather than skidding in my book.

 

2_.jpg

post #135 of 167

Of course inside skis is carving, but in that frame I think he is very close to exit the turn. Just about to go in transition.

You all know, that this is Cuche above.. He is a master of parallel shins. If  anyone would be with parallel shins that would be him..Even though is obvious that the inside ski is bent, but still has smaller edge angle, than  outside ski...

As I mentioned earlier the inside ski allways will carve wider, not tighter arc period.. That is why tracks are diverging and converging, besides the reasons mentioned in the above post plus many other variables..

 

Racers never get to do a full circle turn. What they do  is called comma shape turns and is achieved by releasing early out of the turn by switching weight from outside to the inside ski. This way they will  accelerate/out of turn/ instead of keep carving/into the old turn/ which would make them slower..

post #136 of 167

I'm a bit confused here post 125 and 127 and even 132 say eliminating even the smallest cause of drag (cleanly carving) but in post 135 that stance is softened to as close as possible given the circumstances. Which is what I was saying all along. The rest of this stuff about divergence / convergence / comma shaped / No complete turns / etc doesn't eliminate the requirement that the inside ski stay inside the arc prescribed by the outside ski. Unless you want to cross your tips.

What is missing here is the idea that even if the inside ski is off the snow it will remain inside that arc thanks in large part to it being attached to the pelvis, just like the outside leg is. So the lateral accelerating force keeping the pelvis inside the turn also keeps the inside ski / leg there. That's the something else I was mentioning a while ago but didn't fully share until now. That's also why the stuff in post 125 and 127 about the inside ski needing equal or greater edge angles was something I questioned. Maybe now you can see why I wrote about the inside ski's edge angle being largely irrelevent, Iwe don't need to pressure the inside ski to bend it into a tigher arc, or put it onto a higher edge angle than the outside ski to keep it tracking inside the arc of the outside ski. It will stay there as long as both legs are connected to the pelvis and we are balancing on the outside ski. With the signifigantly less pressure on it we also don't see a lot of contact friction (drag) from a slightly skidding ski. It should also explain why complimentary edge usage will add complimentary off axis turning forces and help the outside ski turn. It's also worth mentioning here an early weight transfer with a severely abducted inside knee and a leg flexed so the hip is below the knee would more than likely immediately blow that ACL. So the step needs to occur after the inside leg gets into a bio-mechanically stronger position (after some ILE). BTW, That more vertical inside shin facilitates this stronger skeletal alignment (needed for ILE and the early weight transfer) sooner and puts the knee at signifigantly less risk. 

 

 

 


Edited by justanotherskipro - 6/8/11 at 10:15pm
post #137 of 167

Carl, you questioned my statements in post 128 and suggested I was speculating. Nope just sharing sound and well studied bio mechanical principles and turn mechanics. You also asked about off axis loads. We focus pressure through the ski edges (not the entire base of the ski / boot) and once we tip the skis onto an edge there is a lateral force component involved. Basically when we tip the cuff, the cuff redirects some of that load laterally just to tip the skis onto an edge. This is why the force vector representing the sum of the system of all the forces involved is not perpendicular to the base of the ski / bottom of the boot.

post #138 of 167



 

Quote:
Originally Posted by justanotherskipro View Post

I'm a bit confused here post 125 and 127 and even 132 say eliminating even the smallest cause of drag (cleanly carving) but in post 135 that stance is softened to as close as possible given the circumstances.


Don't know why you are confused. 125 says "REDUCE", 127 doesn't say anything but refer back to 125, at no point were the words "cleanly carving" used, post 132 starts right off with the word "REDUCE" and ends with a true statement, racers do try to "ELIMINATE" drag. Trying to do something and being able to do it are two different things. Post 135 is right in line with those posts.

 

As I implied in post 135, a racer often have two skis they are carving two different radius arcs and for the reasons touched on in that post.

 

There can be enough pressure on the inside ski after phase 1 of the turn to cause significant drag if that ski isn't up on edge and carving as much as possible.

 

jasp, are you suggesting that racers intentionally keep the inside ski at a reduced edge angle?

 

 


Edited by skiatansky - 6/9/11 at 9:16am
post #139 of 167
Quote:
Originally Posted by justanotherskipro View Post

Carl, you questioned my statements in post 128 and suggested I was speculating. Nope just sharing sound and well studied bio mechanical principles and turn mechanics. You also asked about off axis loads. We focus pressure through the ski edges (not the entire base of the ski / boot) and once we tip the skis onto an edge there is a lateral force component involved. Basically when we tip the cuff, the cuff redirects some of that load laterally just to tip the skis onto an edge. This is why the force vector representing the sum of the system of all the forces involved is not perpendicular to the base of the ski / bottom of the boot.


Maybe I wasn't clear enough? I wrote that I was speculating: "..previous sentence".

Could you write a force diagram perhaps? Using a linear scale please.
post #140 of 167

Carl, Actually that has been done countless times here at Epic. IMO, the best description of this can be found in Vagners work that is available through PSIA. My understanding of that is that just getting the ski tipped onto an edge requires a lateral force to be applied to the boot cuff. So it's levering in the lateral plane that occurs as a direct consequence of that force being applied to the boot cuff. When you draw the force vector it would not be parallel to the shin, it would be laterally perpendicular to it. Even the force coming back from the snow would involve a lateral force vector that would cause a torque that would take the ski /boot back to flat on the snow. If you need a visual image Grab a ski and place a boot into the binding and at rest the base will be parallel to the ground. Tip it over by moving the cuff three inches then let go. The ski will return to the base flat to the ground position.  Hopefully that explains that there are off axis (relative to the shin) force components involved in getting and keeping a ski tipped onto an edge. If we don't include them in the math the conclusion certainly would be that pressure is applied along the long axis of the shin but in reality those off axis force need to be there to explain how e tip a ski onto an edge.

post #141 of 167



 

Quote:
Originally Posted by skiatansky View Post


 

 

jasp, are you suggesting that racers intentionally keep the inside ski at a reduced edge angle?

 

 

Skiatansky, this thread is mainly about speed events. The OP showed an olympic medal run from Vancouver 2010 where Bode has significant A-framing. If A-framing caused a lot of drag he would not have won that Silver (and Gold).

 

IMO there are reasons why you do not want to tip as much as you can in speed events. If you ski with a less agressive platform angle you don't risk that the ski becomes edge locked when you don't want it to. The inner ski can easily end up in a diverging position becuase it bounces around on the ice all the time. If you unintentionally lock the edges at this time things can go bad pretty fast. More innner ski edging can be faster, but it can also be riskier. "If you want to finish first you have to finish".

 

Another factor to consider is line. Line is usally much more important than ideal form. If you need to tighten the radius by edging the outer ski more, and this causes A-framing because of the range of motion in the inner foot, why shouldn't you? To strive for paralell shins by not edging the outside ski as much can be detrimental in this situation .

 

Its pretty easy to freeski with paralell shins, but in a race course you can easily end up in survival mode and A-frame all over the place, subconsiously. In my experience that happens more often when you feel that you are late in the line, and funny enough these are usually the fastest runs.

 

Also, the theory of converging/diverging paths do not really apply as well in speed events, because the radius is so large. (the lateral difference is proportional to the skis radius)

 

JASP, as always from you, great postings.
 

This is Vonn from her famous run in Cortina this year when the inner ski locks but she makes an amazing recovery.
 

 

post #142 of 167

Ski, The mechanical connection at the pelvis, not the amount of carving is the major reason the inside ski tracks inside the path of the outside ski. That's why even when the inside ski is in the air it still scribes a path inside the path of the outside ski. So the mantra that the equal, or greater edge angles are needed to keep that inside ski tracking is a myth. Same goes for the myth that a carving inside ski creates less drag. In this case drag is a function of pressure, not edging or carving. That ski is already moving along it's long axis and will do so regardless of how much it is carving. Adding pressure to make it carve more at that point will only increase the drag not reduce it. Hopefully It should be obvious to you that the carving inside ski mantra you offered doesn't hold up under scrutiny. At least not for the reasons you presented in your posts.

 

 

That doesn't mean knowing how to make the inside ski carve has no merit, it has huge merit. But it is in the complementary edge usage arena where additional centrifugal forces can be created without forcing the snow to shear under more pressure on the outside ski. It's in the additional point of contact arena that allows for more stability in the lateral plane. It's in keeping that ski connected to the snow instead of trying to re-establish that connection after picking it up during the turn. All of those are positives and IMO compelling reasons to actively use the inside ski, instead of just letting it passively come along for the ride. At times that includes carving but at other times it doesn't. It all depends on complimentary objectives and no move can be said to alway be that.


Edited by justanotherskipro - 6/9/11 at 1:53pm
post #143 of 167

The typical path of the skis is divergence and then convergence. This is caused by inside leg retraction and the difference between inside/outside ski edge angle.

 

With regards to drag, who said anything about adding pressure to make the inside ski carve more? The inside ski pressure is a result of turn dynamics. Difficult to keep pressure off the inside ski when the hip is 2" off the snow.

 

jasp, when the inside ski is loaded, as it often is in late phase 2 and the phase 3 of the turn, what inside ski angle will be the fastest? What do you coach your racers to do with their inside ski at this point of the turn?

 

post #144 of 167

I see where your going and yes seperation can be due to the amount of inclination in the legs hips. Higher edge angles require a larger difference in leg lengths. Although pulling a foot up to your butt while standing upright wouldn't require changing the edge angle. The seperation between the feet would still increase though. Not that we would do that during a turn all I'm suggesting is divergence / convergence is not alway about edge angles. Nor is it always about leg length. Abduct a leg and the foot to foot seperation increases without any change in leg length. Wide wedges anyone? Turn a bent leg inward with femoral rotation and the foot will also be abducted thus increasing foot to foot seperation. Knee angulation and a frames anyone?

As far as what I teach I am assuming you mean around the two thirds point in a turn. The actual edge angle varies with the offset and terrain and even if they are using a step transition. Are they tying to get back onto a higher line? Are the setting up for a parallel step? Are they setting up for a stivot? Are they simply rolling the ankles to a new turn? All would change how they use the inside ski at that point. I don't buy the step and roll is always faster but if that's what you think

 

 

post #145 of 167
Quote:
Originally Posted by skiatansky View Post

Sounds like there is an assumption being made that the inside ski needs to scribe a tighter arc than the outside ski to be carving - or as close to carving as is possible given the circumstances. Is there no other possibility to consider? The tracks left by a high level racer will often diverge and then converge. Perhaps the angle of the inside ski combined with the inside leg retraction explains how this happens?

 

Is the inside ski in this picture carving? Close enough to be referred to as carving rather than skidding in my book.

 

2_.jpg

I believe Ski has it right.  In this picture, at this instant, both skis are carving, the inside ski is on smaller edge angle and carving a larger radius than the outside ski, and as a result an instant later the skis will be closer together, and carving as well as possible while using difference in tipping angle to control ski distance is the most efficient way to do it.
 

 

post #146 of 167
Quote:
Originally Posted by justanotherskipro View Post

Carl, Actually that has been done countless times here at Epic. IMO, the best description of this can be found in Vagners work that is available through PSIA. My understanding of that is that just getting the ski tipped onto an edge requires a lateral force to be applied to the boot cuff. So it's levering in the lateral plane that occurs as a direct consequence of that force being applied to the boot cuff. When you draw the force vector it would not be parallel to the shin, it would be laterally perpendicular to it. Even the force coming back from the snow would involve a lateral force vector that would cause a torque that would take the ski /boot back to flat on the snow. If you need a visual image Grab a ski and place a boot into the binding and at rest the base will be parallel to the ground. Tip it over by moving the cuff three inches then let go. The ski will return to the base flat to the ground position.  Hopefully that explains that there are off axis (relative to the shin) force components involved in getting and keeping a ski tipped onto an edge. If we don't include them in the math the conclusion certainly would be that pressure is applied along the long axis of the shin but in reality those off axis force need to be there to explain how e tip a ski onto an edge.


Allright, there's a sideway force. Given a half metre lever (up to the knee) in order to resist 5 cm (half width of ski base), the sideways pressure on the knee is very very low. A force diagram would have made this very obvious.

What you were talking about in post 127 must have been another kind of sideways force if you feel that inside leg extension gives streneous sideways forces on the knee. It definitely sounds like your kind of inside leg extension is directed perpendicular to the slope regardless the amount of inner leg tipping.

If that is indeed how you perform your ILE, I would very much suggest you give OLF a try in order to save your knees while being able to ski without that a-frame.

I am still hoping that I misinterpreted the direction of the ILE force vector you are suggesting in post #127.
post #147 of 167

I'm going to try this differently. if the inside ski is only turning because of the edge purchase and edge angle, when we pick it up off the snow it would do the newtonian thing and fly off on a linear tangent. The fact that it doesn't and actually continues to follow the very same path say it's mechanical attachment to the rest of the body is the major reason why it's turning in the first place. That doesn't go away just because two footed stances have become more common than a one footed stance. Using that inside ski in a complimentary way doesn't change that either beyond adding some additional centripetal force to the entire system. All the hype and hoopla over the rule of parallels is interesting but doesn't change the basic reason why the inside ski turns. The fact that even up through the world cup we still see cup winners using a more vertical inside shin should also make you question the validity of posts that promote inside leg carving as more than it is. 

 


Edited by justanotherskipro - 6/9/11 at 6:20pm
post #148 of 167
Quote:
Originally Posted by justanotherskipro View Post

I'm going to try this differently. if the inside ski is only turning because of the edge purchase and edge angle, when we pick it up off the snow it would do the newtonian thing and fly off on a linear tangent. The fact that it doesn't and actually continues to follow the very same path say it's mechanical attachment to the rest of the body is the major reason why it's turning in the first place. That doesn't go away just because two footed stances have become more common than a one footed stance. Using that inside ski in a complimentary way doesn't change that either beyond adding some additional centripetal force to the entire system. All the hype and hoopla over the rule of parallels is interesting but doesn't change the basic reason why the inside ski turns. The fact that even up through the world cup we still see cup winners using a more vertical inside shin should also make you question the validity of posts that promote inside leg carving as more than it is. 

 

Well, "The Mentalist" doesn't come on for another 1/2 hour and I see there is a post who's validity is in question... 

 

Ok.  I'll have a look..

This is post 125..(edit. the reference to post 125 in the above quoted post was edited out before I could finish my quoting mad.gif)

Quote:
Originally Posted by justanotherskipro View Post

Interesting, why would keeping the inside shin more vertical (relative to the outside shin) facilitate less inside ski skidding? 


That's easy, because if the inside shin is more vertical, it will carve a bigger radius and move over towards the outside ski without needing to skid, but if it isn't, then you have to slide it on over. 

 

Both skis carving as much as possible.  Angles control where the skis go.

 

post #149 of 167



 

Quote:
Originally Posted by Ghost View Post



That's easy, because if the inside shin is more vertical, it will carve a bigger radius and move over towards the outside ski without needing to skid, but if it isn't, then you have to slide it on over. 

 

Both skis carving as much as possible.  Angles control where the skis go.

 

Hm, isn't the skidding caused by the very fact that the skis want to converge so you have to skid it in order to not bring the skis together.

If you dont' want to skid at all you have to put the skis in a diverging position at the turn entry, the more vertical you keep the inside leg the more divergence is needed.

 

 

post #150 of 167
Quote:
Originally Posted by Carl R View Post



Quote:
Originally Posted by justanotherskipro View Post

Carl, Actually that has been done countless times here at Epic. IMO, the best description of this can be found in Vagners work that is available through PSIA. My understanding of that is that just getting the ski tipped onto an edge requires a lateral force to be applied to the boot cuff. So it's levering in the lateral plane that occurs as a direct consequence of that force being applied to the boot cuff. When you draw the force vector it would not be parallel to the shin, it would be laterally perpendicular to it. Even the force coming back from the snow would involve a lateral force vector that would cause a torque that would take the ski /boot back to flat on the snow. If you need a visual image Grab a ski and place a boot into the binding and at rest the base will be parallel to the ground. Tip it over by moving the cuff three inches then let go. The ski will return to the base flat to the ground position.  Hopefully that explains that there are off axis (relative to the shin) force components involved in getting and keeping a ski tipped onto an edge. If we don't include them in the math the conclusion certainly would be that pressure is applied along the long axis of the shin but in reality those off axis force need to be there to explain how e tip a ski onto an edge.




Allright, there's a sideway force. Given a half metre lever (up to the knee) in order to resist 5 cm (half width of ski base), the sideways pressure on the knee is very very low. A force diagram would have made this very obvious.

What you were talking about in post 127 must have been another kind of sideways force if you feel that inside leg extension gives streneous sideways forces on the knee. It definitely sounds like your kind of inside leg extension is directed perpendicular to the slope regardless the amount of inner leg tipping.

If that is indeed how you perform your ILE, I would very much suggest you give OLF a try in order to save your knees while being able to ski without that a-frame.

I am still hoping that I misinterpreted the direction of the ILE force vector you are suggesting in post #127.


It's quite simple really, if the force vector passes on the inside of the knee you have one kind of moment, if it passed on the outside you have another. If it passes through the middle of the knee there is no moment. If you have knee and hip angulation and a lot of weight on the inside ski the force will pass on the inside of the knee.
 

 

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