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Is this aft? - Page 2

post #31 of 71

BB, sorry but even if you are right I also think you are wrong. The pivot is very closely related to this topic. Its important to understand why the skiers in the wc montages look like they are in the back seat. You dont need to pivot in a retraction turn but you cannot beat the laws of physics. If you keep moving straight ahead in a flexed position after the float you will be thrown on your back. In this case your only option is to quickly pivot and do a hockey stop kind of move like Jamt pointed out earlier. But if you start to turn earlier you can carve clean RR-trax without being caught in the back seat. Here is a drawing where I try to show what Im talking about:

 

Backseat001.jpg

post #32 of 71
TDK6--Is it your belief that the only way skis can turn (change direction) is via a pivot (active twist across their direction of travel)?

Happy New Year to all!
Bob Barnes
post #33 of 71

BB, offcourse not. But let me ask you a question insted. How would Marcel have made the turn if he had not used a pivot?

 

MH001.jpg

post #34 of 71
tdk6--come on now--that particular turn by Marcel involved a pivot. If he did not pivot, it would not be that particular turn. (Although I submit that your "stretched view" montage exaggerates the pivot greatly. Unstretch it to "real" proportions, and the pivot is much more subtle, to say the least. As I have described, rotary that serves to guide the skis on their lines, keeping them pointing the direction they are going, is not what I would call a pivot.) But not all of Marcel's turns involve pivoting--I'm certain we could find footage of "arc-to-arc" turns in which the skis point the direction of their travel, in both the carving/pressure phase and the float phase/transition.

Neither the pivot nor the retraction are necessary components of the fundamental principle that is the topic of this thread--whether Marcel Hirscher or anyone else happened to throw a pivot into any particular turn or not. Yes, they make it more dramatic and obvious, but if you think the pivot is necessary, then you must, in fact, believe that pivoting is the only way a ski can change direction. If you don't believe that (and I believe that you don't), then why would you continue to argue about this irrelevant point?

Best regards,
Bob

Edit 1/1/11--here's a very rough version of your stretched montage with the frames accurately registered. While it is very low resolution, unfortunately, you can still see that the pivot is not nearly as pronounced as it appears when stretched out, and the skis actually track quite cleanly on an arc, in this particular turn. Rick's montage in the original post shows a more obvious pivot.

500
post #35 of 71

Quote:

Originally Posted by tdk6 View Post

BB, sorry but even if you are right I also think you are wrong. The pivot is very closely related to this topic. Its important to understand why the skiers in the wc montages look like they are in the back seat. You dont need to pivot in a retraction turn but you cannot beat the laws of physics. If you keep moving straight ahead in a flexed position after the float you will be thrown on your back. In this case your only option is to quickly pivot and do a hockey stop kind of move like Jamt pointed out earlier. But if you start to turn earlier you can carve clean RR-trax without being caught in the back seat. Here is a drawing where I try to show what Im talking about:

 

That's the whole point right there. The whole process is that you're not moving straight ahead, but the body goes a different path than the skis and you end up ahead again. I did this many times today with no pivot, or no skidding. It's not complicated.

Also, one can pivot without float quite easily. I can pivot being quite vertical with no retraction but it's irrelevant to the "aft" discussion.

In the Hirscher montage, if you extend the third image from the right and don't throw in a pivot, there you go, a carved turn.He just wouldn't have made the turn at that gate.

 

The more interesting question here is how to get this concept across to racers and other skiers that have been drilled in "get forward", and associate pressing on the boot tongues constantly with being forward. Just the other day I was listening to someone talk about how he knew he was skiing well  because much his shins hurt after a day of  skiing which meant he was properly forward.

But wait, if one must be forward always, how would it be possible to carve an alpine style turn on tele gear?


 

post #36 of 71
Quote:
Originally Posted by Tog View Post

That's the whole point right there. The whole process is that you're not moving straight ahead, but the body goes a different path than the skis and you end up ahead again. I did this many times today with no pivot, or no skidding. It's not complicated.

Also, one can pivot without float quite easily. I can pivot being quite vertical with no retraction but it's irrelevant to the "aft" discussion.

In the Hirscher montage, if you extend the third image from the right and don't throw in a pivot, there you go, a carved turn.He just wouldn't have made the turn at that gate.

 

 


Tog, in frame three the CoM is completely behind the skis, and the torso is rotating even more backwards. If you do not throw around your skis at this moment you will land on the tails, and soon after you will fall. There are several ways to get out of an aft state, but in this particular state I don´t see any other way than to pivot. For example, pulling back the feet would increase the backward rotation of the torso even more. I have watched many WC racers in slow motion, and I have never seen this type of transition without a pivot. Sure you can do arc to arc with retraction and moments of aft, but in this case the body is not rotating backwards through the transition. In the midst of transition it is already too late. You have to setup for the transition much earlier. 

 

There is no message to get across to racers here, they already know how to work the fore/aft.

post #37 of 71

Here are some good examples of Marcels technique.

 

post #38 of 71


 

Quote:
Originally Posted by tdk6 View Post

BB, sorry but even if you are right I also think you are wrong. The pivot is very closely related to this topic. Its important to understand why the skiers in the wc montages look like they are in the back seat. You dont need to pivot in a retraction turn but you cannot beat the laws of physics. If you keep moving straight ahead in a flexed position after the float you will be thrown on your back. In this case your only option is to quickly pivot and do a hockey stop kind of move like Jamt pointed out earlier. But if you start to turn earlier you can carve clean RR-trax without being caught in the back seat. Here is a drawing where I try to show what Im talking about:

 

Backseat001.jpg



TDK6 why be so thick headed.

 

BB is saying although pivot can be present to do aft retraction transition you dont need it everytime.

 

Epic "footsquirt" awesome I like it.

post #39 of 71

Bush, bother to read the thread through.

post #40 of 71
Quote:
If you do not throw around your skis at this moment you will land on the tails, and soon after you will fall. There are several ways to get out of an aft state, but in this particular state I don´t see any other way than to pivot.

Deeper understanding is needed, and appearances deceive, Jamt.

First, as I have already noted, this particular turn in question was a turn with whatever amount of pivot it had. Hirscher was in balance, and made a great turn. Of course you cannot just make one hypothetical change--like "what if he did not pivot?"--and expect the rest of the turn to work out the same. If you want to discuss a turn with no pivot, look at a turn with no pivot! (On the other hand, please do note that a corrected version of the montage, with the frames accurately registered, shows that the pivot was not nearly as obvious or pronounced as it appears in TDK6's "stretched" version.
500
(This is not to suggest that he did not pivot at all, and certainly not to suggest that other turns do not or should not show very active pivots.)

Second, if we must get hypothetical, let's imagine what would have, or could have, happened if Hirscher had not pivoted in this particular turn. Yes, the skis would have continued even further out away from him for a longer time, making him appear even more aft. Yes, if his body and skis had been on the same paths, he would simply go straight and perhaps "wheelie out" of the course. It happens now and then! However, his body and skis were NOT on the same paths--their paths crossed at the transition, and as his feet went more quickly across the hill, his body (CM) moved more quickly down the hill (in a straighter line). The pivot in this turn (subtle though it actually was) allowed him to engage his edges "early" and carve around the gate. In a different scenario--with the gate perhaps more offset--he could have avoided the pivot, allowed the skis to continue to run further across the hill to the new gate while his body continued down the hill to the inside of the turn, and engaged his edges later than he did here. The prolonged float phase/delayed edge engagement would have (could have) allowed a very clean edge engagement at very high edge angles, somewhat later in the turn. This happens now and then also--quite frequently, actually!

As a common side-effect of this non-pivoted, delayed edge engagement, initiation, you will often see a delayed "weight transfer" as well, with the inside ski engaging first like the classic "white pass turn." Makes sense, doesn't it?--as I've previously described, this principle is more accurately discussed as a lateral, rather than fore-aft, movement. It is the skis moving over to what will be the skier's right for a left turn. That it takes place largely in the transition, when the skier and the skis are traveling across the hill, makes it appear to be a fore-aft thing. But when you factor in the "balance in the fourth dimension" understanding (during the float phase you are more-or-less airborne, so movements there must be considered only as to their effects later in the turn, when pressure is re-established on the feet), you would expect that exaggerating or over-doing the move would result in your body being further inside the turn, resulting in balance on the inside ski for at least a moment.

But why get hypothetical? Let's look at some real turns. Perhaps this video clip will help. EpicSki Academy director CGeib once remarked that, when making dynamic short-radius turns, he felt as if his body was like a heavy medicine ball being thrown around by his skis, tossed back and forth on its S-shaped path, at times floating free across the hill, at other times strongly re-directed through powerful force originating from the skis on the snow. A great image, I thought! I created some rough animations and combined them into this video clip a year ago, to help visualize and explain the phenomenon. Beginning around 3:10 in the video, you will see many examples of great transitions, including the "white pass-like" delayed weight transfer I have just described (see around 3:33 in particular). The race was a Noram Giant Slalom at Keystone, won by Eric Schlopy whom you see in the opening sequence and elsewhere.

Transitions--The Medicine Ball from Bob Barnes on Vimeo

This clip, with the animations, clearly shows that during the float phase, the "catcher" (skis) must move underneath the "ball" (body/center of mass) and get "ahead of it" to be in position to catch and redirect again. If you consider the visualization deeply enough, you will recognize that it also explains turns with "extension" transitions as well as "retraction" transitions--it's all a question of how fast thing things are moving, how much time you have for your skis to make the transition, and how much time you need for that transition. Need more time?--low speed, gate more offset, whatever--extend and give the "ball" more loft and float time. Going fast and need a lightning-quick transition?--retract, throw the ball "flat" through the float phase.

Happy 1/1/11 New Year, everyone!
Bob Barnes

post #41 of 71
Quote:
BB is saying although pivot can be present to do aft retraction transition you dont need it everytime.

Dead on, Bushwacker!

wink.gif

Happy New Year!
Bob
post #42 of 71

What an outstanding explanation, Bob! Thank you very much for taking the time to post it, and on New Year's Day too.

Best wishes to all.

post #43 of 71

BB, please..... Why go through all this trouble explaining exactly what I have been saying all along. Is it so hard for you to admit Im right once and for all. I have said numerous times that you can make a retraction turns and carve edge locked the whole time. No problem. However, Marcel has to pivot in order to make those gates in that video. If you had read my postings earlier you would have been made aware of the fact that in the video TOC posted and from which I took the transition that I streched with the pivot Marcel carved edge locked in the first part of the video and pivotted in the second. And it was not just that turn that he pivotted. He pivotted all turns in that section.

 

Neat video BB, great work. Whish I could do the same. But there is one major component missing from your animation. Gravity. Lets expand that to two components, gravity and gate offset. They are linked closely together. The reason for this is that as you come out of your turn and enter the unweighted float and let your skis, BoS, slide forwards and you get into a back seated position even though you are in balance you need to be quick to let your skis "catch" you as you are falling to the ground. This is what my drawing was trying to point out. Also, you were wrong when you said that if he had continued straight forward he would have "probably wheelie out of the course". No, he would most deffinetly have been thrown on his back and continued in the direction he was flying through the transition. Here is a modification suggestion for your video:

Throwing a ball 001.jpg

You cannot ignore gravity. And you cannot ignore the gate sideways offset. This is totally missing from your animation. Now your ball gets thrown back and forth mimicing short turns. Like Marcel in his first video section. But then the sideways offset is increased. Thats why he carves in the first section and pivots in the second. And why the faces of the bascetball players have turned red.

 

Lets look at my first drawing. I modified it a bit. You can now imagine two things: the skier moved to the right and pivotted his skis and there through retained balance (two dimensional) or he carved to his right and made a turn (three dimensional). In the drawing he is caught at apex. In full balance. So, the animation can show two things: pivotting or carving. And WC skiers do both.

Backseat002.jpg

 

 Or here, a small modification to get that 3D perspective:

 Backseat003.jpg

 

Forgot one thing, here is a pritty good small video I fund just now:

 

 

 

 

 

post #44 of 71
Quote:
No, IMO it makes it [the pivot] necessary.

That's a quote from you, tdk6, from post #28. It is certainly NOT the same thing I'm saying.

Did it hurt when that guy in your drawing peed out that kidney stone? biggrin.gif

Best regards,
Bob
post #45 of 71
Quote:
Also, you were wrong when you said that if he had continued straight forward he would have "probably wheelie out of the course". No, he would most deffinetly have been thrown on his back and continued in the direction he was flying through the transition.

Perhaps you do not understand what "wheelie out" means, tdk6. It means "being thrown on your back and continuing in the direction you were flying through the transition."

How, exactly, is "gravity missing" from my video? The animations are, of course, drawn from directly overhead, so you cannot see the arc of the ball, but that certainly shouldn't stop you from being able to visualize the image from another vantage point. Frankly, though, the vertical aspect is another irrelevant point in this discussion. In fact, that is one of the reasons I drew it from this perspective--to eliminate the distraction of irrelevant components. As I explained, what matters is simply that there is enough time--that the "float phase" lasts long enough--for the feet to move beneath the body to the optimal place for "catching" the medicine ball/CM. Yes, as I described, there are vertical implications there, which would explain why some turns involve retraction and others extension. But to the "is this aft" point of this thread, extension or retraction are irrelevant--the principle runs through both.

For what it's worth, tdk6, I am not disagreeing with a lot that you have posted. Your first post--#3 in this thread--is quite accurate, although already you seemed to be making a big deal about the specifics of this particular turn--the retraction and the pivot--rather than focusing on the principle topic of Rick's original post, which is a critical principle regardless of retraction/extension or skis pivoting or kept in line.

Best regards,
Bob

PS--that is a great little video clip you linked to--especially when viewed in 1080p Hi-Def. Any way you look at these things, it's clear (but not on topic!) that active, precise, purposeful rotary movements, as well as the spectrum from deep retraction to vigorous extension, are very much involved in turns at the highest levels.
post #46 of 71
By the way, tdk6, you are not alone in appearing to fixate on the pivot. The original poster has also stated that the pivot is "key":
Quote:
No one has mentioned the pivot that takes place between images 3 and 4. Can you see it? What effect does that pivot have on fore/aft balance? Hint; this is a key piece in the puzzle.

(Post #8)

One theme that I do like in this thread is the recurring recognition that movements can have effects far beyond the obvious. "Fore-aft" movements can affect edge angle and lateral pressure. Rotary movements affect fore-aft balance. And so on. Tipping movements can involve rotational movements, and can also affect fore-aft and lateral pressure. Good stuff!
post #47 of 71
Quote:
Originally Posted by Bob Barnes View Post



Quote:
If you do not throw around your skis at this moment you will land on the tails, and soon after you will fall. There are several ways to get out of an aft state, but in this particular state I don´t see any other way than to pivot.



Deeper understanding is needed, and appearances deceive, Jamt.

First, as I have already noted, this particular turn in question was a turn with whatever amount of pivot it had. Hirscher was in balance, and made a great turn. Of course you cannot just make one hypothetical change--like "what if he did not pivot?"--and expect the rest of the turn to work out the same. If you want to discuss a turn with no pivot, look at a turn with no pivot!
 

Bob, that was actually the point I was trying to make but not as good as your description. ToG claimed that the state in frame 3 could continue in a turn with no pivot and I was simply trying to explain why it is not so. If Marcel wanted to make a turn without a pviot, he would never be in the state of picture 3. 

 

I would also like to point out that there is a difference between pivoting and skidding in this context. When the trajectory of the CoM cross with the trajectory of the skis with a significant angle there will be pivoting, but not necessarily any skidding. When you retract (just before the crossing) the skis are pointing more up the hill than the CoM trajectory. When you load the skis again they must point in approximately the same direction as the CoM trajectory in order not to skid, and thus the skis must have pivoted in the air. Your animation would be a great tool to point out this fact. If you do a one-footed release with weight still on one foot, this non-skidded pivot cannot occur and the transition will take longer (more common in GS).

 

Great explanation of transitions btw.

post #48 of 71
Quote:
Originally Posted by Bob Barnes View Post



Did it hurt when that guy in your drawing peed out that kidney stone?

 


Ah, that´s why the other guy moved back.

post #49 of 71
Thread Starter 

Bob, the "key" I was referring to was the connection between the pivot and the retraction.  

 

Retractions are slower for getting to the front of the ski when skiing arc to arc than a cross over variety transition is, so they're less used in World Cup Arc to arc turns.  For recreational skiing, where the line a skier takes down the mountain requires less precision and urgency, staying aft longer at the start of the turn is fine, so retractions represent a reasonable option.  In fact, taken to the extreme, well skilled rec skiers can easily get away with hanging out in the backseat through the whole turn, never seeing center balance at all.  Lesser skilled rec skiers sometimes get stuck there, in their attempts to execute linked retraction transitions.  

 

In a race course, where staying on line while condensing turn shape is the goal,  getting to the front of the ski quickly at the start of the turn is critical.  It's why most Arc to Arc turns you see in that arena will include easily seen extension of the old inside (uphill) leg prior to edge angle neutral (good old ILE).  They use it to pull themselves into a fore state of balance quickly and early.  

 

In retraction, extension comes after edge angle neutral.  That's why, in arc to arc turns, the assumption of fore balance comes later when retracting.  It doesn't matter when pivoting, because the redirection of the skis changes the fore/aft line.  Suddenly, allowing the body to project downhill moves it fore, which is not the case in arc to arc.  

post #50 of 71
Got it, Rick.

Great thread, by the way!

Happy New Year!

Best regards,
Bob
post #51 of 71
Thread Starter 

Same to you, Bob.  Great video, BTW, the medicine ball one.  Your animation skills are impressive, and I like the concept the animation portrays. When I first started watching, I was thinking, "wait a minute, that' not the body catching the ball, it should be the skis", then they magically transformed into skis!  Super.  Really gets the message across.  Top it off with one of my race program alumni (Schlopy) starring in the show!  

 

post #52 of 71
Quote:
Originally Posted by Bob Barnes View Post



Quote:
No, IMO it makes it [the pivot] necessary.



That's a quote from you, tdk6, from post #28. It is certainly NOT the same thing I'm saying.

Did it hurt when that guy in your drawing peed out that kidney stone?

Best regards,
Bob

 

Sorry, that remark was Marcels turn exclusively. Not a general comment.

LOL, kidneystone... which guy exaclty?

 

post #53 of 71
Quote:
Originally Posted by Jamt View Post


Tog, in frame three the CoM is completely behind the skis, and the torso is rotating even more backwards. If you do not throw around your skis at this moment you will land on the tails, and soon after you will fall. There are several ways to get out of an aft state, but in this particular state I don´t see any other way than to pivot. For example, pulling back the feet would increase the backward rotation of the torso even more. I have watched many WC racers in slow motion, and I have never seen this type of transition without a pivot. Sure you can do arc to arc with retraction and moments of aft, but in this case the body is not rotating backwards through the transition. In the midst of transition it is already too late. You have to setup for the transition much earlier. 

 

There is no message to get across to racers here, they already know how to work the fore/aft.



Exaclty

post #54 of 71
Quote:
Originally Posted by Rick View Post

Same to you, Bob.  Great video, BTW, the medicine ball one.  Your animation skills are impressive, and I like the concept the animation portrays. When I first started watching, I was thinking, "wait a minute, that' not the body catching the ball, it should be the skis", then they magically transformed into skis!  Super.  Really gets the message across.  Top it off with one of my race program alumni (Schlopy) starring in the show!  

 


Yes the video with the animation is nice. I even caught a glimbs of Sandell.
 

post #55 of 71
Quote:
Originally Posted by Tog View Post

Quote:

Originally Posted by tdk6 View Post

BB, sorry but even if you are right I also think you are wrong. The pivot is very closely related to this topic. Its important to understand why the skiers in the wc montages look like they are in the back seat. You dont need to pivot in a retraction turn but you cannot beat the laws of physics. If you keep moving straight ahead in a flexed position after the float you will be thrown on your back. In this case your only option is to quickly pivot and do a hockey stop kind of move like Jamt pointed out earlier. But if you start to turn earlier you can carve clean RR-trax without being caught in the back seat. Here is a drawing where I try to show what Im talking about:

 

That's the whole point right there. The whole process is that you're not moving straight ahead, but the body goes a different path than the skis and you end up ahead again. I did this many times today with no pivot, or no skidding. It's not complicated.

Also, one can pivot without float quite easily. I can pivot being quite vertical with no retraction but it's irrelevant to the "aft" discussion.

In the Hirscher montage, if you extend the third image from the right and don't throw in a pivot, there you go, a carved turn.He just wouldn't have made the turn at that gate.

 

The more interesting question here is how to get this concept across to racers and other skiers that have been drilled in "get forward", and associate pressing on the boot tongues constantly with being forward. Just the other day I was listening to someone talk about how he knew he was skiing well  because much his shins hurt after a day of  skiing which meant he was properly forward.

But wait, if one must be forward always, how would it be possible to carve an alpine style turn on tele gear?


 


Good posting TOG. I highlighted what I think is important to point out in this discussion. That if the gates are set with such offset that you possibly cannot carve then you have to do something else. In this case a pivot. I too make carved turns while flexing deeply through the gates at some sections of a race course. Or outside the course. I whish I could do it more than I do.

 

The missconseption of always being forward is also very true. Note that as you retract your knees and legs upwards at transition you cannot possibly flex your ancles or hang on your shins. And the stiffer the boot the more difficlut it gets. You can try it at home. Put your boot on and lift it up in the air and try to fex your ancle. Not possible, or lets say the boot does not flex much. The only way you can flex your anlce/boot is to jam it between your CoM and your BoS and maybe some turn forces. Put it on the floor and put your weight over it and lean forwards and bend at the knees. Thats not what is happening at the transition if you do a deep retraction transition. Annother weard thing is when some claim they always keep their hips forwards. Not when they are doing a retraction turn they are. Hope everyone understands why. Some also claim that they pull the feet back under them in the transition. This is also obviously not true. Not if they are doing a deep retraction transition.
 

post #56 of 71

BB, Im I the only one who have been applying your back pedal consept to retraction transition turns?

post #57 of 71
Ah--the "backpedal motion"...you are one of the few, then, who can see that it applies exactly in this discussion, tdk6. Good eye--and good understanding, in my opinion. A high-speed "retraction turn" demonstrates the "virtual bump" concept very well, doesn't it? These dramatic-appearing fore-aft movements of the feet beneath the CM are critical for balance, in the real bumps and out. I think that's the overall take-home message from this thread. Would you agree?

Best regards,
Bob
post #58 of 71

BB, exactly, I agree toatlly icon14.gif

post #59 of 71

 

Originally Posted by HardDaysNight View Post

 

At the point in the montage where Hirscher appears to be (note: "appears to be" not "is") aft, there are literally no forces that he needs to resist using core and/or leg strength - he has been captured at the fleeting moment of neutral where the paths of his feet and CM have been released from the turn and are continuing on their diverging tracks through inertia. By the time the pressure phase of the new turn is reached, the CM will be ahead of the feet again and he will be in an ideal state of balance to resist the forces that build. The neutral point is actually the most effortless part of the entire turn and this position is absolutely something you would be striving for. Unfortunately "striving" is not going to get you there, because it is only through accurate direction of the CM and the feet in the last part of the prior turn that this position can be attained as a result of correct movements made earlier.

 

My reference model will still call this "aft" as a simple matter of definition:  the Centre of Mass (roughly the navel area) is behind the Base of Support (the feet).  Can you clarify for me what you would consider "aft" as a matter of definition? 

 

Of course this simple definition isn’t the whole picture:  to assess outcomes we have to account for forces while in motion.  I can agree that at the point in time shown in the photos, the CoM could be in the process of re-centring over BoS through the force of momentum in the direction of travel, not necessarily active muscular forces.  But there would be a need for pretty good momentum to successfully achieve this re-centring, and the momentum in direction of travel is greatly influenced by the impulse from the previous turn.  In this example, there would have been significant muscular force input to achieve the strong impulse. 


 

 
Originally Posted by Bob Barnes View Post

Mogulmuncher--an interesting thing about this is that in fact, done and timed correctly, this move does not require any core strength or effort whatsoever--indeed, quite the opposite. It results from the complete release, not only of the edge engagement as the previous turn ends, but of all effort. Marcel will not need strength to "pull" himself forward to return to balance--the first converging, then diverging paths of the momentum of his CM and his feet will take care of it all. He merely needs to let it happen. When the pressure phase resumes in the new turn, he will be in perfect balance (if everything happens just right).

And no, it is not a position a beginner will get into, but the principle certainly applies at every level. Beginners don't achieve as high edge angles as experts either, but that should not suggest that they don't edge (or should not be taught to edge). Beginners will never find their angle of inclination (lean of the CM into the turn for balance) as extreme as that of a World Cup racer, but they do incline, to the degree they need to for balance at the lower speeds they travel. If you look at this principle closely, you'll see that the "extremeness" of the hips-behind-feet image is, in fact, directly related to how far the path of the skis will be outside the path of the CM in the apex of the turn.
 

 

As I mentioned above, I can agree that there might not be much or even any core strength engaged at this particular point in time, but I think some pretty good core effort was needed to get to this effortless transition.  In a more forgiving environment, the release movements could be achieved with just a little bit of muscular force for rebound/redirection, as long as CoM stays centred over BoS in the fore/aft plane.

 

Yes, the principle certainly applies, with forces relaxed and angles adjusted accordingly at lower skill levels.

post #60 of 71


It's a great question. "Fore" and "aft" are only meaningful if we specifiy the plane in which we are making the determination. Consider, for example, a line drawn along the direction the skis are moving at the instant in question and passing through the balance point on the ground (where the balance axis intersects the ground). Extend a plane from that line through the CM. Observing in that plane shows that the CM is behind the feet. But, is this the relevant plane? Now, draw a line in the direction in which the CM is moving at the same instant- note that this line points more directly downhill than the line along the skis. Extend a plane down from this CM line again passing through the balance point. Observing in this second plane shows that the CM is over or ahead of the feet. So, which plane of reference is the correct one? I contend that "balance" in this context has to be anticipatory and that the second frame of reference is the valid one - Barnes' concept of "balancing into the future". So, any definition of "aft" has also to specify the plane in which we are at observing the relationship.  
 

Quote:

 

My reference model will still call this "aft" as a simple matter of definition:  the Centre of Mass (roughly the navel area) is behind the Base of Support (the feet).  Can you clarify for me what you would consider "aft" as a matter of definition?    

 

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