How do you see the role of momentum in initiating turns?
How does this affect your instruction?
One very simple analogy that comes to mind is playing catch with a ball. How much "loft" should you give the ball when you toss it to the other guy? How high should you throw it? The answer, of course, "depends." It depends on how fast you throw the ball. It depends on how far away from the catcher you are. Like skiing, this too is a case of "managing momentum"--you have to adjust the trajectory each time before you release, weighing a number of factors. In many ways, skiing is just our feet "playing catch" with our bodies--moving into position, catching and redirecting the body, then releasing and moving into position (through the transition) to do it again in the next turn. The speed and direction of the body--that is, its momentum--at the moment of release are critical. We spend the time leading up to that moment precisely controlling and guiding the body's momentum, so we can release it in the new direction and get ready to make the next turn. If we manage everything right in the previous turn, the transition and the initiation of the next turn are effortless!
And that optimal direction (momentum) has three dimensions: fore-aft, left-right, AND up-down. Whether, and how much, to "flex" or "extend" is entirely driven by the up-down component of the "ideal direction" for the body's momentum for each turn. Flex too much (or too soon), and you'll literally throw yourself into the ground. Extend too much, and you may not come down for a while, or in the right place--delaying the edge engagement ("the catch") for the new turn, or throwing yourself completely off your line.
Manage the momentum! In great turns, great skiers accomplish this with continuous, smooth guiding movements throughout the turn. Unfortunately, most skiers fail miserably at it, employing gross and sudden exertions with staccato stop-and-go effects, instead of smooth, sustained movements. It is exceedingly rare to see skiers who truly "flow" (carry their momentum!) through their transitions as a rule.
But it's a worthy target!
These thoughts place a lot of significance on the efforts and movements we make throughout turns,
especially in the finishing portion, where we literally finish directing our momentum.
In an across the hill series of turns, like in B. Barnes "Dynamic parallel turns" picture, we are literally
changing the direction of our CoM almost a full 180 degress across the hill.
On a clock, with the fall line going from 12 to 6, this puts the end of going one way at 3 o'clock
in a right hand turn or positions 8 and 16 in Bob's diagrams.
The forces to change the CoM's direction are maximum at or just past the apex of the turn.
I am thinking that while the direction changes at 3 o'clock, I am still having to "finish" dealing with the presures from the turn past that point.
How far past is based upon your speed and the steepness of the slope. Let's say this is at 4 o'clock (or 9 in Bob's).
So at this point I have stopped the going left across the slope and the dealing with the forces required to do that.
Now I can start managing the going right across the slope and get set up to turn to the left.
At 4 o'clock (Bob's 9) I can start the efforts and movements required to direct my CoM towards it's future point in the apex of the next turn.
Careful? it's the CoMs apex and not the skis apex? Ditto, I can steer the skis to where they need to go.
For me, that moves the whole turn thought process about 70 degrees sooner around the turn.
Instead of finishing the turn at 6 o'clock and doing whatever I have to do to perform the next turn and direct me and my skis where they should go,
I have to be thinking and acting much sooner and looking out further.
Instead of thinking where my skis will turn, I have to think about where I want my CoM to finish going across the hill.
It takes my thinking of an apex to apex turn to a different level.
OK, so here I am at 4 o'clock and I need to "release" to initiate the process of getting ready for the next turn. This "release" is really "I can stop pressing against the snow to change my direction from going left to going right cause I'm already going right and if I don't ease off on it now I'm going to have to make a much bigger and quicker adjustment later so I can get my skis on the other side of me to be able to stop going right and get me going left again."
If I time it just right, I can let the forces of the turn do the work of moving my CoM to the other side of my skis.
Or is it the skis to the other side of the CoM?
Doesn't "release" mean releasing the CoM to allow it to move downhill and across our direction of travel?
I'm trying for an ILE type turn. This then means that my outside leg stays long, right?
Then with any inclination at all, the best I can hope for if I extend my inside leg is an up and over arc with my left foot as the center of the arc (right hand turn of course).
By my thinking, this causes a slower movement of the CoM down the hill/across my line of movement.
An OLR type turn means I am flexing the outside leg to allow the movement of the CoM down the hill and across my direction of travel.
This seems more direct and therefore enables a faster transition and therefore a faster/tighter turn.
In either case, the flex or extend released my CoM didn't they? And if I allowed my CoM to move downhill and across my direction of travel, without any tipping effort won't the skis eventually change edges?
Or does "release" mean releasing the angle my skis are to the snow because they are headed in the direction they need to be to get on the other side for the next turn? If I don't flex or extend my legs, I can only tip (or untip in this case) my skis with ankle, knee and hip angulation or somehow reduce my inclination. Again, without flexing and extending the legs, I suspect this would be a long drawn out process ending with an uphill stop.
OK, so it's a skill blending of edging, pressure and rotary steering but which came first, the chicken (Flex/extend) or the egg (tipping)?
Seems to me like the chicken came first.
What ya think?
Seems like there is a case building to say that the transition is not the focus area, that the point just after the apex is where it all begins and should be the focal point.
What you describe here is exactly the point! The skis, through their interaction with the snow, apply force to the body (CM), which causes the direction change (turn). Once that redirection is accomplished, we "release" the force, allowing the body's momentum to continue unimpeded for a moment, as we move the feet into position to "catch" and then redirect the body into the next turn. It's a game of continuous, flowing, cyclical motion--not of "stop and go." And you are right--the key is to have the skis and the body moving as needed, each with the optimal momentum (direction and speed), at the end of the turn. So the movements required to make this happen must, obviously, take place in the control and completion phase of the turn you're finishing--it's too late if you try begin these movements at the beginning of the new turn. Unfortunately, since few skiers do this accurately, they cannot merely "release" the forces to start at turn, and must instead create a great deal of force and exertion to get things moving in the right direction AFTER the old turn ends. The result is an abrupt, not-smooth, not effortless transition.
You suggest that the "release" is where you can "stop pressing against the snow to change my direction." Yes! However, it may be more applicable to think of it as the moment the snow stops pressing against you.Sure, it's the same thing--equal and opposite reactions and all that--but the point of that interaction between yourself and the snow is that it is the very force that causes the direction change we call "turning." The snow pushes me; I accelerate (turn). Just as you'd be more likely, when explaining how to throw a ball, to describe it as your hand pushing against the ball, rather than the ball pushing against your hand, I suggest that thinking of the pressure resulting from the snow pushing against you, rather than you against the snow, paints a clearer image of what's happening--and of what we need to "do." Do you try to hit the ball with a golf club--or do you try to hit the club with the ball? Both are accurate descriptions. But one more clearly describes the intent--and the job of the athlete.
Either way, it's a good description.
Regarding your "chicken and egg" question, I suggest that you really can't separate these things, and shouldn't think of them as sequential events. As I described previously, at the moment of release, it's imperative that the body (CM) be traveling with exactly the right direction and speed (momentum), and that the direction of the momentum involves three dimensions--fore-aft, lateral, and vertical. Whether (and how much and when) to flex or extend as we release the forces of the turn is entirely determined--in every unique transition--by the specific and unique needs of that transition. Leading up to the release (in other words, as we complete the previous turn), we steer and guide the body's momentum in all three dimensions, simultaneously,
Indeed, to the point of the original post, it is only when we have finished the turn optimally--with the body (and the feet) ending the turn with the optimal momentum, that we can release the forces and "carry the momentum out of the turn, and into the next." Anything less, and we'll have to exert some effort (produce some force) as we start the new turn, in order to change the momentum.
The skis, through their interaction with the snow, apply force to the body (CM), which causes the direction change (turn). Once that redirection is accomplished, we "release" the force, allowing the body's momentum to continue unimpeded for a moment, as we move the feet into position to "catch" and then redirect the body into the next turn. It's a game of continuous, flowing, cyclical motion--not of "stop and go." ..... Indeed, to the point of the original post, it is only when we have finished the turn optimally--with the body (and the feet) ending the turn with the optimal momentum, that we can release the forces and "carry the momentum out of the turn, and into the next.