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Arc-to-Arc Technical Discussion - Page 2

post #31 of 51
Thread Starter 
Quote:
Originally Posted by disski View Post
big E he also said the above.... so I am traversing straight across the hill with one half of my body leading the other yet I am not countered... I'm confused I admit it...
Terms and their meaning to us are inexorably tied to the understanding/perception of our personal skiing, the skiing of our peers and the skiing of the World Cup athletes. Misunderstanding or a partial understanding of terms can be an impediment to learning, improving our skiing and enjoying the wonders and surprises of teaching people.
The following terms and their definitions should help. Various sources are used to compile this list.

Adduction- Adductor muscles on the inner side of each thigh that contract to pull your thighs toward each other
Abduction- Abductor muscles on the outsides of your thigh and hips that serve to move your thighs apart from each other
Anticipation release- A turn initiation force used to impart a rotary force to the skis, through the unwinding of anticipation.
Arc- (n) Is the pattern left in the snow by an edged, de-cambered, sliding ski when the tail is following the tip. This causes deflection and a change of direction (turn).
ATM/ATS- American Teaching Method / American Teaching System
Balance- Equilibrium; body movements (in search of) to maintain equilibrium.
Braquage- A powerful simultaneous rotary mechanism involving both legs, each using the other as an "anchor" or "fulcrum." Contrary to the current (PSIA) interpretation of braquage the skis do not necessarily receive a corresponding rotary force to pivot them.
Base of Support- The surface structure provided by the ski snow contact patch and the support offered by the equipment.
Christy- A skidding turn
Core- Muscular and skeletal anatomy comprising the pelvic region and overlapping musculature including the lower spine and ribs. (1)
Counter balance- A body movement equal and opposite to the force causing imbalance
Counter Rotation- Turning the skis by twisting the torso and legs in opposite directions. Newton’s law of action and reaction applies. (2)
Deflection- A change of direction resulting from the interaction between the skis and the snow. (3)
DOT- Direction of travel
ENERGIZED- Stored energy in the skis (seen as reverse camber) from ski/snow, mass/gravity deflection process
Energy- (force or power) primarily from the force of gravity 90%, with physiology (muscular and skeletal) applying 10% (1)
Force- The cause of motion or a change of motion/direction, as in deflection from the ski/snow interaction
Fulcrum Turning- A rotary mechanism in which one leg rotates using the other leg as an anchor or ‘fulcrum."
Garland- An exercise involving linked, incomplete turns. From a traverse the skier turns downhill but before matching the fall line, turns back up; tracks resemble a garland draped on the branches of a Christmas tree.
Inside half- Foot, knee, hip and half of torso that are on the inside of the radius of a turn
Lateral Knee Movement- Abduction or adduction of the legs, the knees are moved laterally (from side to side) as a result and are used as a visual reference.
Mechanics- The technique, the specified movements and the associated skills.
Linear- movement along a line, in one plane
Linear hip movements- Hip flexion and extension, perpendicular to skis top sheet
Lower body- both legs, from the head of the femur on down, feet included
Optimum outside leg length- the approximate alignment (flexion) suggested for movement and force resistance/exertion is: ankle@13 degrees, knee @ 26 degrees and hip @ 13 degrees
Outside/Inside half of body- can be thought of as a column or shaft consisting of foot, leg, hip, oblique, shoulder and arm of one side of the body (to the outside or inside of the radius of a turn). For example, this concept allows the stance/lead change from TRANSITION to PREPARATION to be conceptualized and executed. The body has asymmetric movements of its outside and inside half. The adduction/abduction of the legs and the push/pull (extension/flexion) of the hips are two primary examples.
Phase- Any one of the four distinct postures of ARC TECH and the associated body movements
Physiology- the body and its functions as related to skiing (musculature & skeletal)
Pressure- force exerted by physiology to the skis and ski-snow interaction
PSIA- Professional Ski Instructors of America
Re-centering- The lateral knee and linear hip movements of TRANSITION
Rise line- See: Illustrations
Rotary movement- any movement about an axis
Rotation- The process of transmitting rotary momentum of the torso and hips around the vertical body axis to the feet and skis (2)
Skills concept- The body movements of skiing under the umbrellas of turning, edging and pressure control
Sliding- Refers to the ski moving across the snow along it’s longitudinal axis. The ski is parallel to the DOT. Sliding skis as the base of support is a root principle of ARC TECH. See: Illustrations
Slipping- Refers to the ski moving across the snow sideways. The ski is orientated at an angle to the DOT. The ski’s tip and tail do not follow the same track. See: Illustrations
Space- where you are on the hill relative to rise line, horizontal line, angles of entry/exit and exit zones
Stance- body alignment, posture
Stancing- The progression of the proper body movements through the four phases of ARC TECH, (stance changing) with no static positions.
Tactic- A strategy for action, choice of line (space)
Technique- A method, a systematic procedure
Tonus / tone- A functional muscular tension prepared for dynamic activity
Turn (Arc)- A change of direction caused primarily by the force of gravity and deflection
Traverse (verb)- to travel horizontally or diagonally across the hill. This can be done on a sliding or slipping base of support.
UDT- In the PREPARATION PHASE the entire inside half of the body leads - similar to the stance of a normal traverse, but up side down due to the off camber tilt of the slope
Upper body- The pelvis on up (muscular & skeletal)
post #32 of 51
Thread Starter 
Quote:
Originally Posted by BigE View Post
Bolter, your definition of Base of Support is quite non-standard. Normal usage would be something like the area between all points of contact with the snow. Any time your balance vector is in that area, you are balanced.
The combination of the these two views of Base of Support (which i do not find to be mutually exclusive) sums up the proprioceptive clues and the tech aspect of the physics of skiing. Together we've got something.
Quote:
Can you clarify this for me? -> The prepatory movements of the inside hip advancing and flexing suggests that at completion of the turn, the outside hip is ahead, and the outside tip leads. Otherwise, advancing inside hip would imply it opens as the tip lead changes.
I do not know for sure what is meant by turn completion. Tell me, please. Bolter
post #33 of 51
wrt "Base of Support" I do not understand your definition at all. The term 'structure' throws me.

The turn is complete when the center of mass is released from it's arc.
post #34 of 51
Thread Starter 
Quote:
Originally Posted by BigE View Post
wrt "Base of Support" I do not understand your definition at all. The term 'structure' throws me.
.
Base of support- the contact patch of the ski/snow interface and the platform of support it provides
post #35 of 51
ah.... I think they have a different name for that
post #36 of 51
sorry - while i like my lessons simple language style I prefer an instructor that actually understands the biomechanics of the sport he/she is coaching in....

that way if I get stuck I can ask questions and not get tied in knots with the answers....

go ahead and talk guff fellas...
post #37 of 51
Thread Starter 
Quote:
Originally Posted by BigE View Post
Can you clarify this for me? -> The prepatory movements of the inside hip advancing and flexing suggests that at completion of the turn, the outside hip is ahead, .
No, inside lead persists. Up to the point of turn completion outside leg adduction, outside hip extension, inside leg abduction and inside hip flexion continue. Because the knee movement is lateral and the hip movement is linear, the perpendicular body alignment to the skis is retained. Through knee abduction and hip flexion the inside half of the body controls both skis’ edge angle and the hip’s height to the snow.
The inside ski remains on the snow for turning force, balance and stability. Ankle flexion and leg biceps (hamstring) contraction position the heel under the hip, pressurize the ski and stabilize the core.
Hip movement continues linearly. The outside hip is pushing (extending) in relation to the inside hip which is puling (flexing). This creates a high amount of energy transfer to the outside ski while still keeping pressure on the inside ski.


The center of mass begins a new arc path... by the Center of mass and outside ski converging. The inside leg starts independent movement of leg adduction and extension and the abductor of the outside leg "releases" the arc. The hips begin to square up, lessening inside half lead. The inside leg switches to adduction before the outside leg switches to abduction

I refer to this phase of movements as REDIRECTION which can be viewed as having two developments. First, a tightening of the turn radius with all of the associated movements to accomplish this (about which I did not go into detail). Second, an opening of the radius by the Lower Body (LB) movements. This is initiated sequentially by the inside leg switching to adduction, then as the UB and LB converge, the outside leg switches to abduction.
post #38 of 51
Thread Starter 
Quote:
Originally Posted by disski View Post
ah.... I think they have a different name for that
What is it?
post #39 of 51
bolter... if i weight a foot then generally to bear force it is pronated... pronation is a combination of eversion and abduction i thought.... I would generally pronate my downhill foot in a traverse....(are we still on a traverse?)

can you link this to your stuff?
post #40 of 51
Quote:
Originally Posted by Bolter View Post
What is it?
I dunno.. I try to read someof these... but keep getting the feeling I missed the first few lectures...

no-one seems interested in starting at the start of their lecture... they just hammer away using these terms that are confusing....
I am sure there must be some club with secret handshakes or something....

I think Ric B and Rick are the two posters I am most likely to look for... I can understand them they use more plain language and describe the concepts they use...
post #41 of 51
Thread Starter 
Quote:
Originally Posted by michaelA View Post
Disski,
Outside = ‘downhill ski’, Inside = ‘uphill ski’
Adducted = ‘pulling in’, Abducted = ‘pushing out’, Circumducted = ‘and pushing all around’
Circumfused = bewildered about turning technique


that)


Anyway, reading the definitions you’ve provided helps clarify things. I think we’re on the same page WRT unsupportive movements.
.ma
What does the acronym WRIT stand for and what are unsupported moves ? I am circumducted about this. Is it something everyone but me knows?
post #42 of 51
FWIW, and JIC you still haven't FIO, it's not WRIT, it's WRT, and it stands for - with regard to -. This example of confusion JGTS that the best ROT in these discussions is to KISS.
post #43 of 51
Bolton, are you basically advocating here that we should lead with the inside half through the body of the turn, come back to neutral (simultaneous rotational, lateral, edge angle, fore/aft neutral) during the transition, take a moment to regroup at neutral and get prepared for the starting of a new turn, then couple the initiation of the new turn with the initiation of a new inside half lead?
post #44 of 51
Quote:
Originally Posted by Bolter View Post
Base of support- the contact patch of the ski/snow interface and the platform of support it provides
Is there a difference between the contact patch and the platform of support?

What about poles? I can lean on a pole too -- it will support me.
post #45 of 51
Quote:
Originally Posted by Bolter View Post
No, inside lead persists. Up to the point of turn completion outside leg adduction, outside hip extension, inside leg abduction and inside hip flexion continue. Because the knee movement is lateral and the hip movement is linear, the perpendicular body alignment to the skis is retained. Through knee abduction and hip flexion the inside half of the body controls both skis’ edge angle and the hip’s height to the snow.
The inside ski remains on the snow for turning force, balance and stability. Ankle flexion and leg biceps (hamstring) contraction position the heel under the hip, pressurize the ski and stabilize the core.
Hip movement continues linearly. The outside hip is pushing (extending) in relation to the inside hip which is puling (flexing). This creates a high amount of energy transfer to the outside ski while still keeping pressure on the inside ski.
Contracting the hamstrings will lift the foot. Opposite to the assertion that it will pressurize the ski.

Quote:
Originally Posted by bolter
The center of mass begins a new arc path... by the Center of mass and outside ski converging. The inside leg starts independent movement of leg adduction and extension and the abductor of the outside leg "releases" the arc. The hips begin to square up, lessening inside half lead. The inside leg switches to adduction before the outside leg switches to abduction
The abductor of the outside leg was never involved. You originally suggested that the adductor is holding the outside ski on edge. We normally think of release as occuring by relaxing the outside leg, or contracting both hamstrings to retract the skis and stop deflection of the CM, or lengthening the inside leg to allow the CM to switch sides through inertia.

Quote:
Originally Posted by bolter
I refer to this phase of movements as REDIRECTION which can be viewed as having two developments. First, a tightening of the turn radius with all of the associated movements to accomplish this (about which I did not go into detail). Second, an opening of the radius by the Lower Body (LB) movements. This is initiated sequentially by the inside leg switching to adduction, then as the UB and LB converge, the outside leg switches to abduction.
I have to assume that the redirection phase is the transition phase -- from turn completion to turn initiation - between the times that the deflection of the CM ceases and begins again. It sounds like it covers both of your other phases.....

It sounds very much like only the a(b/d)duction process is used for edge control. In otherwords, edge angles are controlled by knee angulation.
post #46 of 51
Quote:
Originally Posted by BigE View Post
It sounds very much like only the a(b/d)duction process is used for edge control. In otherwords, edge angles are controlled by knee angulation.
Ok - that is what I thought i was getting.... knee angulation for edging... so I sort of read some bits the same way you did... not feeling quite so bad now...
post #47 of 51
Quote:
Originally Posted by Bolter View Post
No, inside lead persists. Up to the point of turn completion outside leg adduction, outside hip extension, inside leg abduction and inside hip flexion continue. Because the knee movement is lateral and the hip movement is linear, the perpendicular body alignment to the skis is retained. Through knee abduction and hip flexion the inside half of the body controls both skis’ edge angle and the hip’s height to the snow.
The inside ski remains on the snow for turning force, balance and stability. Ankle flexion and leg biceps (hamstring) contraction position the heel under the hip, pressurize the ski and stabilize the core.
Hip movement continues linearly. The outside hip is pushing (extending) in relation to the inside hip which is puling (flexing). This creates a high amount of energy transfer to the outside ski while still keeping pressure on the inside ski.
Gosh Bolton. Because of the loose and/or incomplete use of anatomical terms your posts are very hard to understand. Sorry to have to say that but it is true.

Again it seems you have the terms ad/abduct reversed coming through the turn. Sure in the release the body actions reverse, but to say that certain actions continue until completion means to me that you are using them backwards. you did correctly define them pretty much though in your "definitions" post.

Knees don't ad/abduct either. They only flex and extend. Any lateral movement away from or to the anatomical body midline is just pure and simple hip rotation.

The skis remains in the snow and under the hip because of the recruitment of the hip extenders (six main muscles including the hamstrings, only one of which is the biceps femoris), the knee flexors (seven muscles including all three hamstrings), and the ankle dorsifleors. All this coupled with lateral movements.

Linear hip movement is about as clear as mud to most folks. Flexion and extension are body actions that happen parallel to the sagital plane. Keeping the hips level to the snow is actually a movement parallel to frontal plane which is an ad/abduction. Probably some lateral spine flexion as well. In fact one of the main muscle groups involved in raising a hip (keeping the pelvis parallel to the snow) is the opposite hip abductors. This happens in walking and skiing. Remember, the muscles may contract and the joint move, but depending on which end of the body that is involved with anchoring the move and the position of the joints, the movement can look very different.

With due respect Bolton, if I was in a clinic and someone started talking like this I would raise the BS flagg as we say in our ski school. Which just means that it is time to simplify or move on. Later, RicB.
post #48 of 51
RicB,

Isn't is amazing that all of that is going on, and yet we can just "go ski?"

The good news is that we don't need to know all of that to ski. We may need to know some of it to help another skier overcome weaknesses or a specific hitch in her giddyup... But, even at that we really don't need to address those things.

Using words without demonstrative movements is certainly a limiting factor!
post #49 of 51
Bolter,

I enjoy a good techno-babble thread as much as anyone (and more than most) but it's pretty hard to follow the myriad of spaghetti noodles that seem to be evolving here.

Normally, we take an idea and peck away at its basic premise - to increasing degrees of detail until we get down to the electron clouds that are actually holding us up on the snow .

Kinda fun sometimes, but in this thread you've flooded us with so many branches of discussion and so many of your own custom terms that it's hard to remember what we're talking about let alone focus on anything.

I think the core of the problem may be a desire on your part to incrementally publish your manual here(?). If so, I suggest you put it somewhere on the Web and Link to it in the kickoff post of a new thread. That way we could see the whole thing (or parts you wish to reveal) and discuss ideas/topics point by point after getting familiar with your material in context.

I don't mind discussing minutia and techno-babble with people but I've no desire for a conversation with a book. In a way that's kinda what's going on here. People are responding to you with in-the-moment conversational discussion but you're responding to them primarily with gobs of disconnected technical-manual clippings.

It's why I decided to drop out of this thread. I've no desire to ask a question and have a respondent dump five technical-manual pages on me to wade thru - as an answer.

There may be some good information in those pages, but I'm more interested in thoughful in-the-moment conceptual discussions.

.ma
post #50 of 51
Thread Starter 
Simplicity or complexity... neither is self-evident, nor is one more appropriate than the other.
I will discontinue posting for awhile to assimilate. Thank you for your feedback. No matter what it would be a shame to ignore the info that I shared on this forum, there is something in there for everyone. Have a great ski season. Bolter (or is it Bolton)
Gee RickB, thanks for the nomination, I have to decline. Being the US Representative to the UN and posting on Epic Ski may have some parallel difficulties but both are worthwile (maybe).
post #51 of 51
Quote:
Originally Posted by Bolter View Post
Simplicity or complexity... neither is self-evident, nor is one more appropriate than the other.
I will discontinue posting for awhile to assimilate. Thank you for your feedback. No matter what it would be a shame to ignore the info that I shared on this forum, there is something in there for everyone. Have a great ski season. Bolter (or is it Bolton)
Gee RickB, thanks for the nomination, I have to decline. Being the US Representative to the UN and posting on Epic Ski may have some parallel difficulties but both are worthwile (maybe).
Sorry I got your name wrong Bolter. I was always struck by a phrase that Horst Abraham said on another forum in another place in time, "the simple side of complexity". Which has been my goal ever since. Don't know that I'm there yet or that I will ever be there yet. What I do know is that when I'm having trouble getting understanding of the things I'm saying, I try changing how I present it, or I simplify how I present it.

I don't think there is anyone in my locker room that hasn't had the BS flag raised on them. Including our examiners, technical director, or lead clinician. Usually we just ski some more and then try a different way of communicating the idea(s). If an idea has value then it is worth pursuing different choices in communicating them. Later, RicB.
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