Bode on Steering

[piggyslayer]

Rusty, ydnar,

Inversion/eversion involves ankle joint and ankle musles as well as metatarsal forefoot area joints and muscles and is involved in passive rotation of femur.

The lateral rotation is originated in hip and actively rotates femur bone.

Here is the list of muscles which create lateral rotation (please note numerous muscles in hip area).

Gluteal Region:
-Piriformis
-superior gemellus
-obturator internus
-inferior gemellus
-obturator externus
-partially gluteus maximus

Anterior Compartment of Thigh
-partially sartorius

Medial Compartment of Thigh
-adductor longus
-adductor magnus

Posterior Compartment of Thigh
-biceps femoris

By contrast here are the muscles involved in inverting the foot. All these end somewhere in the foot mostly in the metatarsal area and FOOT IS WAY BELOW HIP.
I have omitted bunch of muscles which operate toes (but I think nobody will question how high in the kinetic chain they are).

FOOT INVERSION:
Anterior Compartment of the Leg
-tibialis anterior
-extensor hallucis longus

Posterior Compartment of the Leg
-tibialis posterior

Can you be more specific which of the muscles externally rotate your feet?

Robert

[RobertC]

Going back to the first post of this thread, and the link..
What is pitching? It is not a term I have come across.

To me, Bode only says he carves and then skids to control speed. Isn't he only saying he makes sure his skids are in the right direction for the racecourse? I didn't pick up on the steering stuff.

[BigE]

IMHO, and it is just that, an opinion, Erik has performed a move to ensure he skiis the correct line.

He has completed the previous turn, through neutral airborn. Both skis have engaged above the gate. The arc of the inside ski is defining this turn. Even prior to the gate, I see Erik beginning a skating stroke, the apex of the stroke appears as his inside knee strikes the gate.

Look at the amount of tip divergence at this point in the stroke! This is not what carving a turn looks like. It's what skating looks like!

The next frame shows the outside ski in the air, completing the push. He appears to have literally skated onto the inside ski.

If you wish to call that an example of the EWS move, be my guest, the weight has clearly shifted to the uphill LTE, as he has just skated onto it!

In the second last frame, it looks like the inside leg has begun extension, and the outside has touched down for a brief moment. The CM begins to cross over at transition as he sets up the turn.

After he gets the outside leg back underneath, (next to last photo of that in progress) the skaters stride is complete, the pole plant and lightening of the downhill ski starts the new turn.

The slope of the hill also indicates that some skating movements are appropriate to gain speed.

That's my 2 cents. Pretty different view huh?

Edited: Removed reference to inside ski engaging first.

[John Mason]

nice paraphrase - Big E

I think snowdog was right. Most people don't know what the EWS turn really is.

Perhaps it's closer to what you've described as a skating turn.

1. remove pressure from old down hill leg
2. be ready and hold the resulting pressure change on LTE of inside ski
3. this will throw the body into the new turn
4. new turn engages (first turn shows this - bottom turn would show this on the next frame but doesn't in this sequence)

This is the standard SP turn. Skating turn? Hey whatever translates.

[BigE]

The montage is a clear skaters stride.

The EWS turn is far more subtle, and more indicative of what you wrote, but what you wrote is not what is happening on the montage.

10 - old outside ski lifted - moves all weight to the inside about to be outside ski
11 - Because of the removal of support of the outside ski, the body has moved to our right (skiers left) - ski is on snow, but weight still removed (how can we tell?)
12 frame - pole plant, body has continued to cross over the skis proving pressure is still on the new outside foot and removed from the ski closest to the pole plant.

Re: your frame 10: He does not lift the old outside ski to move the weight, he pushes off the old outside ski in frames 8 and 9.

In frame 10 the ski is lifted just to move the leg back after the push, which has max distance in frame 9. If he did not lift it, he'd faceplant.

Frame 11 marks the recovery from the push and shows a delay in the initiation of the next turn, which he coordinates with the pole plant of frame 12.

EWS does not require a skaters stride.

[RobertC]

The moment of inertia of a ski about the vertical axis is way way more than about its longitudinal axis.
Even when standing still, redirecting a ski quickly is imprecise.

[piggyslayer]

Rusty, ydnar:
More on lateral rotation of foot:

I have finally found a good link describing the muscles and corresponding muscle actions:
http://cats.med.uvm.edu/cats_teachingmod/gross_anatomy/lower_extremity/pages/muscles_le.html
As you can see there are many muscles involved in lateral leg rotation, I have listed them in the previous post as well. Skier synergy has a great explanation about foot abilities to rotate in the 'holy grail' thread as well.

The point is that even if there is a small play in the ankle joint allowing its muscles to rotate laterally the foot, there are many muscles up in the kinetic chain, which are involved in this movement as well. Some of them are very large muscles. Skier makes conscious decision to rotate the foot and not to use this and that muscle. All muscles big and small are involved.

One more point which I have tried to make in the ?holy grail? thread but it may not be very clear. Two things typically accompany lateral rotation of the inside foot:

? The outside leg knee rotates inwards and bends laterally inwards. The knee joint is no longer straight.
? The hip rotates inward.

This in turn creates a dominating BTE, it is extremely hard in this position to balance at the same time the outside leg knee joint is far more vulnerable to injury.

So please consider these biomechanical reasoning and reconsider your position on the inside foot ?pointing?. By no means do I want to undermine your expertise as skiers and ski instructors, my only goal is to present some hard to dispute facts that may change your position or give you something to think about. I do not view myself as expert and find SkierSynergy posts having much better biomechanical ground than my posts.

I do see that there is something logical and interesting in your idea of pointing the foot, it would be great if you as well spend some time and thought about what is potentially wrong with this movement.

FYI: I and other Harb Carver users can control the speed very well on steep residential streets. How come? Are we applying rotation to Harb carvers? I do not think so.
It is important that we do not prove that something is not possible defying clear empirical evidence which shows otherwise. Claiming that active rotation is a necessary to slow down is such an attempt.

Thanks, I hope I have changed your position a little bit.

Robert

[skier_j]

Holy smokes Batman!

This thread is gone in more directions than Octopussy has arms!

Yikes. let me summarize.

We have a physiology and kinesthethic (sp) piece about how---precisely---the foot moves.

We have a discussion of Early Waffle Syrup turns goin on err---I mean-----

We have a bunch of folks callin each other names and pointing fingers and going "He said---she said" about what Bode said.

We have folks not attaching credence to anything any one says unless their initials are 2 identical letters.

Have I missed anything of any importance?

Can we have a show of hands to decide just what piece of the pie we'd like to argue about as a group?

It is WAY too hard to think about all these thangs going on at once.

My brain hurts just thinking about it.

[SkierSynergy]

For the next week I am doing a course and testing in biomechanics of the foot. This morning I was going to post some really obvious comments, but most have already been covered.

1. The article quoting Bode said nothing about rotation or leg steering and has nothing to do with it -- RobertC already pointed this out.

2. The movements that Bode describes can be done using the Primary movements in PMTS and do not necessitate any rotation or leg steering to redirect the skis.

3. If he tried to drift as he described with overt upper body rotation, there probably would not be enough fine control and sensitivity to enter and exit the drift consistently fast and in control.

4. The need for this drift move is an artificial artifact of current trends in course setting. The move is only used on certain gates in certain courses.

5. Piggy slayer is so right on in his posts!!!! There is no such thing as rotation originating in the foot or ankle that assists steering. Active rotation of the tibia and/or the femur involve big muscles very high in the leg. Further if you follow the effects of trying to use those muscles to turn the leg into the turn down the kinetic chain, it is very easy to seethat it tends to flatten the ski to the slope and cause skidding in the tail.

6. Inversion and eversion do not need to have any other movements to work. Flexion aids the effects of those movements, but they are not necessary for them to work. Piggy slayer correctly identified the muscle groupps and locations that create those movements. None are high in the Kinetic chain.

Finally, if anyone really wants to counter to PiggySlayer's posts on these issues, meet his challenge. Pick up a kinesiology text, talk to someone with the correect background, take a course, get it together, and describe, in detail, the muscles and joints that are involved in steering that are in the foot/ankle. If that isn't done, then the response has no basis in science or fact.

[skier_j]

Going back to the first post of this thread, and the link..
What is pitching? It is not a term I have come across.

To me, Bode only says he carves and then skids to control speed. Isn't he only saying he makes sure his skids are in the right direction for the racecourse? I didn't pick up on the steering stuff.

At the risk of being attacked by a non-user name folk.

I think you have hit it on the head with the "What Bode said" piece of this thread.

There is no evidence nor discussion in that article to support any conclusion OTHER than this world class skier does not feel the need to carve all turns, in fact my reading suggests he feels that a controlled non-carved turn is essential to getting down most courses.

In my opinion, the article does not suggest that Bode is saying he has to skid on his right foot, it simply states that he has less edge on that foot.

Is that by design? Injury? Genes? Heridity?

My suspicion is that Bode will carve an incredible arc with that right foot----when the situatiuon calls for it.

Your question as to what is "pitching"---my guess is what JM would call weight shift. A CM transition. Taken from the context used, that is my best guess.

[SkierSynergy]

PiggySlayer,

I had a chance to read your post again with a little more time. The main points yyou are maiking are very solid and I still think anyone who responds should do so on the same level. However, there are some some errors in the functions of the muscle groups that you pick out. For example you have included some muscles that are really related to Plantar/Dorsiflexion in your explanation of inversion. They can be involved but they are not the key movers of inversion. Can anyone else pick out any small issues. If you can, then you have done your homework. Again, this in no way negates PiggySlayers main points.

Maybe Harald can post a little on this and provide some references that he believes are good in relatioion to these issues. However, I'll ask that the responses be back on "Holy Grail" along with the other posts related to this issue.

[piggyslayer]

Jay

Thanks for pointing the discrepancies.
I am in the process of learning this stuff, I am searching for good books on this and I think I found some, I will spend some time on them and post the names if I think they very good.
There is a software called Dynamic Human, I wonder if anyone has used it?

My goal was to list ALL possible muscles that can be POTENTIALLY involved in inversion of the foot to prove the point that NONE of them is high in the kinetic chain.
By contrast, ALL muscles I could find which have ANYTHING to do with lateral rotation are way up in the chain.
I wanted to avoid discussions like this: YOU HAVE OMITTED THIS MUSCLE AND IT CAN BE INVOLVED IN THE INVERSION.

In both categories I included some muscles that should not be there if we are talking about strict inversion and lateral rotation, but all of them, I believe, have some role which may be relevant to these movements.

This is sort of mathematical reasoning where you provide UPPER ESTIMATE on the position of foot inversion muscles and LOWER ESTIMATE on the position of lateral rotation muscles in the kinetic chain and show that still UPPER ESTIMATE << LOWER ESTIMATE.

This I think proves that foot inversion is skiing with your feet and foot pointing is skiing with you hip, butt and thigh.

I will be out for next 2 weeks and will not be checking the forum.

AND SORRY FOR POSTING IN THIS THREAD, NO MORE POSTING ON THE SUBJECT HERE, I PROMISE.

Robert

[*skier_j]

Hey Piggyslayer, seems the topic morphed. I doubt there is anything "Off topic" in this thread!