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Balance - Page 7

post #181 of 318
Also, I don't know if walking is as tangible an analogy as pedaling would be. The hardest sell with students is their perception that dealing with stronger forces must mean exerting more force. It is counter-intuitive to think that trying hard might be counter-productive.
post #182 of 318
DM said: You start the movement into the fall line by relaxing the outside leg. But the forces required to power up your uphill leg so it is transformed into a stable base of support (it isn't at the this stage) are not sufficient in this environment. So you have to create the necessary forces by extending first on the uphill leg and then extending on both legs. When you do this you launch baby. And you don't just launch into the fall line either. You launch UP and into the fall line.

Are you sure you want to emphasize the extension of the uphill/inside leg (soon to become the new outside leg) to that extent? Why all that effort to step up to the inside leg? Why not just let the body fall to the inside of the new turn by releasing the old outside leg. There are plenty of forces on you to pull you that way anyway. Are you trying put the skier back in that eccentric contraction? Do you really need to straighten that new outside leg to achieve that? :
post #183 of 318
Uh-oh. I thought the whole point was to let natural forces do the work, e.g. the reaction force from the ground stands you up for the free fall.
post #184 of 318
I don't do any of those things, I just ski and things happen by themselves.

....Ott
post #185 of 318
Ott

You sound like my youngest son!

Are the young and the old the only ones who are wise?

CalG
post #186 of 318
Nolo said: Uh-oh. I thought the whole point was to let natural forces do the work, e.g. the reaction force from the ground stands you up for the free fall.

Exactly what I would have expected. Maybe David M meant the same.

CalG said: Ott, you sound like my youngest son! Are the young and the old the only ones who are wise?

The old are wise, the young are not. The rest of us think we are wise, but the jury is still out!
post #187 of 318
Quote:
Originally posted by nolo:
The hardest sell with students is their perception that dealing with stronger forces must mean exerting more force. It is counter-intuitive to think that trying hard might be counter-productive.
I sometimes explain that concept in this way: If you were a racer, the forces generated by your turns would increase with increasing speed. Therefore, the maximum speed you could travel through a turn must be limited by your ability to resist those forces (strength). If you are using all your strength to resist the centrifugal force of the turn, what can you do to contol yourself? The only thing that does not require more strength is to relax the outer leg, and allow momentum and gravity to take you out of the turn into the new one.
DM- I understand rebound and powering out of turns, but to me it's just not the same as powering into a turn in a sailboat.

John
post #188 of 318
Pedaling a bike and climbing the stairs are both thing I've used for awhile. But it was a student who first said to me as I was standing making this up and down movement with my hands "it's like climbing a stairs". I imediatly added that to my desriptive phrases.

I don't want to talk for DM, but I think the point is that relaxing the outside leg imediatly tranfers the COG and pressure to the new outside foot. It's the slow and deliberate extention of that leg that fully engages the edge. If there is no extention, if the leg muscle is doing isometric work, then you have to wait for the edge to fully engage because the body is already tipping into the turn. It's not a step up, as the COG is imediately moving away from the new point of contact, and the extention is helping the COG move in that direction, or simply put, the extention is to the side, because of the all forces at work. If you looked at the foot movements by themselves, suspended in the air, you would see the feet pumping up and down. The extention allows the long skelletal posture in the middle of the turn. Long and short, empty and full. How can you have an edge without first establishing contact? and how can you establish effective contact when gravity and centrifigal force are moving your COG away from that contact point. You have to grow your root and initiate from the new contact point, and you need to extnend that new leg from your contact point to achieve this. This is (and I'm on shaky ground here), the centripetal force that makes a turn. Have at it folks! [img]tongue.gif[/img]
post #189 of 318
RicB
Just a short post for now as my PC crashed and I am on my wife's lap top.

You are definitely very much in the right direction here in terms of relaxing the outside leg to get COG moving in the right direction (i.e down the fall line) and transfering COG to the uphill leg. Although the physics are a bit more complex the concept is basically right. I need to get into more detail on the reasons why you need vertical force to load the foot. It has to do with correct activation of the foot's sheet-like ligament, solidfying and reinforcing pronation and moving COP (not COG) to the ball of the big toe.

More later

"Luke. Trust the force. Let the force be with you".
Obi-Wan Kanobi, Director of Skiing for the Jedi Knight's Inter Galactic Ski School speaking to his student Starship Pilot, Luke Skywalker

Good advice.
post #190 of 318
Or as my friend Todd M, of the Winter Park SS puts it:

"Dive into danger, Swoop back to safety"...

:
post #191 of 318
Issues relating to a Conducive Environment

“The human lower limbs are one of the most sophisticated systems ever to have arisen from evolution”.
(Can’t recall the source. I have a lot of reference books.)

“Gait (walking and running) is the most common of human movements. Although we usually take it for granted it is one of the most complex and totally integrated movements. It has been described and analyzed more than any other total movement, and scores of laboratories are dedicated to the assessment of gait both normal and pathological”
The Biomechanics of Motor Control of Human Gait: Normal, Elderly and Pathological (2nd edition, 1991) – David A. Winter (past president of the Canadian Medical and Biological Engineering Society).

Winter on recalling our experience as a child before we could walk:
“We see others walking, see what they can do with their walking, what we can not do, and we want to do it too. So, lying on our back or face is not enough. We struggle to crawl – then we crawl everywhere we can”.

Remember this? How soon we forget how long and hard we struggled just to get upright.

I disagree with Winter on one point: skiing is one of the most complex and integrated total movements. It is far more complicated than walking. And as we have learned through experience we do not need a ‘Body Owner’s Manual’ to walk. However, we do need such a manual to ski as easily as we eventually learned to walk. In skiing as in walking we have to crawl first.

Why the strong extension?
There’s a reflex in the body called the ‘inhibitory reflex’. It’s job is to prevent you from doing certain things until it has confirmed that the system responsible for performing the action is ready and especially, to ensure the resulting action is safe. In golf it takes 30 horsepower (yes 30 HP, not 3!) to accelerate a driver from zero to 100 mph! The available horsepower in the arms doesn’t even come close to meeting this. Where do you find such power? In the trunk, especially in the abdominals. The speed at which the spine can rotate is directly related to club speed at ball contact. More is obviously better. If the spine is not adequately stabilized by muscles the inhibitory reflex will limit the speed that the golfer can rotate the spine.

“Screw this” you say. “I will just try to rotate faster and override the dam reflex”. This doesn’t work because the body is smarter than you are. If you try to do stupid things in some situations the body will intervene and stop you. Trying harder will only result in you flailing with the arms. The only way to change this is to give the body what it needs. You have to increase the stability of your spine before it will let you rotate it faster.

A similar situation exists with regards to your feet.

In order to come up to power-up to a stable base of support the aches of the feet need to acquire both tension and stability against an opposing ground reaction force (GRF). The normal tensioning sequence starts in the adaptive state. The lead leg switches from the unloaded state to the adaptive state when the outer aspect of the heel contacts the ground. This is followed by contact of the outer or lateral aspect of the foot and, lastly, contact with the transverse aspect of the foot (i.e. across the balls of the foot from the small toe to the big toe).

At the initial contact of the heel COG pushes the foot forward into contact of the outer aspect of the foot with the ground. As COG comes over the top of the ankle (big ‘IF’ in skiing as in “if it can”) COG squashes (compresses) the arch vertically against the ground force. This tensions the arch triad and drives COP to the ball of the big toe (as far inside as it can get) in preparation for what? In preparation for the old support leg left behind to swing past the new support foot. When it does the body has to be able to push away from the swing foot in order to not fall towards it as it comes by (Newton again – “for every action….”.

What muscles does the body use? Since the foot is pronating, the sole of the foot is turning away from the center of the body in eversion. Eversion is opposed by inverter muscles acting in…… ? You got it. Eccentric contraction. In the above process COP does not run down the center of the foot. Instead it runs along the outer aspect then arcs across the forefoot to the ball of the big toe. This latter effect which is critical to a stable base of support on which to resist the external forces is traditionally thought of as ‘edge control’.

What else should be happening as the arches of the foot are being tensioned?
The heel bone is angling inward on a vertical axis, rotating inward about its contact point with the ground on a horizontal axis and dropping on its toe end. This process is accompanied by the ankle side of the metatarsals rotating on a horizontal axis towards the inner aspect of the foot. Concurrently, on the toe end the metatarsals are spreading like a fan opening. The foot is also getting longer and the top of the arch is dropping. One last thing. The foot is pronating. So the tibia is rotating (with the knee) into the center of the body (medial or internal rotation).

While all this is taking place the foot is still in the adaptive state. The supportive state is on standby awaiting confirmation by the inhibitory reflex that “the Eagle has landed”; i.e. that the foot is capable of supporting the body. How does it know when the foot is ready? The foot is ready to support the body when all 3 arches of the foot have found solid opposing resistance from the ground and the reflex is confident the application of force by COG will not destabilize the foot. Here we make one huge erroneous assumption; our ski boots, bindings and skis are the ground. Not according to Newton. Equipment is a quasi-ground. We still have to get to the snow to connect to the ground.

Getting to the ground drives the requirement for a ‘conducive environment’ that let’s your foot function. Here the present situation would be laughable, even hysterical if it were not so patently absurd. While experts wax poetically on the importance of balance out of one side of their mouth they simultaneously preach confinement and even complete immobilization of the entire foot and leg in the name of improved balance out of the other side. This a bad joke right? Not at all. These guys are dead serious. One has to wonder what planet they have come from.

About a conducive environment. It is an environment where all the described actions must be able to occur without interference that would significantly impede them. What kind of things? Adequate width in the shell for the forefoot for starters. And adequate room for the midfoot to move inward and the heel bone to roll inward on its axis. If the inhibitory reflex detects that even one of the myriad of required actions is impeded it puts the supportive state on hold. As far it is concerned the foot is still adapting to the terrain. It is still seeking contact with the ground. It will not be ready support COG until it has satisfied the inhibitory. The message you get is “sorry, you have to try again.”

“ Screw this” you say. I am going for it anyway. Your prerogative. Flail away baby! [img]tongue.gif[/img]

TBC
post #192 of 318
Very interesting, DM. I'm enjoying the tutorial very much. I have a question on the last reading:

How do we connect with solid ground in deep snow?
post #193 of 318
Up is a relative thing. For me when you add the other forces involved in sking and their effect on the body, and we allow our body to read them like simple gravity on a flat plane, up from the contact point becomes away from the contact point, relative to "all" the forces working together. Really slow speed turns will show more "Up" of the COG, but for really high speed dynamic turns, up is a different direction from whats needed to move the COG in the direction of the new turn and away from the contact point.

Your foot and lower leg mechanics make sense to me, but there may be more than one way to have them integrate into our skiing. We can say being barefoot is the best way to be rooted into our contact point, but how many of us go through the day barefoot? Depending on the task at hand we choose our footwear. If we are doing something that will put excess force on our foot we opt for more support. I worked construction all my life. I never wore the same footwear doing trim as I did if I was stacking a log house. The loads placed on my foot moving and lifting the logs would quickly wear out my foot if my choice of footwear didn't offer enough support to my foot. This light weight boot allowed plenty of foot and ankle movement but had a limit to these movements that allowed some support. How my foot feels at the end of the day is directly related to how effective I was at choosing my footwear. So ski boots are they perfect? No. Footbeds are they perfect? No. They are a compromise to achieve a desired result. We can't just stand on our skis. We need a physical connection between our skis and our foot. So what did you do to create an enviroment that was conducive to balance, and I will now add, that still allowed an effective connection to our skis? What changes to the equipment were made?

I ski a softer boot than I used too. It has a progesive flex, meaning it starts soft, and smoothly and prgressively gets harder. This allows much greater range of motion in the ankle. But they are still stiff lateraly. This allows a solid connection to my ski edge. My footbeds intimately support my foot to reduce the stress placed on it by the forces of skiing (my old footbeds always find a home in other shoes and boots). They reduce the movement of my foot in a way that reduces the stress that causes my foot to feel wornout at the end of the day. What science did your experiments find that conclude that our ski boots and footbeds are illconieved? And what changes did your science prove are nessasary to achieve an enviroment conducive to balance?

Yes, what about powder? My take is that when the surface becomes soft we root by directing our energy down our structure and through our foot. The difference as I see it is that our POC of the ski stays in the middle of the ski as opposed to at the edge of the ski. As has been said before, we ski on the bottom as opposed the edge. How this affects the mechanics of the foot is a good question?

DM, I don't know that I'm seeing the same path as you. Help me see it. [img]smile.gif[/img]
post #194 of 318
TomB
["The old are wise, the young are not. The rest of us think we are wise, but the jury is still out! "]

Wisdom, like wealth, may be knowing when you know enough. Thank you for completing the thoughts on "the rest of us".

ALL

Regarding the inhibitory reflex and the requirement for the foot to sense support in three aspects before one can commit to "standing on it".
I have felt this inhibitory reflex many times, and it seems to be "modifiable" by association. That is, if I think, or know there is something around me I do not wish to step in/on, As I contact the slightest irregularity on the floor surface, this reflex will pull the plug on adding additional weight to that foot. Sometimes by subtle rolling of the foot to redirect the transfer of weight, but usually by collapsing the big muscles in the upper leg.

This happens many times playing adult soccer. If I feel that my foot may be stepping on another's, my leg goes weak beneath me in order to prevent an undesirable result by full weight transfer. There is a perfectly good surface there to stand on (someone elses foot but "I" have choosen to reject this option and have so instructed this inhibitory reflex.
And it works faster than I could ever do on my own.

Applied to skiing, I can see the value of foot beds that really fit the foot. A truely comfortable boot fit. The sensation of even support will always be available, only to vary in pressure magnitude. We train this inhibitory reflex to accept the force sensations present as sufficient in anticipation of the real forces that will develop. When traveling over an uneven surface, the support muscles must be in an alerted state ready to accomodate large changes in position and still provide "correct" pressures. The body mass in motion representing a load that may be 1,+/- 1 G at any time.

CalG
post #195 of 318
A couple of quick points as a I am running late.

nolo: OK remember that I said the hard pack is solid like and powder is fluid like. In powder the weight of your body pushes the snow away from you whereas in hard pack you have to cut a platform to stand on. In powder you ski on 2 skis because you need a large flotation base under you. You still develop a platform because you sink into the snow until you compress it under you into a base dense enough to push back. Newton's Laws again.

As to the issue of numbing the inhibitory reflex you are right. This can be done. After a great deal of persistence you can also reprogram the body do function in incredibly stupid and inefficient ways. In a very real sense your are causing it to revert back in the direction of crawling.

Reference is made by RicB to flexing the boot with the ankle. Can anyone tell the group what muscules you use to flex the boot?
post #196 of 318
I was wondering if people find powder skiing harder because their feet in a sense panic during the adaptive phase when they are seeking (and not immediately finding) the base of support to push them into a turn.
post #197 of 318
Now that's an interesting thought, Nolo. One of the things people typically do when they feel that they will lose balance is clench their toes. Highly unproductive, since clenched toes narrow your base of support, making the loss of balance a self fufilling prophecy.
post #198 of 318
Ric raises his hand. Yes Ric? Well I believe the answer is the anterior tibialis, and the soleus. Ric awaits conformation.
post #199 of 318
Nolo

Like the difficulty of making a water start while water skiing behind an underpowered boat.
Or for a whole body test, a water start when sail boarding in light winds.

In each example, the sensations are mushy, and to "get going" requires holding position while adapting to changing pressures.

CalG
post #200 of 318
Nolo, I would agree with you. definetly seems like one of the disorienting factors people experience in powder. Which is why a solid fluid extention and flexion is so critical to powder skiing. Least that's how I see it. A never ending hunt for the platform. we find it, only to realize we can't hold on to it, so we look further "down" the hill for the next one. Because we want that platform so bad and because we find we can't hold on to this platform in this soft medium, this quickly evolvees into us looking for the release with the same enthusiam as the platform, because only through the release do we find our next platform. The only way to keep that platform is to stop. So we have this dance, or courting of the snow. To win without fighting we have to yield, give in to the forces to harness their energy. We quickly find out that to fight is to lose. Absorb the energy only to give it back. empty and full, back and forth, long and short. I always get carried away when my mind goes to powder.
post #201 of 318
Another quick post as my day is crammed full.

Powder skiing. You guys are good!
nolo: Yes, I think the free fall required to compress the snow freaks out the balance system.

Muscles that flex the boot
So far only RicB has been brave enough to jump in to this one.

Like balance everyone keeps saying you need to be strong to flex a stiff boot. Am I to believe no one else has any idea what muscles are involved. How can you increase the strength of the right muscles if you don't know the answer to this question??
:
post #202 of 318
Flexing the boot

Try this.

1. Put your ski boot on (one boot will do) and deep flex it.

2. Sit on a table with the same leg suspended and flex the boot exactly the way you did on the ground.

3. Think about the results.

4. Tell the group which muscle flexed the boot and how it works.

post #203 of 318
RicB
So ski boots are they perfect? No. Footbeds are they perfect? No. They are a compromise to achieve a desired result. We can't just stand on our skis. We need a physical connection between our skis and our foot. So what did you do to create an enviroment that was conducive to balance, and I will now add, that still allowed an effective connection to our skis? What changes to the equipment were made?

DM: Although it may not seem like it I am getting to this issue. Yes, the ski boot has to be the best possible comprimise. Why? Because when challenged by any situation the body will always produce the best possible outcome or solution.
Many years ago I asked myself this and the same questions you are asking.

1st Breakthrough revelation: Skiing does not require all movements of the foot.

Pronation involves rotation of the long axis of the foot and the vertical axis of the ski into the hill.

Supination involves rotation of the same aspects away from the hill.

Which one is essential to skiing?

"Can I have the envelope please?" :
post #204 of 318
I believe dorsiflexion of the ankle involves the dorsiflexors of the anterior leg: tibials anterior, extensor digitorum longus, extensor hullucis longus, and the peroneus tertius.

Like many athletes, good skiers and cyclists tend to have a nicely developed leg muscles, but what sets them apart is the development of the muscles that run along the front outer quadrant of the lower leg.
post #205 of 318
DM: There’s a reflex in the body called the ‘inhibitory reflex’. It’s job is to prevent you from doing certain things until it has confirmed that the system responsible for performing the action is ready and especially, to ensure the resulting action is safe.

TomB: Sorry, but I don't buy it. If in powder one can wait for the snow to compress and eventually provide you with an "adequate" platform (and eventually it does provide an adequate platform because you are turning), then there is no reason for hardpack to be different. In modern skiing cross-under is similar to the retraction one can do in powder. In both cases the feet can wait for a gradual increase in pressure. The strong extension is simply not necessary.

One more thing: your description of the ski turn (and the analogy to walking) makes it really hard to translate it to skiboarding (or inline skating) where two-footed turns are the norm. In other words, the idea of stepping to the uphill ski with a strong extension is replaced by what?

DM: Getting to the ground drives the requirement for a ‘conducive environment’ that let’s your foot function. Here the present situation would be laughable, even hysterical if it were not so patently absurd. While experts wax poetically on the importance of balance out of one side of their mouth they simultaneously preach confinement and even complete immobilization of the entire foot and leg in the name of improved balance out of the other side.

TomB: Now I am really wondering where this is going. Surely you realize that the above mentioned predicament is the necessary evil to control those long skis through imperfect terrain without ripping out your ankles. If you inline skate you probably know that aggressive riders prefer hard shells despite the loss of mobility. It is simply to protect the foot from the twisting forces that can be created by hard landings. Speed skaters don't need that because they never experience such forces. In skiing I would rather give up some mobility (and balance) than the safety of a hard boot. Wouldn't you?

BTW, if there is one thing about me that is different from the average guy, is that I question just about everything. I am not an instructor and I have never taken a ski lesson in my life. But I never let that stop me from being a pain in the gluteus maximus.
post #206 of 318
Both.

Edit: Consider the one-legged skier. Which is more important--the ability to pressure the outside or the inside edge?

[ November 21, 2002, 02:45 PM: Message edited by: nolo ]
post #207 of 318
Quote:
If you inline skate you probably know that aggressive riders prefer hard shells despite the loss of mobility. It is simply to protect the foot from the twisting forces that can be created by hard landings.
if you're talking about agressive skates being laterally stiff, then you're correct. however, with respect to fore/aft stiffness, aggressive skaters (like me) typically want a pretty soft flex to facilitate the ankle movements required by jumping and grinding. same thing for "aggressive skiing", i.e. newschool, freestyle etc. - softer flexing boots are generally preferred.
post #208 of 318
TomB. I didn't feel like wading through 9 pages of this right now. I will later so that I can get more out of this. But I have a question for you (and feel free to retort, anyone, I'm just exploring a little).

You stated that the cross under situation in powder is similar to the same situation on hard pack. That there should be no difference. My stand would be that although the movement might be similar or even identical, but the application is totally different. Tom, would you think that our POSITION, with relation to the hill, in both instances is identical? I only want to talk about this because I'm Curious George right now.

On hard-pack, we tend to build up "gravity" forces throughout the turn. The best way to monitor these and control speed is to make a round turn, where we finish with our skis facing across the hill. Now when we cross under, our center is projected Down hill, or toward the path of our next turn, whichever applies.

In powder, our skis will tend to "float" a little and "look" for a plane of existence that is more level than the pitch we are skiing on. The platform you were discussing isn't at the same degree of pitch as the mountainside.

Also, the platform we build when skiing powder can only give back to us what is put into it. Try straight-lining through the pow and let the skis find level... now bounce once. Your "platform" has just disintigrated and changed for an instant. It's not a constant. Groomed hard-pack, on the other hand, is much more reliable. A skier can put everything they've got into the snow and it will simply give it all back, with more where that came from. It's surface can be counted on and trusted, and the skis will glide across the same pitch as the mountainside.

So our tactic in powder, as opposed to hardpack, changes from speed control via edging and turn shape to speed control via pressure control and turn shape. When cross-under happens, we can move more intuitively... not so much downhill, while simultaneous with a deliberate rotation of the legs. Because I'm standing more upright, and not relying so much on edging movements, it's really closer to doing low-level, skidded parallel turns than it is to carving on groomers. I realize you never mentioned carving, but there is a difference between high end Pow skiing and high-end Cord trenching.

All the elements are still there, but the blend and intent of those elements are only barely related.

2 cents,
Spag :

[ November 21, 2002, 07:57 PM: Message edited by: Notorious Spag ]
post #209 of 318
Good on you Spag!!

I got into this forum to stimulate intelligent views from intelligent people who want to ski intelligently. So far my intent has found platinum.

PS: I am not sure where TomB got my comments on powder skiing. What I said, while not extensive as your description, was aligned with your views on platforms, etc. I have no conflict with your entire dialogue. [img]graemlins/thumbsup.gif[/img] [img]graemlins/thumbsup.gif[/img]
post #210 of 318
Nolo: I believe dorsiflexion of the ankle involves the dorsiflexors of the anterior leg: tibials anterior, extensor digitorum longus, extensor hullucis longus, and the peroneus tertius.
DM: True. The kind of involvement depends on whether the lower limbs are weight bearing or unloaded. Can you please describe both types of muscle action that dorsiflexes the ankle for us.

nolo: Like many athletes, good skiers and cyclists tend to have a nicely developed leg muscles, but what sets them apart is the development of the muscles that run along the front outer quadrant of the lower leg.
DM: I assume you mean the peroneus longus.

Has anyone done the flex test with the ski boot yet? If so can you please post the results.
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