Friday, March 2, 2012

Centre of Everything

Oh well - a week lost to the flu! Guess it could have been a lot worse.

Rowdy was finally back on top of health issues and back to working on his skiing. On the positive side - despite the gap of three years or more there was a proper sense of continuation and no apparent loss of capacity. 

The Rowdy Paradox
Rowdy is a real paradox to work with because almost every new exercise appears to really sort out the skiing - then afterwards the same old quirks just return again. Skiing is a holistic activity so this complicates things further as the overall motion that emerges is the result of many integrated factors all influencing each other.

Listing the main quirks (flowing turns - not fall-line skiing)
1 - Sink down and pole plant at the end of a flowing turn
2 - Up motion into the new turn
3 - Extra down motion in preparation for the turn completion
4 - Letting the body rotate at the end of the turn and the weight come back onto the heels.
5 - Letting the upper body remain in the vertical unintentionally as the skis plunge downhill
6 - Pushing the body systematically  uphill instead of out into the perpendicular at the turn completion
7 - Pushing feet outwards in the pivot
8 - Inconsistent fore/aft control - sometimes too far forward or too far back

Why should these tendencies persist despite many exercises to prevent them? It appears to me that the common link here is Centre of  Mass (CoM). The most important thing in skiing is the CoM and it should be used to control everything else. All of the extra or unwanted movements are at the turn transitions and they all interfere with the motion of the CoM - blocking either the exit from one turn or the entry to the next.


Centre of Everything
The point here is that while all of the individual actions are trained so that they support the motion of the CoM - it must not be forgotten that skier integrates everything by simply focusing on moving the CoM. The intention has to be to move the CoM - down and into a turn and then back up out of it - like a motorbike - but with rhythm and flow from turn to turn. While the actions of the limbs are part of this (they are part of the body mass) they should not become individually more significant than the overall pattern of motion of the CoM.

Rowdy tries to set a platform between turns or to gain security from a strong up motion. What doesn't happen is the flow of the CoM down towards the snow at the start of the turn. It's the smooth  - mindful - passage of the CoM out of one turn or traverse and across the skis into the next turn that counts. This can be done with weight on any ski and body in any orientation and it will still be absent of all of the quirks listed above. You just have to stand on the leg that can support you best as the CoM moves naturally - nothing more - the skis actually do the rest.

The CoM is an both an abstract concept and a physical reality. It's abstract in the sense that it is used when calculating with Newtonian forces to simplify entire objects down to a single point representation. On the other hand it is a real thing because we can feel it and physically exploit it. Gymnasts spin and roll precisely around the centre of mass - they have to. All athletes exploit this either consciously or otherwise. The skier has to orientate all activity around this centre. Initially, during training all of the coordination being developed is "disconnected" - rock the foot, place the hip, tilt the pelvis, push the foot forwards etc. It's easy to lose sight of that fact that all of those are only supporting skills to help to move the CoM more effectively. The "conductor" of the orchestra should be the CoM itself - with everything esle trained to happen automatically in support.

When Rowdy is focused on completeing a flowing turn with good dynamics - bringing the CoM directly perpendicular to his skis - he then manages to block the drop of the CoM both downwards and forwards into the next turn. If he gets the "downwards" timing correct then he loses the forwards part - adjusting to the change in pitch and acceleration at the start of the turn. This could be linked to his motorcycling. Going into any turn on a motorbike generates a deceleration - but in skiing it's the opposite, there is an acceleration that must be anticipated actively with the CoM.

When Rowdy is focused on the start of the turn he gets the end/preparation phase muddled - it turns into a "platform" event often including an upper body rotation and a stem of the lower ski, extra downsink of the body, inappropriate pole planting, getting back on the heels etc.

The turn transition has to be seen as a single uncluttered event where the CoM passes across the skis. Visually - looking dowwards perpendicularly at the snow - the skis should appear to move from one side of your field of vision to the other. You have to realte to the mountain in the perpendicular and not the vertical.

Our natural state in outer-space is "free float".  On Earth that does not change - we are still in "free float" except that our motion is being blocked by the "elastic" force of the ground. Correspondingly all we feel is this force beneath our feet - it's the only feedback that we have. Placing ourselves on a slope and removing friction then we return partially to "free float". This effect can be interpreted as components of gravity - one component converting into downhill acceleration and the other perpendicular to the slope. The effect is that you still feel "elastic" force under your feet - perpendicular to the ground - but at a level reduced in proportion to the steepness of the slope. The feeling however is exactly the same in every way to standing on flat ground - only reduced in strength. The point is that the only thing we feel - and feel consistently - is pressure through the feet. Our primary sensory perception then has to be the feet. Directing the CoM successfully depends on being connected with your feet - and how they are connected to the ground. It simplifies everything if you realise that you are effectively NOT on a slope - you are on flat ground - but with some "free float" returned - and the feet should reflect this as if you were on flat ground.


Centre of  Power
Rowdy had ended up with a sore back early on during this trip so we looked straight away at how to deal with that. Recently through bringing ChiRunning technique into both cycling and skiing I'd spotted that coordination for all of the activities has to be changed in a similar way - radically.

The key to this change lies close to the CoM in the spine itself. Normally when a turn is made on skis the body coils up in the counter direction of the turn - so turning clockwise the body coils anti-clockwise from the feet up to the neck. Traditionally most of this "coiling" takes place in the hips - below the pelvis but some takes place up through the mid-section. This actually causes the lower ribs to compress in towards the pelvis. There is a "coiling" of sorts but without activating the core muscles in a protective manner. Often the goal is to keep the upper body as relaxed and tension free as possible - but this "relaxation" inevitably leads to lack of support and protection for the lumbar spine. It's just impossible to protect the back from surprise events.

To change this you have to use a different model. Imagine the shoulders and feet fixed and only the centre of the body able to rotate. It's like twisting a rubber bar in the middle with both ends fixed. There is a tension both above and below the centre. In this case the spine twists in exactly the opposite direction from before - but it is not apparent to the observer. In the photograph at the top of the page Rowdy is doing this actively and gives the impression of a classically angulated skier with a close stance - and the legs in good alignment. The main thing is that the spine is now twisted in the opposite direction and this opens the space between the ribs and the pelvis and tenses the core muscles in the process. This tensing effect then compresses the stomach area producing an "hydraulic sac" effect - distributing the load of any vertical shocks going through the body and also protecting against any shearing loads. The acid test on Rowdy was that despite starting the day almost unable to put on his ski boots there was no more back pain from skiing when working on this new movement.

The "rubber bar" analogy is only partially correct because it's like it's fixed in the middle and the ends are free to move at the start of a turn - then it's fixed at the ends and it's the centre that moves at the end of a turn.

The twist goes all the way up the lower spine right up to the 12th vertebra - the rib cage. This implies that upper/lower body separation is spread from the hip right up to the ribs  - and not isolated in the hips.

There has to be an active search for the twist in the spine. We are so used to blocking with the core and trying to protect it - instead of generating power with it. This can be used to stunning effect in running - as per ChiRunning technique.

Short Turns
For myself, I noticed that in short turns it's necessary to use a pole plant almost in line with the ski, towards the front so as to keep the shoulders more in line with the feet. This makes it possible to separate and isolate the middle of the body. With a more open pole plant the short turns become completely confused with respect to the direction of twist in the spine. The relevance of this in slalom "breakaway" gates is striking. The gates are cleared with the outside arm - following the line of the skis - the hips to the inside. This trains the skier to twist the spine in the correct direction - the direction of the turn - not counter to it.




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