Saturday, February 11, 2012

Henri - First Morning

Initial Assessment
Herni has a little experience of skiing but has only been taught ineffective standard concepts. Henri's stance was comfortable and generally perpendicular with the mountain and not relying on his ski boots for support - showing that he had no negative issues regarding dealing with accelerations. The weighting of the outside ski in the turn was causing him to try to move the Centre of Mass in the wrong direction (correct direction as far as his previous teachers were concerned.) This would cause him to skid sideways at speed and to worry about catching the inside ski on something. In addition he was tensing his feet and pushing against the outside sidewall of the boot in order to throw his skis sideways - effectively standing on the wrong edge of his support foot. The overall effect was to make him rapidly very physically tired.

Mont Blanc in the background.

The video shows Henri skiing first of all without changing anything - then with some tentative dynamics added (in the right direction) and finally with some skating step turns.


Dynamics
The session began immediately with an explanation of dynamics and a few standard static exercises. Herni was given an explanation of statics and dynamics - separate branches of mechanics. Standing statically the way to get the weight over any foot is to move the centre of mass above the foot. This is how "pressurising" the ski or "transferring weight" is normally taught in skiing - but it is wrong. Henri pushed against my shoulder with his shoulder to the right so that he could feel pressure on his left foot - then he accelerated his body across a gap (on the right) - against my shoulder so that he could feel the pressure from the acceleration and then sustain it when against me. My body just substitutes the forces from sustained angular accelerations provided by the ski once moving forward. Repeating the exercise slowly moving to the right to bridge the gap Henri could feel the weight then going onto the right foot as the centre of mass passed above it. This difference in effect between static (or constant) motion and acceleration has to be understood very clearly. Skiing requires us to work with accelerations. After a few exercises using dynamics when sliding diagonally downhill and creating turns uphill to stop, we rapidly moved into complete turns and then linked them together. I explained the mechanics with crude reference to Newton's laws - more information on which can be found by searching within the pages of the blog.

Henri immediately felt much less tiredness and stress on his legs than he normally felt when turning. The dynamics were allowing his body to function more efficiently already.

The Feet
Henri mentioned that his feet were very tense - from a grasping action inside the ski boots. We went indoors to work with the feet and stance correctly. I removed both boots so that my feet could be seen but Henri only needed to remove one. I showed how standing on the whole foot can lead to a collapsing of the ankle during flexion and a vulnerable twisting of the knees from side to side if they were forced sideways. The simplest way to make the feet and ankles strong is to stand on the heels and then flex only the knees and hips. This activates the anterior tibialis muscle in front of the shin and makes the ankle strong and supportive. Many people lean on the ski boot for support but this is wrong - the leg only should support you - the boot is only to help you to maintain your stance and push you back into place. Henri was shown how the subtaler joint beneath the ankle permits the foot to be rocked - and how this is accessed by standing on the heel. Holding the toes up also helps to counter the tendency to curl them downwards in a grasping/grabbing action. Rocking both feet to the right the centre of mass also displaces to the right - connecting the centre of mass to the feet - the feet also represent the edges of the skis. The leg of the foot on it's inside edge experiences a tightening of the adductor muscles (skating muscles) on the inside of the leg. Going outdoors we immediately employed the rocking of the feet on a gentle gradient. Herni had no problem integrating the action of the feet.

Combing the Feet and Dynamics
Next stage was to combine the rocking of the feet inside the ski boots, with the dynamics - all working towards the centre of the turn. This was tricky for Henri as he has already developed the habit of doing the opposite of all of those things. I explained how it is a natural emotional response to want to stay upright and to throw the skis outwards - an inappropriate emotional response unfortunately reinforced by his original teaching. Additionally this tendency is reinforced by the illusion of "centrifugal" force throwing you out of the turn  - a force which simply does not exist. Henri now had to make himself challenge all of those things and work in a very counter intuitive manner instead. Everything moves "inwards" towards the centre. While most people are desperately trying to remain upright on skis the aim of the skier should be to fall over - laterally. Bicycles work on the same principle - when the centre of mass falls over the bike responds by changing shape and undercutting the trajectory to bring the cyclist back up. Skis do the same. Bikes lose grip when they go over too far - but a skier's grip increases exponentially as the edges bite. The real problem for a skier is increasing the range of falling because the skis are so powerful that the prevent the skier from getting very far over. In essence the skier's job is to fall over and the ski's job is to bring the skier back upright. The ski is the stronger partner - much to the complete surprise of most people.

Skating
Henri was able to skate correctly so we worked a little at being able to skate across a hill - getting onto both uphill edges. It was a bit tough for Henri to start turns with a skate - except on very flat terrain - but this is normal to begin with. We progressively worked downwards from three skates to two and eventually one during the turn. The aim is to move the centre of mass always inwards and to develop the use of the skating muscles and independence of the legs. Skiing is essentially a one legged activity. Henri has previously learned to rush the start of his turns to get the skis around and below him - this being completely inappropriate. It's hard to switch from that to skating and taking time over the start of a turn. Eventually speed should be controlled through choice of "line" and direction - not through braking. Completing any single turn leads ultimately to a stop.

Timing
Skating has a rhythm and timing. The rhythm is obviously leg to leg - but less obviously this has to be made to last longer on each leg to come into resonance with the skis. Dynamics - itself generates timing. Picture a motorbike dropping down into a turn and coming back up out of it  - the centre of mass goes down and up - it has to. Skiing is exactly the same in this respect and the connecting of turns creates a stabilising rhythm. Slalom courses are set out to specific rules so that rhythms are maintained and broken to strictly determined patterns.

Combining Skating with Dynamics
Henry was able to start to identify the sense of rhythm and timing from combining the skating with dynamics - falling actively to the inside of each skating stride. This is hard to do at first but we worked up to it progressively. I asked Henri to skate aggressively and in an accelerating manner directly downhill (shallow gradient) and then to do one turn to stop with dynamics. Skating aggressively was necessary to prevent the tendency to unconsciously go defensive and push the tail of the ski outwards in a braking action. Eventually Henri was able to stay with the skating and dynamics together well enough to feel the rhythm.

Pivot
To finish with we started to look at pivoting from the uphill edge of the uphill ski. I wanted Henri to realise that inside edge - from snowplough to racing - was NOT what skiing is all about. I supported Henri through his first pivot and then he straight away learned to use pole support - lifting his lower ski off the ground and and using the pole planed directly downhill from his heels to support his weight and prevent the ski from flipping onto the inside edge too soon. This is difficult because it requires pulling the ski sideways with the adductor muscles into the turn - and this is the opposite of pushing it outwards - which Henri is used to doing. I demonstrated to Henri the effectiveness of this sort of pivot and he was able to see the difference between this and "pushing out". Henri was shown how to use the lateral support of the boot to stand on his uphill ski on the uphill edge and let the foot inside the boot rock onto its inside edge - without the ski changing edge. This allows the adductor muscles to work and for the ski to slip into the turn more easily. This type of turning is how bumps, couloirs and any direct fall line skiing are all tackled - keeping the skis below the body on the mountain at all times for security and always skiing on uphill edges. The moment of edge change is when the skis are facing straight downhill.  In racing and turning on the inside edge the moment of edge change is during the turn transition when the skis are more or less across the hill.




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