- Skating
- Snowplough
- Basic Dynamics
- Combining Snowplough with Dynamics
- Side Slipping
Skating/Adductors
Skiing is just disguised skating. The main difference is the skis are wide and have two edges. When diverging the skis outwards at the tips into a skating stance the skis want to flatten on the snow and the stiff shaft of the ski boots will pull the knees outward. The adductor muscles need to be engaged to hold the skis on their inside edges. This is a pattern of muscle use – the adductors of both legs contracting – that should be maintained when skiing parallel. This is partly dependent on the skier’s morphology. If the femurs are naturally directed inwards less adductor use might be appropriate but if slightly bow legged there may be a need to consciously work the adductors.
Only when snowplough braking should the adductors be released to widen the spreading of the tails of the skis from the hip joints.
The other difference between skis and skates: – it’s just that skis bend and scribe arcs on the ground and are generally used on slopes not flat lakes. Skating actions are fundamental for a skier’s development because they involve independent leg action where only one leg at a time is really used. Although skiers can stand on two feet the body is oriented specifically on one hip joint at a time (when turning) and has to function as if standing on one leg. Skating exercises such as skating step turns are helpful in developing basic skills. Skating turns use diverging skis (opposite from snowplough) and incremental stepping of the centre of mass inward toward the turn centre. This is ideally the first sort of turning that any complete beginner should experience – on flat terrain.
Snowplough (Centre of Mass)
The braking snowplough requires the adductors of both legs to be relaxed to open up the hip joints.
First turns are made by simply tightening the adductors in one leg only – to turn left it’s in the right leg. With narrower ploughs then the adductors of both legs should be engaged.
Weight is always maintained on whatever ski is furthest down the mountain so that it can act as an effective brake. Changes of pressure on any ski are due to geometrical effects between the skis and the slope angle – not “transfer of weight”.
Starting a turn when traversing the slope in a plough requires only a slight movement of the Centre of Mass toward the downhill ski. This ski then slowly feeds the skier into a controlled turn. When facing directly down the fall line, the body being held constantly toward the inside ski in the turn, ensures the outside ski can takeover the completion of the turn. The pressure changes on the skis are automatic – just move the Centre of Mass toward the centre of the intended turn and keep it there from start to finish.
Basic Dynamics (skis parallel)
- Skis must be travelling forward – like a bicycle
- This is mainly about using the outside leg (start of new turn) to push the centre of mass into the centre of the new turn – for the whole duration of the turn
- There is no “balance” when skiing – dynamics is the physics of disequilibrium
- You are looking for stability from organised accelerations (ski technology!)
- Notice in the photos below the outside leg is essentially straight in a skating action (flexion for absorption and other purposes is primarily at the hip joint)
- The centre of mass goes down toward the snow – and to complete the turn it comes back up – like a motorbike in a turn
- There is no “Centrifugal Force” acting on the skier – only a deflection inward away from a straight line. This deflection is used to lift the skier up at the end of the turn – which involves “finishing” the turn – I.E. turning almost back up the hill.
- Remain square to the skis (follow the skis around the turn with your body) until you are really comfortable with movement of the centre of mass and clearly aware of moving it.
Combining Snowplough with Dynamics
Dynamics is explained in terms of the mechanics of accelerations. (F=mA Newton’s 2nd Law). In skiing this means you move your centre of mass (either falling or with a push) in the direction you want to turn. You do not transfer your weight to the outside ski as is incorrectly taught in ski schools.
In the Snowplough using dynamics requires the adductors of both legs to be engaged and now the “deflection” is carried out by moving the Centre of Mass (CoM) across the skis in the direction of turning. The displacement of the CoM affects the geometry of both skis with respect to the slope (one goes flatter and the other more on edge) and that’s where the deflection comes from.
On steeper terrain the downhill ski (inside ski of the turn) takes the weight of the body and is used as a brake – pivoting slowly into the turn – until half way through the weight shifts by itself to the outside ski which is now able to take over the continued braking effect.
Side Slipping (Centre of Mass)
The main practical purpose of sideslipping is to get down the mountain without picking up speed. Many learners are deprived of this skill because it is generally undervalued and has become even more neglected due to the complete domination of carving skis. Wider skis are easier for sideslipping in a greater range of conditions. Parabolic skis have some trouble gripping on ice during a sideslip, but modern “double rocker” off-piste skis give a smooth and grippy sideslip in just about every condition, including ice.
The skis are kept on edge by the lateral stiffness of the ski boot shafts. Skis over 100mm wide underfoot begin to create problems on hard snow due to the extra leverage from the edge through the shaft of the boot. Those skis can be very unpleasant on-piste and it’s one limit of how an “all round” ski can be defined. Anything wider than 100mm is not “all round”. In ski teaching the sideslip serves specifically for developing fall-line skiing. Fall-line skiing is where the skier’s body travels directly downhill and not across the hill. This would apply to bumps, steep off-piste such as couloirs and deep powder snow. Slalom is not “fall-line” skiing. The skier should be able to sideslip on either ski or both at the same time. It’s normal to start off with both skis on the snow, skis parallel and with the majority of weight on the lower ski just to get a feel for it. The stance is normally quite narrow to prevent the uphill ski from catching the lower edge. Most beginners have trouble keeping the skis close together.
It should be noticed that only the uphill edges of the skis are in contact with the snow so the downhill edges are in the air. If the fronts of the skis are pushed downhill (Joystick Control – moving the Centre of Mass forward) then there will be no resistance from the downhill edges and so the skier goes into a forward diagonal sideslip. Likewise if the tails are pushed downwards during the sideslip then it turns into a backwards diagonal sideslip. Being able to alternate between straight down the fall-line and the two diagonals is a precursor to the skill necessary for pivoting in the fall-line. Both legs need to squeeze the adductor muscles together – holding the upper legs close together. Pulling both legs together keeps a narrow stance and when the skier practices sideslipping on one leg it ensures the that the geometry of the edge angles to the slope are optimum for pivoting.