- Snowplough (Centre of Mass)
- Dynamics 1 – Being Out of Balance – to Be in Control
- Combining Dynamics and Snowplough
- Everting the Feet
- Skating/Adductors
Snowplough (Centre of Mass)
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 -and if there is some speed then control becomes dependent on the turn shape and increased dynamics.)
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 of 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.
(There’s a tendency for habitual snowploughers to always push out the tail of the uphill ski to get it pointing downhill at the front. Better to push the tail of the downhill ski toward the upcoming turn centre, thus pulling the Centre of Mass that direction. This also reinforces the braking/pivoting action of that downhill ski.)
Combining Dynamics and Snowplough
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 (narrow) Snowplough using dynamics requires the adductors of both legs to be engaged and now the “deflection” (turning in an arc) 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.
Dynamics 2 (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.
Model photos showing unambiguous dynamics…
Everting the Feet
When the skis are parallel the feet still “diverge” (as if skating) inside the ski boot – each foot being turned outward (everted). This obviously isn’t visible. This is to combat the tendency to twist the foot inwards to”turn” the ski directly -a mistake which flattens the ski and causes loss of grip.
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