We started off the session with familiarization with the equipment – cleaning boots, putting one ski on and going around in a circle always falling in toward the side with no ski. We then went onto skating – falling forward and using the adductor muscles to stop the ski flattening. Everyone did well despite nobody having any real skating experience.
All the movements we made were directed towards learning how to move the body (centre of mass) in the direction of a turn.
Video clips
- Natasha – using the inside ski as a solid support and brake. This encourages moving the centre of mass into the turn. It’s all about geometry. Notice there is still very little movement into the new turn.
- Erin – succeeding with dynamics but still tending to be “vertical” on the backs of the skis boots instead of perpendicular to the slope. That makes the skis hard to control.
- Ellie – good dynamics – moving into each turn and perpendicular to the slope.
- Peter – notice the first turn – the body clearly moves to the outside of the turn when a skating impulse on the right leg should have pushed the body into the turn instead. Look at the girls for comparison – they are moving clearly into the centre of each turn.
The following video taken in Tignes in December 2024 shows clearly that skiing is all about moving the centre of mass in the right direction…
The following selection of modules cover the principles that we were working on today – skating, braking snowplough, turning snowplough, modified snowplough (with pivoting inside ski) for Natasha, dynamics for parallel skiing….
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
Dynamics 1 – Being Out of Balance – to Be in Control
When you are making a turn on skis you can feel a force trying to throw you out of the turn – it’s called centrifugal force. You are then told that to make this turn happen you are balancing against this force.
The only snag here is that it’s all an illusion – none of it is real.
Centrifugal force has a few other names – “inertial force”, “pseudo force”, “fictitious force”.
When you, the skier, observe your own turn you are experiencing what’s called a “rotational frame of reference” and it is also confusingly called a “non inertial frame of reference“.
Yes we can calculate centrifugal force – but it’s not real – it’s just mathematics! (The magnitude of the centrifugal force F on an object of mass m at the distance r from the axis of a rotating frame of reference with angular velocity ω is: 
Real forces can be seen from the outside of the system as if you were a drone observing from high above. There’s no force pulling you outwards just a force from the ski deflecting you inwards away from a straight line. This is called an “inertial frame of reference” and it has only real forces – no fictitious “inertial forces”. This real force is called “centripetal force” (inwards – toward the centre) and it is accompanied with an acceleration. The acceleration is a change in velocity (vector) but it’s only a change of direction not speed. Acceleration is the physics of disequilibrium – being out of balance – the official term in mechanics being “dynamics”.
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 Pivot and Snowplough – Lower Ski Stem
Snowplough can provide an important platform for learning how a ski pivots.
While traversing the slope in a snowplough weight must be kept on the downhill ski.
If traversing with skis parallel then a lower ski stem is used in preparation to turn.
(Conventional ski instruction tells us to transfer weight to the uphill ski to start a turn – but that is completely wrong.)
First of all a skier needs to know how to use the plough to generate complete control of speed – and that means NOT transferring weight to the uphill ski. Weight is allowed to always be on whatever ski is further down the mountain. That ski will always be on its uphill edge and so it will act as a supportive brake.
Through the first half of a turn this supporting/braking ski will gradually pivot (sliding sideways) as the plough comes around the turn. Meanwhile the outside ski in the turn requires the adductor muscles to be engaged – so as to shift the body (centre of mass) slightly towards the centre of the turn and edge the outside ski slightly more than the inside ski – to enable a deflection/turning force from the ski. If the skis were parallel before starting the turn then a stemming of the lower ski only (pushing out with the tail) into a plough helps pull the centre of mass in towards the centre of the new turn. Additionally the outside foot of the turn can be pushed forward (Feet Forward Technique) to tighten the turn.
When the plough is pointing directly downhill the outside ski in the turn will take over as being the furthest down the mountain – continue to keep the adductor muscles in that leg engaged until the turn is complete – resisting gravity which now demands extra work of the skier to remain in towards the centre of the turn.
The feet are generally “inverted” when using a braking snowplough as well as having the adductor muscles relaxed – however the first turns a skier should make are with the contraction of the adductor muscle of the outside leg and an “eversion” of the foot inside the ski boot. When the center of mass is well controlled then eventually adductors of both legs can be engaged for the entire turn.
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…
