Steering and coiling
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Using an action/reaction framework, a rotation effort of the feet is created against the momentum of the upper body while the countering of the upper body is created against the ski's rotation into the turn, so there is always a certain amount of tension in the feet, to decouple the two rotations: steering and coiling are connected in the middle of the body.
This leads some to say that we're always steering, but that's a matter of the point of view of how separation is created: there is a difference when the "effort" is active (turning the skis) or passive (following a turning ski).
The point below is to analyze the relationship between the two and clarify why we like to see steering as any effort above and beyond that required to maintain/create separation. The simple fact that there is a tension in the legs does not mean we're always steering...
Steering the lower body under the upper body
In an upper body-centric point of view, (i.e. asserting that the upper body does not want to turn: it is stable and anchored in the aether or its own inertia), then we'd need to steer the skis to the left, to turn them "underneath" or simply to allow them to keep turning left in relation with the upper body i.e. separation (whether they skid or not could be the result of your edging skills).
This view is applicable at low speeds and low tipping angles, where the pivoting of the femurs along their long axis is still related to creating separation.
Also, at the end of the turns, when the skis cross under the body, although rotating the femurs now has a completely different effect. There is certain effort to not allow the skis to pivot and unwind, there.
Tipping and counter-action
If we think instead, that the reaction force from the snow causes an edged ski to turn (i.e. using more the ski design), the lower body simply follows the turning ski and then we turn the upper body the other way to create separation (this is counteraction and coiling).
- at low angles, it is easy to tip the skis on edge and balance on them and witness them turn without steering
- at high angles, the rotation of the femurs around their long axis has more to do with tipping and angulation (counterbalancing) than with separation
- actively rotating the skis when the edges are well engaged at higher angles achieves little in the way of steering the ski: since the tips cannot rotate inwards as the edges would dig into the snow, it wants to lift the tails and disengage the skis, but it takes a lot of effort - pressure and angle management is more effective at high angles
In getting from left to right in the photo below, the only movements are tipping (allowed by the femurs rotation along its long axis), more flexing of the inside ski and extending the outside leg:
Range of possibilities
At one end of the scale, of maximum pivoting/steering and separation, we have sheer twisting and pivoting of the skis, to turn them against the upper body.
At the other end, of no pivoting and no separation, we have tipping with skiing square.
Good skiing is in the middle of that range. The more dynamic, the more active the core and pelvis are and you get to pick if you ski from the body down (steer under a stable body) or from the feet up (coiling on top of a turning ski).
Kinetic chain considerations
However, the two approaches result in different turn mechanics and dynamics and a keen eye can pick either bias in one's skiing, given the way big vs small muscle groups are used (or rather in what sequence?).
If we look at the kinetic chain++ activation (the sequence of muscles and joints that we use to move and transmit actions and reactions throughout the body), the brain can activate it:
- top to bottom, i.e. big muscle groups to small muscle groups, i.e. core, hips, knees, feet. Each segment acts on the segment before it, until the movement is effected from one end to the other.
- bottom to top, i.e. feet, knees, hips, core etc
- mixed, in high performance or emergency situations: a highly tuned athlete could activate multiple segments simultaneously, in anticipation
Racers and high performance skiers insist on skiing from the feet up, focusing on establishing a platform or base of support.
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