In this type of direction change, the Center of Pressure tends to move vertically closer to the Center of Mass. It is also known as “cross-under,” “compact or flexed transition”, “absorption”, “concentric turning”, or “retraction release”.
The edges are changed by flexing (absorbing by legs’ retraction) and the extension after is performed on the “new” edges.Body oscillation is performed not so much towards the center of the new turn (lateral oscillation) like in the Direction Change by Extension but diagonally.
Here, the strategy to change direction is release-and-engage, this is, releasing the downhill and at the same time engaging the uphill ski while both legs are flexing (absorbing-retracting) simultaneously.
This mode of changing direction is mainly used in short turns, on bumps, deep snow, crud/crust snow, or in any other situation where, due to limited space and time, the curvilinear or linear trajectory must be changed quickly.
Although it is the fastest way to change direction, it tends to a loss of snow contact sensation (skis feel “floating”). Also, there is no economy of muscular effort due to the marked activation of the quadriceps and the location of the pelvis in moderate or marked position towards the tails of the skis in the Generation Phase (falling into a “backseat” position).
Therefore, we can say that it is effective but not efficient, however it results in increased stability, it is effective in tight spaces, and it gets better performance in dense snow.
NOTE: To clarify the designation of each ski/foot/knee/leg/hip/shoulder during a turn, we will define them as “outer” or “inner” when the skis are on or close to the fall line. When the skis are across the fall line, we will assign them as “downhill” or “uphill”. There will also be designations as “inner/uphill” or “outer/downhill” when the skis are between the fall line and across it.
Biomechanical Phases
1. Generation phase
The Center of Pressure (CoP) moves vertically toward the Center of Mass (CoM), generating active absorption of both knees and initiating the edge change, which is completed when the CoM crosses over the Cop.
In this phase, the skier breaks away from the previous curvilinear trajectory to begin a new trajectory in the opposite direction. The generating movement is the simultaneous flexion of both legs.
2. Monopodal Phase
The inner arch of the uphill foot (new standing foot) makes contact with the snow through foot pronation. The new leading foot remains lightly or moderately loaded on the edge of the 5th metatarsal (little toe edge), depending on snow conditions or skier’s intention.
3. Oscillation Phase
From the support on the new edges, the active extension of the uphill knee begins, mainly controlled by the hamstrings, and the passive extension of the downhill knee together with the forward movement of the pelvis.
In this phase, the pelvis continues its translation in the direction of the turn to generate and then maintain the Centripetal Posture. The edge change is simultaneous: both skis change edges at the same time.
4. Bipodal Phase
This is the longest phase of the turn, in which the support between both feet tends to level out until the cycle is completed and the Generation Phase is repeated in a new direction change.
