In the past modern era, skiers extended their legs to unweight the skis at turn initiation and flexed to load them at the end. The sought-after effect was to decrease pressure at the beginning to facilitate turn entry, and to increase it at the end to control speed.
In current postmodern time, the opposite effect is pursued: extending to increase pressure at the turn initiation, and flexing to decrease or regulate pressure at the turn finish.
Movement vs. Action
Before diving into this matter, let’s first analyze a common misconception, as movements and actions are often confused. An “action” is increasing or decreasing pressure on the skis; and to achieve this, the “movement” of leg extension and leg flexion are utilized. An action seeks the “effect” being produced and uses movement as “tools” to achieve that effect.
We should not extend our legs simply to seek pressuring the skis; rather, we must seek the effect of pressuring the skis, and this is to create a centripetal turning force through extension. The focus is not on extending for the sake of extending, or flexing for the sake of flexing, but on efficiently managing the pressure we exert or we suffer.
We must shift away from the idea of extending and flexing purely because it is a popular belief or because it is what is traditionally taught. We must seek the effect that extending and flexing the legs produces. Both movements recede into the background; what matters is what we want to achieve the skis to do, what we want to generate: increasing pressure or regulating it, and to do that we count on those two vertical movements.
Divergence/Depression Phase
This is an explanation of the technical and scientific way the movement a skier must make when initiating a turn on a groomed slope to avoid losing grip and maintain control.
To understand it universally, we must break it down element by element:
- “Extension toward the support plane”: Actively straightening the legs by pushing the feet against the snow.
- “Depression”: A loss or “vacuum” of pressure. It does not refer to a physical hole in the terrain, but rather that the skis tend to lighten and lose firm contact with the ground.
- “Divergence of trajectories”: At the start of the turn, the pelvis (Center of Mass) and the skis separate (Center of Pressure). The skis travel along the periphery of the curve while the body leans toward the inside of the turn.
Mechanical Explanation
- The initial separation: When we start a turn, our body and our skis no longer travel along the same line. Our skis move away from our pelvis.
- The pressure vacuum: As the skis move away from our center of mass, the pressure we exert on the snow decreases drastically. The skis become “light.”
- The technical solution: To prevent the ski from skidding or floating during this moment of acceleration, we must generate pressure through extending (straightening) our legs.
- The desired effect: By straightening gradually the legs toward the snow (support plane), we “fill” that distance that was being created, keeping the skis firm against the ground, deforming their wood-core (de-camber), and generate the centripetal force needed to carve the edges smoothly.
In short: It means we must straighten our legs at the start of the turn to fill the space generated when our skis move away from our body, preventing the skis from losing pressure and skidding.
Convergence/Compression Phase
The convergence/compression phase is the half of the turn that occurs immediately after crossing the Fall Line until the end of the curve. It is the moment where the most intense forces are received from the skis.
Breaking down the phrase in a purely technical way, this is what happens:
- “Convergence of trajectories”: After the midpoint of the turn, the pelvis and the skis tend to come closer again.
- “Compression”: A massive increase in external forces and pressure that the snow pushes back into our legs.
Mechanical Explanation
- The collision of trajectories: After passing the fall line, the skis complete the turn and cut across the line the body is descending. The space between our pelvis and our skis shrinks drastically.
- The G-Force peak: Due to high accumulated speed and the effect of centrifugal force, the ski deforms to its maximum. The snow generates an upward push (Ground Reaction Force) so powerful that, if we stay rigid, we will be thrown off balance or sit back (the classic error of getting a “backseat”).
- The technical solution (Flexion): Instead of straightening the legs (as we did at the start), here we must flex our legs by releasing.
- The desired effect: By releasing the legs, we act like a hydraulic shock absorber. We absorb and regulate that excess of pressure without losing edge control, allowing the skis to recover their natural shape (camber) in a controlled manner to initiate the next turn smoothly.
In short: the path of our body and that of our skis close in, creating a crushing pressure peak. To master it, we must absorb that force by folding our legs in a controlled way, preventing the skis from destabilizing us and allowing a clean transition into the next turn.
Note: These phases are inverted to facilitate adaptation to the unevenness of the terrain’s surface. On a groomed slope we extend at the start (divergence-depression phase) and flex at the end of a turn (convergence-compression phase). On a mogul field (bumps), we do the inverse: we will flex to absorb the pressure at the start (convergence-compression phase) at the moment of contact with the uphill face of the bump, and we will extend to generate pressure in the trough or rut after passing the crest (divergence-depression phase).
Furthermore, we must consider the following:
- In the divergence-depression phase, there is an acceleration since the skis are directing themselves toward downhill and external forces tend to be lower, especially centrifugal force.
- In the convergence-compression phase, acceleration tends to decrease because the skis position themselves perpendicularly across the hill and external forces tend to increase.
Debunking the “Terrain” Misconception
An additional common misconception is that extension is utilized to forcefully add more pressure at the first part of the turn due to the terrain’s pressure vacuum from the initiation to the fall line, and flexing to soak up a big bump or rise in the snow at the finish of the turn. On a groomed track, the skier slides down perpendicularly on a mostly uniform surface (inclined plane), which would not be the case on a slope with bumps.
In other words, we don’t stretch our legs because we hit a “hole” in the groomed snow; we extend them because our skis are traveling away from our body, and we must fill that empty space to keep them on the ground. Similarly, we don’t flex at the end of the turn because we hit a “mound“; we flex because the sheer speed and centrifugal force of the turn are pushing the snow violently up into our feet.
Conclusion
To turn a ski, pressure must be generated at the start of a turn on a groomed slope to deform the ski, thereby ensuring that its entire reverse camber (de-camber) is utilized alongside its sidecut to generate the centripetal force necessary for the desired curvilinear trajectory, as we have mentioned above.
At the turn finish, our intention should be to flex in order to manage the excessive pressure on the deformed ski, allowing it to recover its natural shape (camber) and thus facilitating the edge change (amortization/linking phase).
In future articles, we will expand on how pressure management proves to be fundamental for efficient skiing.
Framework Matrix of Pressure Managment
| Skiing Concept / Technical Phase | Terrain Matrix Profile | Trajectory & Geometric Vectors | Biomechanical Mechanism & Execution | Cognitive Focus & Action Output |
| Turn Initiation | Groomed Slope / Inclined Plane | • Turn entry to Fall Line • Divergence of CoM trajectory away from ski track (Depression Phase) | • Active Leg Extension • Progressive lengthening of the lower limbs • Increasing edge angle and ski deflection | • Generating an immediate pressure increase • Initializing early centripetal force • Deforming the ski into reverse camber (de-camber) |
| Groomed Depression Phase | Groomed Slope / Uniform Surface | • Downward acceleration vector toward the fall line • Skis naturally dropping away from the pelvis mass | • Leg extension compensating for trajectory divergence • Filling the structural “pressure vacuum” on the snow • Maintaining high-utility foot-to-snow contact | • Utilizing extension as a tool, not an end state • Preventing traction drop and sidecut washing • Preparing the frame for rising centrifugal loads |
| Turn Finish | Groomed Slope / High Centrifugal Zone | • From the fall line to completion phase of the arc • Convergence of CoM trajectory toward the ski track (Compression Phase) | • Active Leg Flexion • Controlled shortening of the lower limbs • Softening knee, hip, and ankle articulation | • Absorbing the critical build-up of external forces • Regulating pressure on the fully deformed ski canvas • Permitting the ski to recover its natural shape (camber) |
| Groomed Compression Phase | Groomed Slope / Fall-Line Exit | • Skis tracking perpendicularly across the fall line • Natural deceleration vector combined with peak G-force | • Absorption of converging spatial trajectories • Dynamic control of the center of pressure (CoP) displacement • Preventing the core from collapsing into a backseat trap | • Managing and grounding intense centrifugal spikes • Smoothing out the transit into the amortization phase • Facilitating a friction-free, neutral edge change |
| Mogul Compression Phase | Mogul Field / Bump Faces | • Turn initiation occurring at the uphill face of the bump • Immediate, abrupt reduction in spatial distance | • Inverted Flexion Execution • Immediate absorption of the upward pressure spike • Retracting legs up toward the stationary torso chassis | • Using flexion to neutralize terrain-induced pressure • Maintaining a stable upper body mass over crests • Shifting mechanical rules to match uneven surfaces |
| Mogul Depression Phase | Mogul Field / Bump Troughs | • Turn execution down the backside into the trough/rut • Skis dropping rapidly away into the structural ditch | • Inverted Extension Execution • Driving legs down into the trough after passing the crest • Extending the extremities to hunt for support references | • Active generation of edge pressure inside the trench • Maintaining a continuous sliding line without dead spots • Stabilizing balance before the next bump collision |
