Although the term “neutral” may be interpreted as something passive, controlled flexion and extension movements are performed since the vertical separation between the CoM and the CoP tends to vary slightly, unlike the marked displacements caused by the extension or the flexion direction changes. The Neutral Direction Change is considered a combination of the extension change and the flexion change, or an advanced version of the latter.
The purpose of this type of direction change, also called “Middle Transition”, “Cross-through”, or “Direct Edge Change”, is to absorb the Inflexion Point (I.P.), i.e., the point at which the curvature of a curvilinear trajectory changes sense by means of a precise and quick edge change.
In this form of direction change there is no gradual sagittal alignment between the CoM and the CoP, like in the Direction Change by Flexion, since at the end of the turn, approximately ¾ of the way along the curved trajectory, after passing the Critical Point (the point where the speed in the turn is maximum and therefore the external forces supported by the skier are also maximum), the CoM moves explosively towards the new turn (as a reference, towards the tip of the future inside ski).
We are talking about a fore-diagonally translation of the CoM, which is tangential to the curved trajectory, in order to exert pressure on the front part of the outside ski. This translation is oriented towards a combination of the frontal and sagittal body planes, i.e., an intermediate direction between the two which, depending on the skier’s intention or needs, will tend towards one or the other plane.
In the Neutral Direction Change, the skier’s intention is to change the edges just before weight shifting, that is, trying to extend the uphill supporting leg over the big-toe edge already on the snow (active pressure on the ‘new’ edge known as “early edging”) to compensate for the tendency of the pressure to decrease in the Depression Phase, where the trajectory of the CoM splits in the sagittal plane from the trajectory of the CoP (from the I.P. to the fall line or apex).
In this direction-change mode, the primary objective is to manage the pressure exerted or absorbed, which naturally results in contained extension or flexion movements. In other words, these vertical movements are a direct outcome of the skier’s intention to generate or absorb ground reaction forces. This contrasts with the other two types of transitions—by extension or by flexion—where vertical movements are actively used as the tool to manage pressure.
In this turning mode, the strategy to change direction is release-to-engage, this is, releasing the downhill ski to engage the uphill ski.
This type of direction change is effective and also efficient because, by absorbing the I.P., a quick transition is achieved at the end of the turn to economize muscular effort by taking advantage of the generated inertial forces, especially the tangential force, to simultaneously produce a new centripetal force as early as possible.
Biomechanical Phases
1. Generation Phase
This is the exact moment when a rotational retraction of the supporting leg occurs to disengage the edges and initiate the new centripetal force in the opposite direction. In other words, the support on the big-toe edge of the outside ski at the turn’s ending is instantly removed, allowing the CoM to move towards the new turn, while generating a new edge-snow reaction that is completely opposite to the previous one.
The objective of this phase is the active absorption of the Inflection Point (I.P.), releasing the pelvis from the present centripetal posture, so that it is projected fore-diagonally towards the new direction. From neurophysiological and biomechanical points of view, this refers to the precise moment when the nerve impulse is triggered, resulting in a specific muscle contraction of the supporting downhill leg, to trigger the direction change through a quick and precise edge change.
Neurophysiologically, this nerve impulse, as an action potential, is generated in a motor neuron and travels along the axon until it reaches the neuromuscular junction where it connects with the muscle fiber, resulting in its shortening (the downhill leg shortens slightly or markedly depending on the skier’s intention or needs), which produces the necessary movement for the intended action, that is, to release the current centripetal posture in order to generate a new one in the opposite direction.
Biomechanically, this occurs at the intentional moment of the direction change through an active and timely relaxation of the downhill leg extensor muscles -glutes and hamstrings- at the end of the turn, followed by an active flexion of the knee through the main control of the quadriceps, the inversion of the ankle, and supination of the foot with the corresponding dorsal flexion through the activation of the tibial muscles of the leg and the dorsal muscles of the foot. At the same time that the downhill leg contracts and shortens, the uphill leg starts contracting and lengthening through an auxotonic contraction.
2. Monopodal Phase
This phase begins when the ball of the uphill foot makes contact with the snow through ankle eversion and foot pronation. In this phase, the pelvis begins to move fore-diagonally in the direction of the new turn, going over the feet and generating a new centripetal posture thanks to an auxotonic extension of the uphill leg.
An auxotonic contraction is a type of muscle contraction where both the tension and the length of the muscle change simultaneously as it encounters increasing resistance. It combines characteristics of isometric contractions (the muscle contracts without changing length) and isotonic contractions (the muscle contracts with a change in length). In this type of extension, the muscle contracts generating force, slightly changing its length to adapt to the demands of the movement.
The auxotonic leg contraction is functional because it provides a more accurate model for real muscle function, as pure isometric or isotonic contractions are rare in daily skiing.
3. Oscillation Phase
In this phase, there is an active but gradual oblique extension of the uphill knee, mainly controlled by the hamstrings, and a specific support on the first metatarsal (big toe/ball of the foot) of the now standing foot with a slight or marked extension of the ankle (plantar extension of the foot).
Continuing with the oscillation, pressure is transferred through the plantar arch (internal arch) of the outside standing foot, which deforms by lengthening. The pelvis continues its fore-diagonally displacement generating the centripetal posture, which is carried out mainly by the outer hip piriformis muscle. The inner hip moves slightly or markedly on the transverse plane with respect to the external hip.
While oscillating, or ‘rocking-chair’ movement, the CoP is initially located on the outer heel of the uphill foot (toward the tail of the ski) which is slightly supinated. Pressure then moves quickly toward the medial area of the foot (over the middle of the ski) and continues forward until it reaches the forefoot, i.e., the first metatarsal or ‘ball’ of the foot (toward the tip of the ski).
4. Bipodal Phase
This is the longest phase of the turn, during which the support on both feet tends to level out until the cycle is complete and the generation phase is repeated in a new direction change.
There is a slight or marked flexion of the ankle and knee of the inside/uphill leg, depending on the situation. The leading foot remains slightly or markedly pressured on the little-toe edge, depending on snow conditions, skier’s intention and needs, or movement tendencies, and in a marked dorsal flexion.
The inside/uphill hip is slightly or markedly forward in relation to the outside/downhill hip. Both hips tend to remain on the same frontal plane as the ankles or heels, depending on the situation. The pelvis accentuates the centripetal posture through the work of the glutes and, mainly, the piriformis muscle. The shoulders are kept on the same frontal plane as the knees. The arms are forward in relation to the trunk and functionally separated from each other.
Technical Framework Matrix for the Neutral Direction Change
| Spatial Trajectory & CoM/CoP Mechanics | Neuro-physiological Trigger & Kinetic Sequencing | Biomechanical Mechanism & Precise Muscular Actions | Functional Terminology & Edge States | Tactical Line Strategy & Pressure Regulation |
| Controlled Vertical Separation Variability | Tendency of vertical distance between CoM and CoP to vary slightly during the neutral transition | Execute micro-adjustments in flexion/extension to absorb pressure changes without marked displacement | Neutral Direction Change: Advanced cross-through hybrid technique combining extension and flexion features | Maintain continuous tactile sensitivity to minimize vertical dead spots in the arc |
| Trajectory Absorption at Inflexion Point (I.P.) | Point where the curvature of a curvilinear trajectory changes its directional sense | Direct the CoM along a path that cuts cleanly through the geometric transition point | Middle Transition: Direct edge change designed to erase the dead phase between arcs | Eliminate downhill trailing by slicing through the transition zone ahead of the skis |
| Critical Point Threshold Processing | Maximum velocity zone where external forces acting on the skier peak at about ¾ of the turn | Absorb maximum loading safely before initiating the explosive directional change | Critical Point: The specific zone of peak velocity and maximum force accumulation | Brace the skeletal framework to prevent trajectory collapse right before the release |
| Explosive Tangential Translation | CoM moves fore-diagonally along a tangent line relative to the old arc trajectory | Project body mass forcefully toward the tip of the future inner ski at about ¾ turn mark | Direct Edge Change: Sudden, un-aligned translation of mass into the new space | Drive the pelvis down the fall line early to establish a dominant tactical platform |
| Multi-Planar Mass Projection | Mass tracking oriented intermediate between frontal and sagittal anatomical body planes | Match plane bias (frontal vs. sagittal) dynamically to the specific intent of the arc | Fore-Diagonal Translation: Diagonal mass shift prioritizing early tip engagement | Adjust body plane orientation to counter variable rut depth or terrain changes |
| Nerve Impulse Action Potential | Motor neuron generates a precise electrical signal to initiate muscle shortening (Generation Phase) | Coordinate axon propagation to the neuromuscular junction at the exact turn exit | Generation Phase: Active neural command triggering mechanical limb retraction | Synchronize the mental intent to turn with immediate, subconscious muscular release |
| Downhill Support Extensor Release | Timely relaxation of downhill leg extensors at the exact end of the turn | Deactivate glutes and hamstrings instantaneously to drop the old platform | Release-to-Engage: Strategy of unlocking the lower ski to bite with the upper ski | Prevent the downhill ski from hooking or tracking straight by cutting force early |
| Active Knee Flexion & Retraction | Rotational retraction of the supporting leg to disengage active edges | Engage the quadriceps as the primary controller to shorten the lower limb | Rotational Retraction: Simultaneous shortening and twisting withdrawal of the old outside leg | Soften the lower leg rapidly to allow the old outside ski to change edges instantly |
| Foot Supination & Ankle Inversion | Active inversion of the ankle coupled with supination of the old downhill foot | Activate the tibial muscles of the leg and dorsal muscles of the foot | Dorsal Flexion: Upward pull of the foot to clean up the edge release | Cleanly disengage the old big-toe edge to prevent secondary tracking chatter |
| Uphill Auxotonic Extension Engagement | Tension and length of the uphill leg muscle change simultaneously under increasing load | Deploy a combined isometric/isotonic extension to adapt to rising snow resistance | Auxotonic Contraction: Functional limb lengthening under variable external pressure | Match the rate of leg extension to the rising force profile of the new turn entry |
| Uphill Platform Pronation | Ball of the uphill foot makes clean contact via ankle eversion and pronation | Transfer weight onto the first metatarsal of the new outside foot early | Early Edging: Active change to the big-toe edge of the uphill ski prior to full weight shift | Anchor the new big-toe edge into the snow surface right after turn initiation |
| Depression Phase Compensation | CoM trajectory splits away from the CoP trajectory in the sagittal plane | Extend outside supporting leg over the big-toe edge to counteract pressure loss | Depression Phase: Trajectory gap spanning from the Inflexion Point to the turn apex | Pre-load the new edge to maintain solid ski-to-snow contact across the flat zone |
| Oblique Knee Extension Control | Active but gradual oblique extension of the new outside knee during phase entry | Fire the hamstrings specifically to regulate the path of knee extension | Oscillation Phase: Roll-through motion resembling the rocker motion of a rocking chair | Control the rate of knee tracking to shape a smooth, non-hooking entry arc |
| Plantar Arch Deformation Dynamics | Plantar arch elongates and deforms under the influence of progressive loading | Absorb tactile feedback from the snow through the internal arch structure | Plantar Arch Elongation: Structural flattening of the foot to spread load | Utilize foot deformation to smooth out high-frequency vibrations from hard ice |
| Pelvic Trajectory Drive | Pelvis moves fore-diagonally over the feet to create the new centripetal posture | Fire the outer hip piriformis muscle to drive the pelvis into the arc | Centripetal Posture: Lateral body configuration optimized for handling turn forces | Keep the hips moving continuously forward to prevent sitting back on the tails |
| Transverse Hip Separation | Inner hip moves on the transverse plane relative to the external hip | Isolate hip rotation to allow independent leg tracking under a stable torso | Transverse Separation: Disconnected hip positioning across the horizontal axis | Counter-rotate the hips to comply with edge angles |
| Rocker Foot Pressure Tracking | CoP moves from outer heel to medial area, ending at the first metatarsal (ball of the foot) | Execute a rapid heel-to-toe pressure roll along the sole of the foot | Monopodal Phase: Single-support sequence as weight shifts across the skis | Roll pressure forward early to bend the shovel of the ski into the turn |
| Dual Platform Balancing | Support levels out across both feet to sustain the turn radius through its main duration | Maintain the balanced distribution until completion of the cycle repeats the generation phase | Bipodal Phase: Longest phase of the turn characterized by double-foot tracking | Distribute weight evenly across both platforms to maximize track stability on high-speed lines |
| Inner Limb Core Flexion | Ankle and knee of the inside/uphill leg execute a situational flexion | Coordinate joint angles to maintain parallel alignment with the outside leg | Inside/Uphill Leg Flexion: Variable retraction of the inside limb after the apex | Adjust inside leg compression to match the depth of the rut and snow conditions |
| Little Toe Edge Anchoring | Supporting foot holds continuous pressure on the exterior edge boundary | Maintain marked dorsal flexion of the ankle joint to keep the tip engaged | Little-Toe Edge Grip: Inside ski edge tracking mechanism under high tension | Leverage inside edge bite to prevent the inside ski from wandering or drifting wide |
| Frontal Alignment Sequencing | Both hips track forward on the exact same frontal plane as the ankles or heels | Align the shoulders directly on the same frontal plane as the working knees | Planar Synchronization: Coordinated stacking of joints across parallel anatomical planes | Stack upper and lower joints symmetrically to optimize load distribution |
| Deep Centripetal Pelvic Accentuation | Pelvis deepens the internal tilt angle to fight increasing lateral loads | Fire the glutes and piriformis muscle to anchor the pelvic structure | Pelvic Accentuation: Progressive hip drive to deepen edge angles at about ¾ of the turn (Critical Point) | Lock the gluteal base to ensure zero structural collapse at maximum turn depth |
| Forward Upper Body Frame | Arms track forward relative to the trunk to pull the mass down the hill | Separate the hands functionally from each other to maintain lateral balance | Functional Arm Separation: Counter-balanced upper body chassis positioning | Keep hands wide and forward to lead the torso |
Skier: Demian Lasry @demianlasry
