Motion and trajectory are sometimes misused. Motion is the headway in which we move. It is always a straight line determining a starting point and a destination point. Trajectory is the mean used to move on, employing as many trajectories as we need while displacing to the destination point.
Types of Skiing Trajectories
To walk to a destination, we normally orient our body directly towards a particular point adopting a linear trajectory. To change directions when driving a vehicle, we generally guide it performing a curvilinear trajectory. In skiing, direction depends on diminishing the angle between our skis and our destination point, i.e., aligning them towards a specific place of the slope, and this can be executed using both types of trajectories.
Connecting linear trajectories is an improvised behavior that we may adopt when skiing. We tend to abruptly turn our skis because it is difficult for us to plan curvilinear trajectories, which we will get with training. Thus, we tend to perform “Z” shape turns with a marked steering action at the beginning and a linear trajectory until the next direction change. In this reactive procedure, turns are not connected, losing skiing efficiency. Thus, we do not follow the natural arch of the curvilinear trajectory but tend to close the turning angle in a hurried action to rapidly orient our skis toward the desired direction, rather than doing it gradually. Instead, if we choose the curvilinear path is because, in general, we have a built-in linked “S” shape turns which promotes skiing flow.
Exemplifying both models, the “Z” type turn in skiing resembles as driving a vehicle in a city, suddenly turning at each corner, connecting two linear paths through tight turns. The advanced “S” type turns looks like connecting turns as driving on a road with gradual and successive curves. From the efficiency point of view, rather than adopting a turning action that first moves the skis and continues then in a straight line, we should adopt a more efficient motor behavior like steering a vehicle on a winding road, which we gradually orient our vehicle towards the desired direction.
Trajectory Determination
Slope configuration imposes us to select, between several possible paths, a particular trajectory to a determined place. If we do not know to precisely establish our trajectory due to lack of training and visual anticipation, we will suffer higher cognitive and muscle effort having to constantly strive while improvising our descent. This is not the case, because of our experience, if we know how to plan our motions in advance.
Most adult skiers are used to drive their vehicles over defined trajectories on roads with lateral reference lines. In skiing, slope space is relatively wide and there are not trajectories demarcations, except for signs marking slope limits. All skiers have the freedom to choose their paths. The beginner, according to inexperience and/or anxiety, chooses to quickly turn the skis, locating them perpendicular to the slope, location that he perceives as safe. The advanced skier, due to know-how and patience, chooses curvilinear trajectories by diminishing energy expenditure in taking advantage of skis’ geometry.
Trajectory Planning
Establishing destination points and direction changes means having to plan the trajectory that we must follow to reach that place. Setting a path leads to proactive skiing and depends on factors such as terrain accessibility, slope conditions, snow, traffic, shortcuts choice, speed, and visual anticipation.
On the contrary, if we do not visualize our trajectory and depend on obstacles and conditions that are constantly displayed, we act based on the current situation, acquiring a reactive behavior. If we do not plan our trajectories, we generally slow down or stop before an obstacle rather than avoiding it without speed modification.
Direction Change and Skier’s Intention
Turning the skis is modifying the direction of our trajectory. For such purpose, it is observed the use of two strategies according to our intention. Because of the linear paths in which we are moving, our intention in turning may not only be changing direction but also reduce speed using a ‘turning-to-slow down’ strategy.
On the other hand, if we ski mostly in curvilinear trajectories acquiring speed control at each point of the turn, our intention at changing direction may be not just to slow down but to change our headway (in wide turns) through a ‘turning-to-guide’ strategy.
Direction Change and Speed Control
In deciding to change direction, we must take into account our motion speed since this must be consistent with our skill to turn the skis. Speed choice may be a problem as we are still failing to determine the proper speed we should maintain. A reduced speed makes turning more demanding because of the greater skis-snow friction, but a higher speed may compromise skis’ control and our balance.
Visual Strategies, Levels of Steering Control, and the Skier’s Extrapersonal Space
Based on the propositions of some authors (Donges 1978; Salvucci & Gray 2004; Lappi 2013; Lehtonen et al. (2013); Vansteenkiste 2015) and adapted to skiing, our steering behavior could be divided into three path sections related to visual strategies, levels of control, and extrapersonal space:
- An immediate path section referred to the proximate space just in front of us, providing an instantaneous control in our near extrapersonal space (the space which is out of reach for our extremities).
- In the pursuit path section, visual information is buffered (a function of our memory) just a few seconds for a pursuit control mode in the far extrapersonal space.
- The anticipatory path section where visual information of more than a few seconds supplies future path information as an anticipatory control in our extrapersonal space and visual background.
Framework Matrix of Trajectory Orientation and Modification in Skiing
| Trajectory Definition & Mechanics | Biomechanical Mechanism & Execution | Tactical Speed & Line Selection | Cognitive Load & Safety Response | Learning Progression Stage |
| Motion vs. Trajectory Distinction | Moving in a continuous straight line that establishes a definitive starting point and destination. | Utilizing a sequence of multiple intersecting trajectories to navigate toward the final destination point. | Overcoming the semantic confusion and mechanical misuse between straight-line motion and variable trajectories. | Differentiating basic directional headway from complex trajectory navigation during slope descent. |
| Directional Alignment Rule | Diminishing the physical angle between the skis and the designated destination point on the slope. | Aligning the skis directly toward a specific, pre-determined location on the trail. | Eliminating erratic deviations by locking the body orientation toward a specific target area. | Shifting from unguided downhill sliding to intentional, targeted directional alignment. |
| Improvised Linear Connection | Executing sharp, abrupt rotational steering inputs at the absolute beginning of a direction change. | Performing rigid, angular “Z” shape turns characterized by disconnected, static path segments. | Experiencing high physical resistance and a total loss of skiing efficiency between turns. | Adopting a highly reactive, unplanned behavior due to an inability to sketch out curved lines. |
| Hurried Angular Closing | Closing the turning angle in a rushed, aggressive upper-body or leg-steering action. | Forcing the skis to rotate rapidly toward the desired direction instead of following a natural arc. | Reacting out of fear or urgency to check speed instead of trusting equipment design. | Overcoming the rushed steering impulse that disrupts natural turning geometry. |
| Linked Curvilinear Flow | Building smooth, continuous, interconnected “S” shape turns down the fall line. | Executing a gradual, continuous steering action that builds ongoing centrifugal force. | Promoting fluid, uninterrupted skiing flow and maintaining consistent downhill momentum. | Progressing from sharp, reactive corrections to automated, linked curvilinear muscle memory. |
| Urban Driving Analogy | Replicating the physical stress of driving a vehicle in a tight city grid with abrupt 90-degree cornering. | Connecting two distinct linear paths via tight, jarring, high-friction direction changes. | Suffering high mechanical deceleration that requires constant physical re-acceleration. | Moving past the rigid, exhausting “city driving” mental model of technical skiing. |
| Winding Road Analogy | Replicating the fluid mechanics of driving a vehicle smoothly along a winding, curved road. | Gradually and successively orienting the vehicle/skis toward the ever-shifting path direction. | Maximizing kinetic efficiency by eliminating sudden braking and structural energy spikes. | Reaching the advanced stage of treating the slope as a continuous, flowing ribbon. |
| Slope Configuration Selection | Selecting one specific path out of several potential lines based on the terrain layout. | Adjusting body mechanics dynamically to match the macro configuration of the open slope. | Managing the psychological anxiety triggered by wide, open, undemarcated mountain spaces. | Training the eyes and brain to filter open space into highly structured, efficient corridors. |
| Visual Anticipation Deficit | Failing to visually scan the slope ahead to pre-establish the upcoming trajectory. | Striving constantly and improvising physical body positions during the live descent. | Enduring significantly higher cognitive strain and massive, premature muscular fatigue. | Remedying a lack of technical training by actively shifting visual focus down-mountain. |
| Advanced Planning Know-How | Utilizing extensive skiing experience to completely map out descent motions well in advance. | Exercising calculated patience to let the turn develop instead of forcing an early pivot. | Experiencing low cognitive load and minimized physical effort by skiing proactively. | Transitioning from high-stress improvisation to highly organized, predictive trajectory planning. |
| Reference Line Freedom | Operating on a wide slope completely devoid of painted lateral reference lines or lane markings. | Choosing an autonomous path within the broad boundaries of the official slope limits. | Managing the spatial freedom of the mountain without suffering structural disorientation. | Transitioning from highly regulated road-driving habits to open-slope tactical freedom. |
| Beginner Perpendicular Safety | Quick-turning the skis abruptly until they are positioned perpendicular to the fall line. | Engaging heavy edge friction to aggressively stop or severely check downward momentum. | Seeking immediate psychological comfort and a perceived sense of safety from a full stop. | Graduating from anxiety-driven, cross-slope survival mechanics to downhill tracking. |
| Advanced Geometric Leverage | Diminishing overall physical energy expenditure by utilizing the ski’s deep sidecut geometry. | Allowing the postmodern ski’s natural structural shape to slice a clean, curved path into the snow. | Exhibiting high tactical patience by waiting for the sidecut to engage and track. | Mastering equipment-assisted efficiency where the ski shape dictates the physical effort. |
| Proactive Path Variables | Evaluating terrain accessibility, real-time slope conditions, snow texture, and skier traffic. | Planning exact destination points and calculated direction changes before execution. | Adjusting entry speed and choosing intentional shortcuts based on forward visual scanning. | Elevating execution to fully proactive skiing driven by strategic environmental assessments. |
| Reactive Condition Dependency | Reacting blindly to obstacles and changing snow conditions only as they appear underfoot. | Slowing down heavily or coming to a complete stop directly in front of an obstacle. | Operating in a high-stress, defensive state due to zero forward-looking visualization. | Replacing defensive, reactive survival habits with fluid, uninterrupted avoidance lines. |
| Turning-to-Slow-Down Strategy | Using the turning arc primarily as a braking mechanism to dump excess speed. | Forcing the skis sideways against the snowpack to generate high-volume surface friction. | Managing speed through deceleration phases rather than maintaining a continuous tempo. | Moving away from using turns solely as emergency brakes toward using turns for guidance. |
| Turning-to-Guide Strategy | Maintaining precise speed control at every micro-point throughout the entire turning arc. | Changing the structural headway in wide, sweeping turns without losing edge engagement. | Seeking total directional mastery and fluid guiding intentions rather than speed destruction. | Achieving advanced speed management through precise edge angles and smooth line choices. |
| Velocity Consistency Dilemma | Matching the chosen motion speed directly to the skier’s current technical skill level. | Overcoming the mechanical penalty of low speeds, which increase ski-snow friction. | Preventing higher velocities from completely compromising ski control and skeletal balance. | Resolving the speed paradox by finding the optimal velocity for smooth turn execution. |
| Immediate Control Zone | Processing visual input from the proximate space located directly in front of the ski tips. | Executing instantaneous, split-second steering adjustments within the near extrapersonal space. | Reacting to immediate terrain anomalies that are completely out of reach for the extremities. | Utilizing the absolute baseline tier of immediate, short-range survival control. |
| Pursuit Control Mode | Buffering short-range visual information in the working memory for a few critical seconds. | Executing a fluid pursuit control mode to track a continuous line through upcoming terrain. | Anchoring focus into the far extrapersonal space to smoothly link current and next turns. | Progressing to a mid-tier, buffered control system that smooths out jerky movements. |
| Anticipatory Control Range | Scanning the slope more than a few seconds ahead into the deep visual background. | Supplying the motor cortex with future path data long before reaching the physical turn location. | Operating with total mental clarity, zero anxiety, and complete proactive line mastery. | Attaining the highest tier of predictive, elite-level anticipatory steering control. |
