Postural adjustments are regulations prior to movements execution carried out in order to stabilize our body by activating various muscles, initiating their activity before moving a body segment.
These adjustments are muscle contractions and de-contractions made to remain stable and for this, we face two antagonist restrictions: one is to move a body segment or segments involved in the action towards the goal, and the other is to stabilize the segments that are not directly involved in the action. These settings are used to prevent or minimize oscillations of the center of gravity with the aim of achieving efficient movements (Frank & Earl, 1990).
Our nervous system promotes the center of gravity to move automatically when we decide to move an arm or leg in a protective attitude to support a suited stance to the action we want to perform.
Classification of Postural Adjustments
The compensatory postural adjustments, or reactive mechanisms, are employed through feedback mechanisms which are activated by sensory information caused by the loss of the desired posture. In this case, we recover postural control after a not expected disturbance.
The anticipatory postural adjustments are proactive or feedforward mechanisms caused by predicted disturbances that generate muscle responses to aid stability maintenance. Such is the case when we modify our posture ahead of time in relation to a potentially destabilizing situation, as the initiation of a change of direction or turning over a bump.
These settings are generated prior to the onset of voluntary or automatic actions, with the aim of reducing postural disturbances produced by the action. They allow an action initiation creating an initial imbalance as, for example, bringing the body forward to allow turn initiation.
The proactive mechanism relies on visual information to predict trajectories, estimating disturbance anticipation forces. In general, the beginner makes use of reactive postural control or compensatory mechanisms, while the expert skier employs proactive or anticipatory mechanisms. As an example, when we raise our arm to prepare our pole plant, our muscles in the trunk are activated in advance to the muscular activity of the shoulder and arm.
Muscle contractions in the trunk and legs are an anticipatory postural adjustment because they precede the main movement of the arm. Another common example of the compensatory postural adjustment occurs when at turn initiation, we release the pressure of the downhill foot, automatically compensating our stance by locating the center of gravity above the uphill foot without changing the edge of the uphill ski. This strategy makes it difficult to start turning since the upper body is placed vertically over the center of pressure (the uphill edge of the uphill ski), delaying edge changing. Because of this, we tend to rotate our shoulders to start guiding our skis. In the same situation, the anticipatory postural adjustment occurs when, while shifting our support from one foot to the other, we project our pelvis in advance towards the inside of the future turn, assuming a proper centripetal posture.
To change our stance, we must take into account the following factors:
- Mechanical factors describe the limits determined by external forces that are generated while skiing, related to joint mobility and movement amplitude.
- Sensory factors refer to, as posture modification causes sensation changes. This information contributes to posture organization we are looking for.
- Energy factors get involved when our posture is not efficient because it gets away from stability and generates energy translated into more muscular effort.
- Bodily factors refer to when we must be conscious of body segments to be modified, so we should get to know our body first (corporeal consciousness).
- Balance factors suggest that the goal of our posture modification is aimed at improving balance.
- Muscle tone factors relate to situations where muscle tension increases, sensitivity is reduced. This makes us not being aware of minor postural deviations, tensing up, and not noticing the extra effort.
Framework Matrix of Skiing Postural Adjustments
| Skiing Concept / Technique | Sensory & Feedforward Mode | Biomechanical Mechanism & Execution | Cognitive Load & Behavioral Reaction | Learning Progression Stage |
| Pre-Movement Stabilization | Proprioceptive motor cortex priming before limb activation | Pre-activating muscle groups to stabilize the body before moving segments | Subconscious organization of core stability ahead of explicit movement goals | Advanced Functional Layer |
| Antagonist Movement Balancing | Multi-channel somatosensory track segmentation | Contracting task-specific limbs while freezing non-involved framework segments | Managing the dual cognitive load of targeted actions and core stability | Technical Competence Level |
| Gravity Oscillation Minimization | Vestibular tracking of center of gravity (CoG) path sways | Suppressing core sways to maximize mechanical efficiency over the snow | Eliminating unexpected torso drift during high-speed tracking | Auto-Regulated Performance |
| Protective Stance Translation | Subconscious nervous system tracking of limb paths | Shifting the CoG automatically when moving arms or legs defensively | Deploying a protective attitude to support a suited stance configuration | Instinctive Safety Baseline |
| Compensatory Feedback Recovery | High-latency sensory feedback loops tracking traction drops | Executing corrective adjustments after a balance break occurs | Relying on reactive feedback mechanisms after unexpected disturbances | Novice Defensive Phase |
| Anticipatory Feedforward Control | Long-range visual tracking predicting future trail obstacles | Modifying the skeletal framework ahead of time relative to hazards | Deploying proactive feedforward strategies to maintain line stability | Expert Proactive Stage |
| Turn Entry Initial Imbalance | Deliberate perception of transitional weightlessness | Projecting the body fore-diagonally to initiate a turning arc | Overcoming the survival reflex to stand up straight at turn inception | Expert Tactical Initiation |
| Proactive Path Trajectory Scanning | Optical field parsing of topographic terrain layouts | Pre-aligning the hips to counter upcoming centrifugal forces | Utilizing visual metrics to estimate disturbance anticipation force loads | Visual Target Mastery |
| Trunk-Pre-Activation Sequence | Proprioceptive trunk muscle firing logging | Activating core trunk muscles in advance of shoulder and arm movements | Suppressing upper body torque during high-frequency pole placement | Advanced Coordination Step |
| Downhill Pressure Release Error | Plantar detection of sudden offloading under the outside foot | Compensating stance alignment by stacking the CoG over the uphill foot | Experiencing high cognitive delay because edge profiles remain un-changed | Intermediate Structural Flaw |
| Uphill Trapping Rotation Error | Visual over-monitoring of the upper ski edge profile | Stacking the body vertically over the uphill edge center of pressure (CoP) | Executing late, inefficient shoulder rotation to force the skis into the turn | Rigid Maladaptive Cycle |
| Pelvic Feedforward Projection | Deep kinesthetic tracking of pelvic displacement tracks | Projecting the pelvis in advance toward the inside corridor of the turn | Assuming a correct centripetal posture during turns’ transition | Elite World Cup Line |
| Mechanical Joint Mobility Boundaries | Tracking physical joint limits during maximum angulation | Modulating movement amplitude based on structural joint mobility profiles | Managing mechanical constraints imposed by external forces and speeds | Universal Physics Compliance |
| Sensory Feedback Shift Parsing | Real-time monitoring of changing tactile pressure sensations | Altering skeletal layouts to trigger fresh sensory information streams | Utilizing changes in sensation to systematically organize the target posture | Dynamic Discovery Phase |
| Inefficient Energy Dissipation | Kinesthetic tracking of rapid muscle fatigue accumulation | Wasting physiological resources through uncoordinated muscular effort | Experiencing heavy energy drain when alignment drifts away from stability | Novice Exhaustion Stagnation |
| Segmental Corporeal Consciousness | High-utility mental mapping of individual body parts | Systematically modifying targeted segments using deep body knowledge | Developing a rich internal body schema to upgrade physical capability | Corporeal Mastery Level |
| Postural Balance Optimization | Tri-system alignment check targeting ultimate equilibrium | Modifying posture with the singular focus of optimizing sliding balance | Suppressing peripheral slope distractions to prioritize central stability | Strategic Excellence Phase |
| High Muscle Tone Blind Spot | Muted kinesthetic feedback caused by excessive bracing | Elevating muscle tension to a level that completely freezes tracking channels | Experiencing reduced sensitivity that blocks awareness of minor errors | Rigid Defensive Stance |
| Unconscious Extra Effort Trap | Chronic tracking failure of systemic physical fatigue | Executing forced technical gestures without noticing the massive extra effort | Accepting total structural stiffness as a normal component of skiing | Chronic Maladaptive Stage |
