Alpine skiing presents a unique physical environment. Unlike sports where speed and forward
motion are attained by internal muscular effort, in skiing gravity provides the pull while the skier
uses body movements to influence speed and direction. From a technical perspective, there are
two criteria for success:
• The ability to choose and maintain a trajectory: for the racer, their line is imposed by the race
course while a free skier chooses it according to terrain and the desired outcome.
• Efficiency: for the racer this means speed, and for the free skier it means creating any direction
change with the least amount of physical effort and resistance. Defining Efficiency
With gravity as the primary motive force, speed in skiing has much to do with reducing braking.
Carefully timed muscular effort can also contribute to speed, if the skier “pushes” in a way that
compliments gravity. Efficiency applies at all speeds. For recreational skiers of all levels
controlling direction change while conserving momentum and muscular effort produces skiing
that is balanced, relaxed and results in full control of the situation.
This approach is adaptable to the needs of all skier types, as the skier can:
• Generate and/or maintain speed wherever possible.
• Control speed when necessary or desirable. Movement and Motion - 20 years as a technical perspective
The concept of movement and motion was introduced by the CSIA as a perspective on the sport
of skiing. First presented at Interski in 1983, it still successfully explains observed movement
patterns at all skill levels and situations.
Movement and Motion defines balance in skiing as the relationship between the COM and BOS.
Movements are what the skier does to influence the line of mo-tion, or the path of the COM. As
the mass moves down the slope it seeks the path of least resistance, or the most direct line. To
change direction, the skier places the skis, or BOS, at an angle to the trajectory of the COM and
edges them. Skiing on an arc is a series of deflections, with the BOS supporting and deflecting
the COM on every point of that arc.
With the overall goal of being able to follow a chosen trajectory at a chosen speed with the least
possible resistance and muscular effort, the skier must move constantly to maintain balance and
control direction change. Technique vs. methodology
Technique: theoretical or scientific analysis of balance and movement patterns of skiers
according to the principles of physics and biomechanics.
Methodology: practical tools for skier development used by instructors and coaches to develop
good technique in skiers.
A good technical understanding does not necessarily imply effective use of methodology.
Similarly, use of methodological tools should be based on theoretical understanding of technique.
FORCES IN SKIING
A skier sliding down a slope is held to the slope by a portion of the force of gravity acting
perpendicular to the slope. Another portion of the force of gravity acting parallel to the slope
pulls the skier forward and down the hill.
Opposing these forces is the friction between the skis and the snow, and the friction of the air
against the skier.
Turning adds two other forces. Centrifugal force pulls the skier away from the centre of the arc.
To continue turning, the skier resists this pull, creating a centripetal force.
Combined forces
Above the fall line centrifugal force and gravity pull in different directions, and after the fall line
they combine. Gravity and centrifugal force create a combined resultant force. The angle of the
resultant force is the line of inclination that the skier adopts to stay in balance.
BALANCE WHILE SLIDING AND TURNING
Balance is defined in the relationship of the Centre of Mass and the Base of Support. The COM is
supported by the BOS at whatever angle is appropriate to resist outside forces. The Centre of Mass
All bodies have a Centre of Mass. The COM represents the balance point of a three dimensional
object. Gravity and all other forces act on the COM.
• The COM is usually inside an object but not always. In a doughnut for example the COM is in
the hole. It may actually be outside an irregularly shaped object.
• Due to the weight of equipment, the COM is lower in a skier than a non-skier
• The COM is not a fixed point, and moves as an object changes shape. Any body movements
displace the COM. As efficient skiing implies a smooth trajectory of the COM, any unnecessary
movement can adversely affect balance. Expert skiers control their movements so the COM
smoothly moves both within the body and down the slope. The Base of Support
For a body to balance, the force acting through the COM must also act through the BOS. This
means the BOS supports the COM.
• The BOS is the area between all points that support the body. A wider stance broadens the BOS,
increasing stability. A pole plant also momentarily increases the BOS.
• Balancing over a smaller BOS is also possible, although the forces required to push the skier
over are less. A smaller BOS gives less margin for error. Maintaining Balance
A skier balances with continual series of adjustments in anticipation and reaction to the
combinations of forces encountered. To stay in balance the skier must be able to adjust either
COM or BOS quickly. Because the lower body has less mass than the upper body, quick
adjustments are often made with the feet (BOS). Overcoming resistance
Heavy snow, skidding, edging or bumps can continually or momentarily increase ski/snow
friction, or resistance. To stay in balance the skier compensates by moving the BOS forward
relative to the COM so that forces continue to act through the centre of the ski.
MOVING ON AN ARC
When the COM is moving it has momentum. On an arc, the COM wants to fly off in a straight
line called a tangent. The tangent at each point on the arc is the direction of travel at that point in
time. The most natural position for balance is facing the direction of travel. This is why the hips
and torso face slightly to the outside of the turn at any point in the arc.
The angle between the tangent of the arc of the COM and where the skis are pointing is called a
steering angle. With the skier facing the direction of travel, a longer radius turn will show a
smaller steering angle than a short radius turn.
Ski sidecut provides a built in steering angle between the centre axis of the ski and the flare of the
tip. This steering angle decreases down the length of the ski, hence the tips provide more turning
TECHNIQUE - THE CANADIAN APPROACH
The Canadian Approach to ski technique combines theoretical knowledge with practical tools for
skier development. It is the shared approach of the Canadian Ski Instructors’ Alliance and the
Canadian Ski Coaches Federation. 1- Technique (technical base)
Together, physics and biomechanics are the technical tools that provide the theoretical knowledge
for effective skier development. Biomechanical principles and physics apply to all sports and
activities and can help to understand why skiers balance in certain ways and use particular
movements.
Physics and skiing: physics is the foundation of ski technique. With gravity providing the primary
motive force, a skier balances and interacts with the forces provided by an ever changing ski
environment.
Biomechanics and skiing: an understanding of practical biomechanics links ski technique to
physics, and helps to describe efficient and effective body movements. 2- Methodology (assessment and development tools)
These teaching methods provide a structure for skier assessment and development and are the onsnow
development tools that instructors and coaches use.
Turn phases link a skier’s movement patterns with specific parts of the turn. They can help in
prioritizing and sequencing skills.
Planes of balance are a way to analyze a skier’s balance as they move in curved trajectories down
the mountainside. They provide a method for identifying balance problems and respond with
targeted skill development.
Skill development is the core of the Canadian approach. It is a way of understanding all skiing
through 5 elements. The skills system identifies areas for development, and uses a tactical
approach to improve abilities.
ACQUISITION
〉 The skier coordinates and executes the key
components of the movement in the correct order;
〉 Execution is inconsistent and lacks precision;
〉 Cautious execution by skier;
〉 Rough form, lacks synchronization, rhythm and
flow. CONSOLIDATION
〉 Coordination of movements appears
〉 Controlled and rhythmical execution of task under stable
conditions
〉 Some performance elements are maintained, but
are inconsistent when skier is under pressure,
conditions change or demands increase REFINEMENT
〉 Performance is consistent and precise in demanding
conditions
〉 Movements are automatic and done subconsciously
〉 Only minor fine tuning may be necessary
〉 Critical reflection and correction is possible by skier
Teaching:
Meets expectations (M/E) or Needs improvement (N/I).
Angulation: the lateral angles formed between segments of the body. Balance: the use of the neuromuscular system to maintain an athletic posture and alignment of the COM and BOS.
Banking: the tipping of the shoulders and the upper body into the turn. It generally is an unstable position, and it is often associated with rotation. Synonym: tipping. Base of Support (BOS): the area between all points that support the body. It generally is referred to as the feet, but it is any point of snow contact including skis and poles. Carving: turns with little or no skidding, with the tails of the skis following the tracks made by the tips. Christie: a turn or part of a turn, done with the skis parallel. Centre of Mass (COM): the three dimensional balance point of an object. Counter-rotation: the action of upper and lower body turning against each other, based on physical principle of an action having an equal and opposite reaction. If upper or lower body are turned, the other segment will turn in the opposite direction. A weak force and most effective if the skis are un-weighted. Cross-over: the crossing of the trajectories of the COM and BOS between turns; related to edge change. Edge angle: the lateral angle formed between the base of the ski and the slope. Edge change: the change of balance from one edge (or edges) to the other. Extension: the lengthening of the body by un-bending joints. Opposite of flexion. Fall Line: an imaginary line following the inclination of the slope at any point. Where a snowball
would roll if released on the slope. Flexion: the shortening of the body by bending joints. Opposite of extension. Inclination: the degree of lean used to balance against the external forces generated by turning. Lead change: the natural tendency for the inside ski to be ahead as a result of the lower body turning. Line of motion: the path that the COM follows.
Linking: the smooth transition between turning arcs. Related to edge change. Movement: body actions initiated by internal muscular efforts. Can affect balance on all planes. Parallel: a position of the skis where the longitudinal axes are parallel and edge angles are the same. Rotation: the twisting of the hips or upper body into the turn, often causing imbalance. Self steering of skis: the inherent turning tendency of skis, due to sidecut and longitudinal flex. Separation (upper and lower body): refers to the steering effort being led by the lower body, with the upper body naturally facing the direction of travel, or the tangent of the arc. Sidecut: the shape of the ski defined by the width underfoot versus width tip and tail. Ski reaction: the use of stored energy in ski and boot to provide rebound for turn linking. Skidding: the sideways travel of one or both skis across the snow. Necessary for speed control. Sliding: the forward travel of one or both skis on the snow. Steering: the blend of edging and pivoting with the control of the resulting pressure. Steering allows the skier to choose a variety of turn shapes. Different blends of edging and pivoting allow the skier to control speed or to maintain speed or accelerate by reducing braking. Steering angle: the angle formed between the longitudinal axis of the ski and the direction of travel of the skier. Stem: a position of the skis where the tails are further apart than the tips. Seen in Wedge (snowplow) turns as a braking or steering device, or if the tail of the downhill ski skids more than the tip. Stepping: a step, or transferring of weight from one ski to the other. Tipping: the tipping of the shoulders and upper body into the turn. Generally unstable position, and often associated with rotation. Synonym: banking. Traverse: sliding forward on edges at angle to the fall line. Wedge: ski position with tips together and tails apart. See Stemming. Weighting/Unweighting: the control of the load or pressure against the snow. Affected by moving COM quickly up or down, by increasing or reducing steering, and by the muscular forces applied by the skier.
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