TECHNIQUE - Conclusions about Direction Changes

When choosing a direction change mode, while it may come down to personal preference, it is often the best option for the situation at hand. Most skiers use the Direction Change by Extension not only because it may be the only option available to them, but also because it is the one taught by most instructors. More skilled skiers will have the option of the other two modes to change direction.

We conclude these direction change analysis by saying that in the Direction Change by Extension, the tendency of the CoM to move away from the CoP predominates, that is, the edge change occurs at the end of the extension in a “engage-to-release” mode: first the uphill ski engages its big toe edge, then the downhill ski releases its big toe edge. It is executed through a vertical extension of the uphill knee.

Advantages:

This change is effective.
It is suited for all kind of skiers.
It uses a natural weight transfer.
Because it uses larger, more intuitive vertical movements, it is significantly easier to learn and master than the subtle timing required for the Direction Change by Flexion.

Disadvantages:

It is not efficient due to the excessive muscular effort made during the extension while lifting the CoM against gravitational forces.
The edge change takes longer.
It doesn’t take advantage of the tangential forces at the end of the turn.
It doesn’t take advantage of the acceleration phase at the beginning of the turn (loss of snow contact sensation).
It isn’t stable.
The extensor muscles are used to keep the upper body balanced, not to transmit pressure to the CoP.

In the Direction Change by Flexion, the tendency of the CoP to move closer to the CoM prevails. The edge change occurs at the end of legs’ flexion in a simultaneous mode: both skis change their edges at the same time in a “release-and-engage” mode.

Advantages:

It is a stable direction change.
Takes advantage of the tangential forces at the end of the turn.
It allows a quicker and earlier edge engagement.
Improves terrain absorption.
Results in an increased stability.
It is effective in tight spaces and high speeds.
It gets better performance in dense snow.

Disadvantages:

It is not efficient due to the muscular effort made by legs’ retraction during the Generation Phase.
There are chances of falling into a “backseat” position.
It is common the loss of snow contact sensation.
Due to the lack of core strength and timing to stabilize the move, it is not suited for beginner or intermediate skiers.

In the Neutral Direction Change, the tendency to maintain the vertical distance between the CoM and the CoP stands out, i.e., there is less vertical travel between the two.

The edge change occurs just before the start of the uphill leg extension in a quick and precise “release-to-engage” mode: first the downhill ski releases its big toe edge then, almost simultaneously, the uphill ski engages its big toe edge. This moderate extension is executed through an oblique or fore-diagonally uphill knee extension.

This direction change is effective and, from the point of view of muscular effort and time, it is also efficient.

The advantages of the Neutral Direction Change are:

The edge change is quicker and precise since the vertical CoM trajectory is shortened.
Effort is economized since there is no need to lift, to a great extent, the CoM against gravitational forces to project it towards the new turn, as occurs in the Direction Change by Extension.
It allows a controlled extension of the new outer leg over the CoP (inside edge) and takes advantage of the Acceleration Phase (from the I.P. to the fall line).
The skis (especially the outer) bend through their entire curvature from the very beginning of the turn as a result of an early edging.
It is a more controllable transition since the body and skis continue to move at the same speed into the new turn.
It is more stable since no marked upward movements (as in the Direction Change by Extension) or downward movements (as in the Direction Change by Flexion) are used at the critical moment of acceleration reversal (transition from deceleration at the end of the previous turn to the initial acceleration of the new turn).
The tension of the extensor muscles of the new outer leg is used to transmit pressure on the CoP and not to keep the trunk balanced.
It allows maintaining a constant pressure throughout the turn.

In relation with the types of muscle contractions, during the Direction Change by Extension and by Flexion it is utilized a combination of isotonic contractions, where leg muscles change length by stretching (Direction Change by Extension) or by shortening (Direction Change by Flexion).

In the Neutral Direction Change, muscle contractions are auxotonic, combining isotonic (length change) and isometric (static tension) contraction components, i. e., it is characterized by an increasing tension while slightly changing its length.

The main advantages of the auxotonic muscle contraction are:

Allows a quick and efficient edge change.
It deals better to changing pressures.
Improves terrain absorption and variability of snow texture.
Increases joints stability (knees and hips) during critical turning postures.
Strengthens leg stabilizer muscles.
Reduces muscle fatigue.

Differences between Direction Change by Extension, by Flexion, and Neutral

Direction Change by Extension	Direction Change by Flexion	Neutral Direction Change
It is suited for all kind of skiers.	It is suited for more skilled skiers.	It is suited for all kind of skiers.
It uses a natural weight transfer.	It uses a more subtle weight transfer.	It uses a gradual weight transfer.
The uphill leg “pushes” against the snow.	Both legs absorb the Inflexion Point by retracting toward the body.	The downhill leg, through an auxotonic contraction, generates the direction change.
The Inflexion Point is not absorbed since the extension is generated directly on the uphill leg.	The Inflexion Point is absorbed by both legs simultaneously.	The Inflexion Point is absorbed by the downhill leg, allowing a direct transition of the CoM toward the new turning direction.
The pressure to initiate the direction change is applied on the little toe edge of the uphill ski, providing a sensation of firm support.	Although the tendency to apply pressure on the uphill ski, a sensation of “floating” support is generated.	The big toe edge of the uphill ski strongly engages in the snow through an oblique extension.
The CoM moves away from the CoP.	The CoP moves toward the CoM.	There is a moderate vertical variation between the CoM and the CoP.
The body moves over the skis.	The skis move under the body.	The body moves over the skis.
It is more effective in open spaces.	It is more effective in tight spaces.	It is effective in all kind of spaces.
The edge change occurs at the end of the extension.	The edge change occurs at the end of the flexion.	The edge change occurs before the extension.
The CoM moves laterally toward the inside of the turn.	The CoM moves diagonally toward the turn.	The CoM moves fore-diagonally toward the turn.
The speed of the edge change is slow since the CoM trajectory is longer.	The speed of the edge change is quite fast since the CoM trajectory is short.	The speed of the edge change is explosive since the CoM trajectory is reduced.
The uphill ski takes time to bend so early edging is delayed.	The skis tend to bend from the beginning of the turn.	The skis (especially the outer) bend through their entire curvature from the very beginning of the turn as a result of an early edging.
It is a less controllable transition since the body moves slower into the new turn.	It is a controllable transition since there is a tendency to move body and skis into the new turn.	It is a quite controllable transition since body and skis continue to move at the same speed into the new turn.
The extensor muscles of the new outer leg are used to keep the trunk balanced.	The extensor muscles of the new outer leg are used to transmit pressure on the CoP as well as to keep the trunk balanced.	The extensor muscles of the new outer leg are fully used to transmit pressure on the CoP.
The trajectory of the CoM along the longitudinal and transverse axes describes a “V”, or an inverted cone oscillation.	The trajectory of the CoM along the longitudinal and transverse axes describes a “U”, or a pendulum oscillation.	The trajectory of the CoM along the sagittal axis tends to remain almost equivalent, or with moderate variations, to the inclined plane.
The body tends to extend.	The body tends to flex.	The body tends to remain relatively stable at a regular height.
Muscular effort is significant due to the extension of the uphill leg.	Muscular effort is significant due to the flexion (retraction) of both legs.	Muscular effort is limited to contracting the downhill supporting leg.
It isn’t a stable turning mode.	Even that it is a stable turning mode, there are chances of falling into a “backseat” position.	It is more stable since there are no marked upward or downward movements.
Muscle effort is generated through eccentric contractions of the lower limbs.	Muscle effort is generated through concentric contractions of the lower limbs.	Muscle effort is generated through auxotonic contractions of the lower limbs.
It doesn’t take advantage of the tangential forces at the end of the turn.	It takes advantage of the tangential forces at the end of the turn.	It takes full advantage of the tangential forces at the end of the turn.
It doesn’t take advantage of the acceleration phase at the beginning of the turn (loss of snow contact sensation coming from the downhill ski).	It takes some advantage of the acceleration phase at the beginning of the turn (loss of snow contact sensation coming from both skis).	It takes maximum advantage of the acceleration phase at the beginning of the turn.
It is an effective direction change mode.	It is an effective direction change mode.	In addition to being effective, it is also an efficient direction change mode.

In both recreational and racing skiing, these three types of direction change are performed according to the skiers’ intentions and/or needs and the tendencies of their trajectories.

As we can observe, each form of changing direction has its pros and cons. Choosing which one to use is a matter of deciding which features we want to take advantage of and which trade-offs we’re willing to accept with each mode.