Last Updated24 April 2024

The NZSIA has identified four movements to demonstrate how skiing works. This section discusses the four movements and how they are applied when skiing. It is important for instructors and skiers to understand not only how the movements work individually but also how they work with, and affect one another, to create different ski/snow interactions. A thorough understanding of the four movements provides the instructor with the ability to teach skiing effectively and to accurately analyse a skier’s movements.

The Four Movements of Skiing

The four movements of skiing are:

Fore/aft movement
Rotational movement
Lateral movement
Vertical movement

Each of the movements has a direct effect on the skis and how they interact with the snow. The movements and their effect are applied through the base of support (BOS), which is defined as the portion of the ski or skis under the foot or feet. Another important term referred to in this chapter is the centre of gravity (COG) which is defined as the point in the body where all mass acts as if it is concentrated. For example, the body rotates around the COG when it performs a spin in the air. The location of the COG changes as we move and can even fall outside of the body. Standing still in an effective athletic skiing position, the COG will be in our core area, approximately in line with our navel and a few centimetres in front of our spine.

Fore/Aft Movement

Fore/aft movement occurs along the length of the skis and is controlled by the ankle, knee and hip joints, movement in the spine and the position of the arms.

The goal of fore/aft balance is to allow the skier to stay balanced and maintain an athletic stance. The skier’s position along the length of the ski may vary depending on terrain and the desired outcome to be achieved. Fore/aft balance is always being challenged and is often referred to as dynamic balance and skiers will be constantly moving to and from a balanced position.

The benefits of effective fore/aft balance are:

The skier stands in an efficient posture
Even pressure will be maintained along the length of the skis
Ski design is able to be utilised to its full potential
It makes it easier to access the other movements

An Athletic Stance

An athletic stance is the reference point for describing how a skier is standing on their skis. It is described here in a stationary position.

The centre of gravity will be directly above the centre of the base of support and directly between the two skis. The ankles, knees and hips will be bent relatively equally, with the hips aligned over the top of the feet and the upper body tilted forwards. The feet will be about hip width apart with the knees aligned laterally, approximately over the second toe, and the skis flat on the snow. Arms will be held in front of the body slightly wider than shoulder width at approximately navel height. The skier’s weight will be spread evenly between the two skis.

Fore/aft balance is constantly challenged when skiing. The angle of the slope under the foot, the speed of travel and the phases of the turn are always challenging the relationship between the base of support and the centre of gravity.

At a beginner level the environment is relatively simple and only small changes in pressure or forces are felt from the terrain, but at an advanced level, this can become very complex. Fore and aft movements are required for adjusting the body parts as these changes under the feet occur so that we can keep the centre of gravity in an ideal athletic skiing position relative to the base of support and the intent of the skier. One way of doing this is to move the body back and forth along the base of support by flexing or extending the joints in the ankles, knees, hips and spine. The muscles surrounding these joints control this movement. Another option is to move the base of support back and forth under the body. This can be achieved by flexing the ankles (dorsiflexion) to pull the feet back or by extending the ankles (plantar flexion) to slide the skis forward while the upper body remains stable.

Either moving the body fore and aft above the base of support or moving the base of support underneath the body or a combination of both can be used. At a beginner level, it is generally easier to move the body above the base of support. As skiers advance they can develop the ability to manipulate the base of support.

Rotational Movement

Rotational movement occurs when the body or parts of the body move in a circular path around a defined axis. Parts of the body can move in the same or opposing directions.

In skiing the most common ways the body can rotate are:

Rotating the Lower Body

In this situation the femurs rotate underneath the pelvis and each leg becomes the vertical axis. The two points we use to define this axis are the pivot point on the sole of the foot directly under the ankle joint, and the head of the femur. Each leg is rotated independently around its axis. Most of the rotation in this axis occurs/originates in the hip socket and is controlled by using the muscles connecting the femur and the pelvis. As the leg rotates from this joint a rotational separation occurs between the femur and the pelvis.

Rotation of the femurs when skiing requires a combination of medial (internal) and lateral (external) rotation and adduction and abduction (the amount of each element required is dependent on the amount of flexion in the leg). Therefore, during any given turn one femur is medially rotating and adducting while the other is laterally rotating and abducting. The muscles that are used to create adduction are able to create a stronger turning force than those used to create abduction so the leg on the outside of the turn (which is turning inwards) can create greater turning forces.

Rotating the Upper Body

In this situation the spine becomes the vertical axis. The two points we use to define this axis are the cervical spine (neck) and the part of the spine that joins the pelvis (sacrum). The upper body rotates around this axis using the muscles surrounding the spine and mid-section of the body (core area). The rotation occurs along the length of the vertebral column, which results in the separation being incremental between the top and the bottom of the spine. All parts of the vertebral column can rotate to a certain extent but the most rotationally flexible part is the lumbar spine and throughout the thoracic spine.

The Goal of Rotational Movement

The goal of rotational movement is to create a change in direction of the skis. The most effective way to do this is with rotational movements of the lower body because this will have a more direct effect on the base of support.

The benefits of initiating rotational movement with the legs are:

It has a more direct influence on the ski
The skier is able to maintain good alignment
It aids in controlling edge angle
The rate and intensity can be altered with minimal effort

Good alignment is maintained due to the fact that when the legs are used to initiate rotational movement, rotational separation occurs. Rotational separation is the result of combining body and ski performances and it will need to increase, maintain and decrease during each turn. This means that the legs will turn to create a change in direction of the ski and an increase in the ski’s edge angle. Rotational separation occurs in each of the joints in the leg but predominately in the hip joint and the lower spine. The pelvis and upper body will follow the direction of the turn but will in effect lag behind the legs and the skis.

Rotational separation results in stability of the upper body and is controlled through the use of the core muscles. This stability allows the skier to maintain a strong biomechanically aligned position as the skis are turned.

Rotation of the lower body can create an increase in edge angle. To achieve this the legs must be flexed or the centre of gravity must move to the inside of the turn. As the femurs rotate and adduct and abduct, the knees move towards the inside of the turn, creating angulation and increasing the edge angle.

Rotational movements are adjusted depending on the amount of friction on the base of support, the shape of the turn and the forces acting on the body.

As well as leg (lower body) rotation and upper body rotation there are two other types of rotation that are commonly referred to:

Counter rotation is created by turning the upper body and lower body in opposing directions and is an example of Newton’s third law of equal and opposite reactions (see Skiing and External Forces). Counter rotation has a high rate of turning and a short duration and is most effective when the skis have very little or no resistance, such as on the top of a mogul or in the air.

External fulcrum is often referred to as a blocking pole plant and can be useful when skiing steep terrain and in moguls. If the ski pole is placed in the snow with the tip of the pole ahead of the handle, resistance is created that pushes back on the skier’s hand creating torque and a fulcrum to turn around. This works best at the end of the release phase when the skis are flattest in relation to the snow.

Lateral Movement

Lateral movement occurs across the base of support, or from side to side, and is defined in two parts:

Movements of the body or parts of the body travelling in a sideways relationship to the base of support
The base of support moving sideways from the body

The goal of lateral movement is to edge the skis, to balance with the forces, and to allow the skier to balance on the outside ski.

Lateral movement can come from many different parts of the body. Some of the lateral movements can be very slight, others will be much bigger.

Lateral movements to edge the skis will ideally start from the lower body. With the forces of skiing, the centre of gravity must then move inside the base of support, and inclination allows a skier to balance with those forces.

Inclination starts at the feet and moves up through the body. As a skier’s legs incline into a turn, then the centre of gravity moves inside the base of support.

The range of inclination a skier can use depends on the skier’s speed of travel, snow conditions and terrain. Inclination on its own, especially at slow speeds, can leave a skier finely balanced and in danger of tipping into the turn and losing grip on the inside edge of the outside ski. To avoid this loss of outside ski balance, inclination is always used in conjunction with angulation.

Angulation is the result of lateral movements of the parts of the body relative to one another and is achieved by abduction/adduction movements of the femurs. A rotation of the legs from a flexed stance will also allow angulation to be created or decreased. “Angles” are created as the lower body moves towards the centre of the turn and the upper body remains stable or moves towards the outside of the turn.

Lateral movements in the form of angulation allow the skier to maintain outside ski balance, as well as adjust the edge angle without necessarily affecting the degree of inclination being achieved by the centre of gravity. Angulation through the end of the turn also allows the skier to prepare the centre of gravity to transition across the base of support as the new turn starts.

In a wedge, inclination and angulation are created by the skier moving their feet and legs out from underneath a stable upper body, this is done through abduction.

Once turning and forces are greater, but still at lower speeds, inclination of the lower legs in conjunction with angulation allows the skis to be tipped onto their edges creating outside ski balance without the need for the centre of gravity to move too far inside the turn.

At higher speeds with a greater range of inclination and edge angle, angulation is used to allow the skier to maintain outside ski balance as the centre of gravity moves further inside the turn.

Angulation is created at the ankles, knees, hip joint and spine. Angulation at the ankles is created by inverting and everting the feet. Inversion is created by tilting the sole of the foot inside (supination) i.e. lifting the big toe, and eversion is created by tilting the sole of the foot to the outside (pronation) i.e. lifting the little toe.

The timing and range of angulation movements are important and will depend on such variables as turn shape, speed, friction and snow conditions.

The benefits of accurate lateral movement are:

The skier is able to balance against the forces created
The centre of gravity is able to move inside the turn, creating edge angle
Edge angle is able to be maintained, increased or decreased as needed
Grip/pressure is controlled on the skis (primarily the outside ski) causing it to penetrate the snow and make the ski bend, therefore utilising ski design
Balancing on the outside ski allows the use of the stronger adductor leg muscles to make rotation easier

Vertical Movement

Vertical movement moves the centre of gravity closer to (flexion) or further away (extension) from the base of support and is controlled by movement at the ankles, knees, hips and spine.

The goal of vertical movement is to allow the skier to move with the skis, maintain an athletic stance and to continually reposition the body to achieve the desired outcome (balancing, rotating, edging, pressuring) throughout the phases of any given turn. Vertical movements need to be continuous, consistent and controlled to be effective.

As a stand alone, vertical movement simply moves the centre of gravity towards and away from the base of support, but when combined with the other three movements – fore/aft, rotational and lateral – its real benefits are obvious. Accurate and well-timed vertical movements allow the other three movements to blend together and have the optimum effect on ski/snow interaction.

The two components to vertical movement are flexion and extension:

Flexion

Flexion moves the centre of gravity towards the base of support. This is achieved through bending at the ankles, knees, hips and spine. The ankle is limited by the stiffness of the ski boot which means that the knees, hips and spine need to compensate to ensure that the centre of gravity remains over the base of support. Flexion can be active which is achieved through eccentric muscle contraction to shorten the legs, or it can be passive, which is achieved by relaxing the leg muscles. Passive flexion is commonly used to maintain ski/snow contact during changes in terrain.

Extension

Extension moves the centre of gravity away from the base of support. This is achieved through an opening of the ankle, knee, hip and spine. The centre of gravity will still maintain a perpendicular relationship to the base of support in this taller position.

The benefits of accurate vertical movement are:

The skier is able to maintain/increase/decrease pressure on the skis
The skier is able to maintain a desired relationship with the snow surface
Vertical movements provide rhythm and flow
The skier is able to blend the other three movements