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.
Interaction of the Four Movements
Fore/Aft Movement
When the skier is centred on their skis it will have the following positive relationship with the other movements:
- The balance point of the skier will be over the centre of the ski, allowing ski design to be utilised (rotational and lateral)
- The skier will be able to rotate the skis effectively due to effective alignment allowing access to the appropriate muscles (rotational)
- Joints will be able to be turned appropriately and incrementally, creating rotational separation (rotational and lateral)
- The entire length of the edge of the ski will contact the snow when the skis are edged and the ski will bend and be pressured from the middle (lateral)
- Effective alignment will allow all joints and muscles to flex and extend appropriately (vertical)
Rotational Movement
Rotating the legs to turn the skis will have the following positive relationship with the other movements:
- The rate at which the legs are turned affects the skier’s ability to stay appropriately balanced fore and aft. As the skis turn down the hill the slope angle increases and the skis speed up. The faster the skis are turned down the hill the quicker the skier needs to make fore/aft balance adjustments (fore/aft)
- The skier will be able to maintain alignment and balance on the outside ski (lateral) rotating the femurs can increase edge angle (lateral) turning the joints incrementally creates rotational separation. This angles the upper body more toward the outside ski creating lateral balance (lateral)
- Rotating the femurs can increase edge angle (lateral)
- Turning the joints incrementally creates rotational separation, angling the upper body more toward the outside ski creating lateral balance (lateral)
- Appropriate rotational movements will allow the skier to both incline and balance on the outside ski, enabling the skier to manage both centripetal and centrifugal forces which are created by turning (lateral)
- Effective alignment will be maintained allowing the skier to flex and extend as required (vertical)
Lateral Movement
Balancing accurately laterally and effective use of inclination and angulation will have the following positive relationship with the other movements:
- Engaging the edges of the skis will create a solid platform to balance on and to flex and extend from (fore/aft and vertical)
- Inclination and angulation allow the skier to balance with the forces created by turning and to maintain balance along the length of the ski (fore/aft)
- Balancing on the outside ski allows skiers to utilise stronger turning mechanics (rotational)
- The amount of edge angle affects the amount of intensity required to rotate the femurs. The higher the edge angle the more intensity required (rotational)
Vertical Movement
Moving vertically will have the following positive relationships with the other movements:
- Vertical movements allow the skier to balance as required along the length of the ski (fore/aft) the muscles used for leg rotation vary with the posture of the leg (rotational)
- Flexion of the leg will increase the amount it can be rotated (rotational)
- A flexed and rotated leg will increase edge angle (rotational and lateral)
- The centre of gravity is able to be directed inside the line of the base of support (lateral)
- Pressure on the skis is able to be adjusted (lateral)
