• Other key Concepts

    How does it work with skiing really from a technical and mechanical perspective?

    The following gives a comprehensive explanation to the technology behind skiing and the forces involved. Understanding this will help you improve as a skier once you get a better understanding of what really happens when you ski. Basically it's about how much (or little) you edge, pivot and load your skis and how you, through combining these elements and distribute the forces, achieve a better (or worse) balance.

     

    BALANCE

    When something is in balance, that something is stable. An object is stable as long as the force of gravity falls within the support area. If the force of gravity ends up outside of the object's support area, the object will tip over. (Assuming the object is stationary).

    The lower the center of gravity and the greater the support area, the more stable is the object. When you ski, you can regulate your balance forwards - backwards, side - side and upwards - downwards. To obtain a good balance you need to find a base position where you have optimal readiness to move. Balance always equals movement. Fully straightened joints make you stiff and immobile, leading to loss of balance. Always strive for a relaxed enough tension level throughout your body and sligthly bent joints in your ankles, knees, hips, back and arms.


    Watch movie about balance technology HERE...
     


     

     

    ROTATIONAL FORCES

    Pivoting the skis is a prerequisite for turning. You pivot the skis in the direction you want to turn. Depending on how much you pivot throughout the turn you'll achieve different results. Pivoting the skis creates friction between the ground and the skis and make it more or less difficult to pivot depending on the surface, how much area of the ski base that touches and the load onto it.

    You pivot the skis by:

    Pivoting through bending/twisting your ankle and leg, the easiest and most obvious way to pivot the skis. The outside leg rotates inwards and the inside leg rotates outwards.

    Counter-pivoting, which is a rotation in one direction in the lower body arising from rotating the upper body (above the waist line) the other direction. When the upper body turns away from the turning radius a tension in the muscles, especially in the abdomen and back, gets created. This tension generates a counter-movement in the lower body. You can try counter-pivoting through standing (without skis) and turning your feet in one direction while turning the upper body to the other. Jump up and change direction.

    Pivoting along with the skis is carried out through allowing the upper body to stay perpendicular to and follow the skis along the turn, and leads to a slight rotation in the body. At the end of the turn the upper body will continue this rotation and end up pointing up the hill.

    Rotating the upper body towards the new direction of travel to initiate the turn. Twisting the upper body will result in a rotational velocity that transfers down to the lower body and skis, which will then start turning into the new direction.

    A correctly executed pole plant can sometimes facilitate and enhance the twisting and pivoting of your body. Planting the pole for a new turn creates a torque, which helps the pivoting into the new direction of travel.

    Watch movie on different techniques to turn HERE...

     


     

     

    EDGING

    Edging the ski means to angle the ski base away from the snow so the load concentrates more on the edge of the ski. Edging the skis is an absolute necessity in order to turn, stop and to stand still on an inclined slope.
    You can actively edge your skis through:

    Edging with your knees, which is basically an inward rotation of the femur. Out of your ski boots it is also possible to angle the ankle, but with the boots on this movement is very limited. However, there's still some edging to achieve through moving the foot.

    Edging with your hip. With increasing speed, it's near impossible to sustain the increasing forces through edging only with the knees. It's then necessary to involve the hips. To edge with your hip you simply angle the hip inwards and the skis will get on edge.

    Edging with the body. When you're going really fast it becomes necessary to edge the skis by leaning your entire body into the turn.

    Edging entails an ever-changing movement. In low speed the knees initiate the edging in the turn. As you gradually move through the turn the knee edging gets supported from using the hip angle and body lean. Without speed and momentum, though, it's impossible to lean since you'd then fall over.

    Watch movie on different techniques to edge HERE...

     


     

     

    POWER/PRESSURE/FORCE

    When skiing we can control the forces between the skis and the snow through loading and unloading our skis.

    Through our muscles we can flex and extend our hips, knees and ankles and thus, reduce or increase the pressure from our skis on the snow. By simply moving up and down we change the pressure and affect the forces. In other words, by moving up and down (loading and unloading the skis) when skiing we can affect the load on the snow and thereby facilitate our turning (pivot the skis into the new direction when the skis are unloaded). Changes in the pressure from our skis on the snow also arise with changing terrain. When a skier brings momentum into an uphill or a mogul the load increases. Similarly, the load decreases when a skier comes with speed over a crest. You can also actively equalize the pressure when skiing moguls through pulling your knees up towards your chest when going over a mogul and thereby equalize the pressure.

    Various Forces 

    The forces that affect you as a skier are primarily:

    Gravity: Everything on earth is affected by gravity. Gravity is what causes apples to fall to the ground and not up in the sky. Gravity draws us back to the ground again when bouncing on a trampoline instead of continuing upward, and when we jump on skis gravity sees so that we land again.

    Normal Force: Newton's third law states that for every action there's an equal and opposite reaction. Translated to skiing this means that as much as a skier presses down onto the surface, equally much will the surface press up against the skier. The force is exactly the same in both directions and always perpendicular to the surface. Normal Force is a direct counterforce to gravity.

    Friction Force: Friction is generated by roughness on surfaces rubbing against one another. For solid bodies glue is on the one extreme, with a huge friction force, while oil, where almost no friction exists, is on the other extreme. Friction affects a skier when the ski bases glide on the surface (snow). The Friction Force act in the opposite direction of the force that pulls the skier forward. You can minimize the Friction through well-maintained and waxed bases of your skis, reducing the roughness of the surfaces.

    Air Resistance: Air resistance is the skier's "frictional resistance" against the air and is affected by the following three things: the front surface area, the streamline shape and the speed of the skier. Through tucking your body into the shape of a down hill skier, you can increase your streamline shape and reduce the air resistance. Air resistance increases with speed.

    Centripetal Force: Centripetal Force is the external force that causes an object to follow a circular path with a constant rotational speed. The Centripetal Force is directed towards the circle center. Centripetal Forces seem to always stay perpendicular to the direction of the motion. When skiing you're affected by Centripetal Forces generated from turning.

    Centrifugal Force:The Centrifugal Force is the force directed outwards from the center of the turn when skiing. It is a fictitious force, experienced as a result of our body's inertia. The Centrifugal Force is the force that squeezes you against the car door when turning in high speed, or wrings the water out of the clothes, through squeezing them towards the drum walls, in a spinning washing machine. As a skier you are affected by Centrifugal Forces when turning. You sustain these forces with help of your muscles and how you stand on your skis. When a turn or a hockey stop make a motion come to an abrupt halt, Centrifugal Force is what causes the skier's body to continue in the original direction.







     

    Other Key Concepts

    Center of Gravity: The Center of Gravity is the point on the body where gravity pulls from. It is an imaginary point and if one was to hang a body in this point the body would be balanced no matter how one twisted and turned it.
    By understanding your Center of Gravity when skiing, you'll stay balanced easier.


    Support Area: When a skier stands on flat ground with both skis on the ground and both poles planted, a number of support points are formed. The Support Area is the area of the surface inside a straight line drawn between these points. As a skier you'll constantly change your Support Area while riding. You can increase your Support Area through widening your stance.


    Balance: When something is in balance, that object is stable. An object is stable as long as the Force of Gravity falls inside the Support Area. If Gravity falls outside of the Support Area the object will tip over (provided that the object is stationary). The lower the Center of Gravity and the larger the Support Area, the more stable the object.


    The shape of the Skis: The ski shape influences the turn greatly. You have probably heard of different skis having different turning radius The turning radius of a ski depends on how the ski is built and what its waist looks like. (The waist is the middle of the ski, under the binding.) The wider the ski is under foot compared tothe width of the tip and tail, the smaller the turning radius. When placing an unloaded ski on edge, only the tip and tail will lie against snow, while the waist will be in the air. When loading the ski in this position, the entire edge will lie onto the snow, creating an arc. That arc is what makes the ski turn. The smaller the waist, the smaller the radius of this arc.


    Progression: When a skier stands on level ground two forces, the Force of Gravity and the Normal Force, influence him/her. These forces are equal and counteract each other. When the skier proceeds into a hill, he/she will start sliding forward due to Gravity, which is no longer perpendicular to the surface. On an incline Gravity gets divided into a propulsive force and a force pushing the rider towards the surface. The Normal Force is equal to the force pushing the rider to the surface. When the slope steepens the propulsive force increases at the same time as the force against the surface decreases, resulting in less friction and higher speed.

     

    When the skier start moving forward opposing forces appear in the form of Friction and Air Resistance. Friction, as mentioned above, reduces as the slope gets steeper. Air Resistance is dependent on the speed and the front surface area of the skier. When the speed is high enough that the Air Resistance and Friction are equal to the propulsive force, the skier has reached his/her maximum speed.