Let’s take a look at skiing from a nerdy perspective…
Downhill skiing mechanics is mainly about resisting the external forces that act on your body when you are making your turns so that you can keep your balance.
In the vast majority of skiing situations, it is gravity, which is the moving force. The role of our muscles is not as much to make us move as to balance the effect of gravity so we don’t get pushed around.
It is only in special cases that we use our muscles to create a moving force when skiing. If for example we want to jump or otherwise defy gravity. We can also use our muscles to save a crash by creating a moving force in the opposite direction of where we are about to fall.
But mostly when downhill skiing we use our muscles to help us stay in control and not get pushed around.
The safest way to create stable situations is to ensure that the gravity force line is kept within the supporting surface. When this cannot be done, we need to rely on the strength and reactivity of our muscles to make the resultant force stay above the supporting surface.
Just how much strength is needed depends on the terrain, and how aggressively we are skiing. Steep terrain, high speed and actively putting pressure on the ski and driving it are all factors that will increase the reaction forces at play. This is why a strong skier, skiing aggressively can get more tired than the skinny little lady who just cruises along.
Other factors such as heavy snow, skiing in the backseat and deep snow also requires more of our muscles. Of course you decide yourself how much intensity you will put into your skiing and where you want to go. That is provided that you are the one in charge, and not your skis! 🙂
The specific demands that downhill skiing mechanics put on a skier, is why skiing specific training makes such a big difference compared to general conditioning – or no conditioning at all.
If you want to have more fun skiing and not suffer the consequences of not being fit for skiing, pick one of the Strong Skier training videos here and become a better, stronger skier with as little as 6 weeks training prior
Reaction forces seen from the side
In this plane, the supporting surface is much longer because of the length og the skis. This helps us from falling forward or backward. It does however give you a bit more length to control.
It can for instance be hard to control the front of the ski if your weight is far behind and vice versa.
This is why you want to keep your center of gravity somewhat over your feet (blue surface) and not too far back, nor too far in front.
When it goes behind your feet, it is called being in the backseat and when it goes in front, we are talking about being forward.
The upper body will be pushed backward and feet forward and the skier would end up in the backseat, if she didn’t use her muscles to resist this movement. The combined muscle force needs to act as the green arrow to keep a stable position. This can be done effectively by working hip and knee extensors eccentrically. That means, contracting these extensor muscles so as to resist the hips and knees being flexed by external forces.
Reaction forces seen from the front
The effect of gravity (represented by the orange arrow).As you can see, the gravity force line (the vertical red line) falls outside support surface (blue surface). If we remove the green arrow representing combined muscle force, we will fall back into the mountain and the center of the turn.
It is thus muscle strength (the green arrow), that has to counteract the external forces to keep the skier in balance. More precisely we need muscle strength in the legs to put pressure on the skis (especially the external ski), while we seek to edge and carve.We also need strength in the hip muscles (especially gluteus medius and minimus) to keep the angle in the hip that helps getting
your gravity line closer to the supporting surface and thus create better stability. Without angling the hip, our skis will tend to slide away beneath us and we will fall into the hill.
The picture above is limited to show what happens in the transverse plane, but the skier is also affected by the forces in the sagital plane (antero/posterior), as you can see on the following