Skiing on one leg?
A further free extract from “Controlled Skiing”, my upcoming book taking a different slant on how to develop your ability to ski in control at all times on all pistes.
On one leg? Not literally perhaps, although it is perfectly possible, as you can see.
Elsewhere in the book we have considered what it is makes a ski perform the functions we want it to. Mostly these functions are either changing direction, or skidding to resist accelerative onward motion. In all cases this involves tilting the ski and bending the ski.
Forces have to be recruited from somewhere to facilitate these, and those forces result from the interaction of our ski and the snow surface, as acted upon by the motion of our mass through space: our momentum.
Imagine yourself standing up normally, in your everyday life without skis on (perhaps you are standing up, in which case you won’t need to imagine it). Your weight is being supported near enough evenly by each foot. There will be a given amount of pressure in pounds per square inch, or grams per square centimetre, over the area of your foot or feet.
Now lift one foot off the ground and stand on only one. If you were standing on a bathroom scale, there would be no change in its reading, you did not magically halve your weight. It’s a pity but there it is. However, a pressure sensor would recognise that on each square inch or centimetre of supportive surface, the pressure will have doubled. Same amount of weight, half the surface area.
There will be consequences. Do it for long enough and your foot will ache more. A careful inspection of your foot’s sole would show more distortion of your foot; more “squashing”. Your foot would tend to be squashed flatter, and spread out sideways more. In other words the shape of your support would be changed by the simple act of lifting up one foot.
The amount of change would vary according to how positively you lifted the other foot. You would not need necessarily to lift it completely. If you simply lifted it very slightly so that it still offered you support but not as much as previously, the other foot would take the added load and the amount of shape-change in either foot would be a function of the amount by which you did it.
Unsurprisingly, exactly the same thing happens when you do this on skis. That applies whether you are moving or not. If you are not, then you will find (if the snow is soft enough) that the ski you lift becomes curved downward – that is to say the tip and tail will drop lower than the centre. The other ski, the one supporting you, will bend in the opposite direction somewhat more than it did when your weight was evenly distributed.
Same thing happens when you are moving. Imagine you are skiing in an arc, quite a wide “open” one. Now imagine lifting the “inside” ski – the one nearer to the centre of the imaginary circle of which your arc is a part – what will likely happen to the one still on the snow, the outer ski? It has the same surface area as before but now supports all of your weight and the forces of your momentum, rather than only the previous half of it.
It will bend more, won’t it? So long as the snow is not like concrete, the centre of your ski where you ski boot fits, will press down more powerfully into the snow, and while the tip and tail will also do this they will not do it so much. The already-tilted ski will bend more to accommodate an arc which has a shorter radius; an arc describing a smaller circle. A tighter arc, giving a sharper change of direction.
This would be a marvellous result if you wanted to ski down a steeper slope without too much speed building up. You would be able to put in more changes of direction, more arcs, between the top and the bottom, and that would stop you shooting off down the slope in a too-straight line at speeds you might not like.
Here then, we have yet another case of skiing’s counter-intuitive nature. Our old amygdala brain would tell us if it’s steep or tricky “you want to keep your feet firmly planted on the ground, my friend”, but it would be wrong again. In an awful lot of circumstances we will find much more grip and stability if we place our faith, and our weight, more positively on the outside ski, than on either the inside ski, or both of them equally.
Whenever you see an expert skier, they may appear to be skiing on both skis – and of course in a sense they are – but in reality they will be skiing either wholly or in part on only one. During an arc in either direction you frequently only need support from one ski – the outside one – during that arc the inside ski is really just an encumbrance; you’d be as well off without it, but keep it with you because during the next arc it will be the one you need.