My 2c on knee roll (in context of steeps and bumps)

SiyangXie@FB

Knee roll is a very advanced technique in skiing. IMO, it’ll get you from advanced~expert level to solid~high expert level. It’s not a particular drill, not a trick, but it’s the most efficient way to initiate a turn with just the necessary movement and best precision.

I’ll first talk about problems that I observe on many good skiers, particularly on difficult terrains: 1) a little unnecessary/extra body movement during turn init/transition phase, e.g., hop, hand swing; 2) hesitation, even some good skiers hesitate a bit before starting next turn; 3) precision of movement, which is the ultimate challenge to refine skiing technique, e.g., oftentimes skier’s COM lags a little bit and needs to be recovered before making next turn, or COM is a little too forward (too much pressure on the front edge) so you need to drag COM back a little bit to release. All three above are in fact correlated.

What is knee roll?  Put your butt on a chair with upper body straight up and feet on ground. Then, pretending you’re skiing, e.g., just finishing the previous turn with ski about 45-60 degree cross the line that your upper body is facing (i.e., fall line).  Now roll your knee to the other direction as if you are making next turn. Try to simulate the real turn as much as possible. Feel the edge transitioning to new downhill foot. Your upper body, hand, hip all remain still.
Some incorrect movements: a) rotate your ankle more than your knee/femur; b) keep the feet flat on round while only rotating knees/legs.
Let’s do the knee roll more precisely with just one leg: your new downhill foot. This time, let’s just roll it halfway (just the init phase), roll the knee until your foot is flat on the round (without even moving that foot).  Repeat several times back and forth.  Now remember the arc your knee is traveling.  Then, let’s stand up, and imagine you are on a steep slope and trying to turn, try to feel the arc of knee, which gives you the direction to project your COM/hip outwards (down the fall line) while your knee is travel on the arc.  You see? As you are trying to roll your knee to engage the new edge, you naturally drive your COM/hip towards to the precisely correct direction.  Now, sit down again with your hips remain still, can you still roll your knee along the same arc?  No!  Because you must move your hip to allow knee to travel along that arc!

There are a few reasons that I think knee roll works:
1. it gives your the precisely correct direction to drive COM/hip, without having to think about it, which is critical for expert skiing;
2. it makes the weight transfer implicit without your having to think about it or make extra “hop“ movement to shift weight, or load/unload.
3. in a sense, a slow knee roll is very similar to “flex and tip” technique in a medium-long carved turn. But knee roll process is swift and neat.  It enables you to blend pivoting/steering smoothly while setting edge angle, in a sense, it’s more active than “flex and tip” and eliminate the mental “waiting time” and hesitation
4. with knee roll, you can very quickly initiate a turn in moguls at the right time. Otherwise, if you think too much, you’re likely to rush your movement, sabotage your balance or mess up with the turn timing.  Since knee roll is just a very subtle and light movement, your upper body can remain quiet and your vision can stay far, while keeping balance on outside foot all the time.  Yes, the movement of knee roll is critical for mogul skiing.  On flats (no matter how steep) it’s less demanding to move your COM precisely and timely, and thus more fault-tolerant.

If you're interested, I'll be skiing Whistler this spring for at least 3 days, we can hook up to ski together and I can explain the technique better.

westvest

Knee roll 和steering的关系是啥？你滑zipper line的时候,是两个同时使用吗？

常hold的住

膜拜楼主，看上去好高大上啊。
以前只听说过 rolling blade ， or rolling ankles。
偶再想想能否再往上引申为rolling hip

SiyangXie@FB

常hold的住 发表于 2016-1-21 00:58
膜拜楼主，看上去好高大上啊。
以前只听说过 rolling blade ， or rolling angles。
偶再想想能否再往上引 ...

"Knee Roll: As the weight shifts onto the new ski the knees roll into the angle of the new turn."

from http://www.mogullogic.com/Terms.html

btw，Chuck Martin的Mogul logic是全北美最好的两个mogul camp之一，另外一个是whistler的momentum camp。

norman

SiyangXie@FB

westvest 发表于 2016-1-21 00:45
Knee roll 和steering的关系是啥？你滑zipper line的时候,是两个同时使用吗？

我从来没有有意识的去想过要不要steer，我觉得滑雪就是通过去感觉edge上的pressure来精准的控制重心位置和移动，steer我的理解是快速engage new edge并主动用膝部加压同时pivot，就是swing short turn，如果加压稍微缓些让ski多绕出去一些set更大的edge angle(再继续加压)，就是过渡成了carved short turn。不过我倒是觉得深究这些理论对我这个阶段并没有太大的帮助。我的一些进步和体会更多都是mindset上的，就是心理上的一个小hint，比如roll knee，比如vision。

要是说关系，我觉得knee roll作为init turn的movement，可以跟pivot自然的结合。

KuoiGuaBoarder

哇，这么好的东西不买钱啊

KuoiGuaBoarder

just finishing the previous turn with ski about 45-60 degree cross the line that your upper body is facing (i.e., fall line).

大侠能展开一下吗？

upper body facing fallline， 这是滑大弯啊， ski如何能够在一个弯要结束的时候和falline形成， ４５， ６０的夹角。

lulu

好东西。我觉得最重要是说的一种mindset.  练习的时候可以把这个三维运动分解，但是滑的时候因为只能想一个整体，这个knee rolling概括了合在一起的运动方式

cat

god bless the knee