Classic Technique
Kenneth Salzberg
started a while ago. I'm told that the problem with our gateway to the
newsgroup is fixed (have you heard this before?) and so all the folks on
the newsgroup should be able to get not only Ken R's cogent thoughts about
all this, but mine as well (aren't you all lucky?).
I'll check the newsgroup in a couple of days to see if this is true, and
let everyone know one way or the other.
-Ken
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Kenneth Salzberg ksal...@gw.hamline.edu
Hamline University ksal...@piper.hamline.edu
School of Law (651) 523-2354
1536 Hewitt Ave.
Sisu Skier - Team Birke St. Paul, MN 55104
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Ken Roberts
distribution, I received E-mail from Ken Salzberg about a different topic.
While looking at that web page, he had found some other stuff I had been
working on -- some lessons about Classic technique I had discovered only
with difficulty during my last year.
One of those "lessons learned" for me was:
- - The "wax pocket" is centered around the toe of the foot, not the center
of the foot or the heel.
- - So I can get a little better grip any time just by pressing my toe.
for more detail, see
http://www.roberts-1.com/xcski/classic/secrets/wax_pocket.htm
_____________________________________
Ken Salzburg wrote me in his E-mail:
While your analysis of the kick may help beginning/intermediate skiers,
experts focus on two rather different techniques: kicking from the heel, and
knee drive.
If you are thinking about weighting, or kicking, from the toe, you already
have too much of your weight off of the ski (you are already coming up).
Moreover, the part of the ski you are weighting will be forward of the toe
(due to the forward lean of the skier and the movement of the Center of
Gravity forward during the kick). The longer you can have weight on your
heel, the longer your weight and drive (see below) can be applied to the wax
under the ball of the foot.
One of the drills we do in the summer is to get a partner, face up a gentle
hill, and practice falling forward off of one foot and when kicking off,
keeping the heel down. We check this by having our partner put his or her
finger just under the back of the heel, and let us know if we have pressed
our heel down during the kick off (works best on grass).
In video work, our coach is always trying to get us to emphasise driving our
knees down toward the ski at the beginning of the kick. I always have had
trouble with this (my excuse is tight tendons - which I
can't use anymore now that I've been doing Yoga for a year). I find I have
to think about it almost before I'm finished coming up from the last kick.
In any case, the knee drive (because of the geometry of the body) if done
right, moves the hips more forward than down, but enough down to help weight
the wax. When I am "in the zone" - and doing it right, I find I can stride
up hills I slip on when I'm not.
(end of Ken Salzburg's note)
___________________________________________________________
What do you all think?
Gene Goldenfeld
appropriateness of "knee drive," if I understand Ken correctly.
It tends to lower the vertical center of gravity away from the
torso and move the horizontal center back. It also tends to
tighten the knees, while the goal is to have 'soft' knees. I
would suggest instead leading with the torso and in that context
extending the foot with each stride. Also, bending the knees
more on hills and lowering one's hands usually obtains the same
positive grip effects without sacrificing correct body position.
Gene Goldenfeld
Ken Roberts
gentle
> hill, and practice falling forward off of one foot and when kicking off,
> keeping the heel down. We check this by having our partner put his or her
> finger just under the back of the heel, and let us know if we have pressed
> our heel down during the kick off (works best on grass).
It strikes me that this could be a helpful drill -- but for a different
reason. Another possible interpretation is that the _mental_image_ of
kicking from the heel helps many skiers keep their leg-push going _longer_,
because they learn to delay the final toe-off. That fits my conclusion from
physics that "long and smooth" is a more efficient way to ski classic
stride.
But human perception is tricky: Just because you have a strong mental image
of driving the heel does not prove that there is not still objectively
_physically_ a greater force through your _toe_. When I experiment on
dryland, I find that I have to concentrate pretty hard _not_ to have
significant toe-force once my leg is out behind me with the heel touching
down. And it gets even trickier because the natural ending of the leg
stroke is with a "toe-off" motion -- which implies lots of pressure thru the
toe.
So who can really know what's happening physically, especially when you
transfer it to snow and mix it with changing terrain and competition and
fatigue. The only way to know for sure is to put force sensors in your ski
binding. Like now in serious bicycling training they put force and tension
sensors on the pedals or chain -- so the coaching can get beyond mental
imagery / perceptual illusions and find the real weak spots in the pedaling
motion. It's the next stage of serious training, after the heart monitor.
I'm all in favor of creative use of mental imagery. What I will not do is
interpret it literally as objective physics.
> The longer you can have weight on your heel, the longer your
> weight and drive (see below) can be applied to the wax
> under the ball of the foot.
Here it's sounding to me like you're saying that your coach's tip works
because focusing weight on the heel gives better grip than focusing on the
toe -- a claim about the physics.
But with the way the wax pockets of all my classic skis are designed, and
the way all my bindings are mounted, and with the way I normally wax --
that's clearly not where most of my grip wax is.
And in my dryland experiments, pressing the heel is less effective in
closing the wax pocket to the floor than is pressing the toe. To me it's no
surprise that it's more effective to press the wax pocket through its
center, then to press out by one of its ends.
In my on-snow experiments, I've been standing on an uphill slope with all my
weight on one ski focused on my toe, and my grip was holding -- but when I
shifted my weight back to my heel, I slipped back down the hill. I describe
those experiments in detail on my web page:
http://www.roberts-1.com/xcski/classic/secrets/wax_pocket.htm
Have you gotten different results from those experiments? (Maybe your skis
are designed different from mine.) Or do you know some better-designed
experiments?
> In video work, our coach is always trying to get us to emphasise
> driving our knees down toward the ski at the beginning of the kick.
Sounds interesting. Reminds me that Steiner Mundal's suggestion was to
initiate the kick early with the hamstring muscles. Different image, not
sure if it comes out to the same thing.
Sounds to me this is an independent concept/question from my question of
where is the most effective point to focus pressure on the wax pocket. If I
wanted more grip, seems like I could easily combine "drive my knee down"
with my concept of "press the wax pocket through its center, with my toe".
Ken
Kenneth Salzberg
Here is an exerpt from Steinar Mundal's note to Master Skier about
recent changes in Classic Technique (at
http://www.masterskier.com/techniques/first.html):
The main differences in classic technique are as follows:
1. Frequency.
2. Lower position.
3. Start the kick early.
4. Never stand up on a straight foot on the glide face.
5. The same angle for the upper body as the leg from the knee and down
to the foot at the start position.
6. Very little rotation in the hip. You can see this in the best
skiers from behind.
7. The upper body stays stable, not moving back with the kick, just
let the knee bend a little bit more, so you can get a better and stronger
kick.
I think what our coach is trying to get us to be able to do by
talking about "knee drive" is trying to combine the wisdom in 5. and
7. (he has pointed out the need to try to achive 5 during our video
sessions - pointing out those whose angles are close to the same as doing
it right).
So, the question is, how do you keep the torso angle and lower leg angle
the same while kicking? Not by straightening the leg, not by dropping
just the torso, but by driving the knee towards the front of the ski
while keeping the heel weighted, thus bringing the torso down (to put
weight on the wax).
Anyway, that seems to work. As I said, when I get it right, I get more
positive kick. Those of my fellow skiers who do it better than I do ski
faster than I do.
Gene Goldenfeld
refers to forward motion, as in 'drive the leg (or foot or knee)
forward.' I simply misunderstood your reference.
GG
Ken Roberts
moose-hoofs workout over the weekend.
Makes a lot of sense -- also as a way to maintain down-force during the
full-length of the leg-stroke -- so Thanks, Ken.
I tried to mix that with focusing on my toe in the initial landing. Doing
both was trickier, switching the mental images along the way.
Ken