Skate technique USST two cents

Mark Drela wrote:

I have real trouble
accepting technique advice which has no apparent reason to work
from a physics viewpoint, or even a physiology viewpoint.

Technique advice may well deliver improved physics without us knowing about it. It may seem off
in some way on paper but the various drills and mental imagery might be resulting in good physics
anyway.

When you see "press knee to ski tip" that might appear to be nutty in terms of physics, but in
terms of how the whole human functions in terms of sports it might help you go faster!

There's a lot of impt factors involved, all related to each other---the tech and coach ideas are
meant to boost speed is all, not to try to segregate and explain what's going on in some sense.

--

Jeff Potter
****
*Out Your Backdoor * http://www.outyourbackdoor.com
publisher of outdoor/indoor do-it-yourself culture...
...offering "small world" views on bikes, bows, books, movies...
...rare books on ski, bike, boat culture, plus a Gulf Coast thriller
about smalltown smuggling ... radical novels coming up!
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Oops, sorry for forgetting Zach!

And we have some cool wax pros here, too.

And some top racers.

We're doin' fine.

Even with the Physics buffs in the crowd.

No, they're all needed, of course.

---But really I meant Inter/Natl *TEAM* coaches. You know, like with a country behind
em.

--

Jeff Potter
****
*Out Your Backdoor * http://www.outyourbackdoor.com
publisher of outdoor/indoor do-it-yourself culture...
...offering "small world" views on bikes, bows, books, movies...
...rare books on ski, bike, boat culture, plus a Gulf Coast thriller
about smalltown smuggling ... radical novels coming up!
...original downloadable music ... and articles galore!
plus national travel forums! HOLY SMOKES! 800-763-6923

It's interesting how it's individual, as one guy mentioned, yet we also get the case
as Pete reports where Kris Freeman (as I recall) was trying to ski like some other
guys. I found that I made a big jump up in my own sports (to winning local things)
when I first discovered that I had my own personal style and stopped imitating
others. I discovered my own special hand that I could play which had its own
strengths. I was neat, also, to not let others dictate races anymore. You go with the
group only to an extent, then you play your hand, your cards, and see what happens.
Obviously to win you have to do something individual at some point! You have to make
what you do YOUR OWN. But I suppose that if you're going to keep moving up you might
go thru many cycles of this: looking at others, at other ideas, then testing them,
then making them your own then seeing if they work. Somehow I don't think they'll
ever work unless you make em yours. And it would be a strange feeling to really feel
at home with a technique but then judge that it's slower and so you give it up.
Ha...people think you have to be ruthless with others in sport. Probably you have to
be most ruthless with yourself: to give up comfortable style things and go into
awkward new waters. The ability to learn... Perhaps the crux!

Janne G wrote:

I do agree with Pete that you have to try what works for you and not take it for
granted that how you are doing it today is the best for you, eg experimenting or
trying
new ways of doing things is the way for progress.

--

Jeff Potter
****
*Out Your Backdoor * http://www.outyourbackdoor.com
publisher of outdoor/indoor do-it-yourself culture...
...offering "small world" views on bikes, bows, books, movies...
...rare books on ski, bike, boat culture, plus a Gulf Coast thriller
about smalltown smuggling ... radical novels coming up!
...original downloadable music ... and articles galore!
plus national travel forums! HOLY SMOKES! 800-763-6923

Mark Drela wrote:

[ ] I'm talking
about changing from -50% to +90% or whatever. Negative
efficiency IS present in the form of the power-dissipating
muscle action, and it's important to identify it and
to minimize it. That's where the payoffs are, I think.

Maybe that's where relaxation comes in, partly.

I work on technique during the day. But when it comes time for a race
it's funny how it all changes. On the course it's all about doing
whatever it takes to keep the skis flying...and it often includes
techniques with no name and it often includes little thought about
technique at all. At the same time, there's doing whatever it takes to
stay out of the way of the speed: a non-interference policy. Go as fast
as possible. Then try to do zero extra work. Everything except the
speed-moment is total rest. It's quite a funny balancing act! To go as
fast as possible and not blow up.

[ ] A number of the people there
were accomplished physiologists, elite athletes,
engineers, etc, so it was all fairly well grounded
in reality.

Where's the psychologist and priest? Without including DESIRE,
motivation, drive, we're nowhere. : )

I recall in Mike Muha's website report on his parameters lab-testing that
they rated his "pain threshold" or some such thing. So there's that, too!

As Pete says "Ya gotta want it!" ---Or is that as Sten says...

OK, so you guys DO have some "elite athletes"---they should keep you on
track.

--

Jeff Potter
****
*Out Your Backdoor * http://www.outyourbackdoor.com
publisher of outdoor/indoor do-it-yourself culture...
...offering "small world" views on bikes, bows, books, movies...
...rare books on ski, bike, boat culture, plus a Gulf Coast thriller
about smalltown smuggling ... radical novels coming up!
...original downloadable music ... and articles galore!
plus national travel forums! HOLY SMOKES! 800-763-6923

"Pete Vordenberg" skrev i melding
om...


These technique principles are what Kris Freeman is working on AND
what a beginning skier should be working on. The principles apply to
ALL skiers.

The three most important elements of technique are correct body
position, efficient application of power, and using the correct tempo
for the terrain.


....and shape.


--
Terje Henriksen
Kirkenes

"Ken Roberts" wrote in message ...
It's great to see on this newsgroup some goals other than racing -- like
feeling good (Grissy) and looking good (Jay W).

Jay Wenner asked:
Is the goal here to ski with technique that looks
good, or to ski fast regardless of how it looks?

Slow: one of my current goals is to learn to skate slow.

-When Alsgard was in MPLS, he said something to the effect that the
American's biggest mistake is that they're too worried about
technique.

I guess I should preface this post by saying that I have a very
technical background, pchem, statistical mechanics, plus all the math
and biochem...but I think technical is not the way to learn to ski.

1. The reason I asked the question above, is that I think it's very
possible to skate fairly slow (i.e unable to go faster) with technique
that looks good (but is inefficient), or ski fairly fast with only
fair technique that's very efficient. To skate really fast, you have
to have both good conditioning and good technique, or at least good
enough technique. For classic, you simply have to have good technique,
unless the course rewards double-poling. I think classic skiing really
rewards good technique, but I guess we should define good technique.

-I think it involves more than proper placement of various body parts;
it involves very well coordinated muscle movements and precise timing.
It involves very good balance so the body is not wasting energy
regaining balance and the muslce movements result in efficient
propulsion.

2. Another thing to think about is how the really good skiers learned
to ski with the technique you're trying to copy. I can assure you that
they didn't learn by thinking about physics. I think the good skiers
learn to ski well by skiing a lot and getting some occasional pointers
from coaches.

So an analogy. You copy an artist's painting by precisely trying to
mimick the exact shape of the eyes, the colors used, the quality of
the lines, but the artist (in painting the eyes) was simply trying to
convey anger in the eyes.
Trying to copy the technical aspect doesn't give the same result.

Or maybe golf is better because it involves physical movements. I've
seen many people with beautiful swings, mostly technically correct,
but they score pretty bad. On the other hand, some guys have terrible
swings but the hit the ball well and score well. Their terrible
looking swing works well because it repeats and has good timing,
balance, and power just like a really good player's swing. They also
have good touch like the good players. In golf we call these guys
hustlers.

I think the good skiers learn (practice) to ski with balance and
power, and the tons of skiing gives them good muscle efficiency. Some
of the finer technique points come from coaching. I don't think a
coach can "instruct" a skier to good efficient technique. Much of it
comes from the skier own perception and practice.

Jay Wenner

I agree that thinking correct physics doesn't make me ski better.

Jay Wenner wrote:
I think the good skiers learn to ski well by skiing
a lot and getting some occasional pointers from coaches.

That describes much of how I learn to ski better.

You copy an artist's painting by precisely trying to
mimick the exact shape of the eyes, the colors used,
the quality of the lines, but the artist (in painting the
eyes) was simply trying to convey anger in the eyes.

Often what I'm trying to do when I look at videos of elite racers is not to
copy the exact movements (e.g. swing my torso 53 degrees left and 48 degrees
right at 53 rpm because that's what I measured Elofsson doing), but rather
to look for deeper physical principles (e.g. use reactive side-force to add
forward-motion power). I don't always succeed in that, because ski skating
is complicated, but I can keep trying to perceive and analyze better. Then
I try to _feel_ the reactive side-force in my actual skiing.

-When Alsgard was in MPLS, he said something to
the effect that the American's biggest mistake is that
they're too worried about technique.

I'm not sure how Alsgaard knows so much about American amateur masters
skiers, but he might be right about the ones he's met in Yellowstone and
Minneapolis. But I am confident that if he had looked at _my_ skiing or my
videos from four weeks ago, he would have pointed out four major technical
improvements for me to work on.

All I know is that in these last six days I'm seeing the fruit -- from
working a lot on specific techniques, getting videos of my skiing taken
about once a week: Every day I'm seeing my skiing get stronger and more
under control. Like today for the first time I skated uphill in ungroomed
soft snow with no poles. But not only was I _able_ to do it for the first
time -- also by coordinating some specific new techniques (new to _me_), I
was able to climb _slowly_ (yet without stalling), and so keep it all going
for a much longer time than I ever imagined I could.

Maybe next year (or next month?) I'll reach the point where I don't think
about technique much any more -- like in my other long-time sports (road
bicycling, ski mountaineering downhill and uphill). But right now it's
pretty exciting.

Ken

Lots of valuable ideas and analysis here -- thanks for writing it, Mark.

Mark Drela wrote
I don't remember seeing anyone separate the
power-producing (good) and power-dissipating
(bad) muscle action.

I know that I haven't gone that far in my numerical spreadsheet model --
because it's hard work to generate credible numbers at that level --
especially for a fully three-dimensional motion like skating, where each
major body part has six (non-independent) state variables -- subject to
constraints based on bone-joint geometry, etc.

But I agree that it's worth analyzing conceptually -- to look for big
payoffs.

New Payoff?
A different kind of payoff available in _skating_ is to get positive
forward-motion work out of "power-dissipating" muscle action.

Example: Starting the sideways swing of the torso generates a positively
useful reactive side-force thru the edge of the ski into the snow. But with
proper timing, _stopping_ the torso swing _also_ generates a positively
useful reactive side-force, thru the edge of the _other_ ski (provided that
the skier's body weight has been transferred meanwhile to that next other
ski).

A common flaw I see with almost all ski
technique arguments is that they ignore this
"zero sum" cardiovascular constraint.

I'm open to embracing that constraint -- but I'm still waiting to see some
answers to the multiple arguments I made against it in my Jan 16 post --
especially why it should apply to non-elite athletes in 3-to-6-hour-long
events. And if it's a static "zero-sum", then how come XC skiers often have
higher VO2max than bicyclists?

Mark's new points about this from bicycling are valuable evidence, but: (a)
bicycling is the physically-biomechanically simplest propulsive connection
between human muscles and the external environment, while ski skating is
arguably the most complicated; and (b) if it's really all a zero-sum "wash"
even in bicycling, then how come so many serious bicycle racers are
investing in pedal-force sensors to analyze their stroke cycles?

Several of Mark's other ideas are so interesting, I think they deserve to be
spun off as separate topics.

Ken

I appology for the clipping of your posting Jay but i just take those
parts that i will comment on.

"Sly D. Skeez" wrote:

I guess I should preface this post by saying that I have a very
technical background, pchem, statistical mechanics, plus all the math
and biochem...but I think technical is not the way to learn to ski.

;-)))

1.I think it involves more than proper placement of various body parts;
it involves very well coordinated muscle movements and precise timing.
It involves very good balance so the body is not wasting energy
regaining balance and the muslce movements result in efficient
propulsion.
2. Another thing to think about is how the really good skiers learned
to ski with the technique you're trying to copy. I can assure you that
they didn't learn by thinking about physics. I think the good skiers
learn to ski well by skiing a lot and getting some occasional pointers
from coaches.


1.I emphasis on BALANCE, this is the largest part in good technique, without
good balance there's no way you can compensate for that with other means.
2.Timing is crucial for some of the movement but not as important as balance.
3.Se how other does it, try it and from that develop YOUR OWN STYLE that
works for you.

I just got me a lesson from a guy that is wery good classic skier, the result
on my own technique is intresting, to say the least.

I am in favor of Ken's experiment with the camera, it gives you an outside view
of how you do it. This is wery usefull to correct smaller misstakes and especially
your own perception on how you are doing things, because, you don't do it as you
think
you are doing it.

--

Forward in all directions

Janne G

In article , "Ken Roberts" writes:

Mark Drela wrote
I don't remember seeing anyone separate the
power-producing (good) and power-dissipating
(bad) muscle action.

I know that I haven't gone that far in my numerical spreadsheet model --
because it's hard work to generate credible numbers at that level --
especially for a fully three-dimensional motion like skating, where each
major body part has six (non-independent) state variables -- subject to
constraints based on bone-joint geometry, etc.

I think you're making this more complicated than it has to be.
Dissipation by muscles occurs when a muscle is tensed while
being extended in length. Because we have so many muscles,
this is difficult to perceive. Fortunately, there is an
almost equivalent statement in terms of joint motions:

Dissipation by muscles occurs when muscles forces (joint torques
to be exact) are applied opposite to a joint rotation.

For example:

A. In a vertical jump, you apply joint torques at your hip and knee joints
in the same direction as their rotation. The muscles do positive work
which goes into your vertical kinetic energy.

B. In a vertical landing, you apply the same joint torques, but the joints
are now rotating in the opposite direction. The muscles now dissipate
energy.

There is also another dissipative mechanism via impact.

C. In a vertical landing you hold your legs straight and locked (ouch!).
The inelastic impact with the ground dissipates the energy rather
than your muscles.


In skiing, all three types of actions are present. Bad technique
has excessive or unnecessary B and/or C actions which subtract energy
from the positive A actions, leaving less energy for propulsion.
If you can modify your technique so as to reduce B or C actions,
you almost certainly WILL go faster. As I said before, I think this
is the real payoff of better technique. Increased power production
from more vigorous A motions is much less likely, because of the
cardiovascular constraint.

Here are some typical type B skiing actions which should be minimized:

* As the arm comes up and forward to the start of a pole stroke, muscles
reverse its upward motion and force it back down.

It's better to let the arm swing freely and let gravity reverse its motion.
I think fast-turnover V2 poling is inefficient because it seems gravity
can't do this fast enough -- I'm definitely conscious of my muscles
doing some of the motion reversal. Slow-turnover V2 poling seems OK.

* As the arm finishes the pole stroke, muscles reverse its rearward+up
motion, and force it back down and then forward.

Again, better to let gravity reverse the motion.

* Sideways leg motion must involve muscle-driven motion reversals,
since gravity can't help here.

Minimize this by minimizing turnover rate for a given skate angle,
via maximum leg stroke (boots almost touch in the center, toe pointed
at end of stroke).


Here are some type C impact actions which should be minimized:

* Before start of skate stroke, the foot is raised too high and slammed down.

* Poles are slammed down at the start of poling stroke.

The energy put into the leg/ski or arm/pole just heats up the snow
on impact, rather than going into propulsion.



bicycling is the physically-biomechanically simplest propulsive connection
between human muscles and the external environment,

Agreed. Pedaling is an example of "forced motion", where the
rapid motion reversals are provided by the cranks and do not
dissipate power -- there isn't too much to pedaling technique
other than pushing at the right points of the pedal circle.
Skiing is "free motion", where reversals do dissipate power,
and technique matters a lot more.