"secrets" of classic striding
Ken Roberts
learning sound classic technique for racing. As I worked through those
problems, I came across some important concepts that seemed
straightforward -- but I hadn't found them in the English-language books and
videos.
They were like "secrets" to me. So I thought it would help aspiring Classic
skiers if I tried to write each one of them down, and put them all out on
the Web -- so they wouldn't be "secrets" any more. My first try is at
http://www.roberts-1.com/xcski/classic/secrets
Please take a look. I expect you'll notice:
- - things that are rather obvious. ("How could Ken Roberts not have known
_that_ ?")
- - things that are wrong, or at least mis-leading. ("Better post a
corrective note on that one").
- - things that are absent. ("How come the one secret I most need to know
isn't there?") or ("How come the secret I most wanted to _tell_ isn't
there?")
Thanks for all help and further amusement you can offer.
Ken
____________________________________________
"Secrets" of Classic Striding -- quick summary
- - If my skis are fit wrong for my body and my skiing style, it can be
tough.
- - Grip wax also _glides_, usually.
- - If I'm putting any of my weight on something other than the single ski
I'm pushing on, I get less grip.
- - The "wax pocket" is centered around the toe of the foot, not the center
of the foot or the heel.
- - Smoothing out my leg-push force over a longer time can deliver more
total push.
- - Pole-push power can solve lots of technique puzzles.
- - On gentle terrain: I can get both better grip and better glide by
initiating the pole-push during the glide phase, not the leg-push phase.
- - Climbing up a steep hill: Bending forward strongly from the hips sets
me up to quickly get my weight up over the grip zone of my new ski.
For more detail on each and all, see:
http://www.roberts-1.com/xcski/classic/secrets
Gene Goldenfeld
>
> I ran into lots of problems during this last year as I got serious about
> learning sound classic technique for racing. As I worked through those
> problems, I came across some important concepts that seemed
> straightforward -- but I hadn't found them in the English-language books and
> videos.
Did you look in Marty Hall/Pam Penfold's One Stride Ahead and Lee
Borowski's Ski Easier, Ski Faster? Both have excellent chapters
on classic skiing, taking up not only what to do right, but a lot
of the pitfalls and how to correct them. One that comes to mind
is the sore lower back while striding, which is something I
suffered from off and on, with it getting especially excruciating
during races. Since reading Borowski's comment that a sore back
is a sign of inadequate weight shift, both my back and technique
have improved immensely. These books are available in some
libraries and via abebooks.com.
> "Secrets" of Classic Striding -- quick summary
> ...
> - - On gentle terrain: I can get both better grip and better glide by
> initiating the pole-push during the glide phase, not the leg-push phase.
Do you mean while diagonal striding? This doesn't sseem
correct. I seem to recall this issue coming up in your post last
Fall.
> - - Climbing up a steep hill: Bending forward strongly from the hips sets
> me up to quickly get my weight up over the grip zone of my new ski.
It's hard to tell what you're doing here. A focus on the hips is
liable to lead to a butt back position, which is incorrect. I
would suggest focusing instead on forward lean from the ankles
and torso, with relaxed more bent knees and lower hands.
Gene
Scott Elliot
news:a1rv8.37478$QC1.2...@bgtnsc04-news.ops.worldnet.att.net...
Just some additional comments from my way of looking at things if you don't
mind Ken.
> Please take a look. I expect you'll notice:
>
> - - If my skis are fit wrong for my body and my skiing style, it can be
> tough.
Right, and if anything, err on the side of too soft. A local masters skier
was telling me that this year he got skis much softer than he had ever used.
He doesn't understand why he would have used the stiffer skis for so many
years.
> - - Grip wax also _glides_, usually.
That's the secret, glides when its moving, sticks when its planted. If only
we could get it to do that every time. That's why klister skiing is so good
this time of the year.
> - - If I'm putting any of my weight on something other than the single
ski
> I'm pushing on, I get less grip.
Yep, lift that other foot clear of the ground until the kick is finished.
You're poles do take a bit of weight though. Just don't lean on the pole so
you are taking weight off the ski.
> - - The "wax pocket" is centered around the toe of the foot, not the
center
> of the foot or the heel.
Generally correct, but the exact location of the wax pocket varies a bit
from one manufacturer to another. You have to figure it out for each pair
of skis. Mark it on the sidewall of both sides of both skis with an
indellible marker to assist both glide and kick wax application.
> - - Smoothing out my leg-push force over a longer time can deliver more
> total push.
You can only get forward drive when your ski is planted, which is a limited
distance from under your hip to as far back as your foot keeps contact with
the snow. The harder and faster you drive your leg that distance, without
slipping, the faster you will go. The most important factor is to ensure
that most of that power is driving you forward, not just bobbing you up and
down. The powerful forward drive with each stride is the mark of the elite
skier that makes it so hard to keep up with them. Flub one stride and you
seem to lose 5 meters on them.
> - - Pole-push power can solve lots of technique puzzles.
Leg push should always provide most of the power since it uses much bigger,
more powerful muscles. Pole push is an important aid to legs, but never
sacrifice leg drive to get better pole power.
> - - On gentle terrain: I can get both better grip and better glide by
> initiating the pole-push during the glide phase, not the leg-push phase.
On all terrain, the pole is planted with the hand extended in front of the
body and the plant maintained until the hand is extended behind the body.
The foot is only planted from under the hips to behind the body. Since the
poles are planted for a greater distance each stride, the pole push has to
start before the leg push, which generally starts about the same time as the
poling hand reaches the body. This is called the pole assisted glide phase.
A much poorer technique is to plant the pole with the hands out front at
about the same time the kick is initiated, then only pole back to the hips
before the next stride has to begin with the completion of the kick. This
only uses the weakest part of the shoulder and triceps motion so it is
inefficient. An elite skier poles right through each stride. If you are
following too closely behind you have to watch that you don't get a pole tip
in the forehead.
> - - Climbing up a steep hill: Bending forward strongly from the hips
sets
> me up to quickly get my weight up over the grip zone of my new ski.
On a steep hill I prefer to see people keep the hips forward over the foot.
Bending too far forward often results in a face forward, ass hanging out the
back position that makes it very difficult to get a good grip for the kick.
This often results in the kick slipping so that all weight ends up on the
pole. Trying to power up a hill using more pole power than leg power is not
effective unless you are built like a baboon with an upper body more
powerful than the lower body. Great for swinging through the trees though.
> For more detail on each and all, see:
> http://www.roberts-1.com/xcski/classic/secrets
Scott Elliot
Ken Roberts
> Did you look in Marty Hall/Pam Penfold's One Stride Ahead
> and Lee Borowski's Ski Easier, Ski Faster?
No, I didn't. They didn't show up in my primary searches on Amazon and
Barnes & Noble, back when I was looking for resources under the category of
"Cross Country Skiing". And I don't remember seeing them in any XC ski
stores whether on the Web or on location.
When I searched for them just now by specific title and author, I did find
them. But they have publication dates of 1981 and 1986, and notes about
"Please check our network of out-of-print dealers".
And now that I've been around a little, I recognize those authors as helpful
folks. It would be interesting to find out what they were saying back then.
But if that's the availability of two of our best English-language sources
on classic skiing, seems to me it underscores my claim that there are some
de facto "secrets" for those of us trying to learn classic striding
nowadays.
Anybody know any good _videos_ for beginners / intermediates in classic
technique?
Ken
Janne G
>
> "Ken Roberts" <KenRob...@yahoo.com> wrote in message
> news:a1rv8.37478$QC1.2...@bgtnsc04-news.ops.worldnet.att.net...
>
>
> Leg push should always provide most of the power since it uses much bigger,
> more powerful muscles. Pole push is an important aid to legs, but never
> sacrifice leg drive to get better pole power.
Snipped alot usefull stuff.
Scott, there are a speed gradient on how usefull the legmuscles are in
classic skiing, when going uphill the largest part of force is coming
from the legs but as the hill goes down to a flat surface then the force
is comming from the upper body (relativly). Which means that when moving
fast the legs can't move faster than the ground speed and by that not contribute
to the forward motion and therefore the upperbody have to do the most work (which
can move faster than the ground speed) up to the level that it can not sustain the
poweroutput for increasing the speed.
--
Forward in all directions
Janne G
Ken Roberts
> > [in response to] - - On gentle terrain: I can get both better grip and
better glide by
> > initiating the pole-push during the glide phase, not the leg-push phase.
>
> Do you mean while diagonal striding?
Offset pole timing in classic stride is _fun_ to learn, and fun to do.
As for "correctness", see Scott Elliot's response.
Then see my detailed "secrets" page about pole-push timing:
http://www.roberts-1.com/xcski/classic/secrets/desync.htm
That page gives three important reasons from physics why offsetting the
timing is more efficient. And a three-step approach for learning it.
For more on its "correctness":
- - look at slow-motion video of any elite racer skiing classic "diagonal"
stride on _gentle_ terrain (since the timing is different on steep terrain).
- - find the old Team Birkie instructional video on Dryland Training, where
they give multiple exercises for "syncopated" poling.
- - find Borowski's comment in a Master Skier article saying something like
this: the critical timing checkpoint for classic stride is not to start the
leg-push until the pole-push arm motion has reached down to leg.
It's fun.
Try it.
Ken
Kenneth Salzberg
> > Leg push should always provide most of the power since it uses much bigger,
> > more powerful muscles. Pole push is an important aid to legs, but never
> > sacrifice leg drive to get better pole power.
>
> Snipped alot usefull stuff. Scott, there are a speed gradient on how
> usefull the legmuscles are in classic skiing, when going uphill the
> largest part of force is coming from the legs but as the hill goes
> down to a flat surface then the force is comming from the upper body
> (relativly). Which means that when moving fast the legs can't move
> faster than the ground speed and by that not contribute to the forward
> motion and therefore the upperbody have to do the most work (which can
> move faster than the ground speed) up to the level that it can not
> sustain the poweroutput for increasing the speed.
I think this is a good point to mention that as one's speed and strength
increase, the classic stride becomes much more just an uphill (and maybe
only a steep uphill) technique. I have found that while I still need to
stride some slow snow flats, or when I'm _very_ tired, in shorter races as
one comes to easier hills the speed requires kick-double-pole, and then
double pole. So much of this discussion of kick may be best applied to
kick up a more or less steep hill. In that situation, trying for a long
application of power may just result in slipping. I think the steeper the
slope, the short the effective kick can be (something to do with the
geometry of the situation).
-Ken
***********************************************************
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
******************************************************************
Chequama Mama
> Generally correct, but the exact location of the wax pocket varies a bit
> from one manufacturer to another. You have to figure it out for each pair
> of skis. Mark it on the sidewall of both sides of both skis with an
> indellible marker to assist both glide and kick wax application.
>
A "beginner tip" (that I didn't learn for years): when you mark the kick
zone, carry the line all the way to the top of the ski. That way, when
some klister gets on your sidewalls and you want to clean it off, you
don't remove the marker.
Paul
--
remove da MONKEY to reply
Kenneth Salzberg
from the olympics (thank you again).
All of the women seem to me to be using what I've been taught is "knee
drive" - a very quick drop of the knee forward just at the very beginning
of the kick. The problem in this is that it is _very_ quick, as is the
whole kick. For me, if I'm going to be driving my knee down enough to
satisfy my coach, I have to think about beginning the drop just as I'm
coming to the top of the stride. If I do, then the knee begins the drop
at about the right time (a little while after I think I'm "telling" it to)
- this may be do to the age of the wiring I have to deal with.
Remember that at the very end of each stride (focusing on the leg here),
you should try to drive your foot a bit forward. Just before the
beginning of the next cycle, then, your center of gravity is a bit behind
your foot. As it comes forward, and your foot gets under you again, you
begin the kick (driving the knee a bit more forward/down), you quickly
finish the kick (pushing the COG further forward of the kicking foot),
keeping the heel weighted as long as you can. Just as your "back" foot
comes foward to catch you from falling, you begin the glide on that foot
as the kicking foot comes off of the snow (newer technique seems to
suggest less "follow through" - that is the kicking foot ends up lower in
back than in the past - allowing for a quicker turnover with less bobing),
at which time (see the beginning of this paragraph).
This is a lot easier to "talk" about when one is out on skis or roller
skis, with a video camera and a coach. Most of the fine points can only
just be noticed in real time - much clearer in slow motion.
-Ken S.
Jay Tegeder
you own pressure tested. Find and mark the wax pocket on each pair.
All good ski shops can provide this service.
Jay Tegeder
"On the podium if the right people don't show up!" JT
Chequama Mama <pbelkna...@gonzaga.edu> wrote in message news:<3CC04E66...@gonzaga.edu>...
Ken Roberts
Thanks for all your helpful comments.
Be careful, I may add some of them to my web pages.
I'll have to skip over all the parts I agree with already . . .
> > [in response to] - - Smoothing out my leg-push force
> > over a longer time can deliver more total push.
>
> You can only get forward drive when your ski is planted,
> which is a limited distance from under your hip to as
> far back as your foot keeps contact with the snow.
> The harder and faster you drive your leg that distance,
> without slipping, the faster you will go.
All the implications you draw from "limited distance" seem correct to me.
And I'm glad for you drawing my attention to specific point of the limited
distance. It leads me to an over-simplified calculation: If the skier is
going 5 meters per second, and there is 0.5 meter of snow contact allowed by
body geometry, then the time of the leg-push is 0.1 second -- which confirms
what other smart folks are saying.
(a) Seems like that puts an inherent limit on how much "smoothness" can be
achieved -- since by that calculation, at a cadence of 60 strokes per
minute, only 20% of the stroke cycle is getting used for the leg-push -- so
there's an inherent objective physical "explosiveness". Is that what you
(and Rob and others) are trying to get through to me?
But I'm puzzled about where to go with that insight. The "limited distance"
you give is as much as _runners_ get to use for their leg drive. So the
time and length of their force is "limited" also. But I don't remember any
coaching advice for distance runners suggesting that therefore it is good to
_try_ to run more explosively. So how is the insight about limited distance
_actionable_ for skiers?
One interpretation of my "smoothness" idea is that it's a helpful mental
image, even though in the objective physics it is false. The justification
for this image is that it inspires me to try to find ways to extend the time
of the leg push, and to (unconsciously?) perceive and reward myself for
doing that. Seems to me that it would be a very bad idea to make the
leg-push any _more_ sharp and explosive than it is already.
And that's my suggested interpretation of Ken Salzburg's idea of "driving
down and back with the heel".
(b) Turnover -- Perhaps one thing runners do to respond to this "limited
distance" problem is to increase their turnover. The faster the cadence,
the higher percentage is used by the leg-push, so the greater the smoothness
and efficiency. What is it that prevents skiers for going to higher
turnover?
(c) On moderate uphills, the ground speed is slower, and therefore that
"limited distance" determined body geometry takes more time (perhaps 0.2
second?), so the percentage of the stroke cycle taken up by the leg push can
be larger. Seems to me that here's an opportunity for additional smoothness
to be celebrated and enhanced -- not to be quashed by advice to make the
kick "explosive".
(d) From slow-motion video, it looks to me like many of the elite racers
actually start their leg stroke from well _in_front_ of their hip.
Some might wonder how it is possible to get enough grip from that position.
My guess is that the answer is that (1) they press their toe on the center
of the wax pocket (which is OK, since by physics the ski cannot "feel" that
the skier's center-of-mass is actually way behind the wax pocket); and (2)
they don't need as much grip friction at that point, because at that instant
they're in the heart of the pole-push.
> > [in response to] - - Climbing up a steep hill:
> > Bending forward strongly from the hips sets me up to
> > quickly get my weight up over the grip zone of my new ski.
> On a steep hill I prefer to see people keep the hips forward
> over the foot. Bending too far forward often results in a
> face forward, ass hanging out the back position that makes
> it very difficult to get a good grip for the kick.
And I was getting all worried about not bending far _enough_ forward. Now I
get warned about bending too far forward. I guess the only way for me to
know is pay you a visit and get coached -- or else get myself videotaped.
But I definitely agree that if my weight gets caught back, I lose grip.
I just took a look at video of Daehlie on steep uphills in my VHS video "Ski
Faster with Bjorn Daehlie".
Forward lean: I measured forward lean from center of hip as: to upper back
24 degrees, to center of shoulder 32.5 degrees, and to his ear 37.5 degrees.
So not only does he bend at the hip, but he curves his shoulder and head
even further forward. And his lean is pretty stable throughout the stroke
cycle.
Butt position: What I see there is: It's very dynamic. (The same
observation I find about every other "body position" observation for classic
skiing). Sometimes his butt is directly over the foot he's pushing on.
Sometimes it's ahead of the foot. Sometimes it's behind.
There's no doubt that at the moment Daehlie lands the new foot on a steep
uphill, he immediately starts a forward-push with it, and at that moment his
butt is _way_ back behind his new foot -- like 0.5 meter.
My interpretation: Daehlie _fights_ against the "explosiveness" of the
Classic kick.
1 - He refuses to accept the "limited distance" -- He takes every
opportunity to extend the length and time of the leg-push;
2 - He eliminates the glide phase, so the leg-push becomes a larger
percentage of the total stroke cycle.
> > - - If my skis are fit wrong for my body and my skiing
> > style, it can be tough.
>
> Right, and if anything, err on the side of too soft.
I was listening to you carefully when you made that point a couple of months
ago -- so I had already made it the first comment under that point on the
detailed web page. See
http://www.roberts-1.com/xcski/classic/secrets
Ken
Ken Roberts
Is there a machine that directly measures the pressure distribution at
points along the length of the base of the ski (under different real or
simulated skier-weight-and-push forces)?
Jay Tegeder wrote
> I would suggest having every
> pair of classic skis you own pressure tested.
> Find and mark the wax pocket on each pair.
> All good ski shops can provide this service.
Paul wrote
> when you mark the kick zone, carry
> the line all the way to the top of the ski.
Yes, I've started to see the use of base cleaner taking my precious wax
pocket marks off my sidewall. Now if only I can find another indelible
marking pen.
Ken
Ken Roberts
> Remember that at the very end of each stride,
> you should try to drive your foot a bit forward.
> center of gravity is a bit behind your foot.
Yes, we're seeing the same thing in the videos. (always a good start to a
technique discussion).
> As it comes forward, and your foot gets under
> you again, you begin the kick
By "it" I take it you mean the skier's center of mass. (When you look at a
video, how do you decide where that is? I prefer to speak in terms of the
center of the hip joint, because I find it straightforward to identify that
point from a side camera angle.)
Anyway, it's about this initiation point that my opinion differs:
Why wait to begin the kick until my foot gets "under" my center of mass? I
want to start applying forward-force as soon as my foot stops on the snow,
while it's still out there in front of my hip.
And there's no reason I cannot do that. The ski does not know where my
upper body is or my hip joint or my center of mass is. I do not need to
wait for "permission" from my center of mass before I start to push forward.
If I focus pressure on my toe, the ski is "fooled" into thinking that the
force is coming from directly above or slightly forward. Try it.
(and this does not require that my heel or body be visibly lifted up off the
ski. Just lifting it less than a millimeter inside my ski boot is enough.)
Seems to me that starting the kick "from out in front" fits with:
- - Steiner Mundal's idea about starting the kick "early".
- - Why would elite racers be so careful to extend their foot and ankle out
in front of their hip if they're not _using_ it for something important? If
they're not pushing forward from out there, what _are_ they doing with it
out there?
- - Making the leg stroke longer, like in your quote of advice to runners.
(and fighting against the explosiveness of the classic kick).
> All of the women seem to me to be using what I've been
> taught is "knee drive" - a very quick drop of the knee
> forward just at the very beginning of the kick.
I'm very glad you told me about "knee drive". I have no problem with it --
I don't yet fully understand why it's better than other possible mental
images of initiation, or it's objective physical motivation -- and I want to
"work it through" in my own muscle perception.
I do question the idea that it should be the "very beginning" of the kick.
And I do not see how "knee drive" contradicts the obvious usefulness of
focusing force through the toe at initiation.
Ken R
Ken Roberts
> . . . much of this discussion of kick may be best
> applied to kick up a more or less steep hill.
> the effective kick can be
Funny how I've got a completely different analysis:
- - Physics assumption: The shorter my kick time, the larger the peak force
needed to deliver the same forward-push impulse per stroke. The larger the
peak force, the more likely it is to lose grip and slip back, unless much
extra down-force is supplied.
- - Since grip friction is already near its limit on a steep slope, that is
exactly where I should be trying to _minimize_ peak forces.
- - Since my aerobic capacity is already near its limit climbing up a steep
slope, that is exactly where I should be trying to minimize unnecessary up
and down motion, which wastes precious energy. Yes, some extra up-and-down
is needed on really steep slopes, but it is disadvantageous to deliberately
invite more.
- - Longer kick time implies lower peak force, implies lower requirement for
grip friction, implies less extra down-force. Implies less wasted energy --
when I don't have any extra to waste.
> (something to do with the geometry of the situation).
- - Yes, the steep slope makes the extension of the leg stroke out behind is
shorter. But the changed geometry also allows the extension to the _front_
to be longer. The uphill geometry is only a problem if you hold to a belief
that the leg-push cannot begin until the foot is directly under the hip.
- - Since my speed is slower going up a hill, the same effective
kick-ski-snow-contact distance determined by my biomechanical geometry
results in a much longer duration of kick time. The point is to celebrate
this lengthening, not throw it away.
Look at videos of Daehlie going up a very steep slope:
- - Extends his foot to land way up out in front of his hips.
- - Elimination of the glide phase, to increase kick duration as a
_percentage_ of the total stroke cycle. (this percentage is a critical
parameter for how much forward-push impulse the skier can apply without
slipping).
- - Total leg-stride kick-ski-snow-contact length at least as long as on the
flats. (but of course the total stroke cycle distance is shorter uphill,
because of the minimization of glide).
- - Yes, "hopping" or "bounding" to produce extra down-force for grip. But
given that requirement, notice: How quiet his upper body; How steady and
consistent his forward lean.
Ken R
Chris Cline
Getting a ski "pressure tested": aka flex-tested.
Relatively simple measurement (sometimes made more
complicated by marketing) of a) what weight skiier
and/or type of snow or wax (i.e., powder ski, klister
ski) a ski is appropriate for; and b) the boundaries
of the wax pocket(s) of the ski. Typically, there is
a primary wax pocket that should be the extent of the
wax in klister conditions, and a further-extending (in
front of the toe) secondary pocket where you would put
waxes for softer conditions. This measurement for (a)
reason is best done before you buy the skis, and some
say you can't do it for (b) reason after bindings are
on the ski, but I'm not sure I buy that. The tool I'm
familiar with for making the measurement is a
relatively simple caliper attached to a pressure
gauge. Screw down the gauge, which closes the
calipers, which measures how much force is required to
close the wax pocket. Sounds simple to me. However,
I've heard that this is somewhat "old fashioned" and
there is a better, doubtless more complicated way to
do it. Maybe someone else on this NG is familiar with
the newer way.
Ken (Salzburg)--
I was having the same problem with magic marker marks
on my ski sidewalls. I painted over them with red
fingernail polish the other day (as I summer-waxed the
skis). Seemed to be impervious to wax remover; we'll
see how durable they are next season in the face of
cold, abrasion, and plexiglass scrapers.
Chris Cline
SLC, UT
__________________________________________________
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Ken Roberts
Fischer "slider" machine or the "paper test" I've seen is that you can apply
well-calibrated down-force of magnitudes _other_ than the skier's full- or
half- body weight.
Chris Cline wrote
> The tool I'm familiar with for making the measurement
> is a relatively simple caliper attached to a pressure
> gauge. Screw down the gauge, which closes the
> calipers, which measures how much force is required
> to close the wax pocket.
Thanks for the help.
Ken
Christin...@us.mwhglobal.com
Yes- as far as I know.
Of course, you're applying the force to a PAIR of skis, not just one, so I
guess you divide the numbers by two.
I've only seen this gauge used by a "well-calibrated" individual who has
about 30+ years of skiing/coaching experience in his "central processor."
I think the software is at least as important as the peripherals in this
case ;- )
Chris
Edgar
> - - Physics assumption: The shorter my kick time, the larger the peak force
> needed to deliver the same forward-push impulse per stroke. The larger the
> peak force, the more likely it is to lose grip and slip back, unless much
> extra down-force is supplied.
A higher cadence or tempo compensates for the shorter kick durations.
As always, the motor will become the limiting factor on a long hill.
> - - Since grip friction is already near its limit on a steep slope, that is
> exactly where I should be trying to _minimize_ peak forces.
>
> Look at videos of Daehlie going up a very steep slope:
>
> - - Extends his foot to land way up out in front of his hips.
Stepping up hill applies to both skating and striding up steep hills.
The steeper the hill, the more important stepping up and forward
becomes. Any glide that follows the uphill step is a bonus.
> - - Yes, "hopping" or "bounding" to produce extra down-force for grip. But
> given that requirement, notice: How quiet his upper body; How steady and
> consistent his forward lean.
Edgar
Jeff Potter
in the yard. Maybe I'll do a little classic roller ski in your honor though.
Yeah, I always liked my skis a little soft. (But now that I've stopped racing
they're WAY too soft. Har. Joke's on me.) And I like to wax a little soft, too.
With top technique you don't have to, but darn that insurance is cool and it
really just lets you kick like a demon. Of course this works better in hillier
races. I hate flat races. I found that unless I was totally dialed in fitness
and tech wise that I rarely could wax exactly by the book....I'd go a touch
softer. I very often noticed skiers slipping around me. And after races I'd
swap skis with guys and they'd say Ah-ha! So that's what kick is supposed to be
like! Often I couldn't get grip with their lousy stiff hardwaxed skis. I don't
know what they were thinking. ---Skimpin' on wax to get more glide, going with
stiff flex to get more glide. Messed em up real good.
Scott Elliot wrote:
>
> Right, and if anything, err on the side of too soft. A local masters skier
> was telling me that this year he got skis much softer than he had ever used.
> He doesn't understand why he would have used the stiffer skis for so many
> years.
--
Jeff Potter j...@outyourbackdoor.com
http://OutYourBackdoor.com ... a friendly ezine of modern folkways and culture
revival ... offering a line of alternative books ... a world of bikes, boats,
skis ... find great sleeper media in the bookstore, videoshop and musicstore
... "Local Spirit" services include nationwide "Off the Beaten Path" travel tip
forums, bumperstickers and a cool new social magnet sticker game! ...Holy
Smokes!!!
jim farrell
>Yes- as far as I know.
>
>Of course, you're applying the force to a PAIR of skis, not just one, so I
>guess you divide the numbers by two.
>
Newton's Law of forces tells us that every action has an equal reaction.
If you squeeze the two skis together with a force of x pounds,
they are each compressed the same as if
they were each on a board (at sea level) with x pounds on each ski.
You don't divide the weight in half, in other words.
Jim Farrell
Ken Roberts
> A higher cadence or tempo compensates
> for the shorter kick durations.
Clarification: I am _not_ in favor of lower cadence going up hill.
I can get longer kick time but _higher_ cadence, if I also minimize or
eliminate the _glide_ time.
Example:
Cadence of 50 rpm on gentle terrain gives 0.6 second per single-leg stroke.
Let's say that's 0.1 second of kick and 0.5 second of glide.
On a steep uphill my speed drops way down to one-third of my gentle speed,
so now I can increase my kick time to 0.3 second. But if I reduce my
glide-time (and/or air-time) to 0.2 second, then my total duration for a
single-leg stroke is 0.5 second, and I come up to a higher cadence of 60
rpm.
> Stepping up hill applies to both skating and
> striding up steep hills. The steeper the hill,
> the more important stepping up and forward becomes.
I've heard there's some controversy on that point for skating.
> Any glide that follows the uphill step is a bonus.
For Classic striding, I see the physics saying just the opposite:
Any glide that follows the uphill step (or bound) is a "dead spot". This is
bad because:
- - It results in substantial loss of forward-upward momentum. Up a steep
hill, "a ski that is gliding is a ski that is slowing down" -- bigtime.
Physics says that it requires extra work to accelerate a slowed-down skier
back up to speed again. I call this "wasted energy" -- coming in a
situation where I have precious little to waste.
- - Delivering the extra work to get me thru that "dead spot" requires me to
apply a larger peak force during the kick phase. If that larger
forward-force is not going to make me slip, then I need to also apply more
down-motion and down-force. And when performing a motion sequence
repeatedly, "what goes down must come up". Therefore the additional
down-force requires additional up-force -- which implies yet more additional
_work_ which must be delivered by my muscles -- and so more lactic acid,
which now puts me over my limit.
Smoother is more efficient. For (most of us) going up steep hills,
efficiency is critical.
Ken
Ken Roberts
devices?
I remember an article in Master Skier by Peter Hale, and he said something
like:
- - seeing the ski base close to the floor under a down-force of 65-80% of
the skier's body weight is a good flex for dry snow.
- - seeing it "close" under a down-force of 75-95% of body weight is a good
flex for hard snow.
How does that advice sound? Are those ranges targeted mainly for racers?
What would be a reasonable range for a competent non-racing Classic strider?
My initial impression is that being able to use numerical forces on a device
like that should provide more helpful and reliable guidance for ski fit
selection than the "paper test".
Ken
Rob Bradlee
> - - seeing the ski base close to the floor under a
> down-force of 65-80% of
> the skier's body weight is a good flex for dry snow.
He meant of course "soft" snow. I'd lean toward the
65% level for soft fresh powder. In general though a
good range.
> - - seeing it "close" under a down-force of 75-95%
> of body weight is a good
> flex for hard snow.
Also a good range, but I'd put the top at 85%. I had
one pair of skis measure on a pressure gauge bench
(sorry I don't know the name) by Jim Galanes at 92% of
my body weight. By the way these skis were picked for
me by Peter Hale as klister skis. They were excellent
skis, but I can tell you, I could only use them on
HARD tracks with out too many steep hills. Any
mistake in my stride was reflected in a totally missed
kick. I had to be ON to ski on those skis. On the
plus side, when the course was flat to rolling, and I
was rockin', then I had rockets. However, those are
rare conditions here in NE (we got hills) so I sold
them to a heavier guy.
> How does that advice sound? Are those ranges
> targeted mainly for racers?
I don't think it has anything to do with racing. It
has everything to do with technique. Also, we are
only talking about prepared tracks for those kind of
flexes.
> What would be a reasonable range for a competent
> non-racing Classic strider?
65 to 70% soft track, 75 to 85 for hard track.
> My initial impression is that being able to use
> numerical forces on a device
> like that should provide more helpful and reliable
> guidance for ski fit
> selection than the "paper test".
Yes, quite true, but as the many scientists in the
group will attest, you have to be very careful to use
the device properly and consistently, measure many
pairs of skis, and get feedback from the field (do
they ski like they tested?). A great feature of the
bench is that you can partially weight the ski and see
its shape change as you apply more weight. Are there
discontinuities in the flattening? If so you will
have a DOG. Also, remember to test both skis. The
two halves of pair are NOT the same. Should be close,
but not always.
That being said, I've done the paper test on skis that
were bench tested and found them to be fairly close.
Next question will be, who has a measuring bench.
Only place I know in NE is Sugarloaf Outdoor Center
(see Karl Johnson). But I'm sure there are others.
And of course Eagle River Nordic has their own custom
instrumented bench.
Rob Bradlee
Ken Roberts
Thanks a lot -- that was much more than I expected.
> I've done the paper test on skis that were
> bench tested and found them to be fairly close.
One more question, to help me relate the numerical force ranges to the paper
test:
Is the bench test normally done with the measured down-force applied to the
middle of where the binding would lie? or is normally applied to the center
point of the ski?
Ken
Ken Roberts
article on "New Classic Innovations" in the mid-season 2001/2002 issue The
Master Skier magazine.
Mundal talks about initiating the kick with the hamstring muscle. Seems to
me that's not the same as "knee drive" -- since the hamstring muscle does
not drive the knee anywhere. Rather it acts (through the knee joint) to
pull the ankle and foot (and ski) back. Then if there's sufficient grip
friction, the skier will be pushed forward.
Strikes me that's an excellent to get the kick started a bit earlier, while
the ankle is still out there in front of the hip joint. Together with
pressing my toe to make sure I get enough grip to make it work.
Then the obvious scheme is: Call that hamstring-pull move "phase 1" of the
kick (until the foot gets directly underneath the hip joint), and save the
knee drive move for "phase 2" (as the foot continues on behind from under
the hip joint, with the heel still all the way down). Call the final
toe-push move "phase 3" (as the heel comes up off the ski).
Fits with what Ken Salzburg sees the women at Soldier Hollow doing at the
start of their leg moves watching Janne G's videos in slow motion. Follows
Mundal's sage words of advice. (and very important: Justifies me in what I
think I was doing anyway -- modeled on the Elena Vaelbe segment of the 1997
Trondheim video, never suspecting that it was an "innovation").
Which takes me to that perennial Question:
"What is the key ankle-knee-hip position for Classic striding?".
my Answer:
"Depends on when you hit the Pause button on your video player".
Ken
Jay Tegeder
Jay Tegeder
"On the podium if the right people don't show up!" JT
rbra...@yahoo.com (Rob Bradlee) wrote in message news:<2002042318213...@web11508.mail.yahoo.com>...
Rob Bradlee
I've been faithfully lurking. But I get my news via
the email link so when I replied it didn't go out to
everyone. Now that the gateway is wide open (thank
you!!!! to those who fixed it) my comments will again
be visible. Of course, I don't have time to post
quite as often as some people :>
We had 94 degree weather here last week, but last
night it snowed. Good ol' New England.
Rob
=====
Rob Bradlee
Java, C++, C, Perl, XML, OOAD, and Unix Training
Rob Bradlee
> One more question, to help me relate the numerical
> force ranges to the paper
> test:
> Is the bench test normally done with the measured
> down-force applied to the
> middle of where the binding would lie? or is
> normally applied to the center
> point of the ski?
As I've observed it, testers place a form over the
binding so that the pressure screw presses down right
on the balance point of the ski. Usually that's
between the front screw and the two back screws.
Rob
Jeff Potter
> [ ] Strikes me that's an excellent to get the kick started a bit earlier,
> while
> the ankle is still out there in front of the hip joint. Together with
> pressing my toe to make sure I get enough grip to make it work.
I dunno about this toe stuff. When foot out in front, what happens when you
press your toe? Your heel raises! I found the heel-kick to be a big breakthru
for me and perhaps allows me to kick sooner with foot further forward. Maybe
heel-press is done via hams.
> Then the obvious scheme is: Call that hamstring-pull move "phase 1" of the
> kick (until the foot gets directly underneath the hip joint), and save the
> knee drive move for "phase 2" (as the foot continues on behind from under
> the hip joint, with the heel still all the way down). Call the final
> toe-push move "phase 3" (as the heel comes up off the ski).
I'm confused. You have your custom toe-push at the END? I was thinking you had
it to start. It occurs to me that when my heel comes up I'm DONE with that
kick. Maybe also knee drive, knee drop, can happen with foot in front of hip?
>
> Fits with what Ken Salzburg sees the women at Soldier Hollow doing at the
> start of their leg moves watching Janne G's videos in slow motion. Follows
> Mundal's sage words of advice. (and very important: Justifies me in what I
> think I was doing anyway -- modeled on the Elena Vaelbe segment of the 1997
> Trondheim video, never suspecting that it was an "innovation").
She does a great "finesse" move, extending her foot, at the first part of her
kick.
>
> Which takes me to that perennial Question:
> "What is the key ankle-knee-hip position for Classic striding?".
>
> my Answer:
> "Depends on when you hit the Pause button on your video player".
Or....whatever works! ...Fastest!
Ken Roberts
> when you press your toe?
> Your heel raises!
I have a suspicion your _foot_ did not actually get to try this yet -- that
so far only some section of your brain has gotten to play with it.
I just did this dryland exercise "innovation":
- I stood on the floor on one foot.
- I put my hand on my desk for balance.
- I felt the pressure evenly distributed under my foot.
- I pressed my toe.
- I felt lots more pressure toward the toe of my foot, and lots less on my
heel.
- I noticed that my heel seemed to have lifted a very tiny bit, but only
inside my shoe.
- I pressed my toe harder, and the heel of my shoe lifted a very tiny bit
off the floor.
- I eased off a little on my toe pressure until thought that the heel of my
shoe was back in contact with the floor.
- I felt the down-pressure was still almost completely thru the forward
section of my shoe, and almost none thru the heel area.
I then tried to shift the pressure back onto my heel. For some reason this
was more difficult for me to get into and control.
Then I did a little "paper test" under the heel of my shoe while pressing
the toe. This called for a more contorted body position, but seemed to
verify the earlier result.
My analysis from the exercise:
It really is possible to focus lots down-pressure to the toe, without
lifting the heel enough to be worth talking about.
But this new experiment has not yet been tried under the laws of Michigan,
so I am anxiously awaiting report of your results.
Jeff Potter wrote
> I'm confused.
I freely admit that classic striding technique is complicated.
If it were not, I suppose winning Classic ski races would just be an amusing
winter outdoor activity for elite 10K runners.
It is inherently complicated to try to push forward on a ski that has to
switch between gripping and sliding -- while going straight in the same
direction -- and with no mechanical button to push to say which one you're
doing now. And the geometry of the human joints and muscles is way more
complicated than makes any sense for skiing. Put both of those
complications together, and what do you get:
"confused"
And I am aware that what my (and Steiner Mundal's?) "phase 1" is not a
simplification.
> You have your custom toe-push at the END?
> I was thinking you had it to start.
I didn't think there was anything "custom" or "innovative" about finishing
the kick ("phase 3") with a toe-push. Isn't that what everybody's been
doing all along?
The "phase 3" move is a toe "push" : the calf muscle compresses, and this
pushes the toe into backward _motion_ against the ski, and imparts extra
forward motion to the skier.
The role of the toe in the "phase 1" thing is only a "press": a static
downward force with no perceptible movement. The forward push in phase 1 is
only from the hamstring muscle driving the ankle into backward motion. The
role of the calf muscle in "phase 1" is mostly "isometric" (applies tension
without changing length).
So the toe and calf muscle do different things in different phases of the
kick. Likely needs different mental images. I assume it takes a lot of
practice to learn -- and even more to execute it well in stress situations.
This is a gift -- another way to stave off boredom during those long slow
distance sessions.
> Maybe also knee drive, knee drop,
> can happen with foot in front of hip?
Sounds to me like worth trying.
(For all I know, my cerebellum has made that optimization already).
Ken
Jeff Potter
> [ ]
> My analysis from the exercise:
> It really is possible to focus lots down-pressure to the toe, without
> lifting the heel enough to be worth talking about.
There's a diff b/w lifting the heel and unweighting it. When I kick off my heel
there's a definite big, simple, direct, quick popping action to it. Not sure
about how much kicking I'm still doing after my heel comes off the ski near end
of kick. To me, it seems like the kick happens early then the foot just "clears
the area" doing little work past the hip area. Perhaps I find that I have to be
so direct in my transition because otherwise my ski would slip. With just toe
and calf kicking after the hip is passed, I might be slipping. A heel-weighted
burst is enough to give me grip, then the kick is done. ---And in general I use
soft skis. Anyone else here getting much umph from toe, calf work in their
kick?
Edgar
> Edgar wrote
> > Any glide that follows the uphill step is a bonus.
> For Classic striding, I see the physics saying just the opposite:
>
> Any glide that follows the uphill step (or bound) is a "dead spot". This is
> bad because:
>
> - - It results in substantial loss of forward-upward momentum. Up a steep
> hill, "a ski that is gliding is a ski that is slowing down" -- bigtime.
> Physics says that it requires extra work to accelerate a slowed-down skier
> back up to speed again. I call this "wasted energy" -- coming in a
> situation where I have precious little to waste.
>
> Ken
Yes, a gliding ski slows down, but physics of the classical ski
technique requires that the gliding ski come to a stop relative to the
snow. Grip wax works by having a high static coefficient of friction.
The glide ski transitions to the grip ski by coming to a stop as
weight is transfered to the grip ski and the trailing leg/ski is
driven forward.
The need of a classic ski to stop with respect to the snow in contrast
with a skate ski is the theoretical difference in why skating is
faster than striding. Ken's observation regarding forward-upward
momentum certainly is applicable to skating. Ken's observation may
also be valid on short hills with respect to speed.
However, I believe that with respect to efficiency, glide is good in
that riding a glide ski requires only a minimal use of muscular energy
related to balancing with the benefit of forward movement. I believe
that on long, sustained climbs, a faster time for a given skier is
achieved by staying below anerobic. Under this condition, I would
think that glide provides forward (and upward) travel without
expending energy to kill glide with a premature kick.
Edgar
Ken Roberts
> To me, it seems like the kick happens early
> then the foot just "clears the area"
> doing little work past the hip area.
I was thinking that the whole point of "driving the heel down and back" was
to do _lots_ of forward-push work from behind the hip joint. That's that I
_like_ about using it as a mental image for the "phase 2" core of the
kick-motion.
> Not sure about how much kicking I'm still
> doing after my heel comes off the ski
> near end of kick.
And without force sensors in your binding, how _could_ you know accurately?
I'll make a guess that getting more power out of the final "toe-off" is
worth 60 seconds in a 10K Classic race. But if you're not getting money or
glory out of that, then working on it is not necessary.
Some aspects of classic stride motion are foundational for other parts, but
I doubt that final "phase 3" toe-push is one of the "foundations". Looks to
me like it's just one of the helpful extras.
Ken
Ken Roberts
> a gliding ski slows down, but physics of the
> classical ski technique requires that the gliding
> ski come to a stop relative to the snow.
True. I'll re-phrase my key point more carefully:
Up a steep hill, a _skier_ that is gliding is a _skier_ that is slowing
down -- big-time.
Physics says that it requires extra work to accelerate a slowed-down _skier_
back up to speed again. This is serious "wasted energy" -- coming in a
situation where I'm already running close to my limit.
> Grip wax works by having a high static
> coefficient of friction. The glide ski transitions
> to the grip ski by coming to a stop
A key point of physics efficiency for Classic stride is to only stop the
_ski_ for grip, without stopping the whole _skier_. The only part of the
skier's body that should stop is the lower parts of the leg directly
attached to the ski. Yes, there's some work that has to be done to get
those smaller parts started forward again, but it's a lot lot less than the
work needed to re-accelerate the weight of the skier's entire body.
Therefore the optimal motion up a steep hill is not to _wait_ for the ski to
stop. It's to _make_ it stop, real quick, in the instant the kick starts.
You do that by using your powerful leg muscles to push the ski and attached
foot backward relative to your still forward-moving hip and upper body. The
relative backward and the forward motions "cancel", so your ski and foot
match speed with the surface of the snow. Might sound a little complicated,
but . . .
Just go out now and do some running on dryland, and you're already doing
it -- stopping your foot and show relative to the surface of the ground --
many times per minute. Without any "waiting", without any "glide phase" --
without any conscious thought. Your cerebellum just takes care of it:
massive parallel processing with proven software.
Seems to me that those big muscles powerful enough to push your whole body
weight up a steep hill, can accelerate that little weight of your ski and
foot real real quick. On dryland, when I try making a snappy foot-kick in
the air from my knee-joint, my foot immediately looks like a blur. Compared
with everything else going on up a steep hill, the time and work needed to
stop the foot and ski are hardly worth thinking about.
Save the sacred principle of glide for the downhill.
Ken
Ken Roberts
my aerobic zone, I switch to herringbone.
I can see how lengthening the glide phase could help reduce aerobic load on
gentler hills -- though I even there I'm more inclined to consider the
alternative of reducing the intensity of each kick, perhaps along with
reducing the length of each kick.
But up steep hills I don't think lengthening the glide helps -- because it
requires a more explosive kick, and turn more up-and-down motion to provide
enough grip for that. Switching to herringbone gets me out of that whole
problem.
It occurs to me that perhaps Edgar and I have very different definitions of
"steep" and "gentle" and "long". I have a perverse love of hills, and a
very well-formed distaste for long flat sections on Classic courses. So
conceivably his "steep" has a substantial overlap of range with my
"gentle" -- which might explain our difference in viewpoints.
Ken
_______________________________________
Edgar wrote
Jeff Potter
that likely that I'm wasting potential kick. Ya never know but I think I run
the very fine edge of things. Based on how my skiing feels, if I changed
anything I'd start slipping. ---Unless it's to do something that increases kick
power, which I found the heel-emphasis to do. Maybe when going up steep hills I
tend to use the whole foot. The foot can't get shoved as far forward and still
get enough weight on it to get a good kick. It is kept a little closer to the
hips I think. I suppose that I'm still getting grip as my heel is coming off,
when the foot is behind me a bit, due to deep ankle flex, etc., but toe? Well,
whatever imagery works to increase kick, do it! ---I find that I have to put
my weight on my big toe to rollerski in a straight line. I have to use that
imagery or I go crooked and crash. So that's helpful toe imagery for me! : )
Ken Roberts wrote:
> > Not sure about how much kicking I'm still
> > doing after my heel comes off the ski
> > near end of kick.
>
> And without force sensors in your binding, how _could_ you know accurately?
>
> I'll make a guess that getting more power out of the final "toe-off" is
> worth 60 seconds in a 10K Classic race. But if you're not getting money or
> glory out of that, then working on it is not necessary.
--
Gene Goldenfeld
mark as necessary. A pressure or bench test is at best a static
approximation of what will happen when you get on snow.
GG
Jay Tegeder wrote:
>
> This is a great tip. I would suggest having every pair of classic skis
> you own pressure tested. Find and mark the wax pocket on each pair.
> All good ski shops can provide this service.
>
Gene Goldenfeld
to your own post. ;<)
Gene
Jeff Potter
slightly further back than someone who's working on the whole foot or even
the toe.
Gene Goldenfeld wrote:
> Then, to finish Jay's point, go out and test them and adjust the
> mark as necessary. A pressure or bench test is at best a static
> approximation of what will happen when you get on snow.
--
Kenneth Salzberg
> I wonder if someone who uses a distinct heel-kick would have a wax pocket
> slightly further back than someone who's working on the whole foot or even
> the toe.
The rear line is much more dependant on the flex of the ski while gliding
(you know we have more weight on the back of the ski when gliding in
classic, esp. on downhills in a tuck - to, among other things, make sure
the kick wax is off the snow). The way we ususally find it is to put on
some (regular) kick wax, and go skiing for a long time, and then see where
it's warn off in the back. Draw a line there, and glide wax behind there
from then on. If it's being worn off anyway, then having glide wax there
instead will only help. Refine as experence (esp. in races) dictates.
This real-world testing on my skis gave me a wax pocket a bit further
forward than the one I originally marked with the paper test (by about 1.5
inches).
-Ken S.
***********************************************************
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
******************************************************************
Ken Roberts
> This real-world testing on my skis gave
> (by about 1.5 inches).
Very interesting -- thanks for sharing that.
I've long _believed_ in re-marking skis based on real on-snow testing: but
I hadn't gotten around to actually doing it. You just gave me incentive.
Here's a theory about why the realistic on-snow grip wax zone is further
forward than static testing would suggest:
When I initiate my glide phase, I try to "land" my ski out in front ("like
kicking a soccer ball"). So my weight tends to be behind the ski, with
pressure on my heel. Repeating that a few thousand times, it makes sense
that more wax would get rubbed off toward heel and tail (and less toward the
toe).
Apart from striding, I've found that even just gliding down a gentle hill on
my Fischer RCS classic racing skis, I go a little faster if I "sit back" a
little and consciously pressure my heels.
Which leads me to a suspicion that Fischer may have consciously optimized
their classic racing design for best gliding with foot-pressure distribution
skewed toward the heel.
Ken R
P.S. -- which leads to another suspicion, that Fischer might also have
consciously optimized their ski design to respond to some different
foot-pressure distribution for best _grip_
Sly D. Skeez
I used a compression tester (one with a gauge in km) to test a number
of skis this winter. When I narrowed down the lot to a few pair, Tom
(at Finn Sisu gave me the paper test and preferred one pair over the
rest based on his experience of how the paper would slid with weight
on the ski. My point is not to ignore the human measurement an replace
it with a gauge. As I remember, this pair is in the 80% range, and
it's a good pair of skis, but I have to be on top of my technque. I
believe I have another pair that flexes out in that range that is more
forgiving of bad technique.
Jay Wenner
"Make 'em reboot if they have a keystroke error." Comment overheard
during the development of Unix...welcome back Rob