29 Jul 2005 20:01:10
Ken Roberts
double-push skate by ski racers?

I just heard a report from a good source (but not a ski racer) that some
cross-country ski racers have been trying out double-push technique with
skis on snow. After they got good at it, they tried some time-trial
comparisons on snow and found some situations where double-push was faster
than normal ski-skating technique.

Anybody heard something like that?

Double-Push is one you make two pushes in a row with the same leg and same
ski, but in different directions: first one toward the inside, then the
other push toward the outside. My source said that in between the two
pushes, the racer would make a little hop into the air, and change the angle
of the ski while it was up out of the snow. (I tried it myself a year or so
on snow, but I couldn't make it work very effectively).

Double-Push is used by lots of expert speedskaters on inline skates. It's
much easier to perform on inlines because you don't have to hop up order to
aim the skate in a different direction. Also on rollerskis, JanneG had a
video which showed double-push being done on rollerskis, with no hop
required.

What surprises me is not that some super-athletes could do double-push on
snow, but that it actually might be faster sometimes.

Ken




29 Jul 2005 14:17:03
Jim Grau
Re: double-push skate by ski racers?

It would seem to me that any benefit of a ski double push would be
negated by the time and effort required to change the direction of the
ski. With inlines you can change the direction continuously and with
very little effort, so the payoff there is clear. Do you know whether
it was V1, or no-pole? --- I assume V1 would be truly out of the
question because of the faster turnover required.

Jim



30 Jul 2005 04:49:53
Scott Elliot
Re: double-push skate by ski racers?

Many years ago I worked with a coach who used this type of stride as a
training exercise. I think the main purpose was to force skiers who did not
have a very good weight transfer to commit their weight to one side and then
the other. This forced them to commit their weight to the ski that was
doing the double glide phase on each side. It was sort of like doing two
sides of marathon skate on one side, then two strides on the other, etc.

I don't remember it being necessary to do any kind of a hop to re-align the
glide ski. It should have been pretty well unweighted during each push with
the push ski so it could be turned then.

I think it was only intended for weight transfer and co-ordination training
purposes, not for competition. It was fun for kids to play at on easy
downhills and could pick up quite a bit of speed on wide trails.

Scott

"Ken Roberts" <[email protected] > wrote in message
news:[email protected]
>I just heard a report from a good source (but not a ski racer) that some
> cross-country ski racers have been trying out double-push technique with
> skis on snow. After they got good at it, they tried some time-trial
> comparisons on snow and found some situations where double-push was faster
> than normal ski-skating technique.
>
> Anybody heard something like that?
>
> Double-Push is one you make two pushes in a row with the same leg and same
> ski, but in different directions: first one toward the inside, then the
> other push toward the outside. My source said that in between the two
> pushes, the racer would make a little hop into the air, and change the
> angle
> of the ski while it was up out of the snow. (I tried it myself a year or
> so
> on snow, but I couldn't make it work very effectively).
>
> Double-Push is used by lots of expert speedskaters on inline skates. It's
> much easier to perform on inlines because you don't have to hop up order
> to
> aim the skate in a different direction. Also on rollerskis, JanneG had a
> video which showed double-push being done on rollerskis, with no hop
> required.
>
> What surprises me is not that some super-athletes could do double-push on
> snow, but that it actually might be faster sometimes.
>
> Ken
>
>




29 Jul 2005 09:16:14
Peter Berbee
Re: double-push skate by ski racers?

Inline skates follow an arc on the pavement especially when doing the double
push. That is, if one skates through a puddle the wheel track will be
curved.

XC skis are made to go in a straight line and get slow when they are turned
and weighted at the same time.

I believe any double-push with skate skis would have to avoid any turning of
the ski while weighted. I do not think the inline skate movements will
transfer directly.

Peter Berbee

"Ken Roberts" <[email protected] > wrote in message
news:[email protected]
> I just heard a report from a good source (but not a ski racer) that some
> cross-country ski racers have been trying out double-push technique with
> skis on snow. After they got good at it, they tried some time-trial
> comparisons on snow and found some situations where double-push was faster
> than normal ski-skating technique.
>
> Anybody heard something like that?
>
> Double-Push is one you make two pushes in a row with the same leg and same
> ski, but in different directions: first one toward the inside, then the
> other push toward the outside. My source said that in between the two
> pushes, the racer would make a little hop into the air, and change the
angle
> of the ski while it was up out of the snow. (I tried it myself a year or
so
> on snow, but I couldn't make it work very effectively).
>
> Double-Push is used by lots of expert speedskaters on inline skates. It's
> much easier to perform on inlines because you don't have to hop up order
to
> aim the skate in a different direction. Also on rollerskis, JanneG had a
> video which showed double-push being done on rollerskis, with no hop
> required.
>
> What surprises me is not that some super-athletes could do double-push on
> snow, but that it actually might be faster sometimes.
>
> Ken
>
>




01 Aug 2005 13:16:57
janne g
Re: double-push skate by ski racers?

Scott Elliot wrote:
> Many years ago I worked with a coach who used this type of stride as a
> training exercise. I think the main purpose was to force skiers who did not
> have a very good weight transfer to commit their weight to one side and then
> the other. This forced them to commit their weight to the ski that was
> doing the double glide phase on each side. It was sort of like doing two
> sides of marathon skate on one side, then two strides on the other, etc.
>
> I don't remember it being necessary to do any kind of a hop to re-align the
> glide ski. It should have been pretty well unweighted during each push with
> the push ski so it could be turned then.
>
> I think it was only intended for weight transfer and co-ordination training
> purposes, not for competition. It was fun for kids to play at on easy
> downhills and could pick up quite a bit of speed on wide trails.

I can't se that some is going to get something useful forward motion
from doing the "double push" on xc-skiis.
The only benefit would be the "pumping" effect on the muscles that
probobly makes the blod more easy passes through the muscles when doing
the "double push" motion but to the expence of the energyloss that are
involved in doing it (if any).

Janne G


01 Aug 2005 11:23:04
Ken Roberts
Re: double-push skate by ski racers?

Scott Elliot wrote
> training exercise . . . I think the main purpose was to force
> skiers who did not have a very good weight transfer to
> commit their weight to one side and then the other.

Greater sideways weight-shift seems to be one of the two main propulsive
benefits to double-push technique when I look at videos of inline
speedskaters. The extra side-weight-shift from the initial "under-push" on
the outside edge then gets converted into greater force transmitted
propulsively to the ground in the next main push on the inside edge.

The other propulsive benefit is direct push aimed partly backward during the
under-push itself. (I can't see how the path of the skate being curved has
any propulsive benefit -- seems like just an incidental convenience for
skaters.) The odd thing I noticed in race videos is that many inline
speedskaters make the under-push even in configurations where it is
impossible to derive any significant direct-push benefit from it -- so I
figure they must be doing it for the side-weight-shift benefit.

> I don't remember it being necessary to do any kind
> of a hop to re-align the glide ski.

Maybe that's one of the secrets of making double-push effective on snow:
Finding the minimal amount of unweighting required and learning to feel and
control that. Seems likely that this is going to be easier on hard snow.

Ken




01 Aug 2005 11:33:14
Ken Roberts
Re: double-push skate by ski racers?

Jim Grau wrote
> Do you know whether it was V1, or no-pole?

I'm not completely sure -- I sorta think he mentioned something about
working out coordination with poling. Anyway there was no doubt from the
discussion that they intended to use double-push in actual race situations
where poling would be expected.

> I assume V1 would be truly out of the question
> because of the faster turnover required.

Yes, now that you mention it, some sort of V2 poling sounds more plausible.

I'm just starting to see substantial gains (and fun) from using double-push
in my inline skating, so I'm eager to see what it would be like trying it on
snow. Unfortunately I'm not sure I have the athletic power to execute it on
snow more than a few seconds at a time, so it might be more frustrating than
fun for me.

Ken
_____________________________________
Jim Grau wrote
> It would seem to me that any benefit of a ski double push would be
> negated by the time and effort required to change the direction of the
> ski. With inlines you can change the direction continuously and with
> very little effort, so the payoff there is clear. Do you know whether
> it was V1, or no-pole? --- I assume V1 would be truly out of the
> question because of the faster turnover required.
>
> Jim
>




01 Aug 2005 15:55:48
Janne G
Re: double-push skate by ski racers?

Scott Elliot wrote:
> Many years ago I worked with a coach who used this type of stride as a
> training exercise. I think the main purpose was to force skiers who did not
> have a very good weight transfer to commit their weight to one side and then
> the other. This forced them to commit their weight to the ski that was
> doing the double glide phase on each side. It was sort of like doing two
> sides of marathon skate on one side, then two strides on the other, etc.
>
> I don't remember it being necessary to do any kind of a hop to re-align the
> glide ski. It should have been pretty well unweighted during each push with
> the push ski so it could be turned then.
>
> I think it was only intended for weight transfer and co-ordination training
> purposes, not for competition. It was fun for kids to play at on easy
> downhills and could pick up quite a bit of speed on wide trails.

I can't se that some is going to get something useful forward motion
from doing the "double push" on xc-skiis.
The only benefit would be the "pumping" effect on the muscles that
probobly makes the blod more easy passes through the muscles when doing
the "double push" motion but to the expence of the energyloss that are
involved in doing it (if any).

Janne G


02 Aug 2005 03:12:53
Gary Jacobson
Re: double-push skate by ski racers?

This might be an interesting way to experiment with double push on roller
skis:

V2 pole and use only one leg.

There was a time I would have had the strength, coordination and courage to
give it a try. Not now.

Gary Jacobson
Rosendale, NY




02 Aug 2005 03:23:25
Scott Elliot
Re: double-push skate by ski racers?

"janne g" <[email protected]_remove.cad_remove_._remove_luth._remove.se >
wrote in message news:[email protected]
>
> I can't se that some is going to get something useful forward motion from
> doing the "double push" on xc-skiis.
> The only benefit would be the "pumping" effect on the muscles that
> probobly makes the blod more easy passes through the muscles when doing
> the "double push" motion but to the expence of the energyloss that are
> involved in doing it (if any).
>
> Janne G

I don't think it was ever intended to be effective for forward motion. It
was used as a teaching tool only. In Canada we have many people who take up
cross country skiing after playing hockey for many years. When they try to
skate their first tendency is to do a hockey skate where they are always on
the edges of their skates or skis. This does not result in satisfactory
glide to be efficient for skiing. This exercise is intended to force them
to commit more weight to the glide ski so that they will get the balance and
feel of a gliding ski. If you want to do two glide phases on one side you
are forced to get your centre of gravity over the glide ski.

In any case, I have only seen one or two coaches use this technique. I just
noted that young skiers had fun playing with it and it did help the "hockey
skaters" improve their glide.

Scott




02 Aug 2005 01:45:58
nordvind
Re: double-push skate by ski racers?


Ken Roberts wrote:

>
> Greater sideways weight-shift seems to be one of the two main propulsive
> benefits to double-push technique when I look at videos of inline
> speedskaters. The extra side-weight-shift from the initial "under-push" on
> the outside edge then gets converted into greater force transmitted
> propulsively to the ground in the next main push on the inside edge.
>
> The other propulsive benefit is direct push aimed partly backward during the
> under-push itself. (I can't see how the path of the skate being curved has
> any propulsive benefit -- seems like just an incidental convenience for
> skaters.) The odd thing I noticed in race videos is that many inline
> speedskaters make the under-push even in configurations where it is
> impossible to derive any significant direct-push benefit from it -- so I
> figure they must be doing it for the side-weight-shift benefit.
>
>
> Maybe that's one of the secrets of making double-push effective on snow:
> Finding the minimal amount of unweighting required and learning to feel and
> control that. Seems likely that this is going to be easier on hard snow.


Come again?!? Would you please re-phrase this? I am having a little
difficulty understanding what you are really saying.

Thanks!



02 Aug 2005 01:47:00
nordvind
Re: double-push skate by ski racers?


Ken Roberts wrote:

>
> Greater sideways weight-shift seems to be one of the two main propulsive
> benefits to double-push technique when I look at videos of inline
> speedskaters. The extra side-weight-shift from the initial "under-push" on
> the outside edge then gets converted into greater force transmitted
> propulsively to the ground in the next main push on the inside edge.
>
> The other propulsive benefit is direct push aimed partly backward during the
> under-push itself. (I can't see how the path of the skate being curved has
> any propulsive benefit -- seems like just an incidental convenience for
> skaters.) The odd thing I noticed in race videos is that many inline
> speedskaters make the under-push even in configurations where it is
> impossible to derive any significant direct-push benefit from it -- so I
> figure they must be doing it for the side-weight-shift benefit.
>
>
> Maybe that's one of the secrets of making double-push effective on snow:
> Finding the minimal amount of unweighting required and learning to feel and
> control that. Seems likely that this is going to be easier on hard snow.


Come again?!? Would you please re-phrase this? I am having a little
difficulty understanding what you are really saying.

Thanks!



02 Aug 2005 05:46:48
Jim Grau
Re: double-push skate by ski racers?

Ken, are you saying that part of the advantage of double push is the
increased travel distance you get from the main inside-edge push,
coupled with the larger upper-body swing in the opposite direction
(since you've had to lean the other way for the under push)? When you
say: "configurations where it is impossible to derive any significant
direct-push benefit", do you mean they aren't pointing the skate inward
much on the set down but just rocking the upper body outward? I guess
even in classic inline and ice skating you should set down on the
outside edge, so there must be some amount of outside lean to be able
to do that.

-Jim



02 Aug 2005 14:02:39
Ken Roberts
Re: double-push skate by ski racers?

Jim Grau wrote:
> When you say: "configurations where it is impossible to
> derive any significant direct-push benefit", do you mean
> they aren't pointing the skate inward much

Yes, lotsa people in lotsa situations do DP by landing the skate aiming
almost straight forward, so clearly it's not helping them move forward at
that moment. Seems to me that the benefit from that is instead to generate
kinetic energy sideways which is "caught" by the main push toward the
outside. Since the skate on the main push is aiming partly out toward the
side, there is a backward component to the force into the ground, so it
re-directs a substantial portion of that extra sideways kinetic energy into
forward propulsion.

(other skaters definitely aim their skate to the inside, and move it toward
substantially toward the inside as they make their "under-push", which
strikes me as the more "pure" form of double-push).

> are you saying that part of the advantage of double push
> is the increased travel distance you get from the main inside-edge push

For elite racers, I see no significant increase in "travel distance" from
double-push. Because even in normal-single-push, elite ice + inline
speedskaters are landing the skate aross the centerline, inside the hip
joint. I believe that's not just "passive glide" on the outside edge -- the
elite racers are already generating propulsive force by sorta "pulling" on
the outside edge, by using non-obvious muscle moves like hip-abduction and
ankle-pronation. So the elite racers are already getting a much longer
propulsion distance in their normal push than lots of people imagine. I
suspect that's one reason why it's been hard for ice speedskaters to find
much advantage in double-push -- though our American skating genius is
showing them something new.

Maybe some inline + ice skaters did not know they could use their outside
edge for active propulsion, so there were only getting as much range of push
as we normally do on skis. So for them double-push would be a discovery of
much longer range of motion. But for elite racers it's just a question of
which muscles to use, and what kinds of work to generate and transform at
what cost.

The normal leg-push is much more restricted in ski-skating, so the potential
gain from DP is larger. But so is the cost.

Ken
_______________________________
"Jim Grau" <[email protected] > wrote in message
news:[email protected]
> Ken, are you saying that part of the advantage of double push is the
> increased travel distance you get from the main inside-edge push,
> coupled with the larger upper-body swing in the opposite direction
> (since you've had to lean the other way for the under push)? When you
> say: "configurations where it is impossible to derive any significant
> direct-push benefit", do you mean they aren't pointing the skate inward
> much on the set down but just rocking the upper body outward? I guess
> even in classic inline and ice skating you should set down on the
> outside edge, so there must be some amount of outside lean to be able
> to do that.
>
> -Jim
>




02 Aug 2005 09:42:52
Bjorn A. Payne Diaz
Re: double-push skate by ski racers?

XC skis track mostly straight ahead, in large contract to roller blades
(inlines), so I can't see any elite skier even considering trying to
perform a double push.

Jay Wenner



02 Aug 2005 11:02:21
Jim Grau
Re: double-push skate by ski racers?

If by "track" you mean the angle made by the ski relative to straight
ahead, I would certainly not agree. In most situations inline speed is
notably faster than skate-ski speed, so the angle made by inlines is
usually not very large. Then again, I'm probably totally
misinterpreting what you mean.



02 Aug 2005 12:51:55
Bjorn A. Payne Diaz
Re: double-push skate by ski racers?

When you set down a xc ski, the direction is starts is hard to change
unless the snow is fairly hard. In racing, the course is usually
groomed, so twisting the ski to achieve a new direction _while_ the ski
is weighted is (IMO) very difficult. Inlines can turn very easily. So a
person can weave in-and-out of a line of cones while skating on one
foot with inlines. I've done this type of motion while skiing on one
ski (down a long hill at the local downhill area which happens to be
the only place with snow in the winter, but I digress), but the length
of arc is so long that if this was done on the flats, you would lose a
lot of speed.

I suppose this conversation could be a matter of degrees. So if you're
talking about twisting the ski to change its direction by 10 degrees,
deal me in. I think most skiers do that type of action and probably
don't realize it. When I rollerskied behind an inliner last weekend,
the double push motion was do drastic (in terms of changing the
dirction of motion) that I'd like to a see a the wheels paint a line on
the pavement so I could study it as an abstract art project in curved
lines.

Jay Wenner



03 Aug 2005 02:14:26
Gary Jacobson
Re: double-push skate by ski racers?


"Bjorn A. Payne Diaz" <[email protected] > wrote in message
news:[email protected]
> When you set down a xc ski, the direction is starts is hard to change
> unless the snow is fairly hard. In racing, the course is usually
> groomed, so twisting the ski to achieve a new direction _while_ the ski
> is weighted is (IMO) very difficult. Inlines can turn very easily. So a
> person can weave in-and-out of a line of cones while skating on one
> foot with inlines. I've done this type of motion while skiing on one
> ski (down a long hill at the local downhill area which happens to be
> the only place with snow in the winter, but I digress), but the length
> of arc is so long that if this was done on the flats, you would lose a
> lot of speed.
>
> I suppose this conversation could be a matter of degrees. So if you're
> talking about twisting the ski to change its direction by 10 degrees,
> deal me in. I think most skiers do that type of action and probably
> don't realize it. When I rollerskied behind an inliner last weekend,
> the double push motion was do drastic (in terms of changing the
> dirction of motion) that I'd like to a see a the wheels paint a line on
> the pavement so I could study it as an abstract art project in curved
> lines.
>
> Jay Wenner

When I skate on snow a lot I and get pretty good at it, I seem to experiment
with something that is fun to do but may not be the fastest means of
traveling: I set the ski down on the outside edge and a bit forward at an
angle that approximates a scrubbing snowplow. As I arc the ski around I roll
out onto a flat ski at the normal set down point and finally the inside edge
when extended . The length of the push is greater, there's a longer "post"
and it feels powerful. Borowski thinks this is nonsense and I wouldn't argue
that it makes sense, but I encourage folks to try it.

Works with Marwe skate roller skis too- they seem just the right speed.

BTW- I've seen diagrams of double push inline skate tracks and they
certainly are "lacey".

Gary Jacobson
Rosendale, NY




03 Aug 2005 12:40:20
Janne G
Re: double-push skate by ski racers?

Bjorn A. Payne Diaz wrote:
> When you set down a xc ski, the direction is starts is hard to change
> unless the snow is fairly hard. In racing, the course is usually
> groomed, so twisting the ski to achieve a new direction _while_ the ski
> is weighted is (IMO) very difficult. Inlines can turn very easily. So a
> person can weave in-and-out of a line of cones while skating on one
> foot with inlines. I've done this type of motion while skiing on one
> ski (down a long hill at the local downhill area which happens to be
> the only place with snow in the winter, but I digress), but the length
> of arc is so long that if this was done on the flats, you would lose a
> lot of speed.
>
> I suppose this conversation could be a matter of degrees. So if you're
> talking about twisting the ski to change its direction by 10 degrees,
> deal me in. I think most skiers do that type of action and probably
> don't realize it. When I rollerskied behind an inliner last weekend,
> the double push motion was do drastic (in terms of changing the
> dirction of motion) that I'd like to a see a the wheels paint a line on
> the pavement so I could study it as an abstract art project in curved
> lines.

Yeah, it is a matter of degrees.
The motion that we do with the body have some similarity with Doublepush
(Dp) but the skiis curve or lack of curve is not. I at least can't
change the direction of the skii when it is set down and pushed on but i
can do some of the movment with the body that i do when doing Dp on inlines.

If you know anybody taht can do "real" Dp on inlines make him do it
trough a tiny spot of water on the asphalt and the look at the tracks he
is doing. I have tried it and it looks rather funny on the asphalt.

Janne G


03 Aug 2005 15:06:17
Ken Roberts
Re: double-push skate by ski racers?

Janne G wrote
> . . . i can do some of the movment with the
> body that i do when doing Dp on inlines.

Interesting that the same guy who told me about double-push skiing
experiments (using unweight, not curves), also mentioned that he'd heard of
two Norwegian XC ski racers working on incorporating "DP-like" moves into
their technique.

Ken




04 Aug 2005 13:26:50
Janne G
Re: double-push skate by ski racers?

Ken Roberts wrote:
> Janne G wrote
>
>>. . . i can do some of the movment with the
>>body that i do when doing Dp on inlines.
>
>
> Interesting that the same guy who told me about double-push skiing
> experiments (using unweight, not curves), also mentioned that he'd heard of
> two Norwegian XC ski racers working on incorporating "DP-like" moves into
> their technique.

Ken, i belive it is a game of giving and taking here.
Does the skier benefit more when using the inline Dp movment even though
they can't make the skiis curve like inlines?

I do i because it suit me even though i start moving over more to
clssical skating style (on skiis) because i had real problems when the
surface was rough or icy just because of the setdown of the skiis was on
the outer edge and rolled over to the inside edge. The moment/time when
you cross over from outer to inner edge you are WERY prone to slip if
the surface is icy or rough.
But i still uses some of the movment from inlines, ex the dynamic
movment of the setdown leg just to don't get lactic accid buildup due to
static standing on the setdown leg in the beginning of the phase in
classical skating.

I hope this was understandable? ;-)

Janne G


04 Aug 2005 12:47:08
Ken Roberts
Re: double-push skate by ski racers?

Janne G wrote
> i belive it is a game of giving and taking here.

Yes it's a question of trade-offs: add up the propulsive benefits: push with
more muscles in different configurations, relieve lactic acid build-up), and
subtract the costs (increased friction from pivot-skidding, additional
muscular effort to unweight the ski, etc.) -- somehow estimate the power
impact of each of those in Watts (and some interactive effects among them).
Then factor in the risks, especially the one Janne G mentioned about losing
control while switching sides with the same ski.

This is not a matter of deep principle: curves versus lines. It's just
about adding and subtracting Watts. But I think quanitifying the pieces it
is too hard, so it's mostly a matter of experimenting with actual skiing and
controlled measurements of personal time-trials -- try out different moves,
different snow conditions, different performance situations. The physics
just provides useful hints about which experiments are likely to be
promising. (I think Janne G's control problems on icy snow is unfortunate
for DP, because one of the first-known favorable situations for double-push
on inline-skates was on wet pavement.)

Inline: There's still race situations in inline speedskating where
adding/subtracting the trade-offs does not come out in favor of
double-push technique. Like the 200m and 300m oval-track time-trial events
at the outdoor 2004 Inline World Championships were all won using
normal-single-push technique -- "classical" skating. (Despite being solo
performances, I find the video of Luca Presti in the men's 300m TT
breathtaking, and Andrea Gonzales' win of the women's 300m is not only
breathtaking, but gave me new insights into the physics+biomechanics of
skating -- it's not easy to find videos of elite-level non-double-push
technique any more).

Ice: On ice, it was long believed that adding/subtracting the trade-offs
tipped away from double-push. And I have seen elite speedskaters explain on
video that the basic problem is that long-course speedskates cannot follow a
curved path effectively.

Then that American came along. At first they laughed . . .

Ken
___________________________________
Janne G wrote
> Ken, i belive it is a game of giving and taking here.
> Does the skier benefit more when using the inline Dp movment even though
> they can't make the skiis curve like inlines?
>
> I do i because it suit me even though i start moving over more to
> clssical skating style (on skiis) because i had real problems when the
> surface was rough or icy just because of the setdown of the skiis was on
> the outer edge and rolled over to the inside edge. The moment/time when
> you cross over from outer to inner edge you are WERY prone to slip if
> the surface is icy or rough.
> But i still uses some of the movment from inlines, ex the dynamic
> movment of the setdown leg just to don't get lactic accid buildup due to
> static standing on the setdown leg in the beginning of the phase in
> classical skating.
>
> I hope this was understandable? ;-)
>
> Janne G




10 Aug 2005 21:23:31
Ken Roberts
Re: double-push skate by ski racers?

Janne G wrote
> I still use some of the movement from inlines, ex the
> dynamic movement of the setdown leg just to not get
> lactic acid buildup due to static standing ...

It recently hit me that the extension of the knee joint just after set-down
is doing effective propulsive work in itself, not just "pumping" away lactic
acid in preparation for later propulsive work. Because the knee-extension
move raises the mass of the pelvis and upper body, and so increases
gravitational potential energy. (and so does that forward-ankle-flexion
"knee drive" move). In skiing with poles this is payoff is obvious when
later in the cycle this same mass drops down and adds force to the
double-pole-push.

But even without poles, the later dropping of the mass of the pelvis + upper
body adds propulsive force -- to the leg-push. To me the difference in force
of my leg-push with versus without a preceding little knee-extension
"stand-up" is very noticeable when I'm out skating on the streets. Turns out
that this vertical move just after set-down is one of the most effective
ways to get more propulsive work out of the knee-extension muscles /
quadriceps when skating (those muscles can also help some near the end of
the leg-push).

Here's my guess at how double-push _might_ work to increase speed on skis:
It would be incorporated into the V2 sequence on flat terrain at a fast
speed.
(1) Set the ski down somewhat outside the hip, aimed roughly straight
forward in the skier's overall line of motion, on its outside edge. Perhaps
to achieve this edging, the ankle would be supinated some, and the knee
"rolled out" some.
(2a) Immediately on set-down, push the foot toward the inside and the hip
toward the outside, using hip-adductors and other muscles, which adds
side-weight-shift energy. (2b) At about the same time the knee joint extends
(and the ankle joint flexes forward) to raise the hips -- and other muscles
raise the shoulders and arms in preparation for the pole-push.
(3) Just before reaching the high point of the upward motion of hips and
shoulders, unweight the ski, turn it toward the outside quickly, and
re-weight it now aimed somewhat toward the outside, now on its inside edge,
and not far from underneath the hip (which has meanwhile been moved sideways
in reaction to the inward-push in step 2a).
(4) Start the main leg-push toward the outside, also start the
double-pole-push. The main leg-push now has extra force as it "catches" the
extra side-weight-energy resulting from the inward push in step 2a. The
double-pole-push still gets its usual help from the dropping of the upper
body which was raised in step 2b.

Now all we need is snow. Or some better ideas.

Ken
_________________________________________
Janne G wrote
> Ken, i belive it is a game of giving and taking here.
> Does the skier benefit more when using the inline Dp movment even though
> they can't make the skiis curve like inlines?
>
> I do i because it suit me even though i start moving over more to
> clssical skating style (on skiis) because i had real problems when the
> surface was rough or icy just because of the setdown of the skiis was on
> the outer edge and rolled over to the inside edge. The moment/time when
> you cross over from outer to inner edge you are WERY prone to slip if
> the surface is icy or rough.
> But i still uses some of the movment from inlines, ex the dynamic
> movment of the setdown leg just to don't get lactic accid buildup due to
> static standing on the setdown leg in the beginning of the phase in
> classical skating.






17 Aug 2005 12:23:06
Wendy J
Re: double-push skate by ski racers?

I am told that, the concept of the double-push from in-line and speed
skating is used in a number of faster situations particularly in
sprinting. It is nothing particularly new, just the name. It is more
subtle than the in-line version. I say it demonstrated ...

This summer there was a company (www.xczone.tv) filming an elite
in-line racer, Barry Publow from www.breakawayskate.com with some
national sprint skiing champions and nordix racers demonstrating
double-push applications for ski racing (on roller skis). They said if
was for the nordic ski project DVD.

Wendy



25 Aug 2005 21:15:18
[email protected]
Re: double-push skate by ski racers?

While reviewing videos of our team members roller sking this June Coach
Sten Fjeldheim of Northern Michigan University (and I think U.S. Nordic
Coach of the Year, or something like that) pointed out what looked like
the dreaded "Double Push" in a few people and warned us away from it.
This comes from a guy who grew up as a speed-skater training with the
same club and coach as Eric Heiden, so he knows what the double push is
and does on speed skates.



26 Aug 2005 10:55:47
Doug Taylor
Re: double-push skate by ski racers?

"[email protected]" <[email protected] > wrote:

>While reviewing videos of our team members roller sking this June Coach
>Sten Fjeldheim of Northern Michigan University (and I think U.S. Nordic
>Coach of the Year, or something like that) pointed out what looked like
>the dreaded "Double Push" in a few people and warned us away from it.
>This comes from a guy who grew up as a speed-skater training with the
>same club and coach as Eric Heiden, so he knows what the double push is
>and does on speed skates.

For use in inline speed skating, double push is not "dreaded;" it is
pretty much universally accepted as the most efficient technique for
cruising speed. Classic is not irrelevant, but it is mostly used in
"lower gears:" starting, climbing, etc. Once the skater gets up to
speed in flat and rolling terrain, there are very few advanced to
elite skaters who don't use DP most of the time.

Because of differences in surface and equipment, the jury is still out
as to whether or not DP has an application in ice speed skating. Not
in short track: only two straightaway strokes before the corner;
there would be scant benefit

As far as long track, coach Barry Publow's latest take is this:

"Anyone who says itís impossible to skate double push on the ice
either doesnít know how to skate or hasnít seen one of several double
push ice videos that have circulated the web. Double push on ice is
very possible, but the range of its application is much smaller when
compared to wheels. ... That is, less movement variation is possible,
and a great deal of control and balance is required. Because of the
rocker on a long-track (ice) blade (making it less maneuverable than
wheels on the road), double push on ice can only be done at higher
speeds.

The real question with double push on ice is whether it offers the
same advantage compared to skating on wheels. One of the issues with
dp on the ice has to do with the location of body weight over the
skate. With dp on wheels the body weight shifts to the far rear of the
skate by the end of the underpush, then travels forward to the middle
of the skate for the (regular) push.

On ice, the skater wants to shift the body weight forward as the push
extends so that they can engage the clap blade and use the calf
muscles. Shifting the body weight from the heel all the way to the toe
on the blade is quite difficult, so in my opinion true double push on
ice isnít terribly practical under most conditions.

However, I have been able to incorporate some slight double push range
of motion into my ice skating and can utilize some of the mechanical
benefits. This helps lengthen my glide and allow me to be more relaxed
on the straights."

http://inlineplanet.com/Interviews2/part2barrypublow.html

I have skated inline and ice for 10 years and x-c for about 6. DP on
inlines is second nature by now, ingrained in the muscle memory. On
long track, I can do it but don't have much of a clue as to whether is
does any good because I'm not a cutting edge long track skater.

As far as x-c, it simply never occurred to me to try DP. It certainly
is not intuitive. I'll definitely give it a whirl this winter and see
if I can make any sense out of it.
--dt