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- Where this came from
- Like Classic
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Where this question came from
Cross country skiing techniques are some of the most complicated
human-powered propulsive motions. So it's reasonable to try to find
some common themes and ideas to try to simplify understanding them all.
Many people learned Classic striding first, and then want to try
skating. So it's reasonable to try to re-use some of their skills
and concepts. And it's reasonable for instructors to help them build
on their Classic skiing capabilities.
There have also been some coaches who have tried to make "skating is
really like classic" into a general theory of technique design.
December 2005 ideas
Skating is Like Classic
(a) Poling helps a lot for both (at least at low and
moderate speeds).
Some positions and moves are the same because,
"It's what you do for maximum poling power".
(b) There's a backward-push component to leg-push
propulsion power in both.
Some of the same muscle moves help both:
hip-extension (gluteus muscle), ankle-extension (calf muscle), and . . .
(c) "Forward hip rotation" helps propulsion for both.
By this I mean that as I finish pushing with
my right foot, I advance my left hip ahead of my right hip as I step
onto my right foot.
(d) Shifting shoulders sideways over toward the next
pushing ski as step onto it helps both.
Though for completely different reasons: For
classic striding it helps grip. For skating it adds to propulsion (but
only if the timing is right and if it doesn't distract from other more
important things).
Putting (c) and (d) together yields something odd:
Shoulders and Hips turn in opposite directions as step from one ski to
the other.
Not like Classic
Some coaches and writers have said that Skating is
really like Classic. But in some crucial ways, I think Skating is
opposite to Classic diagonal striding:
(a) the sideways component of the leg-push adds major
power to Skating propulsion, but not to Classic striding.
Because push-force can be transmitted to the
ground while the skate or ski is rolling or gliding, Skating can use the
"inclined plane simple machine" principle of mechanics to convert
sideways push into propulsive forward-backward force.
This sideways push engages a different big leg
muscle group for Skating: the quadriceps or knee-extension muscles --
and some additional little-known muscles . . .
(b) muscles along the outside of the leg can add to
propulsion in Skating, by pushing directly out to the side early in the
stroke . . .
with these three muscle moves: tranverse hip
abduction, medial hip rotation (if knee joint is in strongly bent
position), and ankle pronation. (I think these muscles are why the upper
legs of some elite speedskaters look so "wide".)
(c) setting down the foot with ankle out in front of
knee (and pressure on toe+ball of foot) is usually good for Classic
striding -- but always bad for Skating.
Because getting the ankle joint way behind the
knee is the prerequisite to engaging the big quadriceps knee-extension
muscles to push out to the side to add propulsive power to Skating. This
ankle-behind-knee position also adds range-of-motion to the final
ankle-extension "toe-push" for Skating.
(d) overlapping both feet on the ground is bad for
Classic grip, but usually good for Skating power.
Eliminating the mistake of setting the next
foot down before the current leg-push is finished is the crucial
prerequisite for all the advanced moves for Classic striding power.
But smoothly setting down the next foot while
the current leg is still extending is the sign of expert-racer V1 Skate
technique for full continuity of push-force climbing up a hill. (? Is
overlap of timing of both skis skating on the ground actually possible
?)
October 2004 ideas
Like Classic
Both are done on skis
- Balance is important.
- Balance on a single ski is important.
Both use poles for propulsion
Since the most effective physical/biomechanical configuration for
starting a pole-push is with shoulders high and forward, motion techniques
which emphasize the pole-push will have these positions -- at least at the
start of the pole-push:
- strong forward ankle flex -- because this gets the upper body
forward without also making it low.
- forward curl or "slouch" of the chest + back -- with more curve
higher, because bending sharply from the waist is a trade-off between
more forward versus lower shoulders.
- not much flex of the knee (at start of pole-push) -- because this
moves upper body down and back, just the opposite of what is desired.
Skating with No Poling: Note that when "Skating with No
Poling", there is no physical/biomechanical benefit in using a body
position which is high or forward. So it is strange to have ski
coaches advocate practicing skating with no poles in a high hips forward
position -- since it's hard for the skier to feel any positive
benefit from it.
So perhaps the training benefit is that in the high
hips forward position it is difficult to effectively use the big leg
muscles (gluteus maximus and quadriceps) for skating, so it forces the
skier to learn to use the hip abductors and torso rotators for
propulsion.
And if in the name of the "quiet upper body" doctrine,
the coach further forbids torso rotation, then the focus is on the hip
abductor muscles.
Not Like Classic
Leg-push is completely different
- Thrust of the classic leg-push is all straight front-to-back,
. . . but the magic of skating is to push out to the side.
Key point for learning to skate is to start feeling
that special magic. Practice pushing directly out toward the side,
with no backward motion at all. Even try to slice the ski
forward while pushing out to the side.
- Classic leg-push is inherently explosive,
. . . but the skating leg-push is inherently smooth.
The classic striding leg-push "kick" is explosive,
because the ski must be stopped on the surface of the snow (in static
friction) while the push-force is applied. The pole-push in
skating is also somewhat explosive, because the tip of the pole must be
stopped on the surface of the snow during its push.
But the leg-push can be smooth, because it is done
while edge of the ski is gliding on the snow. I don't know any
reason to try to make the skating leg-push explosive (any more than a
bicycle racer should try to push on the pedals sharply or explosively).
Trying to be explosive may feel strong, but in the objective physics it
just puts more stress on muscles and joints without increasing total
forward-motion power.
Side-to-side commitment + motion is different
- Committing all body weight to one ski is difficult to achieve in
classic striding,
. . . but in skating it's nearly impossible to avoid.
- Committing body weight to one side in Classic striding is a
"necessary evil" in order to achieve good grip -- to be done only as
much as necessary
. . . but in skating the side-to-side motion of the upper body adds
propulsive force to each leg push -- to be done as much as
possible, without unduly interfering with the pole-push.
Classic skiing lacks a way to convert side-to-side
action into forward-motion power. So the side-to-side commitment
is an inefficient waste of power in Classic striding. But the
magical physics of skating makes it possible to get useful work out of
side-to-side "wiggling".
Key point is to feel the side-to-side action
driving forward propulsion and learn to enhance that magical
propulsion, not just do "the same as classic".
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