Ski Skating in cross country skiing
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My main questions and ideas
I'm not sure which I'm doing: V1 or
Open Field skate (V2 Alternate)?
My story: I was confused about this for myself for
several months. Fortunately it didn't stop me from having fun
skating. I thought I was doing V1, but I finally I figured out that
all along I had really been doing Open Field Skate ("V2
Alternate"). I think the reason
for my confusion is that "V2 Alternate" to me sounded
complicated and advanced -- and "V1" sounded simple.
Since what I was doing felt simple and natural, it fit for me to choose
the term that sounded to me like that.
Hope this helps you sort it out:
If you're making one double-pole-push for each full both-leg-strokes
cycle, and it feels like a natural rhythm and even timing on both sides ( push on
Left / glide on Right / push on Right / glide on Left / push on Left . .
. ), and you
never had any special instruction -- then you're probably doing Open
If you feel like you're rushing the pole-push side a bit, and you
have to be careful about how you plant your pole tip on your
non-push-side so you don't trip your ski on it, then you've probably
gotten into V1 / offset.
See the descriptions under "skating techniques
and names" for more detail.
The key difference is that Open Field Skate has a
distinct glide-with-no-push phase after landing the new ski and before
starting the pole-push, so there is a distinct "passive" glide
phase on both sides. The main point of V1 offset is to eliminate
this glide-with-no-push phase on (at least) one of the two sides.
distinguishing feature is that if you find that you're tripping over
your pole when you use a normal double-pole-push motion with both hands
at the same vertical level and pushing straight back with both poles,
that's a sign of V1 offset. If you haven't noticed a problem with
tripping over your pole, and you're comfortable starting your pole-push
with both hands at the same height off the snow, that's a sign of Open Field Skate.
The usual solution to this problem
with V1 is to hold one hand lower and plant that pole out to the side --
"offset" hand positions.
It may be possible to have a pole-push timing which is somewhere in
between exact V1 offset and exact Open Field Skate.
For non-racers, there is a continuous "transition range" of useful
motion-technique variations between Open Field Skate and V1
On flat terrain with hardpack snow, there's usually a
substantial passive-glide phase that can be used to prepare for a
maximum pole-push. Up a gentle-to-moderate hill, most skiers
shorten the passive-glide phase so they don't slow down as much before
they start the pole-push.
As the hill gets steeper, the passive-glide phase gets
even shorter -- until there isn't time to get the non-pole-push-side ski
recovered back to the center before pushing on the pole -- so the two
collide. So the pole has to be planted a little ways out to
the side so it doesn't get in the way of the recovering ski -- that's
when it gets into the range of V1 offset. When the passive-glide
phase is completely eliminated, the non-push-side pole has to be planted
way out to the side, and that's "full" V1 offset.
If you watch elite racers going up steep hills, they're almost always
doing V1 offset. And on gentle terrain they usually do V2, so it's not
easy to find examples of Open Field Skate in videos from a World Cup
race or the Olympics.
For them the "transition range" is usually
not continous: "big" V2 on the flats, to
"quick" V2 on moderate hills -- but then to V1 with no
passive-glide and "full" offset poling up steep hills.
Elite racers have such stable balance gliding long on either ski, and
such strong arms to push on both sides, that they have little use for
Open Field skate ("V2 Alternate" / 2-skate).
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My story: Once I figured out that I was not doing V1, of
course I wanted to learn V1, but this proved trickier than I
expected. Perhaps that's because I made it more complicated
than it had to be. But even if you can learn it easier than I did,
Alternate / 2-skate) offers a lot of advantages:
- the fun of the passive-glide phase (you lose at least one of
- a little rest interval during the passive-glide phase
- time to recover your ski back to the center without tripping over
- the full pushing power of both poles
- natural rhythm betwee the two sides
Why go to the trouble of learning a new technique that gives all
The big problem with Open Field Skate is that the distinct passive
glide-with-no-push phase is a "dead spot" from the perspective
of power -- because useful power comes from pushing against the snow
with something. No pushing-against-the-snow work, No power.
To make up for that no-power phase in the stroke cycle, some muscle
group(s) needs to push harder in the other phases to make up for
That might be OK on flat and gentle terrain, but going up a steep
hill that muscle group is already pushing pretty hard to near
their limit in another phase of the stroke cycle. In that
situation, forcing it to push yet harder might put the muscle group over
its "quick recovery" limit, so its performance after that is
- By eliminating the "dead spot", it spreads the
push-force demand more evenly through the stroke cycle, and reduces
harmful "peak forces".
- Also on a steep hill there's the possibility of "stalling
out" during the passive glide phase, even sliding back a little
-- which sounds like a bad idea.
So then why bother to learn Open Field Skate?
- First, lots of people enjoy gliding with no push.
Some say it's the main reason they choose to ski at all -- V1 offset
to get up a hill is only a necessary evil until they can get back to
that beautiful rhythm of push / glide / push / glide.
- And on gentle terrain, Open Field Skate allows a more powerful
pole-push to help go faster -- because there's more time to set up
for the pole-push.
- V2 allows even more pole-push help for going faster, but full V2
requires much better balance, so lots of skaters prefer a solid
strong Open Field Skate to a V2 which is precarious and rushed.
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My story: Hanging out with racers, I came to feel that
using herringbone to go up a hill was an admission of failure. But
when I forced myself to use other techniques, I found that I had to stop
and rest before I reached the top -- or that I made it, but my legs were
burning so much that I felt slow and tired for the next hour. For
me, herringbone works as a way to "skate slow" and not get
So my opinion is that sometimes I should use Herringbone skate.
Or even the Herringbone "walk".
It allows me to operate with lower energy output if
thatís what I need for a while.
And each skate-push gets immediate synchronized assistance from
a pole-push. So if my big leg muscles are burning, this is a way to limit the load on them.
A big disadvantage of herringbone is that it does not provide an
effective way to use the powerful abdominal muscles -- versus offset V1
and Open Field skate which do use the abs.
(Of course if you have not been training for powerful abs, you may
not care about this.)
Also, since thereís no grip wax on skating skis, Skate herringbone
is harder than Classic herringbone.
I have to angle your skis out further to be sure of not
See the discussion of "Is
more glide good?" for Classic striding.
Many of the arguments also hold for ski skating.
In high-force situations, more knee bend than necessary puts more
fatigue-stress on the leg muscles and joints, for a given power-output
For non-elite skiers, most skating situations are high-force rather
than high-muscle-speed. One indication of this is that
turnover-frequency of leg-pushes in ski-skating is significantly lower
than the turnover-frequency for efficient bicycling using good pedaling
technique. Most ski-skating is something like trying to pedal a bicycle
up a hill in a high gear. Certainly most uphill skating for most skaters
is a force-situation.
It is straightforward to verify on a leg-press weight-machine indoors
that the leg-push motion can sustain higher forces with less
fatigue-stress when the knee joint is more straight and less bent.
Therefore in high-force skating situations, most skaters should be
trying to use the least-bent-knee, straighter-leg section of the
Key rules for high-force situations:
- Always press the leg out to full extension.
- Never bend the knee more than you can press out to full extension
-- repeatedly sustained through the full duration of the desired
The benefits of reactive-side-force from torso-swing and other moves
can only help forward-propulsive power if those additional forces are
transmitted to the ski and the snow through the leg. So taking advantage
of reactive-side-force requires the leg muscles to handle higher force
magnitudes -- which tends to push each situation more toward the
Bending the knee more results in the hips and the mass of the butt
and upper body dropping more back, and in that position the force of
gravity applies more torque against the knee joint -- which is even more
fatigue-stress in high-force situations. So recovering the hips to a
more forward position will reduce fatigue-stress.
On the other hand, hips more forward means that the upper body is
higher and the body presents a larger cross-section of air resistance,
which drains away power. Air resistance increases greatly at higher
On another hand, in motion techniques focused on poling -- especially
V2 -- the more hips and upper body start up and forward, the more
effective forward-propulsion work they can deliver as they are dropped
down and back during the pole-push.
- so at higher skater-speed, finding the optimal hip forward-back
up-down position requires a trade-off of air resistance versus gravity
(and effective pole-push).
- at lower skater-speed climbing up a hill, air resistance is
relatively unimportant, while sustaining high leg-push force is very
important, so there's not much "trade-off" -- hips more forward is the
answer. For most non-elite skiers climbing up a hill, that implies
less knee bend, not more. Which implies . . .
Key rule for climbing up a hill:
- Never bend the knees and drop the hips back more than you can
recover them back up and forward -- repeatedly sustained through the
full duration of the desired performance.
The typical hill-climbing error of athletic skaters with strong legs
is to bend the knees too much and allow the hips to drop too low at the
end of each skate-leg-push. At first they can get their hips back high,
but further up the big hill, or on the fifth and sixth little hill, the
hips do not recover all the up and forward, and then it gets a little
worse and a little worse -- and so the fatigue-stress on the leg-muscles
The test of "butt down in the bucket" is not, "Is your knee
bend angle less or more than your team-mates or competitors", or "Does
it look all right to your coach", or "Is it the same angle as that elite
racer in the World Cup video".
"butt down in the bucket" is a dynamic flaw. The test is
whether you are failing to keep on recovering your hips up
and forward to start the next stroke-cycle.
A trap is to try to copy the knee-bend angle of an elite racer. Just
because the elite racer can sustain a big aggressive knee-bend angle,
does not mean that you should try. Even if you can somehow sustain a big
angle, that does not mean you are getting more sustained power from it
-- have to measure.
Especially be careful of observing a big knee-bend angle of a elite
racers doing V2 skate up a hill which is gentle for them, and
using that to justify you using an aggressive knee-bend for doing V1 up
a hill which is not easy for you.
compare with inline and ice speedskaters
Speedskaters on inline and ice skates sometimes skate with their
butts back and lower than most ski-skaters. That's because the
resistance of pavement and ice is lower, and most inline and ice race
courses are less hilly than most XC ski race courses. So air resistance
is a much bigger factor for inline and ice speedskaters, so getting low
is important -- so they train their leg muscles and joints specifically
to support that low butt position and to endure more of that kind of
The basic rule of ankle flex for most ski-skating is:
- The optimal angle of ankle-flex is more.
- ankle-flex brings the hips more forward, which puts the weight of
the butt and upper body vertically more directly over the knee joint,
which decreases the torque on the knee joint.
- ankle-flex brings the hip joint closer into the line of the push
of the ski through the heel of the foot, which is a more effective
leverage geometry biomechanically.
- the more ankle-flex at the start of the leg-push, the more
forward-propulsion work when the ankle joint is extended in the
toe-push move at the very end of the leg-push move.
- A frequent error is to confuse knee bend with ankle flex -- to
make a big knee bend instead of a big ankle flex. Both moves shorted
the critical distance between the hip joint and the ankle joint -- but
they have very different side-effects. The trap is that the knee-bend
feels stronger in the short term.
As long as the skater is using poles, the rule is:
- The optimal angle of forward-lean of the shoulders is more.
- The more forward and bent-over the shoulders, the more the "chest
crunch" flex move by upper-abdomen muscles is aimed backward instead
of just downward.
- The more forward and bent-over the shoulders, the larger
percentage of front-abdomen muscles is "aimed" down-and-back instead
- The more bent-over the shoulders, the less cross-section presented
for air resistance.
- The more forward the shoulders, the more forward the hips, so the
more effective work can be done by dropping the hips down and back
during the pole-push (provided this move is being used: often for the
V2 pole-push, little for V1 offset pole-push).
If you're willing to start falling forward dynamically, you
can get your shoulders further forward than if you limited yourself to
what you could balance statically.
- If you're not leaning forward so far that you would fall on your
face if you did not catch yourself with your poles, the you're
violating the forward-lean rule (above)
But doesn't the fall of the weight of your upper body onto the poles
add power to the pole-push?
Yes, gravitational potential energy is converted to kinetic energy as
the weight of your upper body drops vertically. But this would be just
as effective if you dropped backward onto your poles.
The key driver of the "forward fall" move is the getting forward
aspect. The "fall" is mostly a convenient side-effect.
There's some old American coaching lore that looking from the side of
the skater, the angle of a line through shoulder and hip should be
parallel to a line drawn through the knee and ankle. (Perhaps this was
once an accurate observation of elite racer technique in the late 1980s
- This rule is ignored by elite racers in the 2000s, based on
careful analysis of World Cup videos with slow motion and pause.
- Most racers through most of their stroke-cycle show a lower
angle in the forward-lean of their shoulders than in the angle of
- The only way to discover parallel angles in elite racers nowadays
is to be very "careful" to pause the video at the single instant in
the stroke-cycle that agrees with the desired conclusion. (But still
there are some elite racers that never have those two angles
parallel at any point in their stroke-cycle.)
- The physical and biomechanical drivers of optimality for these two
angles are completely different (see above under
ankle flex and forward lean)
-- so there is no reason to guess that they ought to be parallel.
- For an elite racer, limiting the forward-lean of the shoulders to
be parallel to the angle of ankle-flex would result in a less
effective contribution of the chest-crunch move to the pole-push.
"reactive force" is my term for an "inertial" force: a force on a
physical object that results from accelerating (or de-accelerating) the
mass of some other object. I call it "reactive" because it arises from
Newton's Third Law: "Every action has an equal and opposite reaction".
In a propulsive motion which is repeated, each object connected to
the skier must have the same relative velocity (and position) at end of
the stroke-cycle as that same object had at the start of the
stroke-cycle (which is the end of the previous stroke-cycle).
Therefore every acceleration must be paired with a de-acceleration.
So all the reactive forces must always come in opposite pairs somewhere
in the overall stroke-cycle -- one reactive force from accelerating an
object and another from de-accelerating that same object. The two
reactive forces in each pair are opposite in direction and separated in
Since they are in opposite directions, typically there is no net gain
in useful forward-propulsion work over the whole stroke-cycle. Unless
there's some clever trick for "losing" one force in the pair, which of
course must be the "bad" one which would have had a negative impact on
It happens that with skating motions it is typically pretty difficult
to find a clever way to "lose" the negative members of Up-Down or
Forward-Backward reactive force pairs.
But with some Side-to-Side reactive force pairs, the skating leg-push
motions make it possible to apply both members of the pair
positively for forward-propulsion work. And the inclined-plane
simple-machine of the skating ski angled out to the side on the surface
of the snow provides the "magic" of converting push-force aimed out
toward the side into power pushing the skier forward.
Exploiting reactive side-force is an important aspect of the most
effective skating techniques.
[ under construction ]
The answer to this question is tricky.
The muscles of the leg can transmit a wide range of force magnitudes.
In normal skating their peak push-force is significantly lower than
their maximum capability. So they are capable of transmitting the
additional force total from reactive side-force moves by other muscles
(such as from torso-swing or arm-swing moves).
But the requirement for the leg muscles to transmit additional force
also reduces the power contribution they would otherwise make
from their own push-force.
Because they make their leg-extension move
with lower relative velocity, and Power = Force * Velocity -- but
there's other compensating adjustments (range-of-motion, turnover
frequency, set-down-position) they can make so that the Velocity does
not have to be too much lower.
So there is some cost to adding force from other muscles. But the
extra power from the additional muscles is much larger than this loss --
so you skate forward faster by using reactive side-force (even though it
might be less "efficient").
To make up a semi-realistic numerical model of how much the Power =
Force * Velocity changes as a result of adding more force from a
torso-swing move is very complicated.
Such a model requires many assumptions and
parameters about Force / Velocity / Position / (etc) trade-offs --
perhaps with different trade-offs at different times during the same
leg-push motion -- of which it would be very difficult to get very
So I'm thinking it's better just to try some personal time-trial
measurements to see if adding reactive side-force is making you go
faster -- and what sort of adjustments work better for you to get the
most out of it.
I find that it helps to shorten the
range-of-motion of my leg-extension move -- and select the "straighter"
end of this range-of-motion, for best transmission of higher total
The torso-swing move produces a reactive-side-force benefit to
But the amount of this benefit is not based on the position or
distance of the move. Rather the amount of reactive-side-force benefit
is based on the quickness or maximum speed of the torso-swing move.
Greater distance in the move should be only a result of focus on
quickness and accurate timing.
When non-elite skiers try to imitate the range-of-motion of the
torso-swing of elite racers, they often get counter-productive results.
The big trap is that focus on generating and
feeling the benefits of torso-swing comes to "drive" the rhythm of the
whole stroke-cycle. But torso-swing and reactive side-force must remain
in a role of a secondary aid to other moves which are the primary
drivers: the legs in V1 and perhaps the double-pole-push in V2.
For more details of the problems, see is NKT a good idea?
Big torso-swing that effectively delivers power because it results
from quick acceleration and accurate timing is good. But that only comes
from year-round training of specific muscles (e.g. lower back and
obliques) and tricky coordination of timing with other moves. It's all
different from and irrelevant to any other sport, so most non-elite
skiers are not going to achieve the coordination or maintain the
Most skiers will do better to keep their torso-swing move limited and
- A frequent error is to rotate or swing or tilt the hips and
shoulders together in the same direction.
But actually the two joints have very different roles in the
biomechanics and physics of skating. For reactive side-force, the
motions of the hips and of the shoulders have nearly opposite
impacts on forward-propulsion benefit.
For details see Is NKT a good idea.
What is Weight-transfer in skating?
[ under construction ]
It is true that the skater's hips are usually moving downward at the
moment that the old ski comes off the snow and the new ski lands into
Some skiers and coaches think this has great significance.
So we ask:
- Does this falling help weight-transfer?
- Does this falling help forward-propulsion power?
- Is it a "free lunch" (or even a "cheap lunch")?
- Would it help forward-propulsion to try somehow to increase the
falling force of the skier's weight onto the next ski?
Analysis of skating with no poles:
- The leg-push force always has both an upward component and a
sideways component. The proportion of these components depends on the
vertical angle of the line from the hip joint to the foot and ski.
- In human skating motion, the vertical angle of the line from the
hip joint to the foot and ski varies during the leg-push.
So the proportion of these components varies during the push motion.
- In order to have a repeatable motion, the vertical position of the
hip joint must be the same at the start of the stroke-cycle as at the
- The gravitational force of the weight of the upper body on the hip
joint is constant through the stroke cycle (assuming there is no
- Therefore sometimes during the stroke-cycle the vertical component
of leg-push force must be greater than the gravitational weight of the
upper body, and sometimes it must be less than.
- In the initial segment of the leg-push, the ski and foot is more
underneath the hip, so the angle of push is more upward than sideways,
and the vertical component of leg-push force is greater than the
weight of the upper body, and the hip joint must rise up.
- In the final segment of the leg-push, the ski and foot are way out
to the side relative to the hip, so the angle of push is more sideways
than upward, and the vertical component of leg-push force is less than
the weight of the upper body, and the hip joint must fall down.
- The observed "falling" of the hips is simply an inevitable result
of the fact that the vertical angle of push varies during the leg-push
of a human skater (with no poles).
Does this falling help forward-propulsion in direct push?
- The loss in potential energy of the weight of the upper body
falling is converted partly into a gain in kinetic energy whose direction can
be converted through the inclined-plane machine of the current skating ski
- What goes down must come up (in order to have a repeatable
- When the weight of the upper body rises up in the initial phase of
the next ski's push, its gain in
gravitational potential energy is removed from the kinetic
energy of the skater's forward motion.
- Over the full stroke-cycle with both rising and falling of the
weight of the upper body, there is no net gain in overall
forward-motion power or speed.
- Indeed, because all energy-conversion processes are inefficient,
there will normally be a net loss in power due to the rising
and falling of the hips and upper body (in skating with no poles).
Does this falling help forward-propulsion through
- The loss in potential energy of the weight of the upper body
falling is converted partly into a gain in kinetic energy of the
skier's upper body sideways across toward the next ski, where it can
then help the forward-propulsion of the next ski's push.
- But the downward fall must be slowed and stopped (in order to have
a repeatable motion).
- Stopping the downward fall requires that the ski be landed more
underneath the skier. So push-force is aimed at a more vertical
angle, so there is less push-force available during the initial
segment of the leg-push to push the ski away out to the side, and to
push the skier's upper body mass sideways across toward helping the
next ski's push.
- The more the work from "falling" helps the final phase of the
previous ski's push and the initial phase of the current ski's push,
the more work is subtracted from the final phase of the current
ski's push and from the initial phase of the next ski's push. So over
the whole stroke-cycle there is no net gain in overall forward-motion
power or speed.
- Indeed, because all energy-conversion processes are inefficient,
there will normally be a net loss in power.
Would it help forward-propulsion to try somehow to increase the
falling force of the skier's weight onto the next ski?
- No, not likely. Since the net result over the whole stroke-cycle
is at best no gain (in ideal conditions), and a loss in power due to
conversion inefficiencies (in any real conditions), thus increasing
the falling force is likely going to increase the amount of the
- The greater the force and velocity of falling, the more the next
ski must be landed underneath the skier to stop the fall, and so the
lower the proportion of force is left-over to push the ski out to the
side and back against the snow for forward-propulsion.
But . . .
- adding the complexity of poling allows clever combinations of
motions which might possibly extract some net gain in power out of the
rising and falling of the skater's upper body -- either from the use
of additional muscular work, at the cost of something else.
- the up-down motion of the upper body may also have associated
vertical reactive-force pairs. Normally these reactive-force pairs
will cancel each other out over the whole stroke-cycle when skating
with no poles. But adding the possibility of "jump-skate" might make
it possible to extract some net gain from a vertical reactive-force
pair which does not cancel because one of the pair occurs while both
skis are in the air. But "jump-skate" has additional performance costs
of its own.
"NKT" means having Nose-Knees-Toes aligned vertically after
weight-transfer, at the start of the leg-push on the next ski.
It's an old coaching idea, and it might still have some value:
- possibly to help beginners to learn single-ski balance?
- possibly to help get skiers get started on the torso-shoulder-swing move?
- the concept of Knees-Toes alignment is helpful: pointing the
knee in the direction of the ski (instead of collapsing the knee
inward). Perhaps should change the abbreviation to "HKT", and focus
on Hip-Knee-Ankle alignment.
But there are several reasons why the NKT concept is a bad
(1) NKT says that the amount of reactive-side-force benefit from the
torso-swing move is based on the position or distance of the move.
- Actually the amount of reactive-side-force benefit is based rather
on the quickness or maximum speed of the torso-swing move. Greater
distance in the move should be only a result of focus on
quickness and accurate timing.
- Most non-elite skiers cannot sustain their best benefit if they
try to imitate the Range-of-Motion of the torso-swing of elite racers.
Their torso-swing muscles (e.g. lower-back and obliques) will quickly
tire and become slow and ineffective.
- Maximum reactive-side-force benefit also requires special
timing: The start of the torso-swing move should be held back.
The NKT approach completely misses this aspect of timing.
(2) NKT typically leads to a slower turnover frequency for non-elite
- because it is too much Range-of-Motion for their level of specific
torso-swing training -- since the torso-swing muscles are not used
propulsively in summer sports.
- Slower turnover frequency is bad for most skiers in some
situations -- especially for climbing up steep hills -- the most
critical problem in skating for most skiers.
Slow turnover is bad for climbing up hills
because it requires either (a) each leg-extension push to go through a
larger range-of-motion, which requires more knee-bend and thus more
fatigue-strain on muscles and joints; or (b) insert non-pushing gaps
between leg-pushes, which means either that the legs are not being used
to deliver their full power capacity, or that they are taking on higher
peak-force strains in order to make up for the gaps.
(3) NKT says that the amount of torso-swing should be the same as the
amount of ski side-angle.
- but the physics and biomechanics of torso-swing and ski-side-angle
are completely different and unrelated.
- NKT would say that there should be more torso-swing at slower
speeds when climbing up a steeper hill, and less torso-swing when
going up a gentler hill.
- but for most non-elite skiers, climbing up a steeper hill is
exactly when they need higher turnover frequency in order to survive,
and therefore less torso-swing.
(4) NKT implies that the hips and shoulders and head all turn
together uniformly in the torso-swing move.
- Actually the roles of the hips and the shoulders are completely
different in generating reactive side-force benefit.
- When pushing off the left ski, the shoulders should rotate
clockwise (as viewed vertically from above) to face more toward the
right side (which moves body mass away from the direction of the
skate-push, good for reactive-force). But rotating the hips clockwise
reduces the reactive-side-force benefit (because it moves some
body-mass toward the direction of the skate-push, bad for
- The hips should be held stable, or even better should rotate
slightly counter-clockwise (as viewed vertically from above) to face a
bit toward the left side, toward the currently-pushing ski (which
results in the right hip getting advanced a bit forward, so the next
ski lands a bit forward of the previous ski).
- The motion of the head and nose is largely irrelevant to the
amount of benefit from the torso-swing.
- So another danger of the NKT concept is that the skier will
unconsciously make strange counter-productive tilts of the head and/or
bends of the torso + abdomen in order to force the "alignment of
(5) NKT implies that the ski should be landed vertically underneath
the body, and the upper body should be in static balance over the ski.
- This implies a pause in between leg-pushes, because the ski is not
(easily) edged when it is vertically underneath the body.
- This pause may be OK on flat or gentle terrain, like for V2 skate,
and then the loss in leg-push is compensated by the stronger
- But for V1 skate ("offset") in climbing up a steep hill, this
pause is a power-loss "dead spot" -- because the pole-push is already
being exploited to maximum. The only way to make up for this dead spot
is to increase the peak-force and/or range-of-motion of each leg-push
-- but these compensations put more stress on the leg muscles and
joints, so the skier fatigues sooner.
- Instead the key trick in V1 skate is land the next ski somewhat
out to the side from the hip, so the ski is already edged at the
instant it hits the snow. And start the next leg pushing down and out
before the ski lands, to guarantee full continuity of leg-push
force (which permits minimum peak-force and minimum range-of-motion,
and therefore minimum fatigue-stress on the leg muscles and joints).
(6) Elite racers pay no attention to NKT. Close analysis of World Cup
videos with slow-motion and pause shows that sometimes the elite racers
swing their head and shoulders less than their ski-side-angle, sometimes
the same, and sometimes more.
- Beginning skaters should learn solid single-ski balance -- by
balancing on a single ski (usually with no poling) -- not by looking
for some irrelevant alignment of upper and lower body parts.
- Intermediate skaters who already have some decent single-ski
balance: If they practice no-poles skating, they usually make some
torso-swing move instinctively anyway without being told. The hard
thing for them to learn is hip stability.
- Skaters who want to use torso-swing to help survive climbing up a
steep hill should focus on quickness, not range-of-motion. First find
the best sustainable turnover frequency and range-of-motion for the
leg pushes. Then fit the torso-swing moves into the rhythm of the
The big trap of NKT is that it's easy to feel the reactive-side-force
benefit of a big torso-swing move. However non-elite skiers can only
sustain that big range-of-motion at a slower turnover frequency -- but
it's difficult for them to feel the connection between slower turnover
frequency and earlier leg-muscle fatigue in climbing up steep hills.
[ under construction ]
[ this section needs to be revised to take into account the
advantage of torso-swing and the difference between upper-body and
lower-body weight transfer. Also need to define "weight
transfer" and "complete weight transfer".]
Complete weight transfer has several benefits:
- It's fun to do.
- It's a good practice exercise.
- It's a satisfying achievement.
- It's useful in many situations.
- It's a good mental image for lots of skaters.
- The ability to do it is fundamental to optimal
But from the viewpoint of physics, complete weight transfer does not give optimal speed and
efficiency (mostly a concern for racers). It is not the "be-all and end-all" of skating technique.
not the driver of skating power.
the Pendulum deception
Here's why -- the Pendulum deception: e.g. Lee Borowski says that complete weight transfer is like a "floating pendulum"
(page 13 of "The New Simple Secrets of Skating"). That's a seductive image, because with a pendulum you get true
side-to-side weight transfer for free -- without expending extra energy --
by using gravity. But it's a deception: because true side-to-side weight
transfer when skiing requires real work from the skier's leg and arm
Some skaters may feel that they are using gravity to help, but physics says
that gravity can only be used to shift the timing of the real muscular
work (or make it less efficient). The only way to move the skier's complete
center-of-mass from side to side is to push against the snow.
The justifications I've heard for claiming that complete weight transfer
is so fundamental are:
1 - it feels good ("relaxed balance")
2 - it's the biomechanical configuration of joints in which muscles can
apply the most power.
3 - gliding on a flat ski has lower friction.
The problem with #2 and #3 is that they are not a full picture of the physics of
speed and efficiency. There is also:
4 - complete weight transfer absorbs muscular energy that could otherwise be
applied to forward motion
5 - cadence / turnover: The more times per minute I can push with my most
powerful muscles in their most powerful ranges of motion, the faster I will
Therefore, physics says that the best technique for speed and efficiency is
not just #2, but rather a optimal compromise among #2 and #3 versus #4 and
Puzzles for me
It seems pretty clear that elite racers prefer V2 on gentle terrain
and V1 for steep hills. What's the physics behind this choice?
- V2 is a "high-gear" motion technique in the sense that
some phases of the stroke cycle are conducted in biomechanical
configurations whose leverage geometry favors higher speeds
and lower forces.
- V2 is a "high-gear" motion technique in the sence that
some phases or sub-phases of the stroke cycle are "dead
spots" -- so other phases must handle higher peak forces.
Not a problem at normal power requirements -- but could become a
bottleneck when subjected to higher power demands. A stroke
cycle without dead spots can handle a wider variety of power
- Elite racers are strong enough so that they could climb up most
hills using V2 while staying within their normal not-too-anaerobic
power capability -- if they were doing a solo time trial. But
in mass-start races they need to stay with the skiers ahead of them
in order to "get the draft", get help blocking the force
of air resistance. So a key game in mass-start races is to go
hard up some hills to try to "lose" competitors who are
hanging on in the "draft". So the trailing skiers
also have to go hard up hills to stay "in contact" with
the pack leaders.
Therefore power demands get pushed to the limit on the steeper
uphills. Therefore peak force gets pushed to limits. V1
focuses only on the big muscles that can handle high peak forces -- and
let's the arm and abdominal and leg muscles work together to
deliver peak force on one side.
Dead spots also raise peak force requirements -- and V1 is the best
technique for eliminating dead spots.
- Maximum-work V2 gets the most out of the double-pole-push by using
the big leg muscles to lift the butt and upper body in
preparation. But that style of double poling becomes less
efficient up steel hills -- because lifting the weight of the upper
body through the same range of motion twice is not efficient.
- The leverage of some V1 motions are better set up for delivering
vertical motion component up against gravity. V2 has better
geometry for delivering horizontal components of motion.
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