Ski Skating in cross country skiing
what's here
- - Climb slower with smaller steps |
"backward" pelvis rotation move
- - Engage some muscles more
- - Reduce range-of-motion,
or shift to static transmission
- - Assist weak muscles +
segments
- - Supporting moves | Don'ts
- -
the Steeper the Hill . . .
- - Concepts + Perceptions versus Physics + Video
- - Slow versus Fast
see also
[ under construction ]
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Handling the hills is the biggest deterrent to enjoying skating for most
cross country skiers: Skiing fast and gliding long on the
flats is the fun part. Climbing up a hill is just a struggle, and
even after going over the top, it can leave our legs too burning and tired
to enjoy the next section of long gliding on the flats.
What can be done to survive the hills well enough so we can
enjoy the rest of our skating?
The question is:
Slow -- How to succeed in skating up a hill slowly?
Here we analyze this problem from the perspective of biomechanics and
physics, and propose some solutions.
Priorities
I think the simpler bigger "wins" for most people on
steep hills include:
-
use "backward"
pelvis/hip rotation move to make the vertical climb in each
stroke smaller.
-
practice controlling slow + slower + slowest glide
(and aim the glide more out toward the side)
-
keeping the arm-leg coordination simple with
single-poling / "diagonal" / "herringbone" skate leaves you free to
focus on bigger things.
-
use lots of (accurately timed) side-to-side motion
in hips + torso + shoulders.
-
make sure there's no points where precious muscular
work is being absorbed instead of transmitted (sideways hip-knee and
sideways hip-shoulder are popular areas for failure to transmit
work).
-
keep the shoulders forward, and keep on bringing
the hips up forward - (don't let the hips get stuck behind -- not as
simple as it sounds).
-
set the foot down further out toward the side, and
plant the pole tips farther behind.
-
reduce range-of-motion of most muscle moves -- some
even to zero, just holding stable to transmit forces from stronger
muscles.
Maybe the range-of-motion in some of your
moves is not as big as an elite racer in some video. Or maybe some
biomechanical theory or tip from a National-level coach says that some
move ought to make a positive contribution, but yours is just holding
stable. For most of us non-elite skaters that kind of observation is usually good.
For steep climbing it's normally better to
allow the unconscious neuro-muscular control "super-computer" in the
brain to make the decisions about which muscles to use and how much.
Usually it's better not to try to intervene with conscious rational
analysis and control unless there's a point of unstable absorption of
work. (in which case a long-term strategy might include specific
strengthening of the specific muscles involved.)
Lots of athletes tend to assume that
the basic skating leg-push on flat terrain must be simple, so they focus on other things
like coordinating different kinds of poling with leg-pushes, or clever
modifications for hills. But
actually the 3-dimensional biomechanics of the skating leg-push on flat
terrain is very complicated and non-intuitive -- and it's easy to miss
learning some key aspects -- or lose them when focusing on new things:
see not to forget under
Engage some muscles More.
The three basic problems in skating up a substantial hill are:
(1) Overcoming the resistance of gravity tends to
demand lots of Power (measured in Watts; so . . . How to keep the total
Power required for climbing less than the Power rate which the effective
skating muscles can deliver without "burning out" for the remainder of
your intended perfomance?
(2) Climbing a steep hill tends to require applying
high Force intensity; so . . . How to keep the Force load and Power
demand on each different skating muscle less than what it can handle
without "burning out" for the remainder of your intended perfomance?
(3) Skating up hills with poles effectively is perhaps the most
complicated mode of human-muscle-powered propulsion; so . . . How to
coordinate all the moves? How to learn them?
(A) Reduce the total Power demand by climbing slower.
(B) Increase the total Power supplied, by engaging muscles more (or
at least avoid the need to reduce utilization of some muscles).
(C) Move muscles more slowly or through a smaller range-of-motion (or
even hold some them static), so they can handle more Force intensity
without "burning out"
(D) Find clever ways to reduce the Force load on specific muscles,
e.g. by changing the leverage configuration, or sharing the load with
other muscles, or across different time phases in the stroke cycle.
(E) Identify high-priority moves and methods, and focus on those.
(F) Find simple ways to verify if you are executing the high-priority
methods.
concepts of implementation
(G) Keep some glide in each stride.
The main way to reduce Power demand (strategy
A) is to
reduce the rate of vertical speed. A radical method would be to just
do Classic herringbone "walking" up the hill (we would not still be
skating) -- but then there would be some muscle mass that could no
longer make a contribution to climbing the hill, because their specific
moves can only be transformed into forward propulsion work if the ski is
gliding. So for strategy B it's worth it to figure out how to keep some glide
going.
(H) Finding more muscles to engage for hill-climbing is not likely.
We would like to engage more muscle mass, or
coordinate it more effectively to contribute a higher
proportion of its output into forward propulsion Work (instead going to
waste somehow).
But this is the same goal and strategy that
we're presumably already using for trying to go fast on flat terrain, and skating
up a hill has pretty much same set of muscle moves available for
effective forward propulsion as skating
on the flat.
So there's not much opportunity to find new
muscles to engage specifically for hill-climbing -- though hill-climbing might
be a strong motivator to learn to engage more muscles more effectively
in our general skating.
In fact it would not be surprising if
successfully "surviving" a steep hill-climb supplied less
muscular Power output than skating moderate terrain -- from less muscle
mass. And is using strategy (J), the "survival" method might employ fewer functional muscle moves
(a.k.a. "articulations") in active work mode (as opposed to static transmission
of work from other muscles).
Possible Exceptions:
Hill-climbing can often benefit from using
more side-to-side motion of torso and shoulders than is typically used
on flat terrain.
When climbing without poles, side-swing of the
arms usually helps, though it's not used much on flat terrain (perhaps
because of air resistance).
(J) Avoid lifting the weight of the same body part through the
same vertical range of motion twice.
(K) Generate most of the required power and force from
"Slow Oxidative" (SO) fibers in the muscles -- and avoid engaging lots
more "Fast Glycolitive" (FG) fibers.
High utilization of FG fibers normally
produces lactic acid and depletes local stores of glycogen fuel. This
might be OK if near the end of a performance, but it's a problem if
there's still lots more skating to be done, because it takes time to
"clear" acid from the muscle cells and bloodstream, and even more time
to replenish local stores of glycogen fuel.
High force demands typically engage lots more
FG fibers, or other demands that exceed the capabilities of the SO
fibers. SO fibers seem to be able to handle higher forces if they're in
"isometric" mode, i.e. not moving. It seems likely that they could
handle somewhat higher forces if moving only pretty slowly. And it seems
to help use SO fibers if the muscle is moved only through a smaller
segment of their available range-of-motion, a segment more favorable for
the SO fibers.
Therefore it makes sense that some ways to
avoid high utilization of FG fibers are:
reduce force loads on all muscles
reduce range-of-motion on all muscles
operate some muscles only in static
"isometric" mode -- zero range-of-motion.
use some muscles in selected segments of
their range-of-motion which are favorable for SO fibers
"Gear ratio" selection
(L) Skating Ski: The "gear ratio" of the skating ski is
mostly determined the angle it is aimed out to the side: The
lower the speed, the larger the angle out to the side. The
higher the speed, the closer the ski points to forward.
(M) Poling: The "gear ratio" of the pole is determined by
two angles:
(M1) The closer the pole is to perpendicular
straight up from the ground surface plain, the better for maximum
average Power transfer at high speeds. The farther it is slanted
away from perpendicular (handle closer to the ground) the better for
delivering higher Force at low speeds.
(M2) The more the poles are aimed in the
steepest direction up the slope, the higher average Force over the
range-of-motion of the pole-push. The more the poles are aimed
diagonally across the slope, the lower average Force over the range-of
motion of the pole-push (other things being equal).
... because the Work is less by going a
similar distance across the hill, since Work is mainly proportional to
the product of Body Weight and Vertical Gain (and the Vertical Gain is
less moving diagonally across than it is directly up most steeply). So
if the range-of-motion distance of the pole-push stroke is the same and
the pushing Work = Pushing-Force * Range-of-Motion, then the
Pushing-Force is lower.
Skating on the flats or up a gentle hill is:
-
Not subject to concept (J) -- so moving the upper
body up and down to generate forward motion is often an effective
approach in V2 and Open Field Skate.
-
"Gear ratio" for ski aiming angle (L) makes getting forward less important.
At the higher speeds on the flats, the skis are aimed more forward,
so the push is directed more out toward the
side, with the line of push-force more inward toward the center, less
forward -- so there is less benefit to positioning the skier's
center-of-mass more forward.
-
"Gear ratio" for poling angle (M1) makes getting the shoulders up high
more important. At the higher speeds on the flats, the most
effective pole-push angle is more vertical.
-
Less need on the flats to worry about strategy (G) -- keeping
the glide going (except in slow snow or headwind). And less
problem with strategy (D) -- spreading load move evenly across time
phases in the stroke cycle -- so less need to worry about
"low-power spots", like the pole-recovery phase in V2 skate
and Open Field Skate.
therefore . . .
Differences
between V1 and V2:
-
V1 ("offset", "paddle-dance") and
Single-Poling Skate ("coaches skate", "herringbone skate"), is a more effective technique for
climbing steep hills. While V2 ("1-skate", "double-dance") is
often better for gentle and flat terrain.
Because:
(a) flat terrain permits the full and
efficient use of vertical up-and-down motion of the legs and upper
body to drive the pole-push -- and V2 has more pole-pushes than V1.
(b) flat terrain is forgiving of the "low-power" pole-recovery
period in the V2 stroke cycle, where on a steep hill V2 would either
stall out and lose the gliding "magic" in the pole-recovery phase, or require
high-stress peak forces to make up for the low-power gap in the
stroke cycle.
(c) the aiming of the ("offset") V1 pole-push
diagonally across the slope instead of forward directly up the slope
tends to reduce Force load on poling muscles, while still maintaining
glide speed.
-
Steep V1 skate focuses on optimal skating leg-push, and compromises on
the pole-push. Single-Poling Skate simplifies the poling, to
focus on managing the leg-push. But V2 on gentle terrain focuses
more on optimal pole-push power.
Since strong double-poling makes major use of
the leg muscles, this is not to say that V2 neglects use of the leg
muscles.
In gentle V2 the idea is to fall forward
onto the poles. But in steep V1 the idea is more to stay
forward -- when there's any forward fall, it's to fall further
forward.
Though even in V2, the idea is to drop the hips
down only as far as you have the strength to raise the hips
all the way up and forward to aggressively fall forward
to start the next stroke. Lots of skiers have the flaw
of their butt "getting stuck" sitting back there "down in the
bucket" -- in V2 as well as V1.
Variations on techniques
Even if there were one optimal technique for climbing up a hill, that
does not mean it's smart to use exactly that technique in all skiing
situations. Sometimes it's smart to practice a technique that
partly contradicts some of the principles of physics and biomechanics on
this website. There are several reasons to practice
variations:
-
Simplified technique to manage the complexity while still
learning.
-
Controlled isolation of weaker muscles in training situations --
to strengthen them and raise their sustained-power-delivery
capacity.
-
Avoid weaknesses in fun and race-performance situations.
This is why most of us cannot simply copy the elite racers --
because we have not trained some of those special muscles all year
long.
-
Exploit our strengths in fun and race-performance situations.
Each of us has different strengths from other sports:
Like think of bicyclists versus inline-skaters versus kayakers.
-
Focus -- Prioritize the moves selected in fun and race-performance
situations: Focus on the moves that deliver the most
sustained-power benefit and ignore the others -- so we don't get
overwhelmed by the complexity.
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Which "poling versus leg coordination" motion?
-
Single-Poling Skate (a.k.a. "herringbone skate",
"diagonal skate") and V1 (a.k.a. "offset", "paddle-dance") are better than V2
(a.k.a. "1-skate", "double-dance") or
Open Field Skate (a.k.a. "V2A", "2-skate", "single-dance") for
climbing a steep hill.
see discussion under
Hills different from Flats
Climb slower with smaller steps
to implement
strategies (A) + (C)
Strategy (A) is to reduce the demand
for power (as measured in Watts). For climbing a steep hill, the main
factor that determines the requirement for power is the vertical rate of
climbing. This vertical rate is a product of the vertical gain in each
skating stroke and the number of strokes per minute. So reducing either
factor will reduce the demand for power. For a specific hill of a
certain steepness, the amount of vertical distance gained is
proportional to the forward distance advance of each stroke.
The problem with reducing the turnover frequency instead of the
forward distance per stroke is that it results in larger range-of-motion
and higher peak forces. The larger range-of-motion implies that it is
more likely that the high forces will come in a segment of the
range-of-motion which is not well suited for high force. Therefore it's
usually better to go slower by the method of reducing the forward
advance distance per stroke.
Often the turnover frequency for climbing
hills is higher than for skating on the flats.
There are three factors that determine this forward advance distance:
(a) how far the foot glides in each stride: How small this
factor can be made is a matter of how slow a glide speed the skater can
control. This is mostly determined by the skill of the skater and
how irregular or slow the ground surface is.
Usually slow irregular snow is more difficult
to control, so you can't take the gliding speed as low without a larger
chance of the ski "stalling", losing all its glide. I don't find
occasional stalling to be a problem -- if that's the price of surviving
to the top of a very steep hill -- but if it's happening a lot then it's
kinda disruptive.
I found that with lots of practice at trying
to go real slow (especially climbing up hills with no poles) I could get
much better at controlling my glide.
(b) the aiming angle of glide: The more the ski is aimed out
toward the side instead of forward, the less the gliding distance gets
converted into forward (and upward) distance.
But surprisingly I've found that when I focus
on (c) and (a) I find it much easier to climb up a steep hill even
though my ski tracks in the snow were not aimed so much out
toward the side.
(c) how far forward or backward the hip is at the time of set-down:
This determines how far forward or backward the ski starts
gliding from. At moderate and high skating speeds this choice is fairly
unimportant, but at a very low speed like up a steep hill, it makes a
substantial difference in the forward distance in each stroke.
My experience is that (c) is a big win, and lots of practice with (a)
really helps, but focusing on (b) on its own didn't seem to make a
substantial difference.
Though aiming angle of the foot is surely a
critical aspect in the physics of the gear ratio" of skating, typically
it seems like it doesn't work much to try to control it directly -- it's
more a result of other physical / biomechanical drivers.
The simplest way I've found to do (c) is to rotate my pelvis/hips
about a roughly vertical axis (like the axis of the spine) so the
non-pushing hip moves backward relative to the hip of the leg which is
currently pushing.
So when the Right foot is set down on the
ground, the Left hip is forward ahead of the Right hip. While pushing
thru the Right foot, the Left hip moves backward relative to the Right
hip, so when the Left foot is set down, the Left hip is back behind. As
the Right foot is lifted up off the ground, the Right hip is forward
ahead, in correct position to start its own move backward.
Or can visualize it as aligning the navel with the aiming direction
of the foot.
Just as the Right foot is set down, the navel
is aimed roughly along a line thru the Right heel + toe. Then while the
Right foot pushes against the ground and glides over the ground, the
pelvis and navel turn smoothly away from that foot, and toward the Left
side, so that at the moment the Left foot is set down, the navel is
aimed roughly along a line thru the Left heel + toe.
Not:
Head? Not turn the head to face in the same
direction as the heel-toe line. It likely makes sense to keep the head
quieter, and spending more time looking to check what's ahead in the
direction of overall forward motion. Some people find it helps to make
the head roughly line up with the direction of their double-pole push,
but that's a separate question.
Shoulders? Although it might feel sorta
natural to rotate the shoulders together with the pelvis, it is not
necessary to do so. By twisting the spine, the shoulders can rotate one
direction while the pelvis + hips rotate in the other. Anyway, it's not
the rotation of shoulders that can add positive "reactive force" work,
but the side-to-side motion, which usually includes some tipping or
leaning.
Knee? Not necessarily do anything different
with the alignment of the knee at set-down. Pointing the knee outward
more or less might be helpful, but it's a separate question about adding
propulsive work, not for how to find a "low gear" to climb slower.
Weight transfer sideways? Actually the
"backward" rotation moves more mass connected to the non-pushing hip
toward the currently pushing foot, not away from it. If the
shoulders also rotate in rough synhronization with the pelvis, that
would move some mass away from the pushing foot -- but that shoulder
rotation is not required, and even if exectuted it's not clear whether
the motion of all the mass attached to both hips and shoulders is then
moving more toward or more away from the currently pushing foot.
Timing: This rotation move should be roughly sychronized
with the push of the leg, so it starts just after the foot is set down
on the ground, and finishes just as the next foot is set down on the
other side.
Note that this timing is rather different from
what works for "leading" pelvis/hip rotation move used to add propulsive
work. There's one timing for "gear selection" and another timing for
propulsive work -- and with this rotation, you cannot retain both. (I
would not rule out the possibility of finding a very clever timing which
retains a lesser amount of both, but it makes more sense to just learn
the simpler timing for each and choose which one to use in each
performance situation.)
Amount: Turning less than fully toward the heel-toe line
on each side also works, and then the upward distance of each stride is
less small -- so the muscles work a little harder.
Trade-off: If you normally use the "leading" (or
forward) pelvis/hip rotation move to add some force and power to your
leg-push, you give that up (at least mostly) when you use this
"backward" rotation move to go slower. (Lots of skaters don't use the
"leading" move much, so there won't be any loss for them.) So your
supply of power is reduced slightly. But on a steep hill the "backward"
pelvis/hip rotation move reduces the demand rate for power much
more. Therefore it's a win for keeping your rate of work further within
your sustainable limits of on supplying muscular power.
to implement
strategy (B), but within the constraints of (H) + (K)
As noted under concept (H), finding new muscles to use specifically for
hills is not likely. With most muscle moves, if we try
to use them at higher muscle speed or through a larger range-of-motion,
in the context of the high Force demands of hill-climbing, we usually
engage lots more FG fibers, which soon results in "burning out" the
specific muscle -- or at least many of its fibers needed to handle force
loads or range-of-motion segments important for future hill-climbs in
the intended performance. Many muscle moves not only
need to add propulsive work of their own, they also need to transmit
forces from other muscles, and support body weight. To handle higher
force load without "burning out", the muscle must operate at a slower
speed and/or smaller range-of-motion.
The main exception to these constraints are the
torso-shoulder side-swing muscles and the arm side-swing muscles --
because (a) they do not need to transmit much propulsive force from
other muscles, since they're not between any other muscles and
foot-ground contact; (b) they do not need to support as much body
weight, since much of the mass is below them. Since some
of the other muscles are going into "static transmission" mode anyway on
a steep hill, they're set to handle transmitting the additional force
load from these moves. Torso-shoulder side-swing
Torso-shoulder side-swing tends to be used less for V2
on gentle terrain mainly because the focus is more on optimizing power
from the double-pole push -- for which the torso and shoulder are
important. But for the "offset" poling of V1, the pole-push is aimed
partly toward one side, swinging the torso + shoulders over to that side
actually adds propulsive Work to the early phase of the pole-push.
Though swinging the torso + shoulders again the opposite way toward the
pole-recovery side might "absorb" some of the propulsive Work which
could have been available from the later phase of the V1 pole-push,
there's no other pole-push on that side for it to interfere with.
Timing is critical: If get it wrong, could absorb
propulsive Work instead of adding to it. The basic idea is to start the
move after the Right leg starts pushing, and accelerate the mass
of the torso + shoulders sideways toward Left away from the
leg-push. The highest sideways speed relative to the hips should be
reached as weight is being transferred from one foot to the other. Stop
the side-swing move after the Left leg sets down and starts
pushing, so their mass decelerates while moving toward the
leg-push. It works by Newton's Third Law. Accelerating
or decelerating the mass produces a "reactive" or "inertial" force. The
important thing is to be careful about the direction of the reactive
force. Many humans are pretty good at feeling this for the starting and
acceleration, not as good at feeling it in the deceleration and
stopping. The usual problem is that the
positive Work from starting and acceleration is exactly cancelled out by
negative Work from deceleration and stopping. Which is what happens if
you start this side-swing move exactly at the set-down of the foot, and
finish it exactly as weight is transferred to the other foot setting
down on the ground. Arm side-swing
Arm side-swing is only available while the arm is not
engaged in poling. The obvious situation is for climbing with no poles.
But it can be also be used in V1 poling, by the pole-recovery arm during
its recovery phase.
Arm side-swing tends not to be used at higher
speeds on gentle terrain because the cost in increased air resistance is
much higher at higher speeds. Timing is critical:
like Torso-shoulder side-swing. poling
Shoulder "untwist" to help drive the push by
the poling-side pole in the "offset" double pole-push of V1
skate.
There are other aspects of skating technique which are
not specific to climbing hills, but they provide substantial
benefits when also used on hills. Lots of athletes tend to assume that
the basic skating leg-push must be simple, so they focus on other things
like coordinating different kinds of poling with leg-pushes. But
actually the 3-dimensional biomechanics of the skating leg-push is very
complicated (and there's also some tricks to basic double-pole push).
Here's some key points often overlooked:
-
play with aiming the leg-push more out toward the
side, instead of just toward the back. (On flat terrain, how far can
it go toward straight out to the side, with no backward push at
all?)
-
knee drive / heel drive ankle-flexion move
-
specific focus on the Out-Sweep push moves and
training of their specific muscles (in addition to the Extension
push)
-
upper abdominal "crunch" to add force to the
double-pole push -- it's not just about hands + arms + shoulders.
With many of the effective skating muscle moves, if we
try to use them at higher muscle speed or through a larger
range-of-motion, in the context of the high Force demands of
hill-climbing, we usually engage lots more FG fibers, which soon results
in "burning out" the specific muscle -- or at least many of its fibers
needed to handle force loads or range-of-motion segments important for
future hill-climbs in the intended performance. Many
muscle moves not only need to add propulsive work of their own, they
also need to transmit forces from other muscles, and support body
weight. To handle higher force load without "burning out", we want to
enable the SO fibers to handle most of it, since they normally produce
less lactic acid and are more re-usable again and again later in the
intended performance.
To handle higher forces with its SO fibers, the muscle
must operate at a much slower speed and/or smaller range-of-motion. The
best mode is "isometric" -- just hold static -- no muscle move at all.
This static isometric mode still burns some fuel and oxygen, but the SO
fibers are suited for it (e.g. the SO fibers are normally used by the
body to maintain postural stability, while FG fibers are reserved for
strong + serious moving).
-
Proportions of motion will change: Some
muscles are better at using their SO fibers to handle higher forces
than others, so some muscles are going to retain are larger
percentage of their flat-terrain range-of-motion than others.
-
Some muscles cannot escape higher forces because
their position in the skeleton requires them to transmit forces from
stronger muscles to the foot-ground contact -- and can only hold
stable under the load if they reduce their range-of-motion to zero:
static "isometric" mode.
-
Some muscles could retain some range-of-motion, but
the active contribution of propulsive work would be so small, that
it might just be simpler to put then into static "isometric" mode.
-
Different skaters have different strengths and
weaknesses, so a muscle move that is active for one person skating
up hill might be static for another. It is unlikely to be optimal to
try to copy the range-of-motion distances or proportions from an
elite racer video.
Active work: Here's some likely candidates for
active contribution of propulsive work with larger percentage of
flat-terrain range-of-motion:
-
hip-extension move (e.g. "gluteus" muscles)
-
knee-extension move (e.g. "quadriceps" muscles)
-
medial-hip-rotation move (a.k.a. "inward knee
roll") -- because it's well-positioned for active work when the foot
is set down out toward the side (partly to avoid too much crossing
of the tails of the skis without stepping further up the hill). It's
not a strong muscle move for lots of people -- but it can be
assisted by gravity.
Static transmission: Here's some candidates for
static transmission, or for a smaller move through a smaller
percentage of flat-terrain range-of-motion:
-
ankle-extension move (e.g. "calf" muscles) -- not
because the calf muscle is notable weak, but because it's got so
many big sources of load going through it: hip-extension,
knee-extension, and body-weight.
-
hip-abduction move -- because it's so not
well-positioned for active work when the foot is set down out toward
the side (partly to avoid too much crossing of the tails of the skis
without stepping further up the hill) -- and for lots of people it's
not very strong.
-
ankle-pronation -- because it must transmit
substantial side-force from medial-hip-rotation, perhaps
hip-abduction, and torso-shoulder side-swing moves -- and for lots
of people its not very strong. Many skaters use a high-cuff boot to
help keep this move mostly static. Also it's easier for it to hold
stable in transmitting the high-force load if the ankle is already
somewhat pronated when the foot is set down.
How to decide how much range-of-motion for which
muscles? To control the allocation optimally according to rational
theory, you would need to know the SO and FG fiber composition and
capabilities for each muscle move. But it would be difficult to know
that without doing lots of muscle biopsies. Fortunately there's a
simpler approach:
Leave the allocation of range-of-motion reductions to
the unconscious neuro-muscular control module in your brain. It's not
perfect, but it's designed to be pretty good at that sort of thing --
better odds of it being right than some coaching theory or copying from
analysis of an eliter racer video.
I suspect there's two frequent shortcomings in the
performance of the neuro-muscular control module:
-
It's not good at guessing to use muscle moves that
it has not been well-exposed to, either thru genetic
pre-disposition, early childhood history, or well-designed adult
practice drills.
-
Sometimes it falls into "bad habits" of using one
muscle move to absorb the work of another.
Therefore watch out for cases where it is using a muscle
move to absorb work. Two frequent cases in skating are:
-
hip-abduction to absorbs work from medial-hip-rotation
(a.k.a "inward knee roll") . . . the Left knee moves down and inward
toward the Right as it uses the medial hip rotation move to push the
Left foot propulsively outward toward the Left side. But the Left hip
moves Left relative to its knee, so it is absorbing work from the medial
hip rotation move.
-
torso-shoulder side-swing absorbs work from sideways motion
of the hip and leg . . . the Left hip moves toward the Right as the leg
pushes. But the torso + shoulder move toward the Left relative to the hip,
so they are absorbing work from the leg-push moves.
set down with substantial knee bend?
A puzzle is that it sometimes seems to work to set down
with substantial knee bend while climbing a steep hill. Normally using
substantial knee bend is associated with large range-of-motion in
knee-extension (or also hip-extension) moves -- which is what we're
trying to avoid for "surviving" a hill-climb without "burning out" those
muscles.
An important difference is if it goes with setting down
the foot somewhat out toward the side. In that case it has two benefits:
-
avoids crossing the tails of the two skis too much,
but without stepping higher up the hill.
-
put the medial-hip-rotation into a good
configuration.
But what about its affect on range-of-motion? Perhaps
it is mitigated in this way: The knee-extension move is held mostly
static at first after set-down, while the medial-hip-rotation move (and
perhaps some ankle-pronation) executes. After that move, the whole leg
is in a more Extended position, and the upper body has tended to fall
farther more quickly -- both because the foot was set down further
outside.
So after the medial-hip-rotation both the hip-extension
and knee-extension moves are starting from a more "extended"
configuration (so there is less remaining range-of-motion available to
them). and that extended configuration is a more favorable segment of
their range-of-motion for the SO fibers to handle higher forces (without
activating lots more FG fibers).
Assist weaker muscles and avoid stress segments
to implement strategy (D)
Pair with other muscles
Assist weaker muscles by pairing them with other muscles.
-
On the poling side of V1, we use the poling arm muscles to
assist the weaker hip abductor muscles during the first phase of the
skate-push.
-
On the pole-recovery side of V1, we use the reactive side-force
from stopping the previous torso-swing move to assist the first
phase of the skate-push. And we also use the assistance of the
reactive side-force from immediately starting the next
torso-swing more back toward the poling side.
-
In herringbone skate, we use the single-pole-push on each side
to directly assist the skate-push on each side.
Momentum to assist
Assist weaker muscles with momentum (or "kinetic energy") from
previous work by other muscles.
Avoid weak segments in range of motion
Use muscles in the strongest section of their range of
motion. Avoid putting peak forces on muscles and joints in
the weak sections of their range of motion -- since this results
in rapid fatigue and pain -- sometimes even injury.
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Positions for best "gearing"
When the skier's speed is slower, there is
more of a backward and downward component to the
skate-push -- strategy (L) for leg-push gearing.
(though the side-push remains important).
The further the ski is angled out to the side,
and the more you maintain glide out to the side, the gentler the
overall path. Gliding more out to the side takes the steepness
out of the hill.
Required supporting move: Keep pushing out
to the side with the leg. Use sideways torso rotation
to add more sideways push. The more you glide out to the side,
the less steep you experience the hill.
Warning: If you angle the ski out only to provide
a platform for pushing your body straight up the hill, then you lose
the "gearing" -- because the gearing applies only with the magic of
actual skating. The more you switch to the "walking" paradigm,
the less gearing benefit.
This pole-push angle delivers power most effectively at the slower
speed climbing up a hill -- to support Principle (F) for
pole-push "gearing".
Required supporting move: The shoulders
should be forward and low.
Supporting moves
A problem with aiming the top of the ski more
outward for hill-climbing is that the tail is more inward. Since this
happens with both skis, the tails are more likely to cross. If the
"backward" pelvis/hip rotation move is used to slow climbing speed, the
amount of tail-crossing tends to increase. What to do?
(1) Let them cross. Set the tail of the next
pushing ski down on top of the tail of the previously pushing ski.
You'll hear a "click" sound as they hit. For a short time maybe both
skis will be on the ground at the same time. As you glide onto the new
ski, its tail will come off the previous ski, and then you can lift the
previous ski off the ground.
But there's a limit to how much of this
one ski pressing on the other can be handled, so . . .
(2) Set the foot down more out toward the
side. This goes well with big side-to-side motion of the upper body. It
does not go well with getting maximum range-of-motion from the
hip-abduction move. So just use hip-abduction muscles for static
transmission. If set down with knee well-bent and pointed out toward the
side roughly in line with the aim of the ski, can still get substantial
range-of-motion in the medial-hip-rotation move and ankle-pronation
move.
(3) ? Step up the hill? This does create more
space for the tail of the next skis. But it speeds the rate of climbing,
which increases the power demand. So this method is only for hills well
within the skier's power delivery capability.
If the side-glide is lost, then the "magic" of
skating is lost -- and then reactive side-forces from the torso
rotation moves cannot help with the climbing.
The leg-push on a steep hill is more backward than
on the flats, but it's not all backward. Use the
feeling of strong side-to-side weight transfer and the working of
the little-known hip abductor and torso rotator muscles. Fight
to keep the side-glide.
The "backward" pelvis/hip rotation move helps
with this.
Starting the skate-push from this position
engages the strong quadriceps (front thigh) muscles and
gluteus maximus (rear butt) muscles. With the
whole upper body forward, the diagonal force from the
skate-push against a ski angled out way to the side is aimed
more through the skier's overall center-of-mass.
In
this way the poles are angled further back away from the
vertical, which is more effective "gearing" for the
lower speeds in climbing a steeper hill. The
concept in V1 is to keep recovering the shoulders
forward, not upward. The shoulders are always
slumped forward in V1 -- sometimes even more forward.
Otherwise the torso-rotation away from the
hang-side starts too early.
So its elbow is more bent (a
stronger configuration to transmit force from the
shoulders), and so it's tip can be planted closer in and
further back for better "gearing" and leverage -- and
for longer range-of-motion in its push.
Don'ts
Although that's a helpful move for V2 and Open Field
Skate on the flats, when climbing up a steep hill, it
results in moving the weight of the entire upper
body through the same vertical range twice.
Instead: Always "lock in" the vertical
gain of the hips and upper body. Once you do
the hard work of raising your hips upward, keep them up there.
"Let gravity do the work" is too
slow, and doesn't generate enough reactive
side-force. And if taken literally, puts more
load on the (already-well-utilized) quadriceps
muscles.
Instead: Actively swing
your torso from side to side -- by learning to
engage some little-known abdominal muscles.
Because if the hang-side
hand and hang-side pole tip are exactly aligned with
the skier's overall direction of forward motion, the
strong force of the pole-push itself will
immediately turn the skier's torso away from
the hang-side toward the recovery-side. This
early turning away weakens and shortens the
pole-push. It also applies the reactive
side-force during the first phase of the hang-side
skate-push -- which is less effective than in the
second phase when the ski is more strongly edged.
Instead: Start with the hang-side hand
further out to the side, and the pole-tip aimed
partly inward -- so the force of the pole-push will
be self-correcting of its own side-rotation
tendency, and the torso-swing will be delayed until
the most of the pole-push is over, delayed to the
second phase of the skate-push.
The steeper the hill . . .
-
the more need to shrink the size of
each forward step, by using the backward pelvis-hip
rotation move.
-
the more forward the hips, for less
knee-bend (while retaining full ankle-flexion).
-
the more the aim of each foot is angled out toward the side.
-
the more the foot is set down
further out from the center.
-
the less up-and-down motion in the upper body,
the more the pole-push work is focused in the arms.
-
the more the pole is planted
further back behind.
-
the slower the average speed -- to avoid burning
out for the next hour or two after this climb.
-
the more special neuro-muscular
control needed to handle the ski at such a slow
speed.
practice,
practice, practice, going slow in a variety of snow conditions
-- and finding slow skaters to just follow, to help
enforce skating at a slower speed.
Concepts and Perceptions versus Physics and
Video
As if the physics of the skate-climbing motions themselves were not
already complicated enough, there's the entertaining fact that our
mental concepts and images and sensory perceptions are not well
connected with the objective physics of our body skating. This has
several amusing results:
Mis-perception
I think and feel I'm doing something with a big motion, when
objectively it's only a little motion. Some of my own
hill-climbing examples:
-
I thought my little raising of my back and
shoulders before initiating my pole-push was OK. But in video I could see
that it was a big raising, way more than any
elite racer climbing up a steep hill.
-
I thought (and felt!) that my hips and
shoulders were forward. But in video I
could easily see that I really hadn't gotten
anywhere into "forward" territory, compared with
any elite racer climbing up a steep hill.
-
I thought I had solid side-to-side motion,
and felt that if I had any more it would be
ridiculous. But on video it looked weak
compared to a front-view of any elite racer
climbing up a steep hill.
Advice with unintended consequences
Coaches have found through long sad experience that sometimes just
telling a skier a physically correct concept doesn't work. Because
thinking consciously about one correct thing can sometimes
unconsciously activate two other bad motions. Some
examples:
-
Forward-Step: Thinking consciously about stepping forward
up the hill, can result in forgetting to push out to the side.
-
Toe-Push: Thinking consciously about pushing with the toe,
can result in forgetting to fully engage the big leg muscles to push
out the side, and can result in reverting into "running" on
skate skis.
Concept too early in learning progression
Coaches have found that some motions and perceptions are foundational
in learning. If you try to practice a non-foundational motion too
early, even though it is physically correct, it could block the learning
of a more important motion or perception. Some examples:
They might say: First learn "Quiet Upper
Body" with no rotating or tilting of torso or shoulders or hips --
in order to learn the foundational skill of controlled and powerful
skiing "below the hips". Only after the hips are complete
solid, consider working on torso rotation moves. A more
zealous subset might say that even then any conscious work on upper
body movement could trigger a reversion to unstable hips -- so it's
better for the skiers to discover the best sideways upper-body moves
for themselves unconsciously.
They might say: First get them
practicing turning the upper body sideways to face with the new
direction of each ski. Once they have really solid
ski-to-ski weight transfer, then it's OK to start them on "Quiet
Upper Body" drills.
But then they discovered that many skaters
naturally tend to fall into sitting back "down in the bucket",
and then it was very difficult to get their hips up and forward
again. So now more coaches focus instruction and drills on
strong forward flex of the ankles ("ankle bend" rather
than "knee bend"). And trust that after the ankle-bend is
strong, the knee bend will usually take care of itself (or in
the few students where it does not, the knee bend can be dealt
with some other way).
Instructors not knowing physics
My view is that for a coach to know a sound learning progression
and helpful mental concepts is much more important than to know
physics and biomechanics. It is critical for an instructor to
be able to see the subtle non-obvious things in a skier's
motions that tell where they are now in their learning progression,
and what concepts and drills that skier needs to work on now to make
their next step in learning. If an instructor makes a
justification or explanation which is incorrect in the physics, for some
concept or movement they are teaching -- that does not
disqualify them as a coach. The physics you can learn in books
and websites. The specific personal interpretation for you,
and for you now is much harder to discover than physics.
Different skaters have different goals for different
hills. The obvious goal is try to go fast up a hill. But for many
skaters up many hills, that approach will leave their legs too hurt to
enjoy much more skating that day. There are some differences in
technique for climbing slow versus climbing fast: climbing Slow
-
path goes more from side to side
-
smaller forward advance per stroke, by using the
backward pelvis-hip rotation move
-
glide way out to the side
-
stretch out side-glide to the point of nearly
stalling
-
plant poles further back behind
-
single-pole push ("herringbone skate", "coaches
skate")
-
aim pole-push more out toward the side
-
time the single-pole push to help the shoulders and
torso to swing over toward the other side, as the skater steps from one foot to
the other foot.
climbing Fast
-
path more direct straight up the hill
-
quick into the next powerful push with the other
leg
-
aim pole-push more up + down the hill
-
"leading" pelvis/hip rotation
-
double-pole push ("V1 skate", "offset skate")
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