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Climbing skins are usually used with heavier skis and
boots -- so there's more overhead to making each stride -- so it makes
sense to take fewer strides per minute and get more out of each stride.
There's usually no problem getting good grip with
climbing skins on moderate terrain unless its rather icy.
Usually don't get much glide, but when possible it
helps to exploit it.
Skiers can sometimes get away with stepping
the foot out further forward, because can use the pole-push to help the
rest of the body catch up -- if the snow is dense and firm. But not if
the snow is light and fluffy, so might not step so far forward in that
can also extend the stride further forward by
advancing the next hip forward, ahead of the hip of the leg that is
finishing the previous leg-push -- [
can also extend the stride further backward by pushing
off with the toe at the end of the leg-push
In some situations, the move of recovering the leg forward
can itself add some power.
This adds power because accelerating the mass of the
ski and foot and lower leg forward applies a backward force to the snow -- which
helps push the skier's total body mass forward -- which adds propulsive work.
When the mass of the ski and foot and lower leg
decelerates, there is a forward force against the snow -- which subtracts
propulsive work. But since the friction of the ski and climbing skin against the
snow is less when it is gliding forward, the propulsive work subtracted in
deceleration of the leg-recovery move is less than propulsive work added -- so
there is a net positive propulsive work added to help the skier move forward
faster and farther.
The amount of this added propulsive work is roughly
proportional to the velocity of the forward leg-recovery move just after the
other leg comes off the ground at the end of its push.
So it helps to make the leg-recovery move quicker in
the situation where there's some glide -- by holing it back a little, then doing
That's because if there's no glide, then the friction
between the climbing skin and snow during the acceleration and the deceleration
phases of the leg-recovery move is the same, the positive and negative
propulsive work transmitted to the snow exactly cancel.
The other trick for arranging for the positive and
negative work not to cancel each other out, would be to hop into the air a
little in between the finish of one leg-push and the start of the next one. But
if the skier had enough power capacity to repeat that for a significant duration
of time, then the skier could get a little glide with each stroke.
Pole-push doesn't help much in light soft snow, but in firm or
dense snow it can add some significant propulsive push.
So the rotation of the shoulders helping the pole-push
is opposite to rotation of the hips helping the leg-push. Which feels strange,
and uses unexpected muscles in the abdomen. But it can add power as those
unexpected muscles get developed through regular practice.
Question perhaps a bit tricky.
While upper-abdominal "chest crunch down" can
add force and power to a double-pole push -- I doubt the adding it to
the stroke-cycle is going to add significant net overall
propulsive work when striding with skins. Because the upper-abdomen +
chest must get "un-crunched" upward before they can crunch down again.
If the pole-push is continuing during this "un-crunch" recovery move,
then propulsive work is subtracted from the pole-push -- which offsets
most or all of the positive from the crunch.
They only way to get the positive without the
negative is to end the pole-push before the finish of the un-crunch.
This can be effective at high speeds with lots of glide (like on waxed
racing skis with no skins on gentle terrain), because then the distance
per stride is larger that the distance the pole can push through, so
there's no choice but for the pole-push to end before the start of the
next one -- so if the un-crunch is made during this time gap, it does
not subtract much (or any) propulsive work.
But with skins there skier's forward speed is
slower, there is usually little or no glide. Since the poles can usually
push effectively through a longer distance than the leg-push, cutting
short the pole-push to make an "un-crunch" move would reduce the
distance through which the pole-push can contribute propulsive work.
Better to simply finish the pole-push, in which case the "un-crunch"
move will reduce its force -- but that's better than no force at all.
But if you're planning to "fall forward" with
the torso and head anyway for other reasons, then Yes there is
propulsive benefit to adding some muscular "crunch" to the fall -- and
to making sure the shoulders and arms stay firm to transmit that
force through the poles to the ground (instead of collapsing and
absorbing the force)
Forward fall of torso + shoulders + head
Many skiers "fall forward" with their torso + shoulders
as they are setting down the next ski. Does this help propulsion? Or is
it just extra up-and-down motion that wastes energy? "forward
fall" versus "quiet upper body"?
?? not sure on this one -- here's some thoughts:
With no poles, I think "forward fall" does not
help, because it puts the hip joint further behind the ankle, a
configuration where the leg-push is less powerful. Presumably the
same point applies to deep fluffy snow, where the poles cannot help
With poles on firm snow, putting the hip joint
behind the ankle-joint is not such a problem, because the poles can
help the leg muscles bring them up forward again. So it can add
length to the stride a helpful way.
On gentle terrain, bringing the shoulders closer to
the ground helps aim the pole-push more backward, so a higher
percentage of its force goes into forward propulsion.
On steep terrain, lowering the mass of the torso at
the same time the leg is pushing up the hill, takes some load off
the big leg muscles -- in situations where peak-force-intensity
could put too much stress on those muscles. Then the mass of the
torso is lifted vertically by help from the arms and back muscles,
during the first phase of the pole-push when the push is aimed
mostly downward, not yet backward.
So when the hill gets so steep that the goad
is not speed, but "survival" of the big leg muscles so they're not
thrashed for the remainder of the tour -- then the forward fall move
might help by redistributing the peak force load to other parts of the
stroke cycle -
Perhaps this approach works best when combined
with slowing down the whole stroke-cycle, introducing a "rest gap" --
reducing the turnover frequency. If there is "rest gap", then using
"chest crunch" can add net positive work to the pole-push.
So the sometimes desperate-looking
forward-fall move might not be the inefficient cause of slower
climbing, but a "survival" mechanism for dealing with insufficient
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