air-crunch move in V1 skate

The elite racers are "crunching" their chest and abdominal muscles to drive
their shoulders down strongly into

_ air _

A big surprise to me looking at the videos on JanneG's website of World Cup
racers doing V1 skate ("offset", "paddle-dance") up a hill.

The elite racers crunch their head and shoulders down _before_ they plant
their ski pole tips. Looks kind of amazing: their hands are still coming
_up_ while the head is already going down.

Next surprise: the down-motion of the head slows as soon as the pole tips
hit the snow, and then it stops. So 80% of the down-motion of the head and
shoulders has completed _before_ the pole tips reach the snow. This is
_not_ what I see when I look at elite videos of V2 skate on gentle terrain.

What's the benefit of air-crunch in V1 skating up a hill?
Here's my current theory:

(a) the air-crunch move _avoids_ much of the inefficiency of lifting the
weight of the same body part twice through the same range of vertical
motion. Up a steep hill, most of the visible down-motion of the shoulders
is _relative_ to the rest of the body. Looks like only 5 cm / 2 inches is
truly downward "absolutely" in comparison with the snow and the hill. The
absolute up-motion of the shoulders that precedes it is much larger than
that.

And up very steep hills maybe there's _no_ absolute down-motion in the
crunch (like in the muhleg1.mpg Technique video on JanneG's website, where
the strange camera angle from above could mis-lead a casual observer into
guessing that Muhlegg was skating V1 without using any upper-body
compression (?!), likewise Per Elofson in view immediately behind him (!?).

(b) the quick start of the down-move of the shoulders generates a reactive
force _upward_ on the butt. This helps keeping pulling the weight of the
hips and butt upward during the second phase of the off-side leg-push, where
the big leg muscles are busy with pushing the ski out to the side.

On the flats we think of crunch move as driving the poles down and back, to
drive the whole body forward. Maybe on steep uphills we need a different
image: the crunch is to hold the shoulders in place and haul the weight of
the butt to catch up with the landing of the next skating-foot.

(c) after the pole tips are planted, any downward crunch motion energy
remaining after (a) and (b) can be transferred into the arms as "inertial"
force to add power to the pole-push against the snow.

Ken