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one double-pole-push for each full both-leg-strokes cycle -- with a
distinct glide phase before the pole-push. You join this pole-push with one of the skate-pushes, and recover the
arms during the other skate-push. The full stroke rhythm is:
(1) land ski + glide, (2) pole+skate-push (3) land next ski + glide, (4)
skate-push + pole-recovery.
Most
people find this to be a natural and enjoyable rhythm for skating on
firm snow on flat terrain, conditions often found on an open
field. The explanation
for the confusing name "V2 Alternate" is that the timing-sequence
of the pole-push is like for V2 (coming after landing the new ski with a
distinct glide-with-no-push phase, then the pole-push leading into
the skate-push) -- but you only do the pole-push with every
second (or "alternate") skate-push.
The Canadian term "2-skate" says that there are two single-leg skate-pushes for
each pole-push in the stroke cycle. Another term occasionally used
is "single-dance".
[ under construction ]
For lower-required-force situations: flat or gentle, with
hard snow. When the constraints are relaxed, you can take the
time to enjoy more glide, and to get more out of the pole-push.
As the force requirement rises (steeper hill, slower snow), open
field skate can be adapted by shortening first any passive glide phase
on the pole-recovery side, then the passive glide phase on the
pole-push side -- so it becomes closer and closer to V1
offset.
Disadvantages:
(a) requires solid balance to get enough extra time on a
single ski to get most out of the pole-push.
(b) but if your balance is that solid, then why not instead do V2
(and get a strong pole-push with glide on both sides), or
instead to no-poles skate (and get long glide-with-no-push on both
sides).
(c) the "distinct glide phase" just after landing the
pole-side ski is a "dead spot" in the stroke cycle -- OK on
flat terrain, bad for steep hills.
Despite the physics and balance requirements being somewhat
jumbled, lots of people find they have lots of fun doing Open Field
skate.
Key difference in power generation between Open Field skate and
offset V1 skate: Open Field skate can get the most work out of
the pole-push by taking the time to lift the butt and upper body high
first. Offset V1 limits the work from the pole-push to mainly
the arms and upper abdominal muscles -- but also eliminates the
"dead spot" needed to prepare for a maximum pole-push.
(a) On the pole-push side, to produce maximum effective work out of
each stroke cycle the skater
makes use of that distinct glide-with-no-push phase just after landing
the new ski -- to get the butt and upper
body back up high, to get the most out of the upcoming pole-push.
If the previous leg-push with the other leg (on the
pole-recovery side) was done with good extension out to the side, then
the knee of the next leg is flexed and the butt is low. The
pole-push will have more power if the butt starts high, since then
dropping the weight of the butt and upper body onto the poles will help
push the pole tips back -- and the skier forward. To get the butt
back up, the knee must be extended, by using the quadriceps muscles.
But some folks don't care about pole-push power --
they just focus on enjoying the glide. I like both at
once. Not extending the knee immediately after the landing of the
ski means that the weight of the skier's upper body is gliding for a
period on the skier's bent knee. This puts isometric strain on the
knee joint and quadriceps muscles. So even though it does not
waste working power, it does impact the leg's performance capability
(just try it out on dry land) -- without contributing to the skier's
forward motion. So there is benefit to extending the knee early on
the pole-push side even if you don't care much for the pole-push.
(b) Asymmetry of timing is key to getting maximum effective work out
of the stroke
cycle, based on the physics: There should be a significantly
shorter time spent on the pole-recovery side ski.
Because passive glide puts isometric
strain on the bent knee. But on the pole-recovery side,
extending the knee just after landing the ski is counter-productive,
because the most effective leg-push phase must be started from a
flexed knee. So it makes sense to cut out the passive
glide phase on the pole-recovery side and instead start the leg-push
nearly as soon as the ski lands. Then
on the pole-push side take the extra time to use the
passive-glide phase to get the butt and upper body into a high
position for strongest pole-push. So the timing is asymmetrical
because one side has a substantial phase devoted to lifting the upper
body while the other does not. The problem
with this approach is that it takes good balance to glide on one ski
long enough to get the full lifting of the butt and upper body.
The puzzle then is that if a skier has good enough balance to execute
it on one side, why would they not have good enough balance to have
time for a full lifting of the butt and strong pole-push on the other
side too -- in which case they could be enjoying full V2 skate.
(c) There are three knee-extension pushes in the
stroke cycle that delivers maximum effective work.
One to lift the butt for the pole-push. One for the
skate-push on the pole-push side. One for the skate-push on the
pole-recovery side.
Many skiers add a fourth leg extension -- to
get high just after landing the pole-recovery ski -- so they can enjoy a
long passive glide without the isometric strain of holding the bent-knee
position. From a forward-motion efficiency perspective this is a
waste, since they have to drop their butt low again to start the
maximum-effective-work skate-push on that side. But there's more to life than efficiency.
(d) Many skiers rightly choose to get less than the maximum work
-- because getting the maximum in Open Field skate wastes power or
strains key muscles.
The waste is on the recovery side -- either from the work of a fourth
leg extension without forward-motion benefit, or from isometric strain
of gliding on a flexed knee.
Instead what many skiers do is a "half-leg-extension" just
after landing the pole-recovery ski, to remove much of the isometric
strain. Then they make their recovery-side skate-push from this
halfway position -- so its range of motion is shorter than if it had
been started from a lower position. So the recovery-side
ends with the hips in the half-way position. Just after the
pole-side ski lands, the skier raises the hips and upper body high for
the pole-push.
Result: There is one full leg-extension pushes and
three "half" leg-extension pushes in the whole stroke
cycle. There's still the same total amount of upper-body-lifting
leg-extension (namely one -- as the sum of the two half leg-extension
lifts). The loss of effective work is in the shortening of the
range of motion on the recovery-side skate-push. (I think this
compromise on the pole-recovery is the main reason that elite racers
usually prefer to use V2 over Open Field skate).
(d) Going up hills: Athletic skaters can use Open Field skate
to go up hills. One modification for substantial hills is to not
lift the butt and upper body so much in the first leg-push after
landing the ski on the pole-push side. Less lift means shorter
time lifting, so the distinct glide-with-no-push phase gets shorter --
this way Open Field skate morphs toward V1 offset.
The problems with too much lifting are: (1) it's a passive
glide "dead spot", (2) it's counter-productive to lift a
substantial percentage of the body only to drop it. So instead
minimize the initial downward leg-push, and drive the pole-push
mainly with the arm and upper abdominal muscles, not body weight.
On flat terrain, dead spots are OK if they are used
for substantial benefit. And on flat terrain, lifting the upper
body to power the pole-push is OK. But up a hill the capacity of
the body-lifting muscles is the primary limit on performance, so
adding yet one more lifting task doesn't help -- just takes away from
some other lifting.
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