what's here
Set-down for inward leg-push
Max-In-Push (Front view)
Finish of
In-push (Side view)
Crossing from
inside to outside (Front view)
more . . .
[ under construction ]
see the Double-push sections on
the Set-down observations page
also the Double-push section in the topic of overall
Timing sychronization.
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checkpoint: "Max In-push" = The frame in Front view that
shows maximum inside reach by the foot in inward leg-push.
see more
on Definitions
This is the frame where the foot is aiming straight in
the skater's overall direction of forward motion -- which should be
straight into the camera, if this is truly a Front view.
The tricky question is, "How much of the inside move
from Set-down to Max In-push was just steering the foot into an arc and
gliding passively -- versus active pushing to the inside -- with
transmission of the push to the mass of the upper body?". See
more below.
priority: B
standard-form perceptual check
Foot crossed over to the inside to vertically underneath the other
hip (which just finished it's main outward push).
Pushing hip should be at least as high off the ground as it was at
Set-down.
Extension In-push
Foot should be crossed over to the inside to at least as far as
vertically underneath the other hip.
Sometimes very strong skaters lean over even further to the outside, so
the foot is farther inside than the other hip.
Pushing hip should be higher off the ground than it was at Set-down.
Sweep sideways focus
Foot should be significantly crossed over to the inside from underneath
its own hip -- at least half-way across to vertically underneath the
other hip. How far depends on the strength of the skater's In-Sweep
muscles (hip-adduction, etc.) and on the skating situation (usually
crossing less when going up a hill or into a headwind).
Straight only in-push
Foot should be somewhat crossed over to the inside from underneath its
own hip.
priority: B-
"neutral" = ankle joint in line between ground-contact and knee
joint.
It adds some propulsive work if the ankle is somewhat
"supinated" (ankle joint outside the line from ground-contact to knee
joint).
This is good provided that: (a) the
ankle was not already supinated at Set-down; and (b) the force is
transmitted through the knee (see
ankle-knee-hip) and hip into the mass of the upper body (see
relative
sideways stability); and (c) other muscles have not reduced their
(unconsciously?) their sideways force or range-of-motion in order to
allow ankle-supination to have enough force remaining to show some
positive motion.
If an ankle-supination move is to be made, a
higher proportion of its force goes into propulsion if it is performed
earlier after Set-down than later.
Bad at this checkpoint is if the ankle is pronated (ankle joint
outside the line from ground-contact to knee joint) -- since that is a
failure to transmit propulsive force from leg muscles and upper body to
the ground.
The ankle is a critical point for transmitting In-Sweep forces from the
upper leg and upper body to the ground. Doing a good job in this "stable
transmission" role is more important than having the ankle try to add
work from its own motion -- so it does not help if other muscles reduce
(unconsciously?) their sideways force or range-of-motion in order to
allow ankle-supination to show some positive motion.
Skilled inline speedskaters usually show a "neutral" configuration, but
some of the fastest show some ankle-supination.
priority: C
"neutral" = knee joint in line between ankle joint and hip
joint.
It adds some propulsive work if there has been some
"lateral knee-hip rotation" (knee joint outside the line from ankle
joint to hip joint).
"medial" hip rotation moves the kneecap toward
the inside toward the other leg.
"lateral" hip rotation moves the kneecap
toward the outside away from the other leg.
This is good provided that: (a) the leg
was not already in a "lateral knee-hip rotation" configuration at
Set-down; and (b) the force is transmitted through the hip into
the mass of the upper body (see
relative
sideways stability); and (c) other muscles have not reduced their
(unconsciously?) their sideways force or range-of-motion in order to
allow the muscles for this move to have enough force remaining to show
some positive motion.
Lateral knee-hip rotation is not compatible
with full extension of the leg -- and the usually the leg is not
fully extended in the inward push -- so it could make sense to use
lateral knee-hip rotation to add propulsive Work to the inward push of
Double-push. But I've never seen it in a video.
If a "lateral knee-hip rotation" move is to be
made, a higher proportion of its force goes into propulsion if it is
performed earlier after Set-down than later.
If a "lateral knee-hip rotation" configuration is observed, it is
important to check carefully for stability in hip-adduction and the
upper body -- for details see
relative
sideways stability.
I have not yet observed lateral knee-hip rotation in any video of a
speedskater.
Even though it seems like it makes sense from the physics, and
that it is compatible with the knee being in a flexion configuration.
It would make sense for lateral knee-hip rotation to be used especially
with the "sweep sideways focus" and "straight only in-push" styles of
Double-push, because those are emphasizing more the In-Sweep moves, and
getting less help from Extension moves.
Priority: A
No "wiggly" in the motion between Set-down and
Max In-push:
Every joint and body part moves at least as far sideways outward as the joint immediately
below it.
This is one of the critical differences between just
tracing "S curve" arcs and really making a new effective kind of push.
Basically this is same observation as in the
relative sideways motions + stability on the
Midway page
but in the opposite direction. So see that discussion,
but
-
une "inward" in place of "outward"
(and vice versa)
-
use hip-adduction in place of
hip-abduction
-
use "lateral knee-hip rotation" in
place of "medial knee-hip rotation"
-
use ankle-supination in place of
ankle-pronation
priority: B
See discussion of different approaches to this move on
Finish page.
Pelvis should be tilted sideways away from the leg-push (or
level). Since this In-push is pushing toward the inside, the pelvis
should tilt toward the outside. Hip of the pushing leg should be
lower than the other hip
being set down.
Or for those who believe in keeping hips level
at all times, OK then keep them level.
But the pushing hip at its Finish should definitely not be
higher than the other hip as the In-push is finishing.
priority: B (or A)
This is a priority B if the question is
between gaining power from a torso-shoulder side-swing move or not
gaining. It's priority A if the skater is actually losing power due to
mis-timing of torso-shoulder motion.
Typical problem in Double-push is starting the
torso side-swing move too early, and failing to gain power from it --
but not actually losing power.
Position of shoulders should be roughly centered over hips
(or perhaps somewhat toward the outside) --
and
moving quickly (relative to the hips) across to the side of the
main push outward, moving from outside toward inside.
Except for those believing in the "quiet upper
body" style.
Typical problem seen with Double-push is that the
shoulders have already reached a position over on the inside.
priority: C
This is priority C if the question is
between gaining power from an arm-swing move or not
gaining. It's priority B if the skater is actually losing power due to
mis-timing of arm-swing motion.
view: best observed in front view, not foot-aim view.
If arm-swing is not being used to add propulsive Power,
then this observation can be whatever fits with or helps other aspects
of the skater's motion -- e.g. balance or rhythm.
If swinging the arms and hands from side to side is
being used to add propulsive Power, then the observations should
be like for the position and motion of torso + shoulders under
hips - torso-shoulder
relationship -- e.g. for simple Normal-push, arms roughly in front
of body, perhaps a little to one side -- but not way off to one side or
the other, and
moving definitely toward the set-down side.
If swinging the arms and hands forward and backward is
being used to add propulsive Power, then the observations should be
different from that.
priority: C-
You'd have to work at it to get this observation wrong at this
checkpoint.
In front view, the foot of the recovering leg in the air should still be
further inside than the foot on the ground -- but definitely moving away
from the inside and toward the outside.
The way to get this move wrong would be to hold the recovering leg
toward the inside while up in the air, and not to let it start moving
toward the outside until the foot is pointed straight forward.
Or to get it really wrong: Not let it start moving toward the
outside until after the other foot is angled toward the outside. But
that is difficult.
A way to get it a little wrong would be to exaggerate
the backward aspect of leg-recovery and neglect the sideways aspect just
after lifting the foot off the ground.
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