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There are different motion techniques for trying to skate fast,
and some things about what to look for in video are different, so it's it good
to be clear about which technique the skater it trying to perform.
two main skating techniques, each with variations:
This is the technique used by most people without special
coaching. Each leg makes one push during the stroke-cycle, and that push is
aimed diagonally to the outside (away from the other leg). The foot maintains roughly the same aiming direction throughout its
push. Except there might be a slight tendency to aim less toward outside near
the end of the stroke if "carving through the heel" is employed.
There's a variation where the foot is set down aiming straight (without
pushing), then pivots outside to make its push.
Three variations of Normal-push:
Advantages:
These frictional losses are more important if using a
long ground-contact implement: e.g. long-blade ice speedskate. Very important
for using a normal-length cross-country ski on snow, where simple Normal-push is
usually the only relevant option.
Other possible advantages:
-
pushing can be made continuous through the whole
stroke cycle: no gap.
-
allows focus more on the big strong leg Extension
muscles (e.g. gluteus, quadriceps) for high-force situations.
The foot is set down already aimed diagonally toward
the outside. It's helpful to think of the push in three phases:
(1) Sweep-out: At first while the foot is closer
to underneath its hip, the push is a Sweep sideways, directly outward
from underneath. The line of its push is roughly along the ground
surface, mostly sideways and partly backward. This push engages
little-known muscles on the side of the leg, which could hip-abduction,
medial knee-hip rotation, and ankle-pronation.
These muscles are typically substantially less
powerful the leg-extension muscles. Serious racers, especially ice
speedskaters, do special exercises to strengthen them.
(2) Tween: A lower power segment between
two phases. Not a good configuration for getting a high proportion of
propulsive Work from either Sweep-out or Extension muscles. The
objective for this phase is to somehow get through it quickly.
One strategy for getting through the Tween
phase more quickly could to aim the foot a little more outward at the
start of this phase, then more inward again at its end. A possible
advantage of Double-push is that the skater goes into this phase
carrying more sideways momentum.
(3) Extension: When the foot is a significant
distance out to the side away from underneath it's hip, the push is an
Extension: aimed roughly along the line from the hip through the foot,
so it includes a downward aspect. The Extension push can engage familiar
muscles from walking and running: hip-extension (e.g. gluteus),
knee-extension (e.g. quadriceps), and ankle-extension (e.g. calf).
The theme of the "simple" style of Normal-push is to
get a good range-of-motion distance in each leg-push. Sometimes skater's
with well-developed Sweep-out muscles set down their foot inside from
vertically underneath its hip, to lengthen the range-of-motion in phase
1.
Another strategy is to skip most of Sweep-out phase 1,
and emphasize the big strong leg Extension muscles. Set down with foot
aimed outward to immediately begin pushing.
The theme of this "Simple with Extension focus"
variation is to increase turnover frequency and force-magnitude from the
big leg muscles. Used for high-force situations like climbing a steep
hill, or sprinting, or skating into strong headwind, or on a slow
surface (rough or soft).
This variation is recommended by some speedskating coaches. The
foot is set down aimed roughly straight in the overall direction of forward
motion, then pivoted to aim outward (away from the other leg) for its outward
leg-push.
The foot does not push sideways in this variation. It
only glides and supports body weight.
Pushing outward would contradict the push by
the other leg and/or weaken the sideways weight shift which will add
work to this leg's later push.
Pushing inward could add propulsive Work -- and
by my definition that is one form of Double-push.
There are two possible timings for the pivot from
straight to aiming outward:
-
At or before the time the other foot lifts up off
the ground -- which implies that the foot was set down significanly
before the other foot lifted up, and that the other (pushing) foot
shares in supporting body weight the whole time the foot is gliding
straight.
-
After the other foot lifts off the ground -- so
there's time with the foot gliding straight supporting full body
weight.
Advantage of setting down straight before lift-up of pushing:
This supporting of a longer lower hip position
could also have been achieved with the foot already aimed outward
and starting its own push (especially if it had been set-down further
underneath inside). Or as part of Double-push.
Advantage of continuing to glide straight after lift-up
of pushing foot:
But it is difficult to imagine a situation in
which this additional propulsive work from the arm-swing could outweigh
the loss in Power (measured in Watts) from slowing the stroke-cycle and
reducing turnover frequency. Especially with the alternative of getting
propulsive work from sideways arm-swing which does not require
any gap between leg-pushes.
Fastest technique for expert inline speedskaters for non-short
time durations on gentle
terrain without sharp curves. The foot is set down and then pushed toward the inside, with
the upper body getting pushed toward the outside (toward the side of the new
pushing leg). Then the foot is pivoted to aim outward (away from the previous
pushing leg, toward the new pushing leg), and pushed toward the outside, with
the upper body stopping going toward the outside, then starting to go toward the
inside (away from the pushing leg, toward the side of the next pushing leg).
Three variations of Double-push:
The key distinction between Double-push and Normal-push
(in my definition) is that "Double push" has two pushes in a row by the
same leg, the first toward the inside and the second toward the outside,
with the other leg making no push in between those two. In Normal-push
first leg makes one push, then the other leg makes one push.
Some people define "Double push" as when the
foot makes something like an S curve on the ground, first a smaller arc
to the inside, then a larger arc on the outside. By my definition, you
can steer your foot around all the inward arcs you want -- but unless
you actively push toward the inside, you're still doing
Normal-push. And as long as you push to the inside and then the
outside, there's no need for an "S curve" -- it counts as Double-push.
Advantages:
-
can engage new muscles on the inside of the leg (hip-adduction,
ankle-supination, possibly
lateral knee-hip rotation)
-
moves quickly through the less effective "between" phase into
the more powerful "Extension" phase of the main outward push.
Increase speed because there's an additional
sideways push by the leg (provided this push is transmitted to
the upper body, and provided the timing of the upper body moves
is accurate), and because the leg recovering through the air can
contribute its full sideways speed to propulsive work. In Normal-push,
only the sideways speed that the leg retains thru Set-down contributes
to propulsion.
Extension in-push --
(higher turnover of Extension muscles)
The obvious idea for the inward push of Double-push is
to make substantial use of all the muscles available to help. The
leg muscles available are the Extension muscles (familiar from walking
and running -- and the normal outward push in skating), and the
little-known Sweep-In muscles on the inside of the leg, which can
include hip-adduction, lateral knee-hip rotation, and ankle-supination.
So the In-push is much like the outward main push in
its angles and phases, except that the Sweep-In muscles are substituted
for the Sweep-Out muscles, and the Extension phase 3 is cut short. The
leg does not push to full extension.
There are two problems with going to full
extension: (a) the upper body starts to fall downward to the outward
side, where there's no other leg to catch its fall; and (b) the
leg must be compressed again before it can make its outward main push,
and too much compression required adds time to the stroke-cycle, which
tends to reduce Power (measure in Watts).
Theme of this approach is to get higher turnover frequency of the big
leg Extension muscles (more like the frequency used in
bicycling). The balance and sideways motion required for this variation
tends to feel pretty radical, so (as of 2007) it's only used by a few
elite racers.
This approach focuses on the Sweep-In move (inward push
phase 1), and cuts out much of the Extension move (inward push phase 3
and some of 2). The Sweep-In muscles on the inside of the leg are not
used propulsively in Normal-push skating, and not used propulsively in
walking, running, bicycling, or other effective ways to move across a
significant distance on land. There are used for balance and stability,
and for positioning moves in lots of sports.
Theme of this approach is to engage these little-known
leg muscles for propulsion, and spread the work load across more
muscles, which should enable the skater to sustain a higher rate of
Power (measured in Watts) near their lactate-related threshold -- which
is important for performances longer than sprints.
These Sweep-In muscles are not very big or strong in
most people, so for this approach it likely makes sense to do some
special training exercises to develop them.
Lots of inline speedskaters who are serious about
outdoor racing use this approach, because it's easier to learn to
perform reliably than the "Extenion in-push" variation. People who train
on off-road trailways with limited width are more likely to take this
approach.
This variation keep the foot aimed roughly straight in
the direction of overall forward motion thru the whole in-push. There is
an active push toward the inside, but there is no aiming or arcing of
the foot inside. So there is no direct propulsive work from this
push, but it does increase the speed of the sideways weight shift, which
can be converted into additional propulsive work by adding force to this
leg's outward push which it makes after the foot pivots to aim toward
the outside.
The difference between this and the
Pivot-aim variation of
Normal-push is that this Straight only variation of Double-push does
make an active push (toward the inside) while gliding straight, and the
Pivot-aim Normal-push does not.
It is not unusual for other Double-push variations to
set down with the foot aiming straight (to help support the weight of
the upper body to sustain a lower hip position longer for the Extension
push by the other leg), then pivot to aim inward and push inward. This
pivot is separate from the Aim-switch pivot at the finish of the
In-push.
Advantages of this variation:
This support could also be provided by the
other Double-push approached, but this variation keeps it simpler and
more focused.
-
Adds some propulsive work of its own (unlike
Pivot-aim Normal-push).
-
Less frictional loss and possible edge-control
difficulty than the full Aim-switch of the other Double-push
approaches.
-
Good for maintaining the rhythm of Double-push
while climbing up a hill, where taking the time to aim the foot
inward would leave too large a gap between the high-force outward
pushes.
Theme of this variation is to increase sideways shift
of upper body weight and to support the Extension phase of the other
leg.
For an example of an elite ice speedskater using it,
see Chad Hedrick's medal-winning performances in the 2006 Olympics in
Torino.
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