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Leg |
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see Introduction
on Leg muscle comparison page
?? [ more to be added ]
Normal skating can uses 50% more muscle moves then running,
2 times as many as bicycling, 3 times as many as walking.
Double-push stroking can use more than 2 times as many as
any of those other non-skating motions (ones which do not use ski poles).
Considering that the complexity of the interaction effects
between different factors is typically proportional to the square of the
count of factors, improving technique for higher speed in skating might be
2 or 3 or 4 times as complicated as
running or seated bicycling.
count of muscle moves
number of distinct muscle moves available to contribute
forward-propulsion work:
motion technique:
 |
major
moves
|
simple
min
|
articu-
lations
|
range
articu
|
de-sync
points
|
| skating normal-push |
5-6 |
1-2 |
16.5 |
13-20 |
1.5 (or 2) |
| skating double-push |
8-10 |
2-3 |
25 |
19-32 |
3 |
| walking |
1-2+ |
1.5 |
5.5 |
4-7 |
0 |
| running |
4-6 |
3-4 |
11.5 |
10-13 |
2 |
| cycling seated |
3 |
1 |
4 |
4 |
1 |
| cycling standing |
7-8 |
1 |
10 |
9-12 |
1 |
in list form:
See details below under
Compare complexity of other Motions.
motion technique:
|
major
moves
|
simple
min
|
articu-
lations
|
range
articu
|
de-sync
points
|
| skating no poles |
5-6 |
1-2 |
15 |
12-18 |
1.5 (or 2) |
| skating V1 |
9 |
2-4 |
20 |
18-22 |
2.5 (or 3) |
| skating V2 |
8 |
2-4 |
20 |
19-21 |
2 |
| clas striding no poles |
4-5 |
3-4 |
10.5 |
9-12 |
2 |
| clas striding with Poles |
7 |
4-5 |
17 |
16-18 |
2 |
| pure double-poling |
6 |
1-2 |
12 |
12 |
1.5 |
in list form:
See details on Compare
ski-skating with other skiing motion techniques page.
see also
Upper Body: In addition to the Leg + Hip moves of
skating, there are more muscles with distinct functional roles in the
Upper Body which available to add forward-propulsion work
in skating (without using ski poles to help push):
These are the upper body moves available to add net
positive propulsive work for "simple" straight-angle continuous
ground-contact normal-push stroking.
Variations on normal-push stroking such as
"switch-aim-angle" and "hop" are covered below under
double-push stroking.
major move "functions" (Upper Body)
a portion of another move function has slight benefit:
sub-moves + "articulations" (Upper Body)
upper body side-swing
(two-way side swing, with timing for reactive
side-force)
-
abdomen-torso side-swing
-
chest-shoulder side-swing
-
arm side-swing inward from shoulder
-
arm side-swing outward from shoulder
-
(small contribution) forearm side-swing inward from elbow
-
(small contribution) forearm side-swing outward from elbow
upper body up-down
with timing for reactive down-force: The idea
is to start the torso moving upward during Phase 3, downward during
phase 1 of the push by the next leg, upward during phase 3 of that leg,
etc.
de-synchronization of timing among moves
My analysis of the stroke-cycle shows these points where the amount of propulsive work is
impacted by the accuracy of de-synchronization:
-
0.5 for Starting the phase 1 leg-sweep-outward move
early, perhaps overlapping with phase 3 of the previous push by the
other leg. Then starting the leg-radial-press move later, but with
some overlap between the two different kinds of pushing motions by the
same leg.
-
1 for Delaying start of the arm-side-swing and
spine-torso-side-swing moves until later during the leg's main push
. . . so that their highest sideways speed will be
attained as weight is transferred from one foot to the other, and their
deceleration and stopping will occur during the main push of the next leg on
the other side. The temptation is synchronize the start of the side-swing
moves with the start of the main leg-push move -- but then the deceleration
occurs mostly while the weight is on the same foot whose push is still aimed
toward the same side -- so the resulting reactive side-force yields negative
work which roughly cancels the earlier positive propulsive work.
Actually this is not de-synchronization of
timing, but the feeling of moving linked body parts in opposite directions
is surely is strange for most skaters -- and the concept is
counter-intuitive for many coaches (as of 2006). There is no
de-synchronization of timing, because for maximum propulsive work, the
timing of the starting and stopping of the pelvis-twist move can be
simultaneous with the starting and stopping of the main leg-push.
It might be thought that there is a slight propulsion
advantage to delaying the start of the sideways component of the
leg-recovery move, so it is not immediately on the finish of the main
leg-push, then making the move quicker. But I think a similar propulsive
benefit can come from starting it immediately, then moving it further over
to the other side behind the other leg.
calculate complexity
Results from Leg+Hip complexity:
Upper body moves:
-
add func= 2, artic= 5 (range 4-6) for
upper body side-swing
-
add func= 0-1, artic= 1 (range 0-2) for
upper body up-down
Total propulsive moves available from entire body:
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d-p moves | Upper Body |
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These are the upper body moves available to add net
positive propulsive work for double-push stroking.
Many of these moves are also available for
variations on normal-push stroking such as "switch-aim-angle" and
"hop".
major move "functions"
a portion of another move function has slight benefit:
sub-moves + "articulations"
upper body side-swing
(two-way side swing, with timing for reactive
side-force)
-
abdomen-torso side-swing
-
chest-shoulder side-swing
-
arm side-swing inward from shoulder
-
arm side-swing outward from shoulder
-
(small contribution) forearm side-swing inward from elbow
-
(small contribution) forearm side-swing outward from elbow
upper body up-down
(with timing for reactive
down-force)
I'm only going to give each of these 0.25
contribution to the muscle move count, since I'm not sure they can
effectively be coordinated in a way to make much contribution in way
that doesn't get in the way of other propulsive moves.
upper body forward-backward
(with timing for reactive
backward-force)
arm-swing forward-backward
-
shoulder-flexion (arm swing forward from shoulder)
-
(small contribution)
elbow-flexion (forearm swing forward from elbow)
-
(small contribution) scapula-abduction -- shoulder reach
forward relative to spine
de-synchronization of timing among moves
My analysis of the stroke-cycle shows these points where the amount of propulsive work is
impacted by the accuracy of de-synchronization:
-
0.5 for Starting the phase ip1 leg-sweep-inward move
early, perhaps overlapping with phase 3 of the previous push by the
other leg. Then starting the leg-radial-press move later, but with
some overlap between the two different kinds of pushing motions by the
same leg.
-
1 for delaying start of the second half of the
arm-side-swing and spine-torso-side-swing moves until after the current
leg's main-push finishes.
. . . so that their deceleration and stopping will
occur during the main push (instead of the in-push) of the next leg
on the other side. The "second half" of the range-of-motion of these body
parts is the segment from crossing the center to reaching their farthest
position out on the other side (of the next leg).
The temptation is synchronize the start of the
side-swing moves with the set-down of the next leg -- but then the
deceleration and stopping occurs mostly during the in-push while pushing of
the next foot is aimed toward the same side as the starting and acceleration
-- so the resulting reactive side-force yields negative work which roughly
cancels the earlier positive propulsive work.
. . . so that they will attain a higher maximum
speed at the moment of the Aim-switch between the in-push and the main-push.
The "first half" of the range-of-motion of these body parts is the segment
from their farthest position out on this side (of the currently pushing leg)
into the crossing of the center. (Note that this holding back the start
until after the main-push, is a more radical delay than is most effective
for propulsive work in normal-push stroking.)
Even expert skaters who know to delay the second
half of these moves often cannot resist the temptation of allowing these
body parts to "drift" in toward the center while the main-push is still
going -- thus losing much of the reactive side-force benefit of the "first
half" of these moves -- because what determines the net positive amount of
reactive side-force work is not the distance of the range-of-motion,
but the sideways speed attained at the moment of weight-transfer
between the foot pushing toward one side to the foot pushing toward the
other side.
Actually this is more of a de-synchronization of
direction than it is of timing, because the feeling of moving linked
body parts in opposite directions is surely is strange for most skaters --
and the concept is counter-intuitive for many coaches (as of 2006). (Unlike
for normal-push) there is also some de-synchronization of timing, because
the duration of the pelvis-twist move can be "spread" over both the in-push
and main-push moves, so is it not simultaneous with any other single move.
Delaying the start permits the forward speed at
set-down to be larger. In order to gain net positive benefit from reactive
forward-backward force, the next leg must still be moving forward with
significant speed at the instant of set-down, so that a substantial
proportion of its deceleration takes place after body weight has been
transferred onto it (and off from the other foot). Therefore the next foot
must be set-down near or slightly behind the forward-backward position of
the currently pushing foot, not out in front -- so it has room for
deceleration.
So there is not much distance available for the
acceleration phase of this "recovering-leg kick forward" move. And the
muscles which drive this move are big and strong -- so if they apply their
full (repeatable) force immediately, the foot would reach the set-down
location too early, before the other leg had finished its main-push. But if
they apply less than their full force, then foot does not attain as high a
forward speed -- and forward speed of the leg at the moment of set-down is
what determines the net positive amount of reactive forward-backward-force
work.
Note that in double-push stroking (but not
normal-push) it is OK to allow early "drift" of the sideways component of
the set-down move, inward toward the center, because the work from this
sideways component of Set-down phase ip0 (but not of Recovery phase R) is
necessarily self-cancelling for double-push (but not normal-push).
which yields a total of 2.5 (or perhaps 3) timing de-synchronization
points.
calculate entire-body complexity
Results from Leg+Hip complexity:
Upper body moves:
-
add func= 2, artic= 5 (range 4-6) for
upper body side-swing
-
add func= 0-1, artic= 0.5 (range 0-2)
for upper body up-down
-
add func= 1, artic= 2 (range 1-3) for upper body forward-backward
Total propulsive moves available from entire body:
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