what's here
Leg muscles available to use for propulsion in the leg-push skating for
normal-push stroking, also for double-push stroking -- and also
Upper Body moves for skating with no poling.
see also
other muscle groups
compare with other sports
related topics
[ under construction ]
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This page lists the muscle moves used to do actual physical work for forward
propulsion in skating (and not just prepare the configuration of bones and joints so that
other muscles can
do propulsion work).
The list first gives the muscle moves for normal-push stroking
technique, with legs + hips shown separately from upper body moves. Then
it gives the additional muscle moves available for the "double push"
stroking technique often used by inline speedskaters in longer distance
events.
This list of muscle moves is not the "right" way to skate. Rather it
offers a set of options. Few skaters use all these muscle moves, and I doubt
there is any skater who uses all of them all the time.
The main purpose
of this analysis is to expose skaters and skate instructors to more
choices -- more variety and more freedom. It's up to each skater and
coach to work out which subset of these is best for them in each
situation, and in what "proportion" to emphasize each move in their
chosen subset.
A key puzzle of learning skating technique is how to manage the
complexity of these possibilities. A gifted instructor helps each
learning skater find simplifications that are appropriate for their
current needs and goals.
Finding another set of muscles to use is like getting a bigger car
engine. The main body-performance "bottleneck" for most skaters is in
build-up in the main big leg muscles of chemical by-products from
intense production of work. So spreading the load to other less-obvious
muscles allows the main big muscles to work easier and longer.
Why doesn't our body learn to use all these muscles automatically?
Unlike walking or running, skating is not a natural movement pattern for
humans. So we need help in discovering and developing and then
remembering how to use many of the muscle moves:
-
Our unconscious neuro-muscular control centers need
help in discovering which other
muscles can be effective for skating.
-
How to use -- our neuro-muscular centers also need help to learn
how each muscle can be
effective, since angle configuration and timing matters.
-
Forget -- Even if we learned all the muscle moves once, when we
focus on one or two, we forget one of the others.
Perhaps our
neuro-muscular control centers do not have enough "computer power"
to handle coordinating so many muscles at once -- since the normal
propulsion movements of walking and running use fewer muscles.
-
Save energy -- Often our neuro-muscular control center is
usually trying to save energy -- so it
lowers the usage of most "non-obvious" muscles unless we consciously remind it.
-
Minimize muscle mass -- I suspect that our
neuro-muscular control center is "programmed" to try to re-use the
same obvious big muscles for many different tasks, instead of
recruiting other muscles used at a high power-level only for one
task (e.g. skating).
Because using other muscles at a higher
power-level will increase their muscle mass, and extra muscle mass had
some bad costs in the old evolutionary survival-reproduction
game: (a) higher basal metabolism; (b) more body weight to be carried
around; (c) lower calories-per-kg of stored energy. So it takes
conscious effort for us nowadays, for our own modern purposes, to
overcome this instinct.
If
we don't know all the specific muscles and their moves, then we
don't know how to best train the specific muscles. Not that each
muscle needs its own special exercise, but need to think about where it
gets stimulated in an overall program of training. The default is
simplest: just remember to use that muscle sometimes in normal fun
skating.
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Priorities for better utilization
The hip extension move [
see more below ] likely does
the highest proportion of propulsive work, but almost nobody neglects to
use or train them, since they're used in our natural motions of walking
and running (and bicycling).
Here's some likely opportunities for improvement:
-
knee extension in Phase 3 [
see more below ] -- Major leg muscle but often
neglected, because it's full utilization for skating requires the non-intuitive move of pushing
directly out to the side -- which then often feels like the
lower leg is slicing forward, very strange to our walking instincts
which want to be feeling the leg pushing backward. Also because the
pre-requisite for maximum range-of-motion is ankle-flexion in
Set-down phase 0 or in phase 1 -- another non-obvious move.
-
hip abduction and medial hip rotation in Phase 1 [
see more below ]. Many people think that Phase 1 is a
"passive glide" phase. But actually it's a straightforward
opportunity to start pushing propulsively on the skate or ski.
other notes on usage
Not many people forget the toe-push
move, because it's natural from running.
Except . . .
Some coaches from a long history of ice
speedskating say that ankle-extension is counter-productive, or at least
"sloppy form" -- because in the years before klap-frame speedskates,
ankle-extension really was counter-productive for propulsion on
ice.
Non-klap-frame ice speedskaters sometimes forget the toe-push when they try ski-skating,
because it's not effective on the other skating equipment they practice
with for
more hours for more months of the year.
Inline speedskaters sometimes forget the
toe-push when they try ski-skating, because they think it's not
effective on the other skating equipment they practice with for more
hours for more months of the year.
There are 9 (or 12) distinct Leg muscle moves with distinct
functional roles for legs and hips which are available to add
forward-propulsion work in normal (non-double-push) skating.
Double-push stroking adds more possibilities, with a total number of available propulsive
Leg muscle moves of 14 (or 21).
For more details see
Comparing Complexity
of Skating.
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These muscle moves are available to add forward propulsion power in
skating:
used in these leg-push
phases:
- - Phase
R
later part +
Phase 0: for
Leg-Reactive-Rorce
- -
Phase 1,
also Phase 2: for "direct" push
(sometimes called
inward hip leg rotation
or inward knee roll)
Often thought of as an error, but pronation can
also effective for propulsion -- provided that the starting configuration
of the leg joints and the timing are right.
(this move is often associated with the
"gluteus maximus" muscle)
(this move is often associated with the
"quadriceps" muscles)
(this move is often associated with the "calf"
muscle)
(also sometimes called
forward hip rotation or
forward pelvis rotation)
??
Not clear to me what this move should be
called using technical kinesiology terminology. Perhaps it's a
combination set of multiple kinesiology motions, and perhaps which
kinesiology motions are in the set is different from Phase 1 to Phase 3.
?? Perhaps more accurate kinesiology to call this
move
lumbar spinal rotation. No.
- ?? hip-flexion -- Phase 0. Advances knee and nearby areas of leg
forward at slightly higher velocity against air resistance, which increases
the force of air resistance against those sections of leg -- and
that increased force can be transmitted through the hips to the
other pushing leg and foot.
But this increase in force is so small, and
the move is inter-related non-propulsively with so many other important
things: like the hip joint finishing the previous push lower, and
starting the next push lower -- which changes the range-of-motion of
those moves, likely by making it larger. Even up a hill, though the
hip-flexion move lifts the mass of the leg more, it results in the mass
of the upper body ending lower. Not so clear that it takes much muscular
force to achieve more hip-flexion angle: just let the weight of the
upper body "crush" it down.
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side-attraction recovering-leg moves
These are moves which tend to accelerate the recovering leg's motion
toward its own side, or decelerate its motion toward the other side:
- hip abduction [
more
info ] -- Phase
R
later part +
Phase 0 early part.
- knee-extension [ more info ] (for skiers or skaters) or
- medial-hip-rotation / inward-hip-leg-rotation [ more info ] (for
skaters only, not skiers) -- Phase R later part + Phase 0 early
part.
- lateral-ankle-rotation (small contribution to propulsive work) (for skaters only,
not skiers) -- Phase R later part + Phase 0 early part.
In Phase R + Phase 0, these side-attraction
recovering-leg moves do add
reactive-force work on the leg-push stroke by the other leg, by
decelerating and stopping the recovering leg's inward motion in Phase
R, then starting and accelerating the mass of the leg outward in Phase
0. The tricky question is if this work is cancelled or not.
Normal-Push stroking:
In Phase R with normal-push stroking, the
positive work of this move (in decelerating) mostly just cancels the
previous negative work of the hip-adduction move (in accelerating) in
the early and middle parts of Phase R.
In Phase 0, the positive work of accelerating
the leg away toward the other side to prepare for landing it over there
is partly cancelled by decelerating leg just before and during actual
landing. But since the foot after set-down still has a positive sideways
component in its glide out toward the other side, the deceleration is
less than the acceleration, so there is a net positive of reactive
side-force for propulsion. So the positional result of the Recovery move
is a driver of Power.
Double-Push stroking:
In Phase R with double-push stroking, the
sense of the aiming-angle of the pushing foot changes, so it is possible
to have non-cancelling reactive-side-forces -- provided that appropriate
timing is used.
The appropriate timing is to postpone starting
the side-repulsion recovering-leg moves during the In-push phases of the
pushing foot, until just before the Aim-switch phase A. Since the
side-repulsion recovering-leg moves are positive for propulsion during
the In-push phases of the other foot, the acceleration part of these
side-motions is positive.
If the deceleration of these side-motions is
allowed to happen after mostly after the Aim-switch phase A and
during Phase 0 of the main-push, then the deceleration is also
significantly positive, so the total contribution of reactive-side-force
to propulsion during Phase R is significantly positive.
In phase ip0, the acceleration of the Set-Down
move comes during Phase 3 of the other leg's main-push, so it is a
significant positive. But at the end of set-down and start of In-push
phase ip1, the sideways velocity of the foot must be stopped -- or slightly
negative: So at best the acceleration and deceleration parts of
reactive-side-force during phase ip0 cancel, or there might be a slight
net negative for propulsion.
side-repulsion recovering-leg moves
These are moves which tend to accelerate the recovering leg's motion
away from its own side, or decelerate its motion toward its own side.
These moves make a net positive contribution to propulsive work only
in Double-push stroking.
By accelerating the mass of the entire
recovering leg to move faster (and further) inward toward the other side
during the early and middle parts of Phase R, the
hip
adduction move
adds kinetic energy, which is then transmitted to the snow thru the
other foot when the entire lower leg's side-motion is stopped in the last
part of Phase R. The more quickly and strongly the leg is moved inward, the more
kinetic energy can go into the other foot by reactive side-force. But
this same amount of kinetic energy is subtracted from the other foot
when the lower leg's motion is started in the early and middle parts of
Phase R, so it all cancels and the net contribution to propulsion is
zero.
But the farther the leg is moved over to the
other side during Phase R, the more distance is available to accelerate
its mass during the earlier part of Phase 0, and that positive work from
hip-abduction gets cancelled only partly.
- knee flexion [
more
info ] (for skiers or skaters) or
- lateral-hip-rotation /
outward-hip-leg-rotation [ more info ]
(for skaters, not skiers) -- Phase R middle.
- medial-ankle-rotation (small contribution to propulsive work) (for skaters only,
not skiers) -- Phase R middle part.
By accelerating the mass of the lower leg to
move faster (and further) inward toward the other side during the middle
of Phase R, the knee flexion move (or lateral-hip-rotation move) adds
kinetic energy, which is then transmitted to the snow thru the other
foot when the lower leg's
side-motion is stopped in the last part of Phase R (and then is sent
back outward toward set-down in Phase 0). The more quickly and strongly
the lower leg is moved inward toward the other side, the more kinetic energy can go into the
other foot by reactive side-force.
Prerequisites:
- - knee-flexion move must be preceded
by hip-abduction (to lift foot vertically off the ground a ways) and
outward-ankle-rotation (for a skier, to point the toe and ski tip
horizontally so it doesn't hit the ground)
- - lateral-hip-rotation move must be
preceded by knee-flexion.
Normal-Push stroking
Since the sideways (and forward-backward) motion of the leg is
roughly stopped at the finish of its main-push, which marks the
beginning of Phase R, and roughly stopped at the end of Phase R -- and
the aiming-angle of the pushing foot remains mostly the same -- then the
net contributions of moves for starting and stopping the
sideways-motions during Phase R must add up to zero.
Double-push stroking
Since the aiming-angle of the other leg's pushing switches its sense
of direction in the midst of the recovering-leg's phase R, there can be
a positive contribution from both the acceleration and deceleration
segments of the recovery moves. So for double-push these
"side-repulsion" recovering-leg moves can be propulsive.
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- knee-extension [ more info ]
- hip-flexion
Knee-extension brings the recovering-leg
forward, if it was previously sent backward by Knee-flexion during phase
R.
Hip-flexion brings the recovering-leg forward,
if it was previously sent backward by Hip-extension during phase R.
These moves can contribute
reactive-forward-backward forces positively to propulsion work during
both phase R and phase ip0 for double-push.
But for normal-push all such contributions
cancel each other.
Normal-Push stroking:
In the usual simple "straight-stroke-path" normal-push,
the path of the foot on the ground roughly follows a straight line (a
line that is angled away from the overall forward motion direction). The magnitude of the aiming-angle of the feet in
all phases on both sides is roughly the same. Only the sense of
the angle's
sideways-direction changes as you switch from one foot to the other. Therefore all forward-backward reactive forces
from moves of the recovering leg during its phase R and phase 0 must
cancel out, so their net contribution to propulsive power must be zero.
(see also: Normal-push stroking with a "hop")
There is a way to obtain a net positive contribution of
reactive forward-backward force with normal-push: Set-down with a
smaller straighter aim-angle into Phase 1a, then sometime during phase
1b or phase 2, pivot the foot outward to a larger aim-angle during later
phase 2 and phase 3.
Thus in the Set-down phase 0, the positive-contribution
acceleration of the mass of the recovering leg starting forward in its
set-down phase 0 comes when the other foot is at its most favorable
aim-angle for transmitting the reactive force propulsively to the ground
-- while the negative-contribution deceleration of this recovering leg
comes after the previous foot has lifted up, and this foot is on the
ground in its least favorable aim-angle for transmitting force
propulsively -- so the positive work is greater than the negative work.
In Recovery phase R, a similar mechanism can result in
the negative contribution of acceleration backwards getting outweighed
by the positive contribution of deceleration -- see more on this under
double-push.
Drawbacks of "angle switch":
-
The previous foot should be lifted up before the
new set-down foot decelerates much relative to the skater's
center-of-mass -- because this deceleration is negative for
propulsive work, and if the other foot is on the ground at the large
aim-angle expected for its phase 3, then that negative will be
strongly transmitted to the ground. This might require a shorter
"overlap" time between the two feet in phase 3b and phase 1a, which
might result in lower power, because of longer stroke-cycle time, or
shorter range-of-motion for some move.
-
Setting down with aim-angle more straightforward
might require a lower side-velocity at set-down, which means less of
the positive-contributing reactive side-force from the
recovering-leg just after set-down.
-
Setting down with aim-angle more straightforward
will transmit a smaller proportion of positive-contributing reactive
side-force from the recovering leg as direct propulsive work
to the ground, immediately after set-down.
-
The timing of the starting of other reactive
side-force moves (e.g torso-shoulder side-swing, arm side-swing)
must be postponed to later than for "simple" normal-push -- since
their direct propulsion contribution will also be smaller if their
deceleration comes during the smaller aim-angle phase just after
set-down. But delaying their deceleration into later phase 2 to be
"caught" by the larger aim-angle could be very disruptive for other
aspects of the stroking.
-
Pivoting the foot to change the aim-angle increases
friction. (When skating on skis, the foot must be momentarily pulled
up into the air, which has a significant cost).
Seems like many of these are the same as the drawbacks
of double-push stroking. So why not just do double-push, instead of this
"angle switch" version of normal-push? Why would a skater choose to
incur most of the disadvantages of double-push, while missing out on
most of its benefits?
Hopping up so that both feet are briefly up in the air
is another way to minimize the negative work of forward deceleration. In
this variation, the path of the foot on the ground roughly follows a
straight line, a line that is angled away from the overall forward
motion direction. The deviation is in the vertical direction.
The hop should be timed so that the previous foot
leaves the ground while the recovering foot is moving with maximum
forward velocity. Then while both feet are still in the air, slow the
next foot to a stop relative to its hip (or even to moving
slightly backward relative to its hip?).
Drawbacks of hopping:
-
It wastes precious stroke-cycle time -- the time
during the hop is a "dead spot" for power, which tends to reduce the
average rate of power over the whole stroke-cycle.
-
It wastes work into upward kinetic energy and
vertical potential energy much of which cannot be effectively used
for propulsion, because the next foot lands close underneath
the upper body, not angled out toward the side.
Double-Push stroking:
The forward-backward motion of the leg is roughly
stopped at the finish of its main-push. If the leg starts backward
during phase ip1 of the other foot, the aiming-angle of the pushing foot
is small, near to straight forward, so the impact of
reactive-forward-backward-force on propulsion is small negative.
If this backward motion of the leg is allowed to slow
and stop mostly after the Aim-switch phase A, during phase 1 of
the other leg's main-push. The aiming-angle of the pushing leg during
deceleration is mostly large out toward the side, so the impact of
reactive-forward-backward-force is significant positive -- so the total
contribution during Phase R of the recovering-leg is positive.
Assume that the recovering-leg is held stable during
later phase 1, all of phase 2, and early phase 3. So it has substantial
effective range-of-motion available to start moving forward for set-down
in the early part of phase ip0.
Since the acceleration part of the set-down move comes
during the main-push of the other foot, the aiming-angle of the pushing
leg during acceleration is mostly large (out toward the side), so the
impact of reactive-forward-backward-force is significant positive.
Since the skater is gliding forward, some of the
deceleration of the forward motion in phase ip0 will come after set-down
in phase ip1. The aiming-angle of the pushing foot is small, near to
straight forward, so the negative impact of
reactive-forward-backward-force on propulsion is small negative --
so the total contribution during Phase ip0 of the recovering-leg is net
positive.
So the total contribution of
reactive-forward-backward-force during both Phase R and Phase ip0 of
double-push stroking can be overall positive.
Recovery phase R:
There's no net positive contribution from either
side-motion or backward-motion of the recovering leg in this phase. No
need to hold back and then move it quickly. Can do it smoothly, and
focus on other more important moves.
Make the foot finish in a position far out toward the
opposite side, behind the other leg, to prepare for a positive
contribution in set-down. But there's no need to make it go backward
farther than is convenient.
The "aim-angle switch" version of Normal-push
has different implications -- more like double-push -- but I'm not
seeing much point in using "aim-angle-switch" rather than double-push
anyway.
Set-down phase 0:
The contribution from reactive side-force is positive
and substantial.
Hold the foot out toward the other side behind the
other leg until the start of the move. Don't let it drift in toward the
center.
Positive contribution from reactive side-force will be
increased by these steps: (a) aim the foot more out toward the side; (b)
quickly accelerate the foot to high sideways-speed toward its own side;
and (c) retain that sideways velocity after set-down until the other
foot is lifted up.
Recovery phase R:
If well-timed, reactive side-force contribution is
positive and substantial in both acceleration and deceleration phases.
So try to hold back the start of the sideways recovery -- let the foot
hang out there to the side -- until just before the Aim-switch. The more
that phase 3 overlaps with phase ip1, the less "hang time" is needed.
Then make the sideways move very quickly -- timed together with
torso-shoulder side-swing and any arm side-swing moves.
Reactive forward-backward-force contribution can also
be positive, with the same timing as for the side-moves. Try to avoid
having the foot start drifting backward slowly immediately after
lift-off. Try to keep it forward for a moment, then when the time is
right, pull it backward quickly.
Quick stopping of either sideways or backward
moves is not that important, as long as they don't delay the start of
the Set-down moves.
Having the foot finish in a position further back
behind is good for the next phase.
Set-down phase 0:
Side-motion of the recovering leg is at best neutral
for the set-down move, so no point in holding it back or making it
quick. Just let the foot drift sideways toward center (but not forward)
-- the important thing is to support the other moves, notably the
forward-motion of the leg in set-down.
Reactive forward-backward-force contribution is
positive and significant, so hold the foot back way behind, don't let it
drift forward. Pull it forward quickly into set-down. To minimize
negative transmission of deceleration, try not to set it down way
forward. Prefer to set it down more behind, and keep it moving forward
relative to its hip until all the weight comes off the other foot, then
stop it.
But those suggestions are only what's best for reactive
forward-backward force in this phase. Other moves might dictate
different choices, and usually those other moves are more important for
propulsion.
Likely these recovering-leg moves in this phase make an
overall positive contribution to propulsion for double-push, since
likely the positive from forward-backward is larger than the slight
negative from sideways motion.
Recovery phase R:
-
Normal-push starts immediately after lift-up, and
goes smooth.
-
Double-push holds back after lift-up and through
much of other leg's in-push, then goes quick just before Aim-switch
phase.
-
Normal-push emphasizes finish position more out to
the other side.
-
Double-push emphasizes finish position more behind.
Set-down phase 0:
-
Normal-push focuses on quick side-motion.
-
Double-push focuses on quick forward-motion.
-
Normal-push lands foot close underneath, then into
gliding and pushing out toward side.
-
Double-push lands foot outside and back, then into
slicing forward.
other moves
(this move is often associated with the "shin"
muscle)
This adds to propulsion at most a small
amount: Perhaps by helping to move hip joint forward and up, and
thus helping to raise the weight of upper body (a very little bit),
which adds vertical potential and kinetic energy to later phases. This
requires applying strong force from the front of foot upward against
upper of front of boot. This is most effective on skis with the long
tail to lever against. On inline or ice skates it would mostly just lift
the toe of the skate -- could get slight work from shifting pressure
from front to rear of bottom of boot.
The main purpose of the ankle-flexion move is
to bring the knee joint forward ahead of ankle joint, which "aims" the
knee-extension push better for more effective propulsion in Phase 3, and
adds range-of-motion to the ankle-extension move.
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Double-push /
in-push leg+hip muscles
Double-push already includes all the muscle moves used
in phases 1, 2, 3 of normal-push skating (see above).
Here are the additional leg and hip muscle moves used
propulsively in phases ip0, ip1, and ip2:
more effective if foot is set down further
outside away from its hip
(more effective if knee was earlier rolled inward in phase
ip0).
(most effective if ankle was earlier pronated in
phase ip0).
(also sometimes called forward hip rotation or forward pelvis rotation)
It's basically the same move in the same direction for
both pushes of the same foot.
Therefore see discussion under
Advance-Next-Side move set for
main-push.
But in double-push stroking this move should not be started until after
the completion of Phase 3 of the previous push by the other foot.
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Knee-extension is propulsive in phase ip0 only
if Knee-flexion after Hip abduction was used in Phase R.
Medial-hip-rotation is propulsive in phase ip0
only if Lateral-hip-rotation was used after Knee-flexion in Phase R.
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see also
other muscle groups
compare with other sports
related topics
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|
