what's here

other comparison

see also


Introduction

?? [ more to be added ]

 

summary of results

Normal skating can use 50% more Leg muscle moves than running or bicycling, and Double-push stroking can use about 2 or 3 times as many.

Considering that the complexity of the interaction effects between different factors is typically proportional to the square of the count of factors, improving Leg-motion technique for higher speed in skating might be 3 or 4 times as complicated as Leg techniques for running or cycling.

Number of distinct Leg muscle moves available to contribute to forward-propulsion work:

motion technique:
major
moves
simple
min
articu-
lations
range
articu
de-sync
points
skating normal-push 3 1 10.5 9-12 0.5
skating double-push 5-6 2 17.5 14-21 1.5
walking   1-2+ 1-2 5.5 4-7
running 4 3 7.5 7-8
cycling seated 2-3 1 4   4
cycling standing 4-5 1 7   7

in list form:

  • "simple" normal-push skating -- Leg+Hip:  func= 3,  artic= 10.5  (range 9-12)

  • double-push skating -- Leg+Hip: func= 5-6,  artic= 17.5  (range 14-21), desync= 1

  • walking -- Leg+Hip:  func= 1-2+,  artic= 5.5  (range 4-7)

  • running -- Leg+Hip:  func= 4,  artic= 7.5  (range 7-8)

  • cycling seated -- Leg+Hip:  func= 2-3,  artic= 4

  • cycling standing -- Leg+Hip:  func= 4-5,  artic= 7

  • skating on (non-short) skis with no poling -- Leg+Hip: func= 3,  artic= 9  (range 8-10)

  • classic striding on skis with no poling -- Leg+Hip only:  func= 3,  artic= 6.5  (range 6-7)

Details below under Compare with other Motions.

see also:  Summary of Results for all muscle moves of Entire body (including Upper Body moves)

Complexity of Leg moves in skating

normal-push skate stroking

major move "functions"

  • leg-sweep-outward : moves the foot sideways away from the other leg. Can use these moves: hip-abduction, medial-hip-rotation, ankle-pronation.

  • pelvis-twist : moves non-pushing hip forward ahead of pushing-side hip. Can use these moves: lumbar-spinal-rotation.

  • leg-radial-press : moves the ball of the foot away from the hip. Can use these moves:  hip-extension, knee-extension, ankle-extension.

sub-moves + "articulations"

There are 9-10 distinct muscle moves with distinct functional roles for hips and legs which are available to add forward-propulsion work in normal (non-double-push) skating:

pushing leg

simple advance with "lock-in"

These moves are in phases 1, 2, 3:

  • hip abduction

  • medial-hip-rotation

  • ankle pronation

  • hip extension

  • knee extension

  • ankle extension

  • next-hip-forward-rotation

recovering leg side-swing

two-way side swing -- with timing for reactive side-force

These muscles moves here below all act on the mass of the recovering leg while it is off the ground up in the air. They all occur during the Set-down phase 0, not Recovery phase R. In normal-push, the positive and negative work contributions from the leg side-swing moves during Recovery phase R are self-cancelling (acceleration versus deceleration).

  • hip abduction 

  • medial-hip-rotation  (not for ski-skaters, because the long ski tip gets in the way -- they can instead get a larger contribution from knee-extension, but that might exclude hip-abduction)

  • (small contribution)  lateral-ankle-rotation  (not for ski-skaters, because the long ski tip gets in the way)

  • (small contribution)  hip flexion  (because when next-hip-forward-rotation is used, this move in Set-down phase 0 has a sideways component)

  • (small contribution)  knee extension  (because when next-hip-forward-rotation is used, this move in Set-down phase 0 has a sideways component)

calculate leg+hip complexity

This measure of complexity depends on how you decide to count the moves: strictly or liberally -- we'll show both as a range.

Total propulsive moves available from legs and hips:

  • "simple" normal-push skating -- Leg+Hip:  func= 3,  artic= 10.5  (range 9-12)

  • skating on (non-short) skis with no poling -- Leg+Hip: func= 3,  artic= 9  (range 8-10)

For analysis of de-synchronization of timing of different moves, see page on compare complexity of motions of entire body.

double-push skate stroking

major move "functions"

  • leg-sweep-inward : moves the foot sideways toward the other leg. Can use these moves: hip-adduction, lateral-hip-rotation, ankle-supination.

  • leg-sweep-outward : moves the foot sideways away from the other leg. Can use these moves: hip-abduction, medial-hip-rotation, ankle-pronation.

  • pelvis-twist : moves non-pushing hip forward ahead of pushing-side hip. Can use these moves: lumbar-spinal-rotation.

  • leg-radial-press : moves the ball of the foot away from the hip. Can use these moves:  hip-extension, knee-extension, ankle-extension.

  • leg-in-air-behind-inward : if the leg is in the air behind the other leg, moves the ball of the foot toward the side of the other leg. Can use these moves: hip-adduction, lateral-hip-rotation, medial-ankle-rotation.

actually one of those move functions is used in two different phases (both in-push and main-push): leg-radial-press.

sub-moves + "articulations"

Double-push stroking has several more possibilities beyond the list for Normal-push:

pushing leg during main-push

simple advance with "lock-in"

These moves are made during main-push phases 1, 2, 3:

  • hip abduction

  • medial-hip-rotation

  • ankle pronation

  • hip extension

  • knee extension

  • ankle extension

  • next-hip-forward-rotation

pushing leg during in-push

simple advance with "lock-in"

These moves are made during in-push phases ip1, ip2:

  • hip adduction

  • lateral hip rotation

  • ankle supination

  • hip extension  (same kind of move as already in normal-push)

  • knee extension  (same kind of move as already in normal-push)

recovering leg side-swing

two-way side-swing, with timing for reactive side-force.

These muscles moves here below all act on the mass of the recovering leg while it is off the ground up in the air.

These moves here below are all in the Recovery phase R, not Set-down phase ip0. In double-push stroking, the positive and negative work contributions from the leg side-swing moves during Set-down phase ip0 are self-cancelling (acceleration versus deceleration).

  • hip adduction

  • lateral-hip-rotation

  • (small contribution)  medial-ankle-rotation

  • (small contribution)  hip extension  (because when next-hip-forward-rotation is used, this move in the Recovery phase has a sideways component)

  • (small contribution)  knee flexion  (on recovering leg in the air -- because when next-hip-forward-rotation is used, this move in the Recovery phase has a sideways component)

recovering leg forward-backward

with timing for reactive backward-force

In addition to reactive backward-force, the last two moves (knee-extension and hip-flexion) also make a contribution in overcoming increased air-resistance as they move the surface areas of the upper leg and lower leg with forward at a leg-recovery speed which is higher than the average speed of the overall surface area of the body through the whole stroke-cycle.

These muscles moves here below all act on the mass of the recovering leg while it is off the ground up in the air.

  • (small contribution)  knee-flexion  (during Recovery phase)

  • (small contribution)  hip-extension  (during Recovery phase)

  • knee-extension  (during Set-down phase)

  • hip-flexion  (during Set-down phase)

calculate leg+hip complexity

This measure of complexity depends on how we decide to count the moves: strictly or liberally -- I'll show both as a range. To calculate a single number I'll count each small or debatable move as adding 0.5 to complexity.

  • 7  from pushing leg during main-push

  • (range 3-5)  from pushing leg during in-push

  • 3.5  (range 2-5)  from recovering leg side-swing

  • (range 2-4)  from recovering leg forward-backward

Total propulsive moves available from legs and hips:

  • double-push skating -- Leg+Hip: func= 5-6,  artic= 17.5  (range 14-21), desync= 1

For analysis of de-synchronization of timing of different moves, see page on compare complexity of motions of entire body.

Compare Leg-muscle moves with other motions

These comparisons include Leg muscle moves only, not any Upper Body moves.

see also:  comparisons for all moves of Entire Body (including both Leg and Upper Body moves.

Walking

major move "functions"

  • leg-radial-press : moves the ball of the foot away from the hip. Can use these moves:  hip-extension, knee-extension, ankle-extension.

Just after set-down, the hip-extension move raise the mass of the upper body (building gravitational potential energy). After the ankle passes backward underneath its hip, the knee-extension move starts to execute, and the mass of the upper body falls forward (converting potential energy into kinetic energy). Finally just before lift-up, the ankle-extension move executes.

  • pelvis-twist : moves non-pushing hip forward ahead of pushing-side hip. Can use these moves: lumbar-spinal-rotation.

This move adds propulsive force by accelerating the mass of one side of the upper body forward relative to the currently pushing hip, and by increasing the speed (and thus force) of that side of the upper body against the resistance of the air.

Or there's a different way of looking at the leg-push: That the "origin" of the push through the foot is not its own hip, but the opposite hip joint -- so the pelvis-twist move contributes to the distance of that push by moving the pushing-foot-side hip backward relative to the opposite hip.

for making very long strides on flat ground, this function can also be used:

  • leg-kick-backward : moves the ball of the foot backward relative to the hip. Can use these moves: hip-extension, knee-flexion, ankle-extension.

but this move function is not used much in normal-stride-length walking, and not in walking up a steep hill.

another move function has slight benefit:

sub-moves + "articulations"

pushing leg
  • hip-extension

  • knee-extension

  • ankle-extension

  • lumbar-spinal-rotation (a.k.a. next-hip-forward-rotation)

  • knee-flexion

recovering leg forward-backward

There is no significant net positive contribution for reactive backward-force in walking with continuous ground contact.

These moves make their contribution by overcoming increased air-resistance as they move the surface areas of the upper leg and lower leg with forward at a leg-recovery speed which is higher than the average speed of the overall surface area of the body through the whole stroke-cycle. But at walking speeds this contribution is small.

  • (small contribution)  hip-flexion

  • (small contribution)  knee-extension

calculate leg+hip complexity

I choose to count the "small contribution" or "possible contribution" moves as adding 0.5 each to complexity.

Total propulsive moves available from legs and hips:

  • walking -- Leg+Hip:  func= 1-2+,  artic= 5.5  (range 4-7)

For analysis of de-synchronization of timing of different moves, see page on compare complexity of motions of entire body.

Running

major move "functions"

  • leg-kick-backward : moves the ball of the foot backward relative to the hip. Can use these moves: hip-extension, knee-flexion, ankle-extension.

The knee-flexion move applies direct propulsion work. (the ankle-extension move is not used) The hip-extension move raises the mass of the upper body, building gravitational potential energy for future propulsion work.

But this function and its knee-flexion move are not used in running up a steep hill.

  • leg-radial-press : moves the ball of the foot away from the hip. Can use these moves:  hip-extension, knee-extension, ankle-extension.

The hip-extension move is already executing as the ankle passes backward underneath its hip. Next the knee-extension move starts to execute, and the mass of the upper body falls forward (converting potential energy into kinetic energy). Finally just before lift-up, the ankle-extension move executes.

  • pelvis-twist : moves non-pushing hip forward ahead of pushing-side hip. Can use these moves: lumbar-spinal-rotation.

This move adds propulsive force by accelerating the mass of one side of the upper body forward relative to the currently pushing hip, and by increasing the speed (and thus force) of that side of the upper body against the resistance of the air.

Or there's a different way of looking at the leg-push: That the "origin" of the push through the foot is not its own hip, but the opposite hip joint -- so the pelvis-twist move contributes to the distance of that push by moving the pushing-foot-side hip backward relative to the opposite hip.

sub-moves + "articulations"

pushing leg
  • hip-extension

  • knee-extension

  • ankle-extension

  • lumbar-spinal-rotation (a.k.a. next-hip-forward-rotation)

  • knee-flexion

recovering leg forward-backward

with timing for reactive backward-force.

Also the first two moves also make a contribution in overcoming increased air-resistance as they move the surface areas of the upper leg and lower leg with forward at a leg-recovery speed which is higher than the average speed of the overall surface area of the body through the whole stroke-cycle.

  • hip-flexion

  • knee-extension

  • (small contribution)  ankle-flexion

calculate leg+hip complexity

Total propulsive moves available from legs and hips:

  • running -- Leg+Hip:  func= 4,  artic= 7.5  (range 7-8)

For analysis of de-synchronization of timing of different moves, see page on compare complexity of motions of entire body.

Cycling

major move "functions"

  • leg-radial-press : moves the ball of the foot away from the hip. Can use these moves:  hip-extension, knee-extension, ankle-extension.

  • leg-kick-backward : moves the ball of the foot backward relative to the hip. Can use these moves: hip-extension, knee-flexion, ankle-extension.

  • leg-radial-retract : tries to move the ball of the foot closer to the hip. Can use these moves: hip-flexion, knee-flexion, ankle-flexion.

Casual cyclists tend to focus on the first, but elite racers make use of all three.

Could also cover the pedaling stroke-cycle with three different functions, such as leg-radial-press, leg-kick-backward, leg-kick-forward -- or only two functions, leg-radial-press and leg-radial-retract. But the number of muscle sub-moves or "articulations" remains the same.

Normally the third move usually lifts only part of the weight of the leg and does not actually pull upward on the pedal. The remainder of the weight of the leg is raised by upward force from the pedal (applied by the leg-radial-press move by the other leg as downward force on other pedal).

But in high-force situations, like a quick acceleration, or climbing a short steep hill, sometimes the "leg-radial-retract" force exceeds the weight of the leg and resistance from the other leg's muscles, and there can then be some upward pulling force on the pedal.

standing

standing allows two additional move functions in the legs and hips:

  • leg-sweep-outward : moves the foot sideways away from the other leg. Can use these moves: hip-abduction, medial-hip-rotation, ankle-pronation.

  • pelvis-side-tilt

sub-moves + "articulations"

Bicycling while (quietly) seated has these propulsive muscle moves available in the hips and legs:

  • ankle-flexion

  • ankle-extension

  • knee-flexion

  • knee-extension

  • hip-flexion

  • hip-extension

But because the motion of the legs is strongly constrained in seated pedaling -- at the top by hips resting on seat, and at bottom by the fixed motion of the cranks -- the ankle-flexion and ankle-extension moves cannot add net positive work, because they have a range-of-motion competition with the other leg moves.

Indeed pedal-angle measurements from many elite racers shows negative ankle-extension in the downstroke and negative ankle-flexion in the upstroke. (We might call this "reverse ankling" or "anti-ankling".)

It is possible to design a seat-position / crank-length configuration in which the ankle moves would add positive work, but it is likely that such a configuration would result in lower total power to the pedals.

So for expert technique with a "normal" seat position and "normal" crank length, only 4 moves are available to deliver net positive work:

  • knee-flexion

  • knee-extension

  • hip-flexion

  • hip-extension

standing

moves for the three functions shared with seated pedaling:

  • knee-flexion

  • knee-extension

  • hip-flexion

  • hip-extension

Although pedaling standing is less constrained at the top than seated pedaling, it still seems that the ankle-extension and ankle-flexion moves are not used by expert cyclists -- indeed the negative ankle-extension on the downstroke might be even more pronounced.

moves for leg-sweep-outward function:

  • hip abduction

  • medial-hip-rotation

These moves are available to add positive work only if the bicycle is leaned from side to side so that the hip joint is substantial distance sideways from the seat, and no longer vertically above the pedals.

Perhaps it is also possible to get some net positive work from an ankle-pronation move, but this is uncertain. There may not be enough side-sweep range-of-motion available to get  positive work from all three different possible side-sweep articulations -- so this might be another case for bicycle pedaling where an ankle move is ignored because of range-of-motion conflict.

Actually even if limited to the two side-sweep moves above, there might be significant range-of-motion competition between them.

moves for pelvis-side-tilt function:

  • rocking the pelvis from side-to-side  (which moves each hip up and down)

It's not clear that elite racers actually use this move. It might be that if move of the arms pulling on the handlebar constrains upper body motion, then this move cannot add net positive work -- because of range-of-motion conflict with the leg-radial-press function. (i.e. there's only so much vertical range-of-motion available, so any part taken by the pelvis-rocking is stolen from the arms).

calculate leg+hip complexity

Total propulsive moves available from legs and hips:

  • cycling seated -- Leg+Hip:  func= 2-3,  artic= 4

  • cycling standing -- Leg+Hip:  func= 4-5,  artic= 7

For analysis of de-synchronization of timing of different moves, see page on compare complexity of motions of entire body.

Classic striding on skis

(also called "kick-and-glide" or "diagonal stride")

These are the Leg moves only -- not including Upper Body or Poling moves.

see also

The propulsive Leg+Hip muscle moves for Classic striding in cross-country skiing with no poles are similar to walking and running.

The Upper Body moves for Classic striding with no poling turn out to be different from walking, but similar to running.

major move "functions"

  • leg-kick-backward : moves the ball of the foot backward relative to the hip. Can use these moves: hip-extension, knee-flexion, ankle-extension.

  • leg-radial-press : moves the ball of the foot away from the hip. Can use these moves:  hip-extension, knee-extension, ankle-extension.

sub-moves + "articulations"

pushing leg

simple advance with "lock-in".

  • hip-extension

  • knee-extension

  • ankle-extension

  • lumbar-spinal-rotation (a.k.a. next-hip-forward-rotation)

  • knee-flexion

special case:  using climbing skins for backcountry ski mountaineering:

  • (possible some) ankle-flexion

In situations with very strong grip-friction between the base of a ski with a long "tail" and the ground, an ankle-flexion move during the early part of the leg-push might possibly be used to add propulsive work. This would be felt as a strong upward pressure of the top of the front half of the foot against the upper of the ski boot. This move does not work with a normal inline skate or ice skate or running or walking shoe, because those are too short out behind the ankle joint to provide sufficient leverage to transmit the force to the ground.

But we will not consider this in our measure of complexity for typical touring or racing situations of "cross-country" skiing.

recovering leg forward-backward

with timing for reactive backward-force.

Also the first two moves also make a contribution in overcoming increased air-resistance as they move the surface areas of the upper leg and lower leg with forward at a leg-recovery speed which is higher than the average speed of the overall surface area of the body through the whole stroke-cycle.

  • hip-flexion

  • knee-extension

  • (small contribution)  ankle-flexion

calculate leg+hip complexity

Total propulsive moves available from legs and hips:

  • classic striding on skis with no poling -- Leg+Hip only:  func= 3,  artic= 6.5  (range 6-7)

For analysis of de-synchronization of timing of different moves, see page on compare complexity of skiing motions of entire body.