Ken Roberts

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 ] 

 


Introduction

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.

Why this list matters

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.

  • Develop -- Each specific muscle needs to have its endurance and speed and strength developed through appropriate training exercises, in order to make its best contribution to total propulsion power.

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.

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

  • ankle extension in Phase 3b [ see more below ]. This makes a valuable contribution, close to ground-contact so there's little transmission ineffeciency.

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.

  • ankle pronation in Phase 1 [ see more below ] -- makes its contribution close to ground-contact so there's little transmission ineffeciency.

Complexity of skating Leg moves

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.

Leg + Hip muscle moves

These muscle moves are available to add forward propulsion power in skating:

Side-of-leg-Out moves

 

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.

 

Extension moves

 

(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)

 

Advance-Next-Side moves

 

(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.

 

Recovering-Leg reactive-force moves

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.

forward-backward recovering-leg moves

  • 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.

Normal-Push stroking with "angle switch":

(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?

Normal-push stroking with a "hop":

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.

implications for Normal-push

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.

implications for Double-push

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.

compare normal-push versus double-push

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.

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:

Inside-of-leg-In moves (dp)

 

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).

 

Extension moves (dp)

 

 

 

Advance-Next-Side moves (dp)

 

(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.

 

Recovering Leg reactive-force moves (dp)

 

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.

 

more . . .

see also

other muscle groups

compare with other sports

related topics