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   goals for Leg Recovery

   physics of adding Work from Recovery moves

   simple Normal-push

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goals for Leg Recovery

do not waste time

Stroke-cycle time is precious for Power and Speed in skating. Time wasted during leg-recovery results in a reduction of rate of Power output (in Watts) from every other muscle move -- because Power depends on frequency, and time wasted in leg-recovery reduces turnover frequency.

do no harm ... to Set-down and Pushing

Key thing is not hinder the big Extension push. An important part of the Extension push is to "slice" or "carve" the foot forward (using the knee-extension muscles).

You can't slice the foot forward if the foot does not start backward. There's two ways to get the foot backward: Set it down in a backward configuration already, or move it backward (after setting it down not backward).

Either way, the implication is not to have substantial forward speed of the foot at Set-down.

If your strategy is to move it backward after Set-down, that will use up more of precious stroke-cycle time if the muscles must first slow and stop the forward momentum of the leg before starting the foot moving backward. Also the neuro-muscular control to suddently switch from forward to backward could have inaccurate timing or delays -- not what you want while your muscles are tired and you need to focus attention on other aspects of your skating situation.

(Exception: If choosing to use a backward-forward reactive-force strategy with the Pivot-Aim style of Normal-push, then forward swing of the leg could be helpful.)

Knee out behind versus close:  Therefore, avoid the approach of holding the knee out a ways behind -- because the tendency will be to swing it forward into Set-down.

If you do send the foot out behind during Recovery, start bringing it forward immediately, so its forward motion can be slower just before Set-down.

Or simpler, just don't send the knee so far backward at all during Recovery thru the air. Focus more on sideways motion. (Which also fits with the Finish of the Extension Push being aimed more sideways than backwards).

High versus Low: Recovering the leg higher, and holding it higher, tends to lead to more speed into Set-down, because of the assist from gravity. If you do bring the leg high in recovery, start bringing it downward immediately, so its motion can be slower just before Set-down.

Or simpler, just don't send the foot so high at all during Recovery thru the air.

Foot versus Knee: Bending the knee during recovery has two advantages: Relaxes the knee-extension muscles, and prepares for a bent knee at Set-down. Bending the knee tends to bring the foot backward and upward -- which seems to contradict the other points in this section. But the foot has much less mass than the rest of the leg, and it's easier for muscles to control the speed and direction of the foot moving into Set-down.

add propulsive work

The motion of the recovering leg thru the air can add propulsive Work (measured in Joules) -- which will add Power and speed to skating.

Making this happen is tricky -- because often the Work generated in one phase of a motion gets canceled out by another phase. Critical success factors are: clever selection of the motion, and careful timing synchronization.

see lots more detail under physics of adding Work.

help Set-down and first pushing phase

help start Sweep-Out move

The simple Normal-push style of skating starts by pushing directly sideways outward from underneath the hip, immediately after Set-down. If the leg and foot are already moving sideways thru the air just before setting down, they carry momentum into this initial phase. Also the neuro-muscular control is simpler and more reliable if the move is started before Set-down. Trying to start the move exactly at Set-down might be subject to timing inaccuracies or delays in the neuro-muscular control.

Bringing the foot a little further inward than necessary in Recovery provides the space needed for this outward move into Set-down.

help setting down inside + without pronation

Pointing the foot down or inward (by lateral rotation of the ankle joint) in Recovery for Normal-push:  I find it helps me then set down the foot without ankle-pronation. Or if my strategy is to set down the foot inside from underneath its hip, seems to help with that too.

Also makes my Normal-push recovery move more like my Double-push recovery.

physics of adding Work from Recovery moves

The motion of the recovering leg thru the air can add propulsive Work (measured in Joules) -- which will add Power and speed to skating.

Making this happen is tricky -- because often the Work generated in one phase of a motion gets canceled out by another phase. Critical success factors are: clever selection of the motion, and careful timing synchronization.

Different kinds of skating must use a different kind of recovery motion to succeed in adding propulsive Work:

  • simple Normal-push: from the sideways move of the leg into Set-down.

  • Pivot-aim Normal-push: from the forward move of the leg into Set-down.

  • Double-push: from the sideways move of the leg lifting up and across to the inside.

Simple Normal-push

For more on this kind of skating, see Simple outward aiming angle.

In Normal-push the move from Lift-up to Leg-Recovery cannot add net positive propulsive Work, because both its starting and its stopping are made with the pushing foot aimed at the same angle in the same direction.

But in the "simple" style of Normal-push where the foot is set down already aiming toward the outside, there is a way to add propulsive Work (measured in Joules) from the sideways component of the move from Recovery into Set-down.

The maximum amount of propulsive Work that can be added to simple Normal-push is roughly equal to the kinetic energy of the mass of the leg at the sideways speed of the foot just after Set-down -- maybe a little more or less, but not much more. 

So there's no purpose in bringing the foot and leg further inside toward the other leg than is sufficient to give enough space to easily accelerate the foot + leg up to the sideways speed they will have just after they are Set-down. The sideways speed just after Set-down is determined mainly by: (a) the aiming angle of the foot just after Set-down, (b) the turnover frequency, and (c) the skater's overall forward motion speed.

At "cruising" speed in non-high-force situations, typically the aiming angle is not very large away from straight forward, so the sideways speed just after Set-down is not large -- so there's no reason to bring the foot very far inside in its leg-recovery move.

In higher force situations like climbing up a steep hill, the foot typically lands aiming and gliding more out to the side, and the turnover frequency is typically higher, so the sideways speed just after Set-down is higher. So it makes sense to bring the foot a little farther toward the other side in leg-recovery, to provide enough distance to easily accelerate it to a higher sideways speed going into Set-down.

Note that the "farther toward the other side" is measured relative to where this foot is going to land on the ground -- not relative to wherever the other foot is already on the ground. Since the feet are typically farther apart when climbing a steep hill, it makes a difference how you measure it.

But what matters for the amount of added propulsive Work the speed just before and after Set-down. So if you don't use the extra sideways distance in leg-recovery to add more speed, then there's no benefit. And if you can accelerate the mass of your foot + leg quicker, than you can get by with a shorter sideways distance in recovery. If taking the extra distance in leg-recovery slows down your overall stroke-cycle turnover frequency, then it's likely a bad thing. Quickness is more important than distance.

Pointing the toe down in the Leg-recovery move -- or even pointing it inward toward the other side -- can add a little bit more propulsive Work without slowing down stroke-cycle time. Because then the move of pointing the toe back forward and outward going into Set-down, moves a little more mass sideways, and uses different muscles to do the work of accelerating it sideways.

But for Normal-push the benefit of this is minimal, because it's usually easy to get to the maximum Work from the move into Set-down by using other muscles. I still like to point the toe down because it seems to help me with other aspects of my Set-down configuration, and because it keeps me in practice to do it for Double-push.

Pivot-aim Single-push

See the note about Set-down timing subtleties for the Pivot-aim style of Normal-push, and the note about foreward-backward reactive force.

Double-push

For Double-push, the move going into Set-down cannot add propulsive Work, because the sideways speed of the foot just after Set-down will be in the inward direction, so any move started from Leg-Recovery toward the outside must stop its sideways motion before Set-down -- so the stopping cancels any added propulsive work from the starting. Then the sideways inward just after (and before) Set-down is slightly negative for propulsive Work -- but it's unavoidable it you want to get the large positive propulsive Work from making that inward push.

Therefore the move from Leg-recovery into Set-down can be a bit "lazy": its path and speed don't matter much -- provided it does not slow overall stroke-cycle frequency, and that the foot and leg are going into a strong inward-push at Set-down.

What does add propulsive Work in the leg-recovery move for Double-push is (1) starting and accelerating the mass of the leg + foot toward the other leg, away from the inward push being made by the other leg that was just Set-down; and (2) decelerating and stopping that Leg-recovery move while the other leg is making its outward push.

The amount of propulsive Work added is determined by the recovering leg's maximum speed sideways toward the other side during the Aim-switch. And that work is added to both the inward-push and the outward-push.

Unlike simple Normal-push, there is no limit on how much Work can be added in this way. The limit is how strong your muscles are for quickly accelerating the leg and foot sideways through the air . . . and in how good your timing is in having it hit maximum speed at the moment of Aim-switch, instead of sometime before Aim-switch.

A possible problem (which I have not seen in video) would be in starting and executing the leg-recovery move too early, so its sideways acceleration is already finished while the other foot is still aiming inward, so its speed is slower by the time the foot is aiming outward.

Some skaters might even have to learn to hold back the start of the leg-recovery move -- leave the foot "hanging out there" for couple of momemts after Finishing its main leg-push and lifting up off the ground.

Since the mass of the leg + foot, and the muscles used to move them are both different from the mass and muscles used for the torso-shoulder side-swing move, the timing of the leg-recovery move might be different from the timing of the torso-swing move. (As if Double-push were not already complicated.)

No simple "trigger" trick for timing this move (unlike torso side-swing): Have to check it in video.

Pointing the toe down in the Leg-recovery move -- or even pointing it inward toward the other side -- can add a little bit more propulsive Work, without slowing down stroke-cycle time. Because it moves a little more mass sideways away from the inward push being made by the other leg that was just Set-down, and uses different muscles to do the Work of accelerating it sideways.

But once the other (pushing) foot is aiming outward, this does not matter any more for propulsion in Double-push -- so can relax the ankle-rotation muscles and allow the foot in the air to point more naturally, and aim somewhat outward -- which helps prepare for an outward path into Set-down.

Simple Normal-push

see the discussion of the physics of adding propulsive Work from Recovery moves.

time duration

Especially for Normal-push (where the maximum propulsive Work from Recovery is limited), it is important to observe the amount of time spent in Recovery.

Simplest way is to count the number of video frames between lifting up off the ground to setting down on the ground again.

Serious speedskaters can practice quickness of Recovery, and measure their progress in development.

Can also count the number of frames for the entire stroke-cycle, and see what is the percentage of Recovery.

The amount of propulsive work added from torso side-swing and arm-swing moves is often higher if the foot is set down earlier (if it is alreadly aiming toward the side, not straight forward).

shortly before Set-down

Priority:  B-

Shortly before Set-down, the leg and foot should be more inward toward the other leg than they will be at Set-down.

For how far inward, see the discussion of the physics of adding propulsive Work. Usually it's not as far inward as the other leg.

Note that the "how far inward" is measured relative to where this foot is going to land on the ground -- not relative to wherever the other foot is already on the ground. The recovering foot moves toward the other foot, but for purposes of analysis you do not measure it relative to the other foot.

Whatever else happens in between lifting the leg up off the ground and getting to that inward position just before Set-down is not very important for propulsive Work -- unless it wastes stroke-cycle time.

Moving the leg further inward sideways than necessary does not add propulsive Work, but it might cost stroke-cycle time.

Note that sideways reactive-force moves (e.g. torso side-swing and arm-swing) in Normal-push usually generate a larger amount of propulsive Work if the foot is set down earlier, already aiming outward.

Pointing the foot downward or inward

Usually irrelevant for propulsive Work in simple Normal-push -- except it might add some in a high-turnover high-force situation: like climbing up a steep hill, or sprinting.

But it can help for non-propulsive reasons -- see under goals for Leg Recovery.

side view

see the discussion of the physics of adding propulsive Work from Recovery moves.

There's nothing much important for propulsive Work for simple Normal-push in the side view of the leg recovery.

Lots of speedskaters like to bend their knee -- perhaps it helps relax the leg muscles between pushes.

There's no advantage to the leg going further backward than necessary. What's important for propulsion is the side-to-side motion.

No reason why the knee cannot stay almost as far forward as the other leg. Seems like keeping the leg closer forward fits better with the Finish of its previous push being aimed more outward sideways than backwards.

For possible disadvatages to bringing the leg farther backward or upward see under goals for Leg Recovery.

Key things to watch for:

  • not holding the knee out backward or up high.

  • the foot moving smoothly and gently into Set-down and its move immediately following.

Pivot-aim Single-push

See the note about Set-down timing subtleties for the Pivot-aim style of Normal-push, and the note about foreward-backward reactive force.

Since the physics of getting any propulsive work from this style is completely different from the "simple" Normal-push, some of the leg-recovery motions and video observations will likely be different.

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Double-push

at Aim-switch of other leg

For this checkpoint, use the frame where the other (pushing) foot is aiming straight in the skater's overall forward motion diredtion -- neither toward the inside or the outside.

priority:  B

key observations should be:

  • foot positioned roughly underneath its hip.

  • foot and leg moving rapidly toward the side of the other (pushing) leg.

  • foot rotating its aim toward pointing downward and inward. (priority C)

Not:

  • foot already slowing down its sideways motion.

  • foot already pretty far over to its maximum position sideways inward relative to its hip.

For explanation and more details on these points, see the discussion of the physics of adding propulsive Work from Recovery moves.

? maximum sideways inward position of recovering leg

There's no "right" maximum sideways position in leg Recovery for Double-push.

It's good to practice bringing the recovering leg behind the pushing leg, but in endurance performance lots of very fast skaters move their leg only barely as far as the other leg -- or less.

Anyway what determines the amount of added propulsive Work is not the position of the recovering leg, but the speed in moving it sideways during the Aim-switch of the other pushing leg, as described under at Aim-switch.

The maximum sideways position is interesting only as an indicator of that speed. Even the foot-pointing configuration at the maximum is only indicator of the speed of rotation.

A problem with using maximum position as an indicator is that it does not say much about the timing of the maximum speed -- does not say whether the maximum sideways speed was reached during Aim-switch of the other leg versus before or after -- timing which is critical for the amount of propulsive Work (measured in Joules).

Trying to achieve a certain maximum position might result in taking more time in the stroke-cycle, which would be negative for turnover frequency and Power.

Also, holding the leg at its maximum position is counterproductive for Double-push.

For explanation and more details on these points, see the discussion of the physics of adding propulsive Work from Recovery moves.

side view

See the discussion of the physics of adding propulsive Work from Recovery moves.

Everything above under Side view of simple Normal-push applies to the Side view of the Double-push leg-recovery.

See more under goals for Leg Recovery.

Additional for Double-push

  • for the Extension in-push style, tt's more important to see the foot closer forward near the other leg shortly before Set-down, without much motion in Side view.

because the inward push is shorter than the outward push, so it's important to start the knee-extension move earlier, so the foot must be definitely backward soon after Set-down. So it's a danger to see the foot backward and  upward shortly before Set-down, because of the tendency for it to then swing forward.

  • pointing the foot downward -- or even inward -- is usually beneficial for Double-push, and should be visible in Side view

but the angle is more accurately seen in Front view -- see there for details.

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