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front view or foot-aim view at Finish

some of these checkpoints are better viewed from the "foot-aim" view (in the line through heel and toe).

See key timing relationship between Finish of one leg and Set-down of the other.

ground contact to hip relationship: This is determined mainly by other observations. See more further below.

knee - ankle - ground relationship

priority:  B-

See discussion of ankle-pronation on the Midway page.

Most of the analysis for Finish is the same as for Midway.

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ankle - knee - hip relationship (front)

priority:  A-

view: best observed in Foot-aim view, but Front view should be OK.

See discussion of medial hip-knee rotation on the Midway page.

Medial hip-knee rotation is normally bad at the Finish, because it's a sign that the knee joint is not close to full extension.

standard-form perceptual check

Straight line in foot-aim view thru ankle + knee + hip.

simple Normal-push

Straight line in foot-aim view thru ankle + knee + hip.

Double-push

Straight line in foot-aim view thru ankle + knee + hip.

At the finish of the in-push, any medial hip-knee rotation or lateral hip-knee rotation observed would be bad for propulsive Work.

pelvis hips side-tilt

priority: B (or A)

B for having the hips roughly at the same vertical level, priority A for not having the non-pushing hip significantly lower than the hip of the leg finishing its push.

view: best observed in front view, not foot-aim view.

There are three approaches to "pelvis hips side-tilt":

  • tilt pelvis sideways slightly toward the pushing leg during its final push: The advantages moving the pushing hip lower are that (1) the percentage of the push which is along the ground surface and so directly propulsive is higher, and less of the push is aimed down into the ground; and (2) the horizontal distance of the push is slightly longer.

  • keep pelvis + hips level at all times: The advantage of this is that it's simple, and it makes sure the skater is not doing something wrong with timing of pelvis side-tilt.

  • tilt pelvis sideways away from leg-push during its final phase: The advantages of this are: (1) more fully engages the big gluteus maximus muscle for hip-extension push (more so in Double-push where there are two leg-pushes in a row which can benefit from this position); and (2) can put more force + quickness into the torso-shoulder side-swing move.

My view from these arguments and from looking at elite racer videos is first, that the degree of tilt if any should be small -- so "roughly level" is a helpful approximation. Second, that serious skaters can develop the appropriate muscles for pushing more out toward the side, while the advantages of having a lower pushing hip are simple and irrefutable -- so likely it's worthwhile to try to move the pushing-side hip lower.

At Finish this implies that the hip of the pushing leg should not be significantly higher than the other hip which is being set down.

standard-form perceptual check

The approach that makes sense to me for educating percerption is to have two perceptual checks for this: one for staying level with no tilt, and one for moving to maximum tilt:

(a) Pelvis should be level: both hips at the same height off the ground.

(b) Pelvis should be tilted sideways toward side of Set-down.

simple Normal-push

Pelvis should be tilted sideways away from the leg-push (or level):  Hip of the pushing leg should be higher than the other hip being set down (or level with it).  But the pushing hip at its Finish should definitely not be lower than the other hip.

Double-push

Pelvis should be slightly tilted sideways away from the leg-push:  Hip of the pushing leg should be higher than the other hip being set down.

Then as the inward push of the other leg starts, the amount of sideways tilt should be getting larger, and it reaches maximum somewhere during the In-push -- tilting toward the side of the In-pushing leg. Then during Aim-switch it is moving back toward tilting the other way, but it's position is not tilting toward the outside usually until just before the Finish of the main outward leg-push.

But it would likely be advantageous to get the pelvis tilting sideways outward farther earlier in the main outward push.

hip - torso-shoulder relationship

priority: B  (or A)

This is a priority B if the question is between gaining power from a torso-shoulder side-swing move or not gaining. It's priority A if the skater is actually losing power due to mis-timing of torso-shoulder motion.

view: best observed in front view, not foot-aim view. 

see more discussion on the Set-down page.

standard-form perceptual check

if practicing torso-shoulder side-swing style:  Position of shoulders should be roughly centered over hips (ideally somewhat away from the side of the leg which is finishing) -- and moving quickly (relative to the hips) across to the side of the set-down.

if practicing the "quiet upper body" style: Shoulders centered over hips, chest facing straight forward.

simple Normal-push

Position of shoulders should be roughly centered over hips (ideally somewhat away from the side of the leg which is finishing) -- and moving quickly (relative to the hips) across to the side of the set-down.

Double-push

Shoulders roughly centered over hips, and not moving (much) sideways -- is what is usually seen in the fastest inline speedskaters in videos around 2004-2006.

What physics says might add more propulsive Power (in Watts) would be to have the shoulders somewhat off to the side away from the set-down, and not moving at all (relative to the hips).

see more discussion on the Set-down page.

hand - arm - shoulder relationship

priority: C

This is priority C if the question is between gaining power from an arm-swing move or not gaining. It's priority B if the skater is actually losing power due to mis-timing of arm-swing motion.

view:  best observed in front view, not foot-aim view. 

If arm-swing is not being used to add propulsive Power, then this observation can be whatever fits with or helps other aspects of the skater's motion -- e.g. balance or rhythm.

If swinging the arms and hands from side to side is being used to add propulsive Power, then the observations should be like for the position and motion of torso + shoulders under hips - torso-shoulder relationship -- e.g. for simple Normal-push, arms roughly in front of body, perhaps a little to one side -- but not way off to one side or the other, and moving definitely toward the set-down side.

If swinging the arms and hands forward and backward is being used to add propulsive Power, then the observations should be different from that.

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side view at Finish

 

toe - ankle - knee relationship

priority: A-

intro: The toe-ankle-knee angle is the key measure of the ankle-extension move. Long coaching tradition from before the success of klap-frame ice speedskates said that the heel should stay down all the way through the Finish.

This configuration was optimal based on the physics of ice skating on a non-klap frame, because pushing thru the ball of the foot increased pressure unevenly toward the front of the ice blade, which greatly increased friction.

But nowadays with the newer skating gear (inlines, cross-country ski-skating, and ice klap-skates), the physics is different, so fast skaters in the "final final" phase of their leg-push often use their ankle-extension muscles to add a little propulsive work by pushing the ball of the foot down to in increase their leg-extension distance.

The klap-frame tends to distribute push-force more evenly along the blade, even if the push is thru the ball of the foot. For cross-country ski skating, the binding is essentially a "klap" design, and the camber (flex shape) of the ski is designed to have low gliding friction with pressure thru the ball of the foot.

Inline skates: When the push is finished thru the ball of the foot in normal non-klap frame on inline skates, the push force is transmitted to the ground thru a single wheel, the front wheel. Transmitting push-force plus body-weight thru a single wheel has higher rolling friction than transmitting thru four wheels, but the increase is nowhere near as big as with uneven forward pressure on an ice blade. On non-klap ice speedskates, the large increase in friction outweighs the additional work from ankle-extension, but on inlines the gain in propulsive work from the ankle-extension move usually outweighs the loss from the small increase in rolling friction.

I suspect that usually the unconscious neuro-muscular control module in the brain takes care of this ankle-extension move without the skater's conscious mind being aware of it -- because it's a "natural instinct" from walking and running. I suspect that usually it is counter-productive for the skater to think consciously about it (see "the danger" below). 

The danger is that a skater trying to add ankle-extension to their push will instead substitute ankle-extension  for knee-extension. This is a bad trade, because the knee-extension muscles are bigger and usually better trained for propulsive work.

So many coaches think it's better to direct the conscious attention of the skater to moves or rhythms which the unconscious muscular control module is not so good at -- like the "forward slice" of the foot driven by the knee-extension muscles.

Full knee extension alone is better than full ankle extension alone -- because the knee-extension muscles in most athletes can sustain a higher power output than the ankle-extension muscles. (But even better is full knee extension plus good ankle extension.)

Even though with modern equipment the advice of "push thru the heel all the way thru the Finish" is no longer optimal in the physics, it's usually still good advice to give to the skater's conscious mind.

Implication for observation + analysis:

When large ankle-extension is observed (toe-ankle-knee angle much larger than 90 degrees), be extra careful to check the knee-extension (ankle-knee-hip) angle. Make sure that the knee joint is close to straight at the moment of lift-up. If the knee joint is close to straight, than large ankle-extension is good. If knee joint is not close to straight, then the large ankle-extension is bad.

Elite-aspiring racers: There might be a few cases where an accomplished racer is using less ankle-extension work than is optimal for maximum speed + power. Perhaps they took the good advice about "push thru the heel" a little too literally, and went too far in retraining their unconscious muscle control module to override the natural instinct from walking and running. Comparing video observations toe-ankle-knee angle with the world's fastest could be a way to check for this. (Good side-view video segments of Pascal Briand and Joey Mantia have been available publicly or at a reasonable cost). But of course it's not enough to copy the angles of the fastest skaters -- also must develop the specific strength + endurance of the ankle-extension muscles.

Pitfall: When the coach observes significant ankle-extension ("toe flick"), it's easy to assume that the skater must have a problem with not using full knee-extension. But that's not always true, so the coach must take the second step of observing specifically the knee-extension -- see ankle-knee-hip relationship.

Too small an angle?  Observation of a toe-ankle-knee angle significantly less than 90 degrees is also not good, because it's a sign that the skater achieved neither the benefit of full knee-extension nor the benefit of solid ankle-extension.

Avoiding ankle-extension is not the objective. The true goal is to increase knee-extension work. Focusing on negative advice like "toe-pushing is bad" could have a negative result that the toe-flick is removed but without substituting anything better. This video observation is a sign of a problem like that.

More versus Less in what situations?  Typically higher-force skating situations (e.g. starting sprint, climbing a steep hill) should show less ankle-extension at the moment of lift-off, while lower-force situations (e.g. constant speed cruising on gentle terrain) will show more ankle-extension.

This is because higher-force situation call for more emphasis on the highest force muscles, which for most athletees is hip-extension (e.g. gluteus) and knee-extension (e.g. quadriceps). Ankle-extension (e.g. calf) muscles are typically somewhat strong -- but not as strong as those. So in higher-force situations the ankle-extension joint tends to emphasize more stable transmission of force + propulsive work from those bigger muscles, less on forceful motion of its own.

standard-form perceptual check

toe-ankle-knee angle roughly 90 degrees.

inline: heel wheel still down in contact with the ground: Heel and toe lift off the ground together.

ice (klap-skate): heel of boot down in contact with blade assembly.

ice (classic non-klap): rear of blade still in contact with ice. Rear and front of blade lift off ground together.

snow skating ski: heel of boot still down in contact with top of binding.

simple Normal-push

toe-ankle-knee angle somewhat greater than 90 degrees: heel of boot somewhat up relative to toe.

Angle of only 90 degrees (or less) could be a sign of having missed the opportunity to add some propulsive work from the ankle-extension muscles -- provided that the ankle-knee-hip angle is almost straight.

Except that non-klap ice speedskates should have the heel down at moment lift-off, so rear and front of blade lift off ground together -- toe-ankle-knee angle roughly 90 degrees.

Double-push

At Finish of main outward push:  toe-ankle-knee angle somewhat greater than 90 degrees: heel of boot somewhat up relative to toe.

but at finish of In-push, normally heel should be down.

ankle - knee - hip relationship (side)

priority: A+

Knee joint should be extended to almost straight. The feeling of this typically includes a feeling of "slicing" or "carving" the foot forward.

If having trouble finding enough strength to get the knee to almost straight, normally the best response to set down the foot with the knee in a position closer to already straight (less knee-flexion, less knee bend) -- rathen than for "settling for less" than full extension.

Pitfall: Substituting ankle-extension for knee-extension. This is a bad trade, because the knee-extension muscles are bigger and usually better trained for propulsive work.

standard-form perceptual check

Knee joint should be extended to almost fully straight.

simple Normal-push

Knee joint should be extended to almost fully straight.

Double-push

Knee joint should be extended to almost fully straight.

For those using the "emphasize higher turnover frequency from the big leg-extension muscles" strategy of Double-push, the same observation applies to the finish of the In-push.

pelvis hip rotation

priority: B-  (or for climbing a steep hill: A)

Rotation of the pelvis about the axis of the spine is a key determiner of the "gearing" of skating, especially for climbing hills. It can also add a little propulsive Work.

see discussion on Set-down page.

 

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more on Finish

ground contact to hip relationship (front view)

What's of particular interest in the Finish is the height of the hip joint above the ground. For more detail on the implications of how far the hip drops, see this note.

The angle of the line from hip to ground-contact is not directly relevant, but useful as a secondary check . . .

The angle that the line between pushing hip and ground contact tilts away from vertical is fully determined by other factors most of which are directly relevant to propulsive Work: (a) how low the pushing hip is allowed to drop before the other foot lands and supports the weight of the upper body, (b) far out to full extension the knee-extension and ankle-extension moves go, and (c) how much ankle-pronation and medial-hip-knee-rotation is used. The more of each of these factors (other things being equal), the more the propulsive sideways range-of-motion in the leg-push.

Ankle-pronation increases the propulsive range-of-motion, provided its sideways motion is transmitted to the hip by stability in the hip-abduction and medial-hip-knee-rotation moves.

Ankle-extension (a.k.a. as "plantar flexion") substantially increases the propulsive range-of-motion of the leg-push. Those who insist on keeping their heel down to the very end of the stroke miss out on some propulsive distance. There's a reason why winning ice speedskaters use klap-skates, and why winning ski-skate racers on snow use a binding design that allows a "klap" motion. Inline speedskaters don't need klap-frames, because they can just push thru the toe-wheel even with a standard non-klap frame.

Most accurately observed in Foot-aim view, since what determines the amount of propulsive Work is the distance of motion along the surface of the ground perpendicular to the aiming direction of the foot.

This is different from torso-shoulder side-swing and arm side-swing where the amount of propulsive Work is determined by the speed of motion perpendicular to the skater's overall forward motion -- therefore those are most accurately observed in Front view.