A study on skating jumping power.

[supra]

http://iceskatingresources.org/Triple&QuadJumps.html

I thought it was a good read. Has lots of information in it.

[4711]

I came across it a couple of weeks ago, even for me as non-skater, it helped me visualize some of the more intricate elements.
(for the story)

[discombobulate]

Hey
Thank you for posting this. It's pretty helpful. As a student who just took physics, I like seeing it applied to skating! So cool

[Query]

I can't pretend to tell anyone how to do triple and quad jumps.

But, in terms of basic three dimensional rotational physics, it seems to me that there are at least four important elements to making efficient use of one's momentum that she didn't discuss.

1. If your axis of rotation changes its tilt during the jump, some of the angular momentum is wasted making that change. This means that you should balance your upper and lower body motions, and/or alter how close your arms and legs are vertically to the center of mass, so all the angular momentum is available to create the desired spin.

As an example, the statement that the number of rotations is equal to the time in the air times the average angular speed need not be correct, if the angular velocity during different parts of the motion are not aligned.

2. If you have extra vibrations or loose motions during the jump, some of the angular momentum is wasted on producing those motions. This is why you want a lot of stabilizing muscle use to prevent these extra motions. Of course, too much stabilizing muscle use, especially if it is at the wrong time stages during the jump and/or at the wrong parts of the body, will interfere with creating the linear and angular momentum in the first place, and will make internal injury more likely.

3. She has not explicitly discussed the fact that some of the angular (rotational) momentum is converted from linear (straight line) momentum, due to interaction with the ice. This means that it helps to have a lot amount of linear momentum prior to the jump, and you can interact with the ice in a manner that efficiently converts some of the linear to angular momentum (such as creating friction on the side of the blade that you are spinning towards).

Edit: Perhaps skidded jumps alter this - i.e., the conversion to angular momentum may also be accomplished by rotating the foot into the direction of the spin, so that the forefoot drag accomplishes the same purpose?
4. Needless to say, since it is expected that one "check" the rotation after the jump, you need a way to interact with the ice that reconverts much of the angular momentum back to linear momentum.

----

Maybe these elements so elementary and obvious that the author believes they need not be mentioned, at the elite training levels that the article is aimed at.

But at the much lower levels of spinning and jumping that many of us struggle at, these elements make a big difference, and may be at least as important as the strength training that the author discusses in such detail.

Edit: BTW, stabilizing muscle use may also involve strength training.

[Query]

Two other points:

5. Some of the same vibrations and loose motions mentioned in 2 above may cause a rocking motion that cuts back on speed and linear momentum while the blade is still on the ice.

6. I am not sure that I am interpreting the way that jumps are scored correctly, but as near as I can tell, the amount of net in-air rotation is not measured on the body as a whole, but is measured on the foot, or more precisely the boot (since that is what we see), about the vertical axis, from just after take-off to just before landing.

It appears to me that televised skaters in the ISU Grand Prix competitions deliberately pre-rotate their foot (or more precisely, the exterior of their boot, since that is what we see) against the jump spin direction prior to take off, and in the jump spin direction prior to landing. Even for an inflexible person like me, that increases the available foot rotation by almost 90 degrees (1/4 rotation), frequently sufficient to affect scoring. On a hyper-mobile athlete, like many skaters, more rotation is likely to be available this way.

Presumably such rotation occurs primarily in the hip joint, but a significant amount of rotation is also available in the foot, ankle and knee joints. It is my imperfect understanding that excess rotation in ankle and knee joints may be problematical to long term joint health, particularly in hyper-mobile athletes who are inclined to have dislocations or injuries of ligaments and joint capsules. But it is conceivable that a competitive freestyle or pairs skater might decide that it is worth it.

[discombobulate]

^ Very insightful! Thanks for your imput.
btw, you are interpreting the jump scoring correctly 

2. If you have extra vibrations or loose motions during the jump, some of the angular momentum is wasted on producing those motions. This is why you want a lot of stabilizing muscle use to prevent these extra motions. Of course, too much stabilizing muscle use, especially if it is at the wrong time stages during the jump and/or at the wrong parts of the body, will interfere with creating the linear and angular momentum in the first place, and will make internal injury more likely.

Why do you say that too much stabilizing muscle could interfere with the angular momentum?
Do you think that costumes can cause levels of vibration that could interfere with jumps?

[Query]

Edited

>btw, you are interpreting the jump scoring correctly

Watching the recent Grand Prix performances, I see that the body does stay fairly well aligned with the foot. I don't think they take foot rotation relative to the torso to anything close to 90 degrees. It has to be much more subtle to look good.

As an example at a much lower athletic level, I can't imagine anyone appreciating a half-rotation jump (like a waltz jump) in which no torso rotation occurs in the air, but the rotation is simply obtained by hopping from foot-to-foot in 180 degree turn-out (spread eagle-like position, torso facing sideways). Just as many people don't appreciate Mohawks that depend entirely on 180 degree turn-out in place of on-ice rotation.

>Why do you say that too much stabilizing muscle could interfere with the angular momentum?

Basic physics. Stabilizing muscles, by definition, interfere with motion. For example, if you contract muscles next to the skin, they press down on the inner layers of body tissue, creating friction between them. That eliminates excess vibration, but the body's muscular-skeletal system isn't isolated enough to control vibration without slowing down desired motions, wasting energy and momentum.

It's called "moving with resistance".

And the extra friction also creates abrasion. The teacher of a Dance Kinesiology class I took at the University Of Maryland emphasized that "over-control" (what we are talking about) increases wear and tear on the body, and reduces range of motion (flexibility).

>Do you think that costumes can cause levels of vibration that could interfere with jumps?

If you had heavy rope tassels, they must absorb some momentum, but I've never worn that sort of thing and don't know whether it is important.

If I wear a heavy jacket, or a loose jacket, it adds a lot of angular momentum that slows down my spins. But I guess "real" figure skaters wear less, and this might not be so much of an issue.

Anyway, like a lot of things, it is a compromise:

Heavy boots store angular momentum, but also require more energy to lift and move.

A retired master said that Evan Lysacek said that he wanted heavy boots to store more angular momentum for jumps. Yet many skaters tell me they get less tired skating with much lighter boots.

In any event, the motions of the foot are better controlled than uncontrolled motions of the body and loose attachments.

I'm sure that long hair is involved in angular momentum transfer too - but it too can perhaps be controlled, and it adds a beautiful artistic effect. I love the way many ladies spin out their ponytails during fast spins.

[discombobulate]

I haven't mastered skating with my hair down haha. but I do like how it looks


I could see how heavier skates might help. It would be fun to try elements with ankle weights ontop of your skates 

Edited

>btw, you are interpreting the jump scoring correctly


>Why do you say that too much stabilizing muscle could interfere with the angular momentum?

Basic physics. Stabilizing muscles, by definition, interfere with motion. For example, if you contract muscles next to the skin, they press down on the inner layers of body tissue, creating friction between them. That eliminates excess vibration, but the body's muscular-skeletal system isn't isolated enough to control vibration without slowing down desired motions, wasting energy and momentum.

It's called "moving with resistance".

And the extra friction also creates abrasion. The teacher of a Dance Kinesiology class I took at the University Of Maryland emphasized that "over-control" (what we are talking about) increases wear and tear on the body, and reduces range of motion (flexibility).

I see what you're saying about how stabilizing muscles limit movement, however I do not understand how stabilizing muscles/over-control wears out the body, if (only?) ROM, and momentum are affected.
Are you talking about wear and tear to tendons/ligaments or muscles or joints in general?

p.s. I would LOVE to take that class 

[Query]

Are you talking about wear and tear to tendons/ligaments or muscles or joints in general?

About all of those. Greater pressure means more wear on everything that moves against anything else.

BTW, that doesn't mean dancers don't ever move with resistance. Ask a ballet dancer to let you try to move her/his arm.

p.s. I would LOVE to take that class

Many aspects of the class were inapplicable to me, because I am inflexible rather than super-flexible. (Hypo-mobile rather than hyper-mobile.) Most of my injuries have been muscle pulls ("muscle strains") and bone fractures which were probably caused by excess tension from tight muscles. I have never had a full or partial dislocation or ligament/joint capsule sprain, and my only instance of cartilage wear occurred due to improper knee alignment during jump landings and shoot-the-duck.

But it is hard to find classes on how not to hurt yourself during athletic activities that apply specifically to you.

Many College or University dance programs have a class by some name on injury prevention for dancers. The department may or may not allow non-majors and non-College age people to take it. Regardless, check the textbooks those courses use.

E.g., my teacher, Laura Cox, favored

  Blandine Calais-Germain, Anatomy of Movement
  Blandine Calais-Germain, Anatomy of Movement: Exercises

not

  Daniel D. Arnheim, Dance Injuries.

You might also look up rsk8d's posts on this forum, and her www.sk8strong.com for stuff specific to skating, and her competitor Kat Arbour's (Ice Dynamics)

  Strength Conditioning and Injury Prevention

and my website on falling gently.