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Thread: Some scientific analysis of Mao's 3A

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    Dreaming and dancing Bennett's Avatar
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    Some scientific analysis of Mao's 3A

    I read an interesting article on jumps. According to Yasuo Ikegami, Prof of Sports Biomechanics at Nagoya Univ (a top-tier research univ in Japan), the hangtime of Mao's 3A in the air is 0.45 sec in comparison to Miki's quad, 0.58 sec, and Yukari's 3A, 0.55 sec. A 10% increase in body height results in a 20% more difficulty in rotating a jump. Mao has grown 20 cm since she was 13 yrs old. Her hangtime was 0.55 at that time. So it has decreased by 0.1 second since then. Her personal trainer says she now compensates the decrease in hangtime by physical training to rotate faster.

    http://vancouver2010.nikkansports.co...02-581814.html

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    Quote Originally Posted by Bennett View Post
    I read an interesting article on jumps. According to Yasuo Ikegami, Prof of Sports Biomechanics at Nagoya Univ (a top-tier research univ in Japan), the hangtime of Mao's 3A in the air is 0.45 sec in comparison to Miki's quad, 0.58 sec, and Yukari's 3A, 0.55 sec. A 10% increase in body height results in a 20% more difficulty in rotating a jump. Mao has grown 20 cm since she was 13 yrs old. Her hangtime was 0.55 at that time. So it has decreased by 0.1 second since then. Her personal trainer says she now compensates the decrease in hangtime by physical training to rotate faster.

    http://vancouver2010.nikkansports.co...02-581814.html
    Interesting stuff, but I don't think Mao has grown 20 cm since she was 13. She has been the same height since age 16 (163 cm) meaning she grew 20 cm in 3 years, which is 7 inches. If she is 5'4" now was she really only 4'9" when she was 13? At 15 she was 5'2" meaning she would have grown 5 inches in 2 years, and has only grown 2 inches in the past 4 years, and hasn't grown much at all in 3 years. I don't think her struggles with the 3a are due to a recent growth spurt...

    Another thing, Mao is only a cm or two taller than Miki

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    Dreaming and dancing Bennett's Avatar
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    Quote Originally Posted by silverlake22 View Post
    Another thing, Mao is only a cm or two taller than Miki
    The prof also divides jumpers into two types: 1) Those who jump high and 2) those who rotate fast, and he says that Mao is the latter type.

    Although no mentioning in the article, I would think that Miki would be the former type. Miki is more powerful than Mao regardless of the body height. I feel that her lutz, for example, goes up very high in the air.

    Midori Ito may be the prime example of the former type. Midori's 3A is so powerful, has amazing height and distance, rotates slowly, and finishes rotation comfortably before landing. It's just amazing.
    Last edited by Bennett; 01-03-2010 at 12:49 AM.

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    A very interesting thread. A couple of comments.

    Mao and Yuna have always appeared to be the same height even when ISU or Wikipedia showed them at different heights. It would seem to me that Mao and Yuna have grown considerably in the past 2 years.

    On jump height and spin speed, it would also seem to me that height and therefore additional jump time would provide the jumper with more option/ability to correct or save an imperfect jump. The shorter jumping time Mao has right now maybe the primary reason her success is so inconsistent. Also, the anxiety of the moment (big events) would have a larger impact on a jump requiring greater spin speed and less air time. Meaning large muscles vault more (and give more time) when anxiety goes up whereas smaller muscles dealing with timing and spin are likely to perform more poorly when anxiety goes up.

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    Quote Originally Posted by Ptolemy View Post
    Mao and Yuna have always appeared to be the same height even when ISU or Wikipedia showed them at different heights. It would seem to me that Mao and Yuna have grown considerably in the past 2 years.
    Currently on wikipedia, Mao is listed as 163 cm and Yuna is listed as 164 cm, so they are both about 5'4" which is average height for a woman. I think they are this height and not taller if you look at this picture of them with 5'2" Joannie Rochette: http://www.zimbio.com/pictures/vGNse...LSwv/Yu-Na+Kim

    Another thing is I don't think Mao has grown much in the past two years because she is also the same height as her sister, Mai, who is also listed as 163 cm. They appear to have been the same height for a while.

    2007- http://cache.daylife.com/imageserve/...EJ013/610x.jpg

    2009- http://18.media.tumblr.com/oAHKGjfZP...h0d1o1_400.jpg
    http://6.media.tumblr.com/oAHKGjfZPq...h0d1o2_250.jpg
    http://farm4.static.flickr.com/3524/...683f86b7b5.jpg

    Depending on the picture/angle Mao or Mai can both look taller/shorter than the other but in all cases they are very close in height, less than an inch apart, and look to be nearly the exact same height.

    Here is a picture of Mao, Yuna, and Carolina Kostner from 2008. Carolina is listed as 169 cm (5'6"- 5'7") and looks about 3 iinches taller than Mao and Yuna, maybe more. I wouldn't be surprised if Carolina is taller than listed or if Mao/Yuna are shorter. http://www.japanskates.com/bios/Mao/MaoBio11.jpg

    Finally, here is a picture from a show this summer,
    http://farm3.static.flickr.com/2503/...6ec201b7a2.jpg Mao and Miki are standing next to each other and appear to be very much the same height, Mao just slightly taller. Miki is listed as 162 cm so I think Mao's current listed height is about right.

    From the looks of things, Mao is between 5'3" and 5'5", most likely right about 5'4", and has been this height for about 2 or 3 years. I have heard from people who have met Mao in person that she is very tiny.
    Last edited by silverlake22; 01-03-2010 at 08:33 AM.

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    End subjectivity,reduce PCS, fix the COP! schiele's Avatar
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    Quote Originally Posted by Bennett View Post
    The prof also divides jumpers into two types: 1) Those who jump high and 2) those who rotate fast, and he says that Mao is the latter type.

    Although no mentioning in the article, I would think that Miki would be the former type. Miki is more powerful than Mao regardless of the body height. I feel that her lutz, for example, goes up very high in the air.

    Midori Ito may be the prime example of the former type. Midori's 3A is so powerful, has amazing height and distance, rotates slowly, and finishes rotation comfortably before landing. It's just amazing.
    Whatever the correct version of Mao's height growth, I am pretty certain what Bennett here explained is accurate for Mao's 3 Axel. I remember Nicky and Chris from British Eurosport mentioned a couple of times that the reason Mao can get her 3 Axel is because she rotates it very fast despite the lack of height and time spent in the air (if they say so, I'll believe it. )
    Midori Ito's 3 Axel was monsterous in terms of height and distance.. Same goes for Harding I think..

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    Quote Originally Posted by schiele View Post
    Whatever the correct version of Mao's height growth, I am pretty certain what Bennett here explained is accurate for Mao's 3 Axel. I remember Nicky and Chris from British Eurosport mentioned a couple of times that the reason Mao can get her 3 Axel is because she rotates it very fast despite the lack of height and time spent in the air (if they say so, I'll believe it. )
    Midori Ito's 3 Axel was monsterous in terms of height and distance.. Same goes for Harding I think..
    You are probably right. Mao does rotate quickly. I think Miki would be another example of a jumper with big height and distance, allowing her to do the quad, as opposed to speed like Mao. Usually little girls are known for being able to rotate fast and that is why they often lose the harder jumps when they grow. It's amazing that Mao can still rotate that fast.

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    Beliver in Sasha's Perfect Program Tinymavy15's Avatar
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    Quote Originally Posted by silverlake22 View Post
    You are probably right. Mao does rotate quickly. I think Miki would be another example of a jumper with big height and distance, allowing her to do the quad, as opposed to speed like Mao. Usually little girls are known for being able to rotate fast and that is why they often lose the harder jumps when they grow. It's amazing that Mao can still rotate that fast.
    Yes, but she used to be more of a high jumper. Watch the videos of her skating as recently as 2008 worlds and her jumps soar through the air. I think this was helped by the fact that she entered them with more speed. Mao was forced to train herself to rotate fast because she no longer gets the height.

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    I like scientific stuff, that's a very intersting study!

    Quote Originally Posted by Bennett View Post
    A 10% increase in body height results in a 20% more difficulty in rotating a jump.
    I knew the height would make jumps more difficult, but didn't expect such a huge impact. This would make me appreciate taller skaters more.

    Considering the fact that Evan is 15% taller than Nobunari, his height would cause 30% more difficulty in rotating a jump than Oda!

    On NBC's Olympics page, Evan talks about his frustration with his height:
    Growing up I would grow three, four, five, and one year six inches in a year. [I'd have to] learn how to work my new legs and my new arms and the jumps didn't feel the same, the spins didn't feel the same and so I had to relearn almost all my elements. I wanted to be short.
    So Kudos to him for his hard work!

    Mao grows a few inches in the past years, but not extraordinarily tall as Evan, so if Evan can still improve his 3Axel, so can Mao. Good luck to both!

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    Quote Originally Posted by ae9177 View Post
    I like scientific stuff, that's a very intersting study!



    I knew the height would make jumps more difficult, but didn't expect such a huge impact. This would make me appreciate taller skaters more.

    Considering the fact that Evan is 15% taller than Nobunari, his height would cause 30% more difficulty in rotating a jump than Oda!

    On NBC's Olympics page, Evan talks about his frustration with his height:


    So Kudos to him for his hard work!

    Mao grows a few inches in the past years, but not extraordinarily tall as Evan, so if Evan can still improve his 3Axel, so can Mao. Good luck to both!
    Yeah, I mean Evan is actually TALL, like 6'2" and he can do a good 3a. I know people think Mao is tall, but she really just looks tall, she is actually petite (maybe tall for Japan? In the US she would be small/average). I don't think size is a major issue for Mao, there are plenty of skaters that are a lot taller than her, but granted most of them don't do 3a.
    Last edited by silverlake22; 01-03-2010 at 01:51 PM.

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    Tripping on the Podium Yschntä's Avatar
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    I don't think Evan has a good triple axel. He does a unusual prerotation before he jumps up. I once read an article about that and the author wrote that Evan should get a downgrade for all of his axel jumps.
    But I love Mao's triple axel and I wish her good luck that she can still improve it.

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    Quote Originally Posted by Yschntä View Post
    I don't think Evan has a good triple axel. He does a unusual prerotation before he jumps up. I once read an article about that and the author wrote that Evan should get a downgrade for all of his axel jumps.
    But I love Mao's triple axel and I wish her good luck that she can still improve it.
    Maybe not, but his jumps are just fun to watch because he has great height and looks like an NFL player next to the likes of Oda and Takahashi

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    Quote Originally Posted by Bennett View Post
    A 10% increase in body height results in a 20% more difficulty in rotating a jump
    This is difficult to believe. Is there a reason given?

    Skaters who have high jumps (long air time) don't need to learn how to rotate exceptionally fast in the air in a controlled way. They have plenty of time to get around. Skaters who don't have the height have to rotate significantly faster than typical to make up for it.

    A hang time of 0.45 seconds is rather low for any jump, no less a triple Axel. That means Mao needs an everage rotation rate of 7.7 rotations per second during the jump, compared to the example of a Miki quad of 6.8 rotations per second in the air. (And peak rotation speed will be greater than the average.)

    The faster the rotation the more perfect the control has to be for the jump to be successful. Above about 6 rotations per second, the success rate drops off quickly.

    Is the author saying a taller skater can't jump as high? Or is the author assuming a taller skater is also a wider skater? The rotation rate of the skater is determined by the moment of inertia of the skater. In the air this can be roughly modeled as a cylinder. For rotation around the long axis of the skater the moment of inertia is the mass of the skater times the square of the radius (half the width) of the skater. For two skaters of different height but the same mass and width, the moment of inertia is the same and the inertia against rotation is the same. A skater that is 10% wider has a 20% greater moment of inertia which makes the rotations 20% more "difficult." Greater mass also makes the rotation more "difficult" -- linear with the increase in mass.

    Evan, though tall, does not have wide shoulders or hips, thus his height is not an impediment to rotation. He also gets good air time, so he is not forced to rotate extraordinarly fast to complete 3A or 4T in the air time he has available.

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    Quote Originally Posted by gsrossano View Post
    A hang time of 0.45 seconds is rather low for any jump, no less a triple Axel. That means Mao needs an everage rotation rate of 7.7 rotations per second during the jump, compared to the example of a Miki quad of 6.8 rotations per second in the air. (And peak rotation speed will be greater than the average.)

    The faster the rotation the more perfect the control has to be for the jump to be successful. Above about 6 rotations per second, the success rate drops off quickly.

    Is the author saying a taller skater can't jump as high? Or is the author assuming a taller skater is also a wider skater? The rotation rate of the skater is determined by the moment of inertia of the skater. In the air this can be roughly modeled as a cylinder. For rotation around the long axis of the skater the moment of inertia is the mass of the skater times the square of the radius (half the width) of the skater. For two skaters of different height but the same mass and width, the moment of inertia is the same and the inertia against rotation is the same. A skater that is 10% wider has a 20% greater moment of inertia which makes the rotations 20% more "difficult." Greater mass also makes the rotation more "difficult" -- linear with the increase in mass.

    Evan, though tall, does not have wide shoulders or hips, thus his height is not an impediment to rotation. He also gets good air time, so he is not forced to rotate extraordinarly fast to complete 3A or 4T in the air time he has available.
    This is all very interesting, but where Mao is not tall, heavy, or broad I have trouble understanding why her hang time is so short. Does she just not have the strength to jump very high? Is it something to do with her build? She and Yuna are about the same height and weight though Yuna has broader shoulders and hips, and yet Yuna has very high, wide jumps. Miki who is also about the same height/weight as Mao jumps differently (bigger, wider) than Mao too. Maybe is it just a matter of Mao's jumping technique?

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    Watching Mao's 2A jumps she appears to jump higher than just about any of the lady skaters. She appears to get up pretty high on her 3A's too.

    Some big jumps that come to mind would be Yuna on her 3lz and 3F.
    I noticed recently Miki gets very high on her 3Loop.

    Maybe I will have to watch some clips - but I never thought Mao had a problem with little or low jumps. In fact what seems special about Mao is how high she jumps at times but can still have such soft, feathery landings.

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