General Skating Chat

[meoima]

9 hours ago, LadyLou said:

RE: the unfamous article I know most has been already said, it has been said like hours ago, but now I have time to write my bit, so bear with me

 

So that article is saying:

skater A has bigger jumps than skater B, which means he has more airtime.

skater A rotates faster than B

Both are doing 4 rotations

if rotational speed = turns per second (or any other unit of time) = n°of rotation / airtime

it means that  

                               n°of rotation = airtime * speed

skater A is doing n°rotation = longer than B * bigger than B

so the same article is telling me skater A is be doing more rotation than B

 

Those two things just cannot coexist.

 

The End.

 

Of course there are many more issues that have been already mentioned, like the lack of info about the method and the sample chosen, and the choice of the sample itself. tbw, a one jump-sample isn't nearly enough to make any conclusive analysis. Not to mention that the numbers are joke.

If that "analysis" had been posted by a fan on a forum it would have been called a troll, because that's exactly what it is. But it was published by a supposedly trustworthy professional. Too bad "ipse dixit" doesn't work when you have numbers and evidence against you.
So, one of these two must be true: 1) this professor is a fraud and can't do his job and doesn't even know how to do his job (doubtful) or 2)he has 0 work ethics.

Either way, he should just be fired. If that's the kind of people who help Shoma with his jumps, I'm not surprised he has hard time getting better or that he needs to go to USA to have some serious jumping training.

I can't see any purpose in that kind of article if not to shade Yuzuru on a level that not even NA press has reached (or dreamed. Or maybe they dreamed of that, but couldn't find anything they could use). If even the US press couldn't jump in and criticize the quality of Yuzuru's elements (of any of his elements) and they only try and play the inconsistency card or at most "he has hard time keeping up with Nathan on quads" (or scoff at Pooh), you know any other criticism has not even the faintest basis, or they would been already attacking full force by now.

Just till yesterday I was thinking about how glad I was that jpn media were, after all, still supportive of Yuzu and not trying to force the rivalry with Shoma anymore, I was even feeling bad for having been so distrustful, but this is disheartening. And counter-productive, because Shoma, among the top 6 or 7 male skaters, happens to be the very one with the smallest jumps and more questionable technique (yes, Javi has some questionable take-offs himself, but he jumps big).
I understand that they want to support their skater, but why like this? Why don't they just trust their skater a little bit more? And actually help him to work on his weaknesses? without e.g. suggesting him self-harming temporary measures like moving the placement of his blades, that caused more strain on his joints and pain. 

I know Shoma has a great relationship with Miyoko and she seems a nice and kind lady, but I really wish he could change environment. I remember watching a documentary in july, where he talked about his blades, and there was this professor that said that they took care of Shoma to prevent injury and so on, and I felt still a bit doubtful but relieved that they were not overlooking anything and knew what they were doing, but now I have this terrible feeling that that professor was the same professor who gave that idiocy of an article to the press and I just want Shoma far, far away from him

 

 

On a side note, I'm not sure "height" of the skater is the main factor in how high skaters can jump (and how much air time they can achieve), but of course it can factor on e.g. rotation speed (and so the minumum air time they would need), if we talk about a skater like Caro vs one like Satoko, who is not only shorter but also way slimmer.

iirc it was mentioned (here?) that the fiber composition of your muscles counts a lot. It allows some people to get more "spring" on e.g. jumps, and iirc in part it can be modified with proper training but in part is also genetic (I don't remember where I've read this tho).

So there are short people who can jump big. Anastasia Tarakanova is listed at 1.52 m of height, Satoko at 1.49, so only 3 cm of difference. I would expect they could potentially jump quite the same, having almost the same height, but no, there is a huge difference in the height and ice coverage of their jumps. Same with Sasha Trusova, she is small and rotates fast but she doesn't jump as small as Satoko (she doesn't jump small at all). Rika Kihira is listed 1.52, too, and she manages to do a 3A and she isn't even as thin as Satton (meaning she probably can't rotate as fast), so obviously she needs to get much more air time and she does.

Mika is 1.67 m, which isn't the highest among men, but he jumps really really high. So imo it's still possible to make jump comparisons among skaters with different body type. Tho the "visual impact" can be very different depending on body type, of course. Am I explaining myself?

Of course, body type (meaning height but imo most important shape and...let's call it "radius") has an obvious mathematical correlation with rotational speed. The thinner the axis, the faster the rotation. About that there's nothing much skaters can do, if they are already fit (and obviously athletes are fit, it's not like they can lose some fat here or there and reduce their "radius"). So it isn't surprising that Satoko, being so "small" (in radius, an in weight too) can rotate really fast. Faster, for example, than Wakaba that has a completely different body. But it's because of their muscles and bone structure e.g. width of hips (you can't make your hips shorter, they're just the minimum radius you'll have and you have to work with that).

 

 

 

This blog post said similar thing http://the-real-xmonster.tumblr.com/post/169861159069/have-you-seen-asahi-news-published-data-of-a

[Xen]

23 minutes ago, meoima said:

This blog post said similar thing http://the-real-xmonster.tumblr.com/post/169861159069/have-you-seen-asahi-news-published-data-of-a

Amazed this professor has the courage to publish his data in a newspaper in asia. Pretty sure physics is considered a mandatory subject in middle school (at least in China it is). I give up with this news article already...Yuzu just needs to publish his own math notes and call it a day.

 

Now mathematically, if Yuzu can maintain the airtime of his lutz (roughly 0.8 secs) , at 5.3 rotations per second in the air he can get a 4A (4.24 rotations), and if he goes up to 5.7 rotations per second  he could theoretically do a quint (4.56 rotations in air). Considering that russian blog's stats, Yuzu might be able to pull off 4A since 5.3 is pretty much his RPS speed for 4Lo and 4S. Quints might be harder, since the only guy who rotates that fast so far is Nathan and maybe Boyang-and given airtime, Boyang might actually win due to the height and distance of his toe jumps. Hmm. Okay, don't kill me, please.

[WinForPooh]

19 minutes ago, Xen said:

Amazed this professor has the courage to publish his data in a newspaper in asia. Pretty sure physics is considered a mandatory subject in middle school (at least in China it is). I give up with this news article already...Yuzu just needs to publish his own math notes and call it a day.

 

Now mathematically, if Yuzu can maintain the airtime of his lutz (roughly 0.8 secs) , at 5.3 rotations per second in the air he can get a 4A (4.24 rotations), and if he goes up to 5.7 rotations per second  he could theoretically do a quint (4.56 rotations in air). Considering that russian blog's stats, Yuzu might be able to pull off 4A since 5.3 is pretty much his RPS speed for 4Lo and 4S. Quints might be harder, since the only guy who rotates that fast so far is Nathan and maybe Boyang-and given airtime, Boyang might actually win due to the height and distance of his toe jumps. Hmm. Okay, don't kill me, please.

_{Don't even talk about quints, I worry enough about long-term impact of quads on their joints! All of them, but especially Yuzu.}

[WinForPooh]

42 minutes ago, meoima said:

This blog post said similar thing http://the-real-xmonster.tumblr.com/post/169861159069/have-you-seen-asahi-news-published-data-of-a

Wow, the difference in their loop takeoffs - it is so obvious! Just look at the angle of their skates the moment they leave the ice.

[Xen]

18 minutes ago, WinForPooh said:

_{Don't even talk about quints, I worry enough about long-term impact of quads on their joints! All of them, but especially Yuzu.}

Forgive me for I have sinned! I can't help myself when maths is brought up. But in all seriousness, I also recall reading an article before that says quints might not be physically possible: https://www.scientificamerican.com/article/is-the-quintuple-jump-in-figure-skating-physically-possible/

 

 

 

[xeyra]

2 hours ago, WinForPooh said:

Wow, the difference in their loop takeoffs - it is so obvious! Just look at the angle of their skates the moment they leave the ice.

 

Yuzu likes his outside edge VERY much. 

[xeyra]

3 hours ago, meoima said:

This blog post said similar thing http://the-real-xmonster.tumblr.com/post/169861159069/have-you-seen-asahi-news-published-data-of-a

 

There is a commenter on this post that has a different opinion, actually. Anyone with physics knowledge who wants to comment on it? I'm curious now, because that poster says the math is correct if one assumes a perfect isolated system without friction of air and ice, and Yuzu's jumps just look bigger because he's taller so it's plausible that they might be only 48cm high to Shoma's 55cm. They think the rotational speed is actually the data that is wrong. 

[Altie]

Since Yuzu is taller, his jumps should look smaller, not bigger, relatively... That makes no sense.

I'm a physicist, and this sounds a lot like total nonsense to me. Without friction of air and ice, the trajectory is a simple parabola, and that's it, and as was said before there is no way thoses numbers make logical sense.

OK, mechanics are not my field, but optics is and the same poster states later that "watch the jumps from a gif is like pretending to watch the stars with binoculars instead of a telescope" and that is just BS. You can still measure the distance between stars with binoculars, so I'm pretty sure you can see in a gif the height of a jump if you know the height of the athlete. It's not even physics, it's basic geometry.

 

[Xen]

2 hours ago, xeyra said:

 

There is a commenter on this post that has a different opinion, actually. Anyone with physics knowledge who wants to comment on it? I'm curious now, because that poster says the math is correct if one assumes a perfect isolated system without friction of air and ice, and Yuzu's jumps just look bigger because he's taller so it's plausible that they might be only 48cm high to Shoma's 55cm. They think the rotational speed is actually the data that is wrong. 

Well would video analysis persuade this poster? There are 2 posts on Perform Live's blog:

Yuzu's 4 Lz (which also has Nate's): http://perform-live.com/blog/video-analysis-of-figure-skating/231-quad-lutz-what-else.html

Shoma's 4 Flip: http://perform-live.com/blog/video-analysis-of-figure-skating/164-how-to-do-a-quad-flip-by-shoma-uno-japan.html

Nevermind height and distance etc, that all contribute to airtime. If Shoma's generating that much more absolute height than Yuzu, they need to explain why Shoma's airtime is significantly less than Yuzu's, and closer to Nate's airtime for the 2016 4Lz (roughly 0.60 seconds).  And if Yuzu is generating so much more airtime, despite having significantly smaller jumps-other than something being wrong with the logic, I guess Yuzu just has such great technique that it allows him to defy gravity or something. (Sorry, not a physics major, apologies if I get this wrong.)

 

Even if we compare jump height to skater height for perform live's data- Yuzu's 4Lz at 69 cm, is about 40% of his height of 172 cm. Shoma's 53 cm, while good for his height, is about 33% relative to his height. Meanwhile Boyang, based on the data Perform live uses, is clocking in at about 38% of his actual height (170 cm).

 

From a skating perspective, I'm trying to remember where, but I recall hearing somewhere that more explosive jumpers tend to pre-rotate less. And too much prerotation tends to have a negative effect on jumps, since you don't get the full "pole-vault" effect for toe jumps.  For more explosive jumpers, it is the lutz jump that is favored since it permits little to no pre-rotation.

 

Edit: I went and checked that specific poster's blog, and well.....<---the more in depth explanation made me do that.

 

[yuzupon]

I am also going to add this, since usually WE, fanyu, are the ones accused of bias no matter what we do.

Spoiler

 

The additional poster to the-real-xmonster's post add this in their tag:

#apparently except judges #as someone stated #even physics seems to be on the side of shoma uno #shoma uno #yuzuru hanyu #quads #analysis #jumps #figure skating

In case we're wondering if there's any bias whatsoever on their side. When are the judges not on Uno's side?

 

5

 

For me, the fact that the 'findings' have so many missing parametric data is enough to invalidate it.

[Neenah]

This is a rant about "skating analysis" so you can ignore it if not interested

Spoiler

 

I am seriously annoyed with all the crap that is being posted by some people as "analysis". What the hell do they think scientific analysis is? stating an opinion is not analysis. If you want me to accept your results you have to answer a lot of question, like for this particular case;  What is the data sample? What jumps are being studied? How many jumps were used as data points?Were the jumps chosen in the first or second half of the program? Why were these data points considered enough for a conclusion?  How was the data collected? Did they use videos or a special software? Did they record their own data or used someone else's? How was the height and rotation speed calculated? what methods were used? why were these methods used and not others? What is the error ratio?  

 

I can go on about the missing information from both the article and friendly physicists that came to their defence but there is no point in that. No researcher worth anything can accept baseless results. Data analysis is science that requires attention to details and rigorous methodology not "I have been studying this so I am an expert". Any results that cannot be replicated is not accepted and in this case it is impossible to replicate because we have no idea how it was done in the first place. Just yesterday, I was told by my supervisor about how my analysis needed to be verified by another person or else I cannot claim unbiased results 

 

If I do what they did in my thesis, I will be physically kicked out of the door and the University 

 

 

[meoima]

13 hours ago, xeyra said:

 

There is a commenter on this post that has a different opinion, actually. Anyone with physics knowledge who wants to comment on it? I'm curious now, because that poster says the math is correct if one assumes a perfect isolated system without friction of air and ice, and Yuzu's jumps just look bigger because he's taller so it's plausible that they might be only 48cm high to Shoma's 55cm. They think the rotational speed is actually the data that is wrong. 

There is a physics teacher on Twitter says the data that the professor at Chykyou university was wrong. If you want to ask her what's wrong about it then here: 

 

I talked to Perform - live and he showed me his data of the quads he collected. He also stated that the Japanese professor's data is unreliable. But since he used those numbers for his living I am not allowed to share what he told me here.

There is this one tiny data though I think I can share: in general, Yuzuru's quad (and 3A) can be longer than Shoma's quad (and 3A) around (almost) 77-80cm when it comes to ice coverage. 

 

In my opinion, that Japanese professor might indeed use some real data but the way he used the examples was selective for the following reason:

- The camera angles? Why no video/photo to show the camera angles and how they got the data? Look at what Perform-live do. he based his analysis on photos + video angle with certain error margin.

- The starts of the jumps were not counted the same time (certainly they count pre-rotation time for Shoma as airtime already)

- The jumps which were used were not the same type of jump with same quality (it's easy to pick out a bad jump from skater A to compare with a great jump from skater B)

- There is no indication of how many jumps they collect, no real standard of jump mechanism... DO YOU KNOW THAT AMONG ALL THE JUMPS, the LOOP HAS SLOWEST ROTATIONAL SPEED and LEAST ICE COVERAGE? That's why, with the same skater, the same number of rotation, the Loop will always be the smallest jump in general. And this is why -3lo combo is always fricking difficult. Now if you use one's Loop jump to compare to a Toe Loop jump to talk about which is bigger... you get the idea?

 

and YES to all of this below:

Quote

If you want me to accept your results you have to answer a lot of question, like for this particular case;  What is the data sample? What jumps are being studied? How many jumps were used as data points?Were the jumps chosen in the first or second half of the program? Why were these data points considered enough for a conclusion?  How was the data collected? Did they use videos or a special software? Did they record their own data or used someone else's? How was the height and rotation speed calculated? what methods were used? why were these methods used and not others? What is the error ratio? 

 

 

Anyway, since it's near Olympics I don't think there is anything new here. I think people should stop playing the political correct. What the professor at Chukyo University is doing is obvious for a reason: to boost his favorite and to talk down Yuzuru.

 

If that professor is fair, why he only chose Yuzuru and Shoma (and yet the article used Nathan's photo instead), there is NO indication of all the questions that @Neenah has mentioned above. If you're a serious and fair researcher you should show all of that to prove your point but NOPE there is NONE. Everything in that Asahi article was vague and questionable.

 

If you're fair and only want to count the numbers for the sake of it, look at the Russian blogger, he did his research on a huge scale. Whether his numbers were correct it is a different issue. It simply shows that he did not pick out any skater and he simply did the calculation for all the ladies as well. The way that Asahi news article was doing, sorry, is trying to make Yuzuru look worse and make their favorite look better with dubious data. There is no other explanation. 

 

I would rather trust people who have no bias /no relationships with the said skaters (Perform live guy has no relationship with the Japanese skaters, his clients are mostly European skaters), and the Russian blogger, his numbers might be questionable but he used the same scale on everyone. He is technically a nerd who used Mishin's method.

[Aotoshiro]

8 hours ago, xeyra said:

 

There is a commenter on this post that has a different opinion, actually. Anyone with physics knowledge who wants to comment on it? I'm curious now, because that poster says the math is correct if one assumes a perfect isolated system without friction of air and ice, and Yuzu's jumps just look bigger because he's taller so it's plausible that they might be only 48cm high to Shoma's 55cm. They think the rotational speed is actually the data that is wrong. 

This commenter assumes that the Chukyo professor friggin kidnapped Shoma and Yuzuru and made them jump quads in the perfectly isolated system with no friction, a.s.o. That's enough for me to go 'Lol nope' Brian.

 

Spoiler

If you provide DATA, you have them based on an ACTUAL.REPORTED. SITUATIONS. You can create them in your lab, you can observe them in the nature, BUT THEY HAD TO HAPPEN. Saying DATA along with a word ASSUMPTION automaticaly changes DATA or THESIS into HYPOTHESIS (as in, my HYPOthesis is I can jump quads. My thesis is, I splat on the ice so effectively half of the rink comes to see if I didn't kill myself, My brother can provide footage on the second one, the first one IS probable, as long as I stay on the ice, but let's be honest, it's not gonna happen). That's the basics of any.friggin.research. And I'm in THE FRIGGIN LINGUISTICS FIELD AND STILL HAVE TO OBEY THAT RULE! <-it me when I discover you do not have to prove your random thoughts by hours long analysises and repeatable researches when you get title of a doctor.

Putting my rant in the spoiler, bc it should make way to actual counterarguments provided bu @meoima and the rest of the field. Also, how come this is my sixth post as 3A, and only now do I notice that...

On a sidenote, while I do believe Yuzuru, with his alien blood and all, would be able to jump a quad in space/black hole just through the power of sheer stubborness*flashbacks to Yuzuru's 4S!Shooting stars meme*, I'd rather Shoma NOT try this. Quads are dangerous enough on the ice.

[EisElle]

Please note that I am a chemist, not a physicist, but I had my share of physics, statistics and analysis at uni. But this is not the point (and ipse dixit doesn't applies to me just as it doesn't apply to some professor, head of some figure skating department of some University). That article lacks even the basis for being called a scientific research. Pretty much like @Neenah and others pointed out, even not taking into account the ridiculous puzzling datas they gave in that article (and those they didn't give) and how they are absolutely contradictory, it's the whole (lack of) scientific method that discredits the content (and who wrote it. And the institution behind him, too).

 

About that (allow me to call it dumb) reply from the poster who claimed you shouldn't use gifs to measure jumps: it's not like in real time people are watching gifs, but they still think Yuzuru's jumps are bigger than Shoma's. Then what about all the other people who made the calculations and found Yuzuru jumps quads of 60 cm height, or more? And what about that 4A simulation from Asahi, did they take their 3A datas from a gif too, and got fooled? Just wtf! It's not like giffing a video suddenly makes a 48cm jump became a 60 one!

Of course to make the accurate calculations you don't use gifs, if they have not enough quality and don't allow you to do your measurements as accurately as possible. But even in gifs you can have a rough estimate of height, using the body of the skater as a unit. And no, I usually don't watch how high the head of the skater reaches, but how high his skates get, and I relate that to the skater's body.

Also, small jump from a shorter person "looks" much much bigger than a smaller jump from a taller skater.*

It's a matter of relationships, like when you see Yuzuru next to Satoko and he looks tall, but then you see him next to Ondrej and he looks so tiny and short and want to cuddle him, but it's because we as human beings are used to measure the world comparing things, no using some absolute scale.

*So If that doesn't happen...well... it means something is very off, and maybe the taller skater isn't jumping smaller at all

 

some other boring musings under spoiler

Spoiler

the same poster says "The truth is that it’s impossible to find plausible datas without putting a dynamometer on the blade of the boot."

WRONG.

Why would we need dynamometer to know plausible height, distance and duration of a jump?

I don't need to put a dynamometer on my foot to know if I can get enough force to jump 20 cm off the ground. I can just go to my staircase, whose steps are 20 cm high, and jump. Oh wow, I can jump 20cm high! but apparently it isn't plausible enough. Oh well.

For figure skating jumps, parameters like height and time of flight, that will allow you to calculate all the missing parameters (e.g. take off angle and initial speed) can be measured without using any kind of sensor on the skater. You just need a good camera angle, or even better multiple good camera angles. Maybe you won't have 100% accuracy (but you won't ever have 100% accuracy, not even with a chip inside the foot of the skater), but you will have plenty of plausible datas that have an acceptable accuracy for the scope of the research.

e.g. I can measure 150g of chocolate for the cake I have to bake with my body weight scale (hugging the chocolate bar, because otherwise the scale won't even register a thing) but it won't be accurate at all, at best it can tell me if I have about 100 g or 200 g. I can use my cook digital scale, who will allow me to measures the 150 g, so I can be quite sure I'm not using 155 or 145 g. Or I could steal a precision balance from my lab and measure 150.00 g, or why not, steal an analytical balance that will allow me to measure 150.0000g.

Thing is, my cake won't give a f*** that I've measured exactly 150.0000 g, the cake will be fine even with 150,05 g of chocolate and even with 153 g. Or 155. So, even if the cook digital scale isn't 100% accurate, it is accurate enough for my cake.

 

I'm also quite about what the heck does "They are right if we assume a perfect isolated system without friction of air and ice" means.

I don't get how you can have datas which are correct for a perfect ideal system with no friction from ice and air (so a jump in a vacuum) when the datas you have collected are those of a non-ideal system. The rotational speed you calculate is that in the non-ideal system, air friction already included.

ok, let's say the rotational speed reported in the article is the "ideal rotational speed" calculated from the "real rotational speed in non-ideal system", after considering that the" ideal speed" is "slowed down to real speed" because of the "air and ice friction" (also...ice friction...I'm not sure it is supposed to happen during the time of flight, it would be as if I was considering the friction with the ground for a bullet shooting through the air...ok).

But air friction is quite tricky to calculate and depends on things like air position (tight or not, leg wrap, tano and so), body type and even costumes and it even changes throughout the jump. Then is the article telling me Shoma would rotate faster than Yuzu in the vacuum? But what's the point? It's not as if skaters will be skating in a vacuum anytime soon.

(I know, I know, that poster is just grasping at straws. Burned straws.)

 

Also, the article claims the take off angle is 60 degrees (which would be correct, if the other numbers were correct...) for both Yuzuru and Shoma. This means that the two parabolas of Yuzuru's and Shoma's jumps have the same shape. Which would mean that, with lower max height, Yuzuru's jumps are shorter in lenght, too.

 

ETA: I edited a comparison because dragging Yuzu in comparisons about heights is always a good thing

 

[Neenah]

I finally found this, been looking for since yesterday

https://www.goldenskate.com/forum/showthread.php?53491-Measuring-Skater-Jump-Height

The post is old (2014) but it is a good example of how to do analysis. The poster explain their methodology, calculate the error ratio and clarify why it is there,  then they produce results based on it. The whole process is explained and can be replicated, which is what a true analysis looks like.

 

The result the article published are not the problem for me, but the lack of methodology is. The professor could be right, but without knowing what they studied exactly, it is impossible to verify those results which is why I cannot accept them. This has nothing to do with me being a Yuzuru fan, but everything to do with me being a researcher in STEM. I personally don't care how high Yuzu's jumps are. I like them because they are beautiful and effortless and their size is fine for me. I also have no problem with Shoma or any other skater's jumps since they are doing something I personally can't do and I have great respect for them.

 

Btw, my criticism in not directed toward the professor as I don't know if they wrote the article themselves or just did the research and someone else is reporting on it. Since I can't read Japanese there is a lot I could have missed and the professor could have done proper research but only the results made it to the media. I hope they clarify it soon because something like that is really bad for the reputation of any researcher and I do wish them the best.