# Understanding jump landings.

#### CoyoteChris

Record Breaker
I need a bit of help understanding jump landings. As I understand it, most all jumps are landed on a curve. So I assumed that when a skater's toe pick/blade hit the ice, it would define a point for a tangent line to that curve to determine if a jump was under rotated or not. My dear Wakaba got a "Q" for being right on the 90 degree point of landing her 3A. So I took Tara and Johnny's super slow mo of the landing and slowed it down even more. It doesnt look to me like the judges have a big screen tv in order to do what I can do at home. In the first pic, the front of the blade has landed and also the flat of the blade. Lots of shavings. But I could see how that could be called a Q and not a UR. But the second pic was taken a tad sooner than the first. Again, the toe has landed and then the blade is either almost down or down. That looks like a UR. Is my thought process right? I would assume camera angle is important but flying ice trumps camera angle.

A short time before

#### Mathman

Record Breaker
Considering that for a triple Axel the skater rotates 1260 degrees in less than a second, I do not envy the judges their task. I believe that the limits of the human eye is about a tenth of a second, so a skater might easilty rotate an extra 90 degrees or so between one "subjective instant" and the next. Don't blink!

In real time, I thought the landing was right at the quarter mark, so I agreed with the panel who gave it a "q." Given a binary choice, I would have leaned toward "no call" rather than "<."

There is also the question of whether the call should take place at the instant anay part of the blade touches the ice, or whether "landing" means that the blade is bearing at least some of the skater's weight. It always seemed to me that Mirai Nagasu got a lot of UR calls because she seemed to "reach down" with her toe pick before actually "landing" -- if that makes sense.

#### treblemakerem

On the Ice
There is also the question of whether the call should take place at the instant anay part of the blade touches the ice, or whether "landing" means that the blade is bearing at least some of the skater's weight. It always seemed to me that Mirai Nagasu got a lot of UR calls because she seemed to "reach down" with her toe pick before actually "landing" -- if that makes sense.
I think this is the reason many skaters have now adopted a flexed foot air position rather than pointed toes. You get a split second longer before landing to finish rotation.

#### Flying Feijoa

On the Ice
As I understand it, most all jumps are landed on a curve. So I assumed that when a skater's toe pick/blade hit the ice, it would define a point for a tangent line to that curve to determine if a jump was under rotated or not.
I don't think it's a tangent to the landing curve only, because you can have hooked landings (the ones that curve sharply on contact) without being underrotated (e.g. if the free leg gets a bit swingy). Maybe comparing the tangent of the landing curve to that of the takeoff curve would be more accurate. However, determining at what point the skater takes off is kind of controversial owing to jump mechanics (I don't want to delve into that pre-rotation fuss).

Alternatively, after leaving the ice the skater is travelling linearly in the x direction (at least I think so, because they aren't spherical or discoidal and heavier than a soccer ball, so the Magnus effect doesn't act on them). Therefore a fully rotated jump could be taken as facing backwards directly parallel (or up to 90 degrees clockwise for an anticlockwise skater) to the x-direction in-air trajectory of the skater at the point of landing.

I think this is the reason many skaters have now adopted a flexed foot air position rather than pointed toes. You get a split second longer before landing to finish rotation.

Regarding the definition of the point of landing, I agree with Mathman that whether the blade-to-ice contact is weightbearing should be specified but isn't. I would prefer toe pointing on landing not to run the risk of an UR call, since it might be biomechanically healthier. Apparently stiff skate boots have been linked to a higher rate of ankle injury during off-ice training, because the skater can get used to relying on the boot itself for shock absorption instead of rolling through the foot and adopts the same habit even when the boot's not there.
I would assume camera angle is important but flying ice trumps camera angle
Flying ice can occur from a heavy landing even when the skater is fully round, especially if they land with their weight forward on the toepick (false positive). Conversely, sometimes skaters UR without noticeable flying ice (false negative).

#### CoyoteChris

Record Breaker
Considering that for a triple Axel the skater rotates 1260 degrees in less than a second, I do not envy the judges their task. I believe that the limits of the human eye is about a tenth of a second, so a skater might easilty rotate an extra 90 degrees or so between one "subjective instant" and the next. Don't blink!

In real time, I thought the landing was right at the quarter mark, so I agreed with the panel who gave it a "q." Given a binary choice, I would have leaned toward "no call" rather than "<."

There is also the question of whether the call should take place at the instant anay part of the blade touches the ice, or whether "landing" means that the blade is bearing at least some of the skater's weight. It always seemed to me that Mirai Nagasu got a lot of UR calls because she seemed to "reach down" with her toe pick before actually "landing" -- if that makes sense.
I would have to say that when Terry, Johnny and Tara would talk about "cheating" a jump by finishing the rotation on the ice, I thought they were saying that a skater whose toe part of the blade hit the ice first, then the skate rotated before it came down to be flat. I think you are correct in that Mirai was accused of that. We seem to have a better view of what happened than the judges in that the NBC replay person picks the best camera and slows the landing way down for the replay. The poor judges are looking at that dinky screen from ...what?...one angle?

#### CoyoteChris

Record Breaker
I don't think it's a tangent to the landing curve only, because you can have hooked landings (the ones that curve sharply on contact) without being underrotated (e.g. if the free leg gets a bit swingy). Maybe comparing the tangent of the landing curve to that of the takeoff curve would be more accurate. However, determining at what point the skater takes off is kind of controversial owing to jump mechanics (I don't want to delve into that pre-rotation fuss).

Alternatively, after leaving the ice the skater is travelling linearly in the x direction (at least I think so, because they aren't spherical or discoidal and heavier than a soccer ball, so the Magnus effect doesn't act on them). Therefore a fully rotated jump could be taken as facing backwards directly parallel (or up to 90 degrees clockwise for an anticlockwise skater) to the x-direction in-air trajectory of the skater at the point of landing.

Regarding the definition of the point of landing, I agree with Mathman that whether the blade-to-ice contact is weightbearing should be specified but isn't. I would prefer toe pointing on landing not to run the risk of an UR call, since it might be biomechanically healthier. Apparently stiff skate boots have been linked to a higher rate of ankle injury during off-ice training, because the skater can get used to relying on the boot itself for shock absorption instead of rolling through the foot and adopts the same habit even when the boot's not there.

Flying ice can occur from a heavy landing even when the skater is fully round, especially if they land with their weight forward on the toepick (false positive). Conversely, sometimes skaters UR without noticeable flying ice (false negative).
ref flying ice. One thing is for sure....if there is flying ice, there is contact, whether the skate is around or not.
I will leave it up to Mathman as to gyroscopic precession is a factor once the skater is in the air but to me, "Pre rotation" would seem to be kind of a non sensicle term on edge jumps....I will let the experts quarrel over that one...but some day the Japanese will come up with a technique to determine when a blade first touches the ice....you may depend upon it. Rotation has taken on a life of its own in importance
over the last few years....it is better to have a jump judged fairly in this age of triples and quads even if the ref has to say, "Please put up this or that jump landing on the jumbotron in slow motion". Sour grapes are very bitter....
The guy without the peizo electric contact transmitter in his boots.

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