Jump, Spin, Glide: The Science Of Figure Skating

What’s the secret to landing a quadruple lutz, or speeding your death spiral? A figure skating researcher weighs in.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Ira Flatow?

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• 0:15Speaker 01

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• 0:33Ira Flatow?

  Hi, it's Ira Flatow, and you're listening to Science Friday. Today on the podcast, we're in training for the final events in figure skating at the Olympics. When I watch the athletes spin and jump and glide while balancing on a razor-thin skate blade, I wonder how some of these seem to defy the laws of physics. And they test the limits of what the human body can do, don't they? Especially the quadruple axel and the backflip performed by Ilya Malinin. Well, here to guide us through the biomechanics of the fantastic feats on ice is Dr. Deborah King. She's a professor of exercise science and athletic training at Ithaca College in Ithaca, New York. Welcome back to Science Friday.

• 1:18Speaker 02

  Thank you, Ira. Happy to be here.

• 1:19Ira Flatow?

  Nice to have you. Let me just ask, do you skate yourself?

• 1:23Speaker 02

  I am not a figure skater, no. I grew up just skating around, like, outdoor rinks or ponds, but it was never a sport I participated in.

• 1:32Ira Flatow?

  Me neither. I did a couple of times on ice, but I don't even want to talk about what the results were, so. So to non-skaters, I mean, don't they make all these difficult jumps seem so effortless? I have a difficult time telling the hard elements from the easy elements, so that's why you're here. What's the hardest skill for a figure skater to do physically?

• 1:56Speaker 02

  Today, in men's figure skating specifically, the hardest technical skill that's being done is the quadruple axel, which is only being done in competition by Ilya Malinin.

• 2:08Ira Flatow?

  Describe what that is.

• 2:10Speaker 02

  Okay, so the quadruple axel is a jump that is unique in that as an axel jump, the skater steps forward and is facing forward when they jump into the air. And people might not have noticed this when they're watching the Olympics, but if you pay a little attention to the landings, you'll notice they're always landing their jumps backwards. So that means if you're jumping off forward and doing a quadruple jump, there's actually an extra half revolution you have to complete so that you're facing backwards. So it's a four and a half revolution jump compared to the other quadruple jumps, which in and of themselves are very difficult, but require four revolutions because they take off backwards. You do four revolutions and land backwards.

• 2:50Ira Flatow?

  Now, I would think you have to be up in the air long enough and you have to be able to spin fast enough.

• 2:55Speaker 02

  You're absolutely right. In the quadruple axel, you're probably seeing air times 0.8, 0.9 seconds. They're usually in the air only about, just a little under a second. When you watch the jump, it looks like it takes a little longer because you're watching the approach and you watch the glide out of the landing. But just the airtime itself is just under a second. But if you're doing four and a half revolutions in a second, that is spinning amazingly fast.

• 3:21Ira Flatow?

  I know if my head were spinning that quickly, I couldn't balance myself or know where the heck I was.

• 3:27Speaker 02

  Right.

• 3:27Ira Flatow?

  But you have to be able to do that, right?

• 3:29Speaker 02

  Right, like your body awareness in the air. So you know like what revolution you're at. And I don't know if anybody's of your listeners have noticed this while they're watching skating, that you don't see skaters like spot, like if you were watching ballet or something and doing turns that head spots while they're doing rotations. But if you're doing four and a half revolutions in a second, you're not going to be able to spot and turn your head. So having your body awareness to be able to know where you are in the air and land is obviously amazingly difficult.

• 4:00Ira Flatow?

  Wow. And so why is it that he's able to do this? Does he have a special talent or is it practice or what?

• 4:08Speaker 02

  I think it's going to be sort of all of the above. One thing, if you watch him jump, that I think is amazingly impressive about his jumps is how high he goes. So he gets off the ground really quickly, has a lot of power and just... Goes really high, but while he's doing that, if you watch his body position, it seems like he has almost immediately gotten into a really straight, tight body position. So his legs are straight underneath them. They're pressed really tight together. His arms come in really tightly across his chest. So he's going high, but snapping into his rotating position so quickly.

• 4:44Ira Flatow?

  Right.

• 4:45Speaker 02

  So there's not like a moment wasted while in the air where he's not able to rotate really fast.

• 4:49Ira Flatow?

  One of the problems he said he had during his failed attempts was that his head wasn't on straight, so to speak. I guess the mental side of this is is major.

• 4:59Speaker 02

  Oh, absolutely. The pressure to perform and he's been world champion and winning so many competitions and programs over the last, what, almost four years? And the Olympics only come around once every four years. So that's a pretty heavy expectation that everyone has for you. But those are really, really difficult skills to do and no one's going to land them perfectly all the time. And unfortunately, you've got to put the physical performance together and the mental performance together, all at the right moment.

• 5:30Ira Flatow?

  Yeah. So I guess all the elements vary from one skater to another. I mean, does, does body size matter?

• 5:37Speaker 02

  Oh, body size is a hugely important factor in figure skating jumps. There's a quantity in physics that we call the moment of inertia. And it really is a measure of an object's resistance to angular acceleration. So when he goes in the air, he wants to have a little resistance to angular acceleration so he can rotate really fast. And objects that can rotate really fast with small moments of inertia are really narrow. So you don't want your body parts sticking out. You don't want wide shoulders. You don't want wide hips. So people who can be really long and narrow, almost like a pencil in the air, have an actual smaller moment of inertia and that will allow them to rotate faster than someone who doesn't have a small moment of inertia. So that's one way body shape can make a difference.

• 6:22Ira Flatow?

  So that's like why you spin faster when you pull your arms in?

• 6:26Speaker 02

  Absolutely. Anybody who's ever like gone to the playground and played on the tire swing or the merry-go-round and you can make it go faster by pulling your arms in? That's the concept right there. But you also might notice when you try to pull your arms and legs in on the tire swing, it feels like they want to pull away from you.

• 6:42Ira Flatow?

  Right.

• 6:43Speaker 02

  So you have to be really strong to hold them in so that you can keep rotating fast and you don't slow down in the middle of the jump.

• 6:49Ira Flatow?

  So how much of a performance is dictated by the physics? You mentioned this a bit. If you, if you position your arm or your leg in a specific way at a specific time, if you don't do that, you're going to affect your performance because of the physics involved.

• 7:06Speaker 02

  Absolutely correct. So I think every skater is constrained by the laws of physics and needs to utilize their technique to be sure that they can optimize their performance within the laws of physics. Not that they cognitively need to think about the laws of physics while they're jumping, but the techniques that they use will allow them to work within those constraints of the time that you have in the air and your rotation speed. Need to be balanced out so you don't under or over rotate the jump. For example, if we're just talking about completing four and a half revolutions.

• 7:40Ira Flatow?

  Well, let's talk about the laws of physics and, and, and the backwards flip that was just mind boggling. Is it a really hard thing to do or just something that your average good skater can do?

• 7:52Speaker 02

  That's a really good question. If you think about it from a physics standpoint, you need to get enough, I guess, I would call it flip momentum that you can get all the way over so that you get your feet back underneath you because you don't want to come up short. Because if you come up short, right, you're going to land sort of on your knees or your face, which would not be good. And you don't want too much flip momentum that you sort of over rotate and then end up falling on your back.

• 8:19Ira Flatow?

  Yeah, yeah, I hate it when that happens. I'm sure the skaters do too. One, one thing that always stuns me is how they can go from spinning really fast to standing still or from a spin to moving in a straight line. I mean, how do they shed all that momentum without seeming to slow down?

• 8:40Speaker 02

  I think there's two different concepts that are being used to slow down their momentum. So one is that moment of inertia that we talked about. Generally, they're spinning really fast and then all of a sudden you see them open their arms up. Um, so they're extended out from their body. And so that's going to slow you down a lot. And the other thing that is probably harder to visualize when you're watching them would be any torque being created from their skate against the ice. So skaters use um the way they glide into a jump and the way they move their body on their blade to generate torque as they're skating. When you see skaters skate, they skate on curves. So they're coming in on a curve as they go into a jump. They come in on a curve as they go out of a jump.

• 9:21Speaker 02

  So they have angular momentum as they come in and they still have some angular momentum as they come out. So it's hard to see that they're generating angular momentum. The same would be true in a spin, which you were talking about. That they come in and they're on a curve. So that's generating angular momentum and then they just snap their arms and legs and they go really fast. And then they can open up and they'll slow down, but they can also, when they stop, like, put the toe pick of their other foot in the ice, for example, and that will help create a force that'll stop their angular momentum.

• 9:50Ira Flatow?

  Right. Well, speaking of forces, is it possible to measure the forces that that are on the skater's feet in their ankles? And compare it to something non-skaters might understand?

• 10:02Speaker 02

  Um, yes, sort of. We don't have a lot of really good equipment that naturally goes with a figure skate. To measure the forces on the ice, there are a bunch of researchers working on it, but we have some really good estimates. Um, some of the probably better estimates that either I've tried to look at or other people have looked at are for jumps that are probably as high as Ilya's quad axel are. He could be having forces up eight to 10 times his body weight when he comes down. A lot depends on your landing style or technique. You can land very stiffly and have a higher force or land absorbing force through your ankle and hip and have a slightly lower force.

• 10:44Speaker 02

  So we probably need to give a range because it hasn't necessarily been measured directly for him. So eight to 10 times your body weight. Gosh.

• 10:52Ira Flatow?

  Eight to ten Gs?

• 10:53Speaker 02

  Exactly. Yeah, that high force is only for several milliseconds. So it's not like a fighter pilot or race car driver going around a corner for a long period of time. That would be pretty much hard to withstand by the human body. But you're talking like a hundredth or two hundredth of a second, you get this big impulse shock wave up your leg. That's going to be close to for a jump that high, eight to ten.

• 11:15Ira Flatow?

  Wow, without breaking any bones or pulling any muscles.

• 11:18Speaker 02

  Ideally, yes.

• 11:21Ira Flatow?

  I'm trying to compare it to a ballet, a ballerina, or somebody who's on their toes like that. I guess they're not jumping that quite that high and coming down that fast.

• 11:30Speaker 02

  Well, I think a ballet dancer probably jumps that high. I think, I don't hundred percent know, but I would think they could come close to that height. I think a difference in a ballet dancer in the landing versus a figure skate is for at least most ballet that I've watched, when they land, they land on the ball of their foot and they go through a bigger range of motion. So they lower themselves through the ankle, knee and hip more gradually towards the ground. So it's less abrupt. So it won't take quite as much force to act on the body during the landing to stop the person's downward momentum. You could think of it a lot like a safer barrier in NASCAR.

• 12:07Ira Flatow?

  Yeah.

• 12:08Speaker 02

  Or the shock absorption in a football helmet, that if you have something that can absorb forces and deform when you land, in this case, like a ballet dancer's ankle, knee and hip can go through a range of motion and spread the impact over a longer time period. So the forces can be lower. In skating, that's a little more challenging to do, but you do see skaters who have more of a neat deep bend and more of a hip flexion when they land. And sometimes they come down a little more stiff. And so that's why you maybe some of them you might see it's probably closer to six times body weight. And sometimes they come down really stiff and it might be closer at 10 times body weight.

• 12:43Ira Flatow?

  Do you think some of these of the skaters might perform well in the other acrobatic events, the half-pipe, snowboard, freestyle skiing?

• 12:50Speaker 02

  Oh, that's a great question. So I think what is unique to skating is that they mostly do twisting, except for, like you said, the backflip that we saw from Ilya. Another sport that does a lot of twisting in the Winter Olympics is aerials. But when you see like the half-pipe, they're doing a lot of twisting, but they're also doing a lot of flipping and inverts at the same time. So I think it might depend on the sport, which one it would be easier for them to transfer their rotational skills to. I would think aerial skiing, even though you would now have long skis. At least the twisting, they are inverting in aerial skiing because they come off the ramp and they are flipping while they're

• 13:31Speaker 02

  going, but the motion they pick up is really a twist motion, which is much more like skating.

• 13:36Ira Flatow?

  Yeah, you know, there are a lot of skating events at the Olympics. How different is this skating from a different kind of skating, like speed skating or other kinds of skating? Is it a whole different thing?

• 13:50Speaker 02

  I'm going to go as a whole different thing. Not that a skater who figure skates does, they know how to skate. So could they put on a pair of speed skates and go around?

• 14:00Ira Flatow?

  Yeah.

• 14:01Speaker 02

  Probably. But even the equipment is very different, particularly if you look, well, if you look at all women short track, speed skating, the boot comes up over the ankle, but the blades, if you look down from the top, the blades are offset from the middle so that they can lean going around the corners. And if you look at a speed skate that's for the long track, when you look at their boots, the boots usually are not coming up over the ankle and they have a hinge on the front. So when you push off, you can have a more smooth transition of force all the way through the stroke. So I think people could probably put them on. And skate not immediately fall over like I might, but they

• 14:44Ira Flatow?

  My ankles aren't even strong enough.

• 14:46Speaker 02

  From one to the other.

• 14:49Ira Flatow?

  I get it. The free program, that's only about, well, only, it's only about four minutes long. That's pretty long for me if I was skating.

• 14:57Speaker 02

  Right.

• 14:57Ira Flatow?

  But there's so much athleticism packed in. So I'm saying and thinking that endurance, cardio must be a very big component here.

• 15:07Speaker 02

  Yeah. The free skate, so your reps, they write four minutes. That's an extremely difficult length of time to train for. That's like a miler in track and field. So it's a combination of both aerobic power, where you're using oxygen, and then your anaerobic energy systems. And so that's a particularly difficult time to train for because it's not predominantly aerobic and it's not predominantly anaerobic. So it involves you training both systems and you need to obviously get through the four minutes, but you need to get through the four minutes while you're doing jumps, but then transitioning to gliding beautifully across the ice and then doing something with a very immediate need for power, like

• 15:51Speaker 02

  another jump and balancing on one leg. So it's challenging your energy systems while you also have to present yourself like beautifully, doing really difficult skills that are fast, but also skills that are slow and under the control of your body, if that makes sense.

• 16:09Ira Flatow?

  It does make sense. My last question for you, and it's a question about questions. I mean, what are the big questions in figure skating physics? What are sports scientists interested in learning?

• 16:22Speaker 02

  So I think one thing is really quantifying the loads with landing and seeing how the loads are related to the difficulty of the skill. For example, are the loads that we're seeing from different skaters, do they relate to overuse injuries that we see in skaters that we could have some really evidence-based advice on training and scheduling training to try to reduce injuries? And another one would be thinking about off ice training and how targeting different muscle groups and different abilities and aspects of skating off ice training, is that really translating into techniques on ice that are either one helping with their performance and/or helping to reduce injuries?

• 17:07Ira Flatow?

  Do you have an Olympic weakness? I mean, a sport that you have to watch?

• 17:12Speaker 02

  I have more than one Olympic weakness, cross-country skiing, absolutely have to watch, and the downhill.

• 17:20Ira Flatow?

  Hmm. See, I'm more of a curling guy.

• 17:24Speaker 02

  Oh, my gosh, I love curling, too.

• 17:29Ira Flatow?

  It's been great to have you back on the show.

• 17:32Speaker 02

  Well, thank you so much. It's been a pleasure.

• 17:34Ira Flatow?

  Deborah King, Professor of Exercise Science and Athletic Training at Ithaca College, of course, in Ithaca, New York. This episode was produced by Charles Breckwurst, and honestly, we'd love you to rank our elements high for both technical merit and artistic impression. Rate and review us wherever you get your podcasts. I'm Ira Flatow. We'll see you soon.