Jump Height vs. Distance

[Isk8NYC]

When you're jumping, what factors affect:

Height

and/or

Distance

[newskaker5]

Well I am no expert since I havent been skating very long - I have up thru the lutz. According to my instructors I have great "spring" to my jumps and get good height. My distance isn't the greatest except for the loop where I travel pretty far.

i find my knee bend as well as not leaning forward (on toe jumps) incrases my height. Speed seems to help my distance, of cource leaning forward on the take off also does not help distance haha

[techskater]

Knee bend, ankle bend, natural spring, and openness of the jump affect height and distance.

[Isk8NYC]

Knee bend, ankle bend, natural spring, and openness of the jump affect height and distance.True, but which affect height and which affect distance?

[dbny]

In the height vs. distance equation, isn't trajectory the determining factor? In that case, I would think use of the free leg is crucial, along with jumping on a tangent to your edge rather than into it (the circle it describes). I'm sure someone else can elaborate.

[Mrs Redboots]

I know it's knee-bend and speed into the jump, but I'm not sure which affects what, as I jump very little. It's to do with turning horizontal motion into vertical motion, rather like high-jumpers do, but that's not something I've ever been able either to understand or emulate.

[Mercedeslove]

i have neither. Apparently I lose.

[Emberchyld]

In the height vs. distance equation, isn't trajectory the determining factor? In that case, I would think use of the free leg is crucial, along with jumping on a tangent to your edge rather than into it (the circle it describes). I'm sure someone else can elaborate.

Definitely trajectory. Height is determined by knee bend and use of arms, distance by entrance velocity and angle. (for an equal balance between both, I'd say that a "take-off" angle of 45 degrees would be best) Free leg definitely has a lot to do with it, because ir contributes to the overall momentum.

This thread made me pull out my free body diagrams, and for a load of extra engineering geekiness, pulled out my copy of "Physics and the Art of Dance" (Isk8NYC, I'm positive that your school's library or one of the physics profs would have a copy-- the old titles include "The Physics of Dance".. the author is Kenneth Laws, if you're curious. There's a good chapter on "Motions without Turns" for the physics behind both "horizontal" and "Vertical" jumps-- and combining the two).

FYI, according to a study referenced by the above book, net gain on jumps increased approximately 25% when arms were used! Believe me that I'll be taking my coaches more seriously now about the arms!

Whew. I need someone to write a copy of physics and the art of Phigure skating!:lol:

[Sessy]

Distance is affected by technique, takeoff angle (I remember from school athletics, distance jumping, that 45 degrees is apparently the optimum for the largest distance), actually achieved height and speed before takeoff (not neccessarily speed on approach, since you can slow down quite a bit in the 3-turn and on toepicks instead of an edge right before takeoff).

Height depends very largely on biological factors - and not just whether you're muscly or not but also how long and springy your tendons are and other untrainable factors, on technique (knee & anckle bend and efficiency of transferring all forces into an upward force - as in how little of the force you loose on making a hole in the ice and other frictions), on physical (trained) condition, on your blades and skates (material: how heavy and how large a toepick and such) and on your general health (as in, are you getting enough proteins and vitamins and minerals, how's your blood sugar and oxygen, do you have any other health problems)

Also, more knee bend is not more height, as there is such a thing as too much of a knee bend. There's an optimum for all of that stuff.

[Sessy]

Whew. I need someone to write a copy of physics and the art of Phigure skating!:lol:

Plushenko's trainer Mishin wrote a whole dissertation. Also, take a look:
http://www.google.nl/search?hl=nl&client=firefox-a&channel=s&rls=org.mozilla%3Aen-US%3Aofficial&hs=FEB&q=physics+of+figure+skating+jumps&btnG=Zoeken&meta=

[Sessy]

True, but which affect height and which affect distance?

Openness is friction with the air so I'm gonna say that's gonna affect distance mostly, the rest affects both since height affects distance. If you jump higher, you spend more time in the air during which you cover more distance.

Mind that I also only have through to the lutz and am no expert

Also, keep in mind that rotation is just as important, and rotation isn't only about pulling in. It's also about not doing anything that counter-acts to rotational force while in the jump, to keep it maximized. Kevin van der Perren used to "spot" his jumps, he doesn't anymore because it's not effective.

[cathrl]

Openness will affect distance, but it'll have far more of an effect on speed of rotation because of the angular momentum (think how much difference pulling your arms in on a spin makes).

[Sessy]

I meant of the two choices - distance or height. It'll affect height some (same reason - friction) but compared to the gravitational forces that's practically none. You're right it makes a giant difference on the rotation. Which is more important than distance anyway. At least for the toeloop/loop/lutz/salchow/axel/flip jumps. For falling leafs, splits etc rotation is of course not an issue.

[Team Arthritis]

What does everybody think about getting multirotation jumps? Many of the high level skaters at our rink are constantly trying to ballance jump height with rotational rate - seems that the more oomph you put into height, the less you have for snapping in, or is it applying rotational force to the ice as you take off?
Lyle

[sue123]

I remember when I was taking physics, for some reason, I Just wasn't understanding the whole velocity, height, distance things. We had a lot of trajectory problems, such as you shoot a canon at an angle of x degrees, how how does it go and how far does it travel. For some reason, I could not wrap my head around it until I went skating and my coach, hwo never studied physics, was explaining a jump to me, and suddenly it made so much sense.

The reason 45 degress is best I think has something to do with the sine or cosine which is in the equation. I prefer to think of it much more logically. If you throw something straight at 90 degrees, it will go straight up, have lots of height but no distance. At the other extreme, if you throw at 180 degrees (or 0 degrees if you wish) it'll have lots of distance but no height. 45 degrees is right in the middle therefore giving you the most of both.

[Team Arthritis]

ANother thing that I don't see mentioned is that hang time is independent of distance, only depends on heighth so if you only have a finite amount of energy to put into your jump, and the jump's height is limited by that energy then jumping straight up would give you the most height and longest time to complete your rotations. Now that obviously doesn't work, so what's the answer?
Lyle

[Isk8NYC]

Emberchyld - Thanks for the engineering perspective. That helps a lot.

I'm glad other people mentioned hang time, because that's what I answered when this question was posed to me yesterday. Guess I'll have to go back to studying for the PSA exams using non-PSA materials, right DBNY? (LIKE THIS (http://www-personal.engin.umich.edu/~gcoch/jumpphysics/jumpphys.html)) I was caught off-guard and felt stupid not knowing the answer that was being looked for by my coach.

It came about during a loop jump lesson because I was going into the by-the-boards exercise too fast. Which explains the
"Thump Heard 'Round the Rink" as I slammed into the boards. (I'm fine, really.) LOL

Here's the answer I was given yesterday:
Jump Height results from the deep knee bend and quick spring action.
Jump Distance results from the speed and cleaness of the jump entry.
Rotation speed results from body position and tightness in the air.

[Emberchyld]

ANother thing that I don't see mentioned is that hang time is independent of distance, only depends on heighth so if you only have a finite amount of energy to put into your jump, and the jump's height is limited by that energy then jumping straight up would give you the most height and longest time to complete your rotations. Now that obviously doesn't work, so what's the answer?
Lyle

You have to just balance the two and pick the best scenario for what you're trying to do. Frankly, if I was trying for more rotations and height, I'd up the angle to 60 degrees or higher and "to heck" with distance (at that point, you just need to give yourself enough distance to land and finish). (of course, I can barely jump, so this is all theoretical here).

Remember that once you're in the air, you're not going to affect height or distance (because you're already on the set trajectory), so to get the most rotations out of every jump... first you have to get up there, and then quickly pull everything in to decrease your moment of inertia. You can give the illusion of "hang time" by playing with your body positioning (most good dance and skating textbooks have "tricks" on how to increase balon), but it's that initial push and then pulling into the rotations as quickly as possible (while pulling your body perpendicular to the ice) that will get you more rotations.

[Sessy]

The reason 45 degress is best I think has something to do with the sine or cosine which is in the equation. I prefer to think of it much more logically. If you throw something straight at 90 degrees, it will go straight up, have lots of height but no distance. At the other extreme, if you throw at 180 degrees (or 0 degrees if you wish) it'll have lots of distance but no height. 45 degrees is right in the middle therefore giving you the most of both.

Actually, throwing at 180 degrees will give you no distance at all, since the gravitational force will immediately pull the object onto the surface, where it will grind to a halt. Throwing something at 45 degrees gives the object the longest distance because it counter-acts the gravitational force optimally. You only need to counter-act the gravitational force for the duration of the flight of the object, and not for any longer than that, because then you're wasting energy into height that you could've put into distance, and vice versa, wasting energy into distance that you could've put into height.

Now, why are you wasting energy. In the case of throwing too high/steep, this is because the object's horizontal (distance) speed will be slowed down by the counter-force from the friction with the air. So the object's horizontal speed gradually slows down until a point where it is so low, that it is barely travelling forwards. At this point, it pays to put more energy into the horizontally pushing force instead of into the vertically pushing force, because if you put more energy into the vertical force, of course the ball will be longer in the air, but during this added air time it will barely cover any extra distance because of the low horizontal speed.
In the case of throwing too low/horizontal, this means that the ball hits the ground under the influence of the gravitational pull of the earth while still travelling at a very high horizontal speed, and the friction with the ground will absorb the energy. At this point, it pays to throw higher because, while taking away from the horizontal speed some - you had excess horizontal speed anyway - you're giving the ball extra air time in which to cover more distance.


The rest of this is also coming from somebody who's not even got an axel yet:

For the most rotations, I'd also have to say that 45 degrees is not going to be the optimum. Height jumpers, which are using essentially the same physics principles as toepick jumps, transfer nearly ALL of their horizontal speed and force into a VERTICAL force. They leave just enough horizontal speed to pass the distance of the pole about twice - with the highest point of the arc that they jump being exactly where the object hanging in the air is. But other than that, as much of their horizontal speed as possible is going into height. Same with figure skating. Long, drawn-out jumps are great for the looks of it but what scores far more than the artisticity of a jump is its number of rotations and for that, you need the maximum of air time you can get with the restriction that you do still need to be able to land and ride out the jump - among others, to actually stop the rotation and grip the ice with an edge you'll need some horizontal speed. Else you end up going into a backspin.

For the sal, loop and axel I think what plays a role there is that you need the rotation as well as the height. Now to get the most height, you'd wanna swing your free leg as high as possible. However, then you're not going to be able to snap in for the rotation optimally. I THINK! That's how it works in my mind but as I've said I can't do the axel so don't pin me down on it.

[cathrl]

ANother thing that I don't see mentioned is that hang time is independent of distance, only depends on heighth so if you only have a finite amount of energy to put into your jump, and the jump's height is limited by that energy then jumping straight up would give you the most height and longest time to complete your rotations. Now that obviously doesn't work, so what's the answer?
Lyle

I'd guess, it's because you have no backward momentum as you land - so no backward glide away, you'd have to do something else to get some momentum. Assuming you'd managed to jump absolutely straight up. If you had a small sideways or forwards component you'd be landing going the wrong way altogether. Not good.

[cecealias]

Sessy's right on key... one thing i'd add is that in skating to get the height for the multi rev jumps you have to figure out how to maximize compression before take off.

And compression is not simply a matter of just bending the knees but a combination of timing, body angle, core compression (abs, lower back, chest, ankle, edge lean). Your body has to compress like an accordion, or like a rock in a slingshot.

The arms strength, precise alignment, and especially PATIENCE and meticulousness are key in finding the precise spot so that you can repeately get consistent jump height over and over again.

And you want consistency in height, amplitude and distance in your singles if you stand a prayer to get consistent double, triple, quadruple.

D

Height depends very largely on biological factors - and not just whether you're muscly or not but also how long and springy your tendons are and other untrainable factors, on technique (knee & anckle bend and efficiency of transferring all forces into an upward force - as in how little of the force you loose on making a hole in the ice and other frictions), on physical (trained) condition, on your blades and skates (material: how heavy and how large a toepick and such) and on your general health (as in, are you getting enough proteins and vitamins and minerals, how's your blood sugar and oxygen, do you have any other health problems)
.

[sue123]

I am now officially lost in this discussion. I think I'll just go back to practicing my jumps and hope I figure it out eventually on my own. I always did hate physics, sent me to tears several times actually.

[doubletoe]

This is what I've learned from my personal experience and coach's input (although the physics discussion is fascinating and want to read those thoroughly later! :D ):

HEIGHT: Comes from deep knee bend before takeoff, pointing the toes of the takeoff foot on takeoff, and pulling up with your upper body (and free leg thigh). The right timing is always important, too.

DISTANCE: Comes from speed going into jump, coupled with deeper knee bend and farther reach back in the case of pick jumps. The right timing is also important. Also, in the case of a single toeloop, waltz jump or salchow, you'll get more distance by reaching forward with the free leg like you're jumping over a big puddle.

[Emberchyld]

I am now officially lost in this discussion. I think I'll just go back to practicing my jumps and hope I figure it out eventually on my own. I always did hate physics, sent me to tears several times actually.

I think the professor/teacher's approach and the context really helps. One prof was great enough to put it all into a real-world context-- making physics a lot of fun (pop quiz to find out the velocity of his baby's projectile vomit that morning was the best!), but let's simplify the basics:

Height: Your legs are the equivalent of a spring. So, the more you compress the spring (to a point-- compress too much and you work against yourself!), the more the spring bounces up. Try to jump with straight legs and nothing happens. Because of gravity, you have to create a downward force greater than your body weight to get off of the ice. (easy so far, right?)

Pole vaulters take this one step further and have a springy pole that helps them get height-- that's why they go straight up and down.

Distance: The way that you get distance is from your sideways force-- you want to travel horizontally and that speed going into the jump is what pushes you in that direction-- like a rocket or you suddenly falling on the ice and skidding for a while.

Long jumpers use this when they get as much speed as possible and really throw themselves (and lead with their legs) forward to get the most distance-- but if you watch, the height is minimal.

Now, skaters (or a dancer in a grand jete)-- you're jumping in an arc. That arc is your trajectory.

Force is kind-of one-way. If you drew a picture of someone jumping in an arc and wanted to make a picture of the forces, you'd draw an arrow pointing up for vertical force and an arrow pointing sideways, to represent horizontal force. Unfortunately, our force is limited, and we have to combine the two. And that means that the resulting force (the force that you're going to go into the jump with) is going in with an angle. (plus, because we do most jumps not from a stop, we already have the horizontal force happening to us, so we don't have much choice there! Otherwise, (if the landing could be fudged somehow) we could have some jumps with amazing height and time for lots of rotations (but getting those started from a stop on ice is a totally different story!), like some male ballet dancers pull off.

The angle:
So, now you have a problem. If that angle is low (0 degrees being completely horizontal, 90 completely vertical), you get lots of distance and little height, and vice-versa if the angle is closer to 90. That's why a lot of people on this thread like 45-- that's right in the middle and gives you an equal amount of height and distance.

But say you're trying to do a jump with lots of rotations-- you want more height, right? So then you have to sacrifice distance to get that height because now you have to up the angle to get that height. If you wanted to really travel though-- and have practically no revs, like a waltz jump, you might drop that angle a bit so that you could cover more ice.

The forces:

Height comes from the knee bend, upward force on the toepick for "takeoff", and use of the arms and the kick through to get you up.

Distance comes from the sideways force on the toepick (thanks to the angle!), entrance speed, and the kick-through (again, angular forces working in our favor-- those things give you both horizontal and vertical force!).

Rotation:

I'm not really getting into this, but the biggest point that I can get home on this is that the closer your body looks (to the outside world) like a cylinder, the faster you'll spin. You see this already when you pull your arms in during a spin and you go faster. Being vertical is a big thing, too-- just like a top, you don't spin as efficiently if you're tilted in any way. So to spin more efficently, you have to pull in and upright. Basically, you're changing your moment of inertia from an inefficient mass with a whole bunch of sticky-outty-parts (that physicists and engineers hate!) into a nice, tight shape.

What does this all mean?

Well, the cool part about all of this is that skaters and dancers had figured this all out without all of the equations and diagrams, so you don't need a physics degree to skate! Most of the time, when your coach tells you something like, "Use those arms more" or "I need you to really kick through in that jump", he/she is telling you how to basically use the forces I described above to optimize your jump. Knowing about that arc, though, will help you understand what your coach is trying to say so that you can quickly alter those factors to maximize your trajectory. There actually are some people out there analysing top skaters and trying to see if there's any way to constantly better their jumps and spins-- and physics helps you learn how to use your body more efficiently, so that you can get the most bang for your buck out of your jumps.

Just don't trust the physics they babble off in Ice Princess! That movie is a physics (and skating) fact nightmare (albeit fun to watch!)

Whew.

[renatele]

...
but let's simplify the basics:
...


Hah! I'll bring up this discussion next time we skate together - I guess by that time you might be working on more than one jump, so I'll have fun getting you to apply the principles of physics :twisted:

[Emberchyld]

Hah! I'll bring up this discussion next time we skate together - I guess by that time you might be working on more than one jump, so I'll have fun getting you to apply the principles of physics :twisted:

:lol: :lol: :lol: :lol: :lol:

Ah, but remember the old saying, "those who can't do... babble about it all in physics terms!"

[renatele]

Ah, but remember the old saying, "those who can't do... babble about it all in physics terms!"

:giveup: :giveup: :lol: :lol: :lol:

[sue123]

Emberchyld, let me thank you for typing all that out. And honestly, a lot of it actually makes sense, just as it made sense when I was studying it and something my coach said to me while we were practicing jumping made it click. I did well in the class, and learned what I had to for the MCAT, and then promptly forgot all of it.

But I'll take teh physics babble out of your post (moment of inertia, who needs it :D ) and it was actually pretty interesting. Thank you for taking all the time to dumb down everything.

Now I have a question about this angle thing. I'm assuming this angle has to be between the ice and something else, but what is it? Your knee, ankle, blade right before it leaves the ice? Heck, even I said 45 degrees because that;'s what I remember from physics, but I'm not sure what the angle is formed by.

[Emberchyld]

Thank you for taking all the time to dumb down everything.

Now I have a question about this angle thing. I'm assuming this angle has to be between the ice and something else, but what is it? Your knee, ankle, blade right before it leaves the ice? Heck, even I said 45 degrees because that;'s what I remember from physics, but I'm not sure what the angle is formed by.

:lol: Trust me, it wasn't dumbing it down-- it was putting the physics terms into real words. The problem with a lot of teachers/professors is that they can make physics into this impossible thing full of too much math, a whole bunch of greek letters, etc. I was lucky enough to have some incredibly fun teachers who made me fall in love with it before I realized that it was full of math (which I hate!). :D

Well, the angle is the angle of the path of your center of gravity-- following that little dot that they always have in diagrams as your center of gravity. It's hard to say what that is with relation to the blade or your legs, especially since that changes with each jump. And, unfortunately, I'm not sure how to put that into practice (beyond waltz jump, because that's how far I've gotten!), but maybe someone else here might have ideas?

FYI, as I'm typing this, I'm watching a replay of the men's long program at Worlds-- and am having a lot of fun watching these guys and trying to correlate what we're typing here to their jumps. So far, the angle thing is looking right for the major rotational jumps....

[doubletoe]

Emberchyld, you rock!!
Yes, it's true. When you do a single jump, you can focus on distance (especially those where you take off and land on a different foot). But starting with the axel, we are all taught to jump UP, not OUT. At a skating seminar I attended, I remember seeing diagrams of height vs. distance and how the distance covered was shorter as the height and number of revolutions increased.

Another thing one of the guest coaches pointed out to me (it was Michael Weiss' coach, Don Laws) was that you need to adjust your jump height depending on how much speed you have. I always jumped my flip BIG, even if I went into it without much speed, but if I didn't have enough speed, I would have no outflow on the landing. It was though I had chosen height instead, and run out of distance, LOL! So I needed to learn to make the jump smaller and rotate quicker if I didn't have enough speed going in, so that I'd still have some outflow.

[Sessy]

Just don't trust the physics they babble off in Ice Princess! That movie is a physics (and skating) fact nightmare (albeit fun to watch!)

Whew.

Having taken the most physics I possible could at school, I was completely unable to identify anything of what she had in her notebook except some radius equations here and there. There also were surprisingly little letters f in those equations as I recall?

Also pulling in on the sit spin so you'll spin faster in order to CENTER it? Centering is not about speed last time I checked.

It's a fun movie though to watch of course. If you can turn off your brain entirely, because frankly, why did she even need a zamboni on her pond, she could've hosed the pond down with a garden hose and gotten mirror ice as well.
And how come the zamboni didn't fall through the ice surface into the pond.

[jazzpants]

Ah, but remember the old saying, "those who can't do... babble about it all in physics terms!"Sounds like my husband!!! Once primary coach "corrected" me on my arm position and then hubby butts in and start babbling about inertia and center of gravity. :roll: I tell DH "*YOU* try bringing your arms in when you're spinning on the ice and you tell me if it's easier to do that!!!" :twisted: :P :lol:

Cheers,
jazzpants, whose DH was a physics major and was a thesis short of finishing his MS in Physics... and got suckered into dating him thru his charms as my physics tutor... :halo: (and no, neither of us wants him on the ice! He's not fun to take to the ER!!!) :x

[Team Arthritis]

Or how about when Plushenko said to Gaebles something to the effect of "you jump too high, that's to hard, jump lower and rotate faster", anyone remember that beside me (no really I swear I'm not making that up, realllllyy)8O
Lyle

[Team Arthritis]

Another question is where does the upwards force come from - its much more complex than these already complex discussions have described! The springiness of the tendon and muscle is actually quite small. The reason that you sink onto a tight muscle right before you jump is mainly that this elicits a stretch response reflex that increases your force of muscular contraction by recruiting more muscle bundles. Just like when you bang on the patellar tendon to trest reflexes at the knee, timing is everything because it takes a specific and reproducible amount of time for the muscle to contract eather after your brain tells it to or after you stretch it. The hard part is to tell your muscle to contract so that the nerve signal (which is a voluntary and slow signal traveling all the way from your brain to you leg) gets to the muscles at just the same time as the much faster reflex arc which only travels from the tendon, up to the spinal cord and back to the leg muscles.

And then there is the physics of blocking off the edge verses skidding the edge, not to mention rolling up on the rocker and toepick., Sigh, what fun
Lyle

[Sessy]

SO does this explain why I like to sink on my knee, get back up a little and sink on it again before jumping off for maximum height?

[jazzpants]

SO does this explain why I like to sink on my knee, get back up a little and sink on it again before jumping off for maximum height?Yeah, I sometimes do that too on my waltz jump! My primary coach HATES that habit!!! Lucky for me, somewhere along the way I either A) broke that habit and he's moving on to other things to bug me about or B) gave up on fixing it!!! :lol: (I think it's A really...) ;)

[Emberchyld]

And then there is the physics of blocking off the edge verses skidding the edge, not to mention rolling up on the rocker and toepick., Sigh, what fun
Lyle

:D :giveup: I wonder if we can con any physics grad/doctoral students out there want to tear all this apart for us?

jazzpants: :lol: Your husband reminds me of how I was... until the first time I tried to spin!

Sessy: I was amazed at how a movie about a "physics genius" could have so many blatant mistakes-- they could have actually looked in that textbook they made "casey" carry around (good, clear textbook, btw)!

Two points to anyone who can identify the major mistake they made in the movie when "casey" is first filming the video for Harvard (and demonstrates the jumps)-- hint, hint... we've covered it in these posts!

[Sessy]

No, I'm still really big on physics, because it does make things easyer but ALL has to come together. And that's where it's often lacking for me.

Emberchyld: Increasing the moment of inertia will make her spin slower, not faster like she says. She's actually increasing her velocity to keep the rest constant as the inertia decreases.
And inertia decreases because: I = k x M x r^2
Decrease the radius (distance from the centre) by tucking your arms, keeping the k contstant and assuming that the amount of weight you're sweating out as sweat is negligible, and the moment of inertia has gotta decrease.

[Emberchyld]

Emberchyld: Increasing the moment of inertia will make her spin slower, not faster like she says.


:D Two points to Sessy! That one line was a 8O 8O 8O 8O 8O moment in the movie theatre.