An object in motion has energy, and will have it until it slows down or stops. I've found that changing directions requires energy, and if you consider a ball rolling across a room, you pretty much know that allowed to roll straight over a smooth surface it may have some left over energy when it gets to the other side. If you roll that same ball at the same speed across the same room, but put some miniature "speed bumps" where it's to roll, it will have to change directions in an up and down direction, and will lose energy with every up and down motion, so much so, that it may not even make it across the room. The same thing happens if the direction changes are side to side, just like at the bowling alley when beginners use bumpers to keep the ball in the lane......
So the idea is to keep direction change as slight and infrequent as possible. Looking at a high hurdle for a punch front, you see the kid running at a fairly consistent height above the floor. When they hurdle they usually lose some of their motion forward by using some of it to go up into the hurdle, and the higher the hurdle....the more energy is lost.
But wait, there's more! Just pay separate processi.....oops, wrong words, right idea, as in with one direction change to go up, the kid has a new direction of energy to deal with because what goes up...must come down. When it comes down there's going to be another "charge" against the original energy that was available just before the hurdle started, because the kid has to stop going down (a direction change) in order to rebound up into the front tuck....so you get a "two for the price of one" loss of energy with a high hurdle.
A low hurdle can be done with very sight to zero direction change, so it makes more of the kid's (the object's) energy available to rebound....and to create to salto's rotation........Basically it's a two-fer you want, because you can go higher and rotate the salto with more ease.
I mentioned frequency and magnitude, right? Figure this out. A vaulter takes around 12 steps from the start of their run to their hurdle....then they hurdle....contact the board....contact the vault table. So that makes it....like, 12 opportunities to lose energy, once on every step that sways slightly to the side....even if it's so small you can't see it, that sway is taking away energy....and then another three chances to lose energy when they hurdle to high +2, add 1 more if the hurdle goes slightly to one side of the board, when they come onto the table cooked and have to correct their direction....plus if they come on too high.......
The funny thing about gymnastics is that the skills aren't the hardest part about of the sport......it's the little things like forcing youself to run balanced, with a tight core that will eliminate as many "wobbles" as possible.
So if you ever wondered how our olympic team members make it look so Maroney....well, spend a little time thinking about it, and let me know if you need me to take it the rest of the way.
Thanks for posting, my DD has a very high (dancer like) hurdle and the coaches have been on her about changing it. I never thought of the physics behind it, I just thought it looked pretty.
