Elitetrack: Sport Training & Conditioning

I have been browsing the existing posts on the forum about high jumping. I would like to start a thread dealing with how the approach, takeoff and flight dynamics can work together to produce a jump that wastes as little of the energy you put into the jump as possible. I will start with a statement of my basic premises, and add detail in subsequent posts.

The basic premises are:

1. All the rotations that are necessary for efficient bar clearance during the flight must be present, at appropriate rates, at the beginning of the flight. This means that they must be started during the takeoff drive. As I will explain later, the necessary rotations will produce a half-cartwheel with a half twist during the flight. The jumper will land up-side-down and facing in the direction of travel.

2. The highest flight path you can attain is one in which the impulse velocity at takeoff is directed vertically as viewed from the front or rear of the jumper at takeoff (separation from the ground). Taking off at any other angle reduces the upward velocity at takeoff and reduces the height attained by the jumper’s center of mass.

3. The center of mass of the jumper should reach the high point of the flight directly over the center, the low point, of the bar.

4. The horizontal velocity of the of the jumper that is left over from the jumper’s approach run should be used to “get into the pit”. None of the impulse of the takeoff drive should be diverted for this purpose (see #3).

5. All of the above must be set up by the approach. If the approach is wrong, you can not fix the problem by anything you do later in the process.

6. The approach should designed to be easy to visualize and easy to adjust to meet the criteria above.

More later

Glen

Part 2:

Approach design:

To meet all of the criteria set forth in my previous post, and to make the approach transitions smooth, I set up the approach as follows:

Beginning at the end of the approach - the takeoff, I set the takeoff point so the flight distance is centered over the bar. Finding the flight length is accomplished by simply measuring from the jumper’s takeoff point to the jumper’s center of mass at first contact with the pit. No need to try to get precise about this measurement at first, you will probably have to adjust it later anyway because the flight length will change a bit with the new approach. Divide the measured flight length by 2 and place the new takeoff point that distance from the center of the bar at an angle of 25 degrees. 25 degrees is a bit arbitrary, but it seems to be a workable angle with which to start. Mark the spot on the ground.

From this point I will be more general for this post and come back to specifics on a later post.

The curved section of the approach is next. It will be connected to the flight line such that it is tangent to the flight line at the takeoff point. Being tangent to the flight line means that when the jumper reaches the takeoff point he/she will be traveling in the direction of the center of the bar. Thus, no energy need be used to cause the jumper’s flight to take him/her over the center of the bar.

At the other end of the curve (what Todd Acheson calls the intercept point) the initial straight run segment of the approach is also tangent to the curve. This makes possible a smooth transition from straight to curved run during the approach.

Note, that I have not yet talked about the exact shape of the curved portion of the approach. There are, indeed, an infinite number of possible curves (non-straight paths) one might run between the intercept point and the takeoff point that are also tangent to the flight line and the initial straight run. However, only a small subset of these will put the jumper in the proper position at takeoff to allow him/her to perform the half-cartwheel with a half-twist that is needed to efficiently cross the bar. To carry this a step further, a still smaller subset of curve shapes are easily and reliably reproduced by a jumper, and a yet smaller subset of curve shapes are easily used to facilitate adjustments to the approach.

My favorite is the simple, constant-radius curve. When used correctly by the jumper, a constant radius curve can be run accurately and adjusted precisely to deliver the jumper to the takeoff point with the proper lean and traveling in the correct direction to execute the flight to best advantage.

More later

Glen

Part 3:

As I stated in Part 2, “My favorite is the simple, constant-radius curve. When used correctly by the jumper, a constant radius curve can be run accurately and adjusted precisely to deliver the jumper to the takeoff point with the proper lean and traveling in the correct direction to execute the flight to best advantage.“

So, what is the proper lean angle. Most jumpers recognize that they should be leaned away from the bar in the approach, but probably don’t know why. We want to be leaned away so we can leave the ground vertically (as viewed from the back or front of the jumper at takeoff) and also begin the cartwheeling spin during the takeoff that spins us around the bar during the flight. The proper lean angle is the angle needed to generate the proper rate of cartwheeling spin; and the proper rate of cartwheeling spin is that which takes the jumper from vertical at takeoff to horizontal at the peak of the flight. If you will accept that for the moment, I will go back to the lean angle that this requires and what determines how much lean you need to get that spin.

If you use my method of setting up the approach, then the lean angle you hold during the curve and the time you spend on your takeoff foot during your takeoff drive determine the cartwheeling spin rate you attain at takeoff. So, the lean angle you would like to have when you plant your takeoff foot is that which, combined with the character of your takeoff, will cause you to leave the ground vertically and spin at just the right rate to become horizontal at the peak of your flight.

Of course, the higher you lift your center of mass in the jump, the longer time you spend in the air, and the slower the required cartwheeling spin rate you need to get horizontal at your peak.

More later
Glen

Glen:

I am sorry, but you have over complicated the high jump either to a coach who is new at it or an athlete who competes in the event.  This is the second least complicated jump of all the jumps.  For a flop approach, one would finish their approach on a curve, whether it’s a constant radius or a tightening radius really needs to be the jumpers preference.  A curved approach with a natural inward lean (away from the bar) from running the curve is needed to successfully execute a flop high jump.  This curved approach is what gives the athlete the necessary rotations to clear the bar around all three axises.  The biggest problem with high jumpers is coaches allowing them to get too close to the bar, letting their athletes square off an approach, and coaches not understanding that the path of bar on a missed attempt should have a direct correlation to a flawed approach or the athlete is at their maximum height. 

Also, the feedback and communication between athlete and the coach should be positive reinforcements of what to do that they messed up and not negative reinforcements of what they did. The best example i can give is of an athlete who jumps into the bar.  I often hear coaches at meets or at club practices repeating that line of “you are jumping into the bar”  or something very similar instead of focusing the athlete on maintaining a curved approach which will prevent them from jumping into the bar.

I will try to answer the previous post one piece at a time.

dbandre:
“I am sorry, but you have over complicated the high jump either to a coach who is new at it or an athlete who competes in the event.“

Glen:
No, it IS complicated, and if one is to explain how it works and what needs to be changed in the common perception of the approach, then a full (even if complicated) explanation of the physics involved, and the interaction of approach, takeoff, and flight should be aired.  The goal is to improve approach technique from the present “wave of the hand and leave it to the jumper’s preference”, to something that is reliable, predictable, and adjustable.

dbandre:
“This is the second least complicated jump of all the jumps.“

Glen:
Interesting assertion. Has nothing to do with the question at hand.

dbandre:
“For a flop approach, one would finish their approach on a curve, whether it’s a constant radius or a tightening radius really needs to be the jumpers preference.“

Glen:
How does one teach a jumper to hit the takeoff mark, be headed across the center of the bar, and be leaned away from the bar the correct amount if one can not even define the shape of the approach being run. Any deviation from the planned curve, whatever it’s shape will cause the jumper to miss the takeoff mark, and probably the lean angle and final direction of travel as well. This, in addition to simply having the stride length vary as occurs in any jumping event. And, not being able to define the approach shape, how can you possible adjust it without countless hours of experimentation by the jumper to get back “on”.

dbandre:
“A curved approach with a natural inward lean (away from the bar) from running the curve is needed to successfully execute a flop high jump.  This curved approach is what gives the athlete the necessary rotations to clear the bar around all three axises.“

Glen:
Agreed. 

dbandre:
“The biggest problem with high jumpers is coaches allowing them to get too close to the bar, letting their athletes square off an approach, and coaches not understanding that the path of bar on a missed attempt should have a direct correlation to a flawed approach or the athlete is at their maximum height.“

Glen:
Yes, and I believe that it is largely because coaches and jumpers have no plan for their approach. They “wing it” as best they can. And once they find something that sort of works, they stick with it. Forget that they are under rotated and dragging the bar with their legs whenever the jump is close. At that point, it’s “good enough” or they fish around to see if they can adjust it - if they even recognize under rotation when they see it. Adjust it, you say? How? How do you adjust an approach that is some decreasing radius conglomeration. More guesses? Infinite fishing? Be my guest. Waste your time fishing, I’m going to use a path that allows me to tie down the approach in such a way that I can teach a jumper to run it, that I can predict what it will do, and that will enable me to adjust it to get the jumper into the proper configuration at plant.

dbandre:
“Also, the feedback and communication between athlete and the coach should be positive reinforcements of what to do that they messed up and not negative reinforcements of what they did. The best example i can give is of an athlete who jumps into the bar.  I often hear coaches at meets or at club practices repeating that line of “you are jumping into the bar” or something very similar instead of focusing the athlete on maintaining a curved approach which will prevent them from jumping into the bar.“

Glen:
Absolutely! Teach them exactly what approach path to use. Teach them exactly how to get to the takeoff point leaned away from the bar, and headed toward the center of the bar. Don’t rely on teaching or letting them use some half-baked constantly varying approach curve that the coach can’t possible understand, verify, or adjust. Break free of the old, unusable idea!

A couple of quick items.  My second sentence was in reference to my first.  I look at the high jump as basically a long jump on curved approach.  As for a reducing radius curve, this ensures inward lean in the approach.  Teaching it to developing jumpers without calling it as such is easier than getting them to hold a constant radius curve and maintain speed/acceleration in the approach.  As a developing jumper gets stronger/faster and their approach changes and the developing jumper will finally get into a constant radius.  I cannot as a coach sacrifice maintaining speed in the approach to maintain a constant radius.  As for getting them to run any curved approach it takes practice and i take sidewalk chalk and mark up jumping area with a color for each jumper and with lines about 1-2 times every 21-28 days.

One piece at a time again.

dbandre:
“A couple of quick items.  My second sentence was in reference to my first.  I look at the high jump as basically a long jump on curved approach.“

Glen:
Sorry, my oversight.

dbandre:
“As for a reducing radius curve, this ensures inward lean in the approach.  Teaching it to developing jumpers without calling it as such is easier than getting them to hold a constant radius curve and maintain speed/acceleration in the approach.“

Glen:
With this I disagree. It is precisely the developing jumpers who can’t find the handle on anything BUT a constant radius curve. When I put them on a constant radius curve and have them do almost all their acceleration on the straight - BINGO! They immediately begin to hit their takeoff point. I have them judge the curve by holding a constant bank angle.  It works!. They can hold a constant bank angle very well. And it’s not that they hold it perfectly, it’s that trying to hold it perfectly gets them close enough that their own judgment during the run can make the fine compensation necessary to nail the takeoff point. In my opinion curves other than constant radius curves are the single most frustrating and debilitating element of the whole event.

There are two big troubles with curved paths other than constant radius. First, they can’t be found, can’t be verified, and can’t be adjusted; and second, any curve that is difficult to duplicate will cause wide variations in the plant point due to being inside or outside the planned path.

Also, since the the rate of lateral spin at takeoff MUST be correct for efficient clearance, and because the lateral spin is dependent on the lean angle at plant, any path that does not allow the jumper to nail the lean angle at plant is useless.

dbandre:
“As a developing jumper gets stronger/faster and their approach changes and the developing jumper will finally get into a constant radius.“

Glen:
How fast they are does not matter; It only matters that they are mostly up to speed prior to entering their curve. Otherwise there are simply too many variables for a jumper to have any hope of hitting the takeoff accurately. Why work with an impossibly complex situation when a simple one is available from the start?

dbandre:
“I cannot as a coach sacrifice maintaining speed in the approach to maintain a constant radius.“

Glen:
Would you explain this objection further. I’m not sure I am understanding it correctly.

dbandre:
“As for getting them to run any curved approach it takes practice and i take sidewalk chalk and mark up jumping area with a color for each jumper and with lines about 1-2 times every 21-28 days.“

Glen:
What shape curve do you draw on the pavement?

PS: Sorry for the delay in this reply. The power went out in our neighborhood yesterday for most of the evening.

Glen Stone - 10 June 2008 07:44 AM

One piece at a time again.

dbandre:
“A couple of quick items.  My second sentence was in reference to my first.  I look at the high jump as basically a long jump on curved approach.“

Glen:
Sorry, my oversight.

dbandre:
“As for a reducing radius curve, this ensures inward lean in the approach.  Teaching it to developing jumpers without calling it as such is easier than getting them to hold a constant radius curve and maintain speed/acceleration in the approach.“

Glen:
With this I disagree. It is precisely the developing jumpers who can’t find the handle on anything BUT a constant radius curve. When I put them on a constant radius curve and have them do almost all their acceleration on the straight - BINGO! They immediately begin to hit their takeoff point. I have them judge the curve by holding a constant bank angle.  It works!. They can hold a constant bank angle very well. And it’s not that they hold it perfectly, it’s that trying to hold it perfectly gets them close enough that their own judgment during the run can make the fine compensation necessary to nail the takeoff point. In my opinion curves other than constant radius curves are the single most frustrating and debilitating element of the whole event.

There are two big troubles with curved paths other than constant radius. First, they can’t be found, can’t be verified, and can’t be adjusted; and second, any curve that is difficult to duplicate will cause wide variations in the plant point due to being inside or outside the planned path.

Also, since the the rate of lateral spin at takeoff MUST be correct for efficient clearance, and because the lateral spin is dependent on the lean angle at plant, any path that does not allow the jumper to nail the lean angle at plant is useless.

dbandre:
“As a developing jumper gets stronger/faster and their approach changes and the developing jumper will finally get into a constant radius.“

Glen:
How fast they are does not matter; It only matters that they are mostly up to speed prior to entering their curve. Otherwise there are simply too many variables for a jumper to have any hope of hitting the takeoff accurately. Why work with an impossibly complex situation when a simple one is available from the start?

dbandre:
“I cannot as a coach sacrifice maintaining speed in the approach to maintain a constant radius.“

Glen:
Would you explain this objection further. I’m not sure I am understanding it correctly.

dbandre:
“As for getting them to run any curved approach it takes practice and i take sidewalk chalk and mark up jumping area with a color for each jumper and with lines about 1-2 times every 21-28 days.“

Glen:
What shape curve do you draw on the pavement?

PS: Sorry for the delay in this reply. The power went out in our neighborhood yesterday for most of the evening.

No problem with the delay as I have to make this reply short.

My younger high jumpers take a wider and somewhat longer approach than most kids their age.  It’s something that has worked well my coaching style.  A wider turn requires less lean, but as it tightens in the last few steps it requires greater lean and has produced good results.  Think it of like an ellipse.