[tfjaguarstrength]

I recently received my Chronojump system and had some questions about the estimated jump height.

When compared to a VJ tester (vertec, etc) I notice that the measurements are far different on the Chronojump read out than what I get when actually touching the vanes on the vertec (17in on the Chrono and 26" on the vertec). I know that it is based on flight time but I have used other products in the past (Just Jump Mat) and the measurements were very similar.

Is anyone else noticing the same issues?

Is there possibly something wrong with my setup (measures are fairly consistent, just drastically lower than what is touched)?

Is there a better way to test the validity of this that I am unaware of?

Thanks for the help.

[xavi]

Hello

Measurements on Chronojump mat are reliable. If you want you can take a high speed camera (1000 frames per second), record the jump, then see the recording using Kinovea and count the frames to know the jump time. With this you can calculate jump height.

Cheers

(09-24-2013 07:50 AM)tfjaguarstrength Wrote:  I recently received my Chronojump system and had some questions about the estimated jump height.

When compared to a VJ tester (vertec, etc) I notice that the measurements are far different on the Chronojump read out than what I get when actually touching the vanes on the vertec (17in on the Chrono and 26" on the vertec). I know that it is based on flight time but I have used other products in the past (Just Jump Mat) and the measurements were very similar.

Is anyone else noticing the same issues?

Is there possibly something wrong with my setup (measures are fairly consistent, just drastically lower than what is touched)?

Is there a better way to test the validity of this that I am unaware of?

Thanks for the help.

[tfjaguarstrength]

Xavi,

So, you are saying that in order to measure jump height accurately I will need a camera system as well?

If not, then I was wondering why there is such a difference across contact mats (Chronojump and Just Jump). When using both combined with a vertical jump measuring device such as a vertec, there is a considerable difference is estimated jump height (different formulas?). The measure for the Chronojump are consistent among themselves. Sorry to keep going but I am just curious by nature.

[xavi]

(09-25-2013 02:31 AM)tfjaguarstrength Wrote:  Xavi,

So, you are saying that in order to measure jump height accurately I will need a camera system as well?

Chronojump is a system that works, cheap, validated and used by lots of people. You don't need anything more. But if you are unsure and you think it doesn't work ok, then one reliable way is to record a jump with Chronojump and a high speed camera. then you will see if there any differences.

(09-25-2013 02:31 AM)tfjaguarstrength Wrote:  If not, then I was wondering why there is such a difference across contact mats (Chronojump and Just Jump). When using both combined with a vertical jump measuring device such as a vertec, there is a considerable difference is estimated jump height (different formulas?). The measure for the Chronojump are consistent among themselves. Sorry to keep going but I am just curious by nature.

Vertec is a different thing, people make a movement with the shoulder in order to arrive higher, but this movement of: "try to reach the top with the hand" produces a high value in Vertec but is not related to a higher jump, just a higher arm extension.

I haven't tried Just Jump and I cannot tell if that works as expected. If you care about the formula, see that Chronojump gives you the flight time and then this is converted to jump height. The formula should be the same on both products.

Here you have the validation of Chronojump tools:

http://www.cafyd.com/REVISTA/ojs/index.p...ad/528/288

Cheers.

[trener]

Hello Xavi and everybody,

I have the same question. I tried to do some jump tests and the results was a far away lower than real. I recorded jumps with camera and it was obvious. I don't talk about 1 or 2 cm difference, it's more like 10 or 15 cm! I don't know what to do, can you help me?

Best regards

[xavi]

(09-27-2013 06:40 AM)trener Wrote:  Hello Xavi and everybody,

I have the same question. I tried to do some jump tests and the results was a far away lower than real. I recorded jumps with camera and it was obvious. I don't talk about 1 or 2 cm difference, it's more like 10 or 15 cm! I don't know what to do, can you help me?

Best regards

Hello

What are you exactly measuring?

Note that the measurement is related to the center of gravity. Then if you measure the height of the foot or the height of the head, the body has to be fully extended (and the foot also), in the same way that it is when your toes leave the floor. If you want you can attach pictures of the body fully extended just when leaving the floor and in the air (in maximal height situation).

Thanks

[xavi]

(09-27-2013 06:18 PM)xavi Wrote:  

(09-27-2013 06:40 AM)trener Wrote:  Hello Xavi and everybody,

I have the same question. I tried to do some jump tests and the results was a far away lower than real. I recorded jumps with camera and it was obvious. I don't talk about 1 or 2 cm difference, it's more like 10 or 15 cm! I don't know what to do, can you help me?

Best regards

Hello

What are you exactly measuring?

Note that the measurement is related to the center of gravity. Then if you measure the height of the foot or the height of the head, the body has to be fully extended (and the foot also), in the same way that it is when your toes leave the floor. If you want you can attach pictures of the body fully extended just when leaving the floor and in the air (in maximal height situation).

Thanks

Another way is measure time counting the frames in the high speed camera. You need fully extension on jump and on landing, for this reason is good to do a bounce when you are landing as this helps to land in full extension.

Assuming you have done it correctly, then you will have the flight time, and the height of center of gravity in centimeters will be:

height = 100* 4.9 * (flighttime / 2) ^2

Bye

[trener]

I found reason of problem - it was unstable soil!

I performed tests on artificial grass. I thought it's stable and solid enough, but obviously it has negative effect on flight time.

So my recommendation would be to be carefull when choose ground for testing.

Cheers

[Nicola]

(10-03-2013 05:37 AM)trener Wrote:  I found reason of problem - it was unstable soil!

I performed tests on artificial grass. I thought it's stable and solid enough, but obviously it has negative effect on flight time.

So my recommendation would be to be carefull when choose ground for testing.

Cheers

to make measurements on soil type grass you can use tools such as inertial sensors type Sensorize http://www.sensorize.it. They measure the height of the jump second protocol Bosco, or measure the height derived from the time of flight, but also also estimate the maximum height that the center of mass of an individual reaches. In addition, you will also have many other data related to the elongation phase of muscle shortening of the lower extremities in vertical jumps and much more ...

[xavi]

(11-27-2013 05:28 PM)Nicola Wrote:  

(10-03-2013 05:37 AM)trener Wrote:  I found reason of problem - it was unstable soil!

I performed tests on artificial grass. I thought it's stable and solid enough, but obviously it has negative effect on flight time.

So my recommendation would be to be carefull when choose ground for testing.

Cheers

to make measurements on soil type grass you can use tools such as inertial sensors type Sensorize http://www.sensorize.it. They measure the height of the jump second protocol Bosco, or measure the height derived from the time of flight, but also also estimate the maximum height that the center of mass of an individual reaches. In addition, you will also have many other data related to the elongation phase of muscle shortening of the lower extremities in vertical jumps and much more ...

Systems with accelerometers like Sensorize, Humotion, Axlo, Keimove, Myotestor or Vertimetric don't need a platform. Usually they have the problem on detecting the start of the jump, but they are improving this. Another problem is accurate knowing jump height, because they rely on double-integration from acceleration to space, and this has an accumulated error. On the other hand, as the jump is a know movement and it's cinematic data is easy to model, they have algorithms to fix this error.

Another solution is infrared or laser platforms. They have to be very close to the floor and you have to take care that floor (grass) is not interfering. We are working on releasing one of this platforms because we don't like accelerometers.

Cheers.