There are a lot of great pieces of equipment that we use in training. However, we don’t always know how these pieces of equipment work. If we do not know how the equipment we use work, then we cannot optimize it.
The Jump Mat
The jump mat is a piece of equipment that nearly every single coach has seen in action. People stand on a mat, they jump up in the air, they land and it tells you how high you jumped. The question is, do you know the mat got that number?
How It Works
In simple, the jump mat measures how long you are in the air based on pressure sensors inside of the mat. Depending on the mat you have, it determines the start of flight time when the pressure sensors read 15 pounds or less (not all mats do this). Then, based on a simple physics formula, the jump mat calculates the time interval between its loss in pressure (leaving the ground) and its registering of pressure (landing).
Click HERE if interested in the math and further details on flight times in relation to vertical jump heights. This is not my site referenced in the link, but it provides a lot of really useful information on this topic.
Jump height and time in air relationship
What Does This Mean?
So, if flight time is being measured, it means that vertical jump height is being calculated indirectly (via a formula). Because the jump height is being calculated from flight time, the athlete has the ability to “cheat” the test. If landings are not regulated properly the athlete can skew their jump heights. One might not think that not a huge deal, but if you want to use jump heights as a measure of readiness and your athlete knows how to squeeze out an inch or two on their vert, they might be screwing up your parameters.
For example, lets say whenever someone scores a vertical jump that is 5% less than their average you have them back off of training that involves high neural stress for that day. Now, lets say the athlete is fatigued and if they tested properly they would fall right below the 5% mark. If they know how to cheat well, they will be able to add an inch or two, which would register as not being too fatigued when they actually are. This could then lead to possible overreaching and eventually overtraining, which is something you cannot afford to run into in season.
Make It Consistent
Also, because flight time is being measured, in order to optimize flight time they need to jump straight up and straight down. So, even though it may seem minimal, making sure they go straight up and down will insure a more accurate reading. To get around this issue you might create a small chalk or tape box on your max. If the athlete lands outside of this box, you might deem the rep not acceptable and can make them retest.
Reduce The Error
We want to make our testing as reliable as possible. Granted, some of the tools we use are not the most valid. They might have some level of systematic error in them (they constantly register too high or too low), but for the sake of comparison we want reliable. In order to make the equipment as reliable as possible, we need to avoid all human error we can. This means we have to have standards for what proper landing form is and then methods of enforcing it.
Image: 1 http://marcocardinale.blogspot.com/2008/11/vertical-jump-tests-how-to-perform.html