Most people make it way too complicated, but it is straightforward.
Below are the 3 things that will help gymnasts jump higher.
Lose extra weight
Parents are worried about girls eating too little and ending up anorexic.
However, at least in Finland, the problem usually is that girls are overweight for AGG.
Not overweight for the average girl off the street.
I said overweight for AGG.
A sport that even has the word “aesthetic” in the name and that gets more and more competitive every year.
The problem is too much fat (dead weight) and too little muscle (useful for force production).
If you need to lose some body fat, do it the painful way: SLOWLY.
If you want to perform like an athlete, you must eat like an athlete.
Put more force into the ground
The easiest way to do this is by improving your maximal and sub-maximal strength inside the gym.
Notice that a year or two of serious training is a minimum time to do this.
If you try to do this on your own, you will end up injured or overtrained.
Get an experienced coach that can show you the basics of strength training.
It will be money well invested.
Put force into the ground quicker
If you already are strong, you may not need to spend much time lifting heavy.
Instead, you can spend more time doing plyometrics (jumps with a short stretch-shortening cycle) and lifting in “speed-strength” velocities, where the load on the barbell is between 30% and 60% of your one repetition maximum.
If you are lifting with light loads, move the barbell as quickly as possible on the way up as if you were to take off like a rocket.
If you are training plyometrics, keep the stretch-shortening cycle as quick as possible.
This type of training will improve your ability to produce high forces in a short amount of time.
You will hear a lot of nonsense about different ways to increase your vertical jump.
However, it comes down to simple physics.
Get fit, get stronger, and put your strength on the ground quicker.
Nothing else will give you results.