If you test your max height vertical jump onto boxes then you are more than likely testing your hip mobility the most!
Yes, you see some mad people on Instagram that can jump on a box the same height as them. It is impressive, but there are three things you have to have mind….
1) Its ‘For The Gram’.
2) There landing position resembles more of a frog position with their knees by their head as opposed to a good landing position.
3) You are training triple extension not how many inches you can jump on to.
The main reason why we jump onto a box with any plyo exercise is to reduce impact on landing. This will control the landing better and save your joints from taking a hit if landing back onto the floor.
A good landing position will be body weight even distributed through both feet with a slight bend in ankles, knees and hips. With knees tracking over the middle toes. If you are landing in full hip flexion then all you have done is brought your knees to your head. You haven’t actually jumped any higher.
Someone with good ankle and hip range of motion could be seen to have a better vertical jump then someone with poor range of motion in their ankles and hips. However, if you were to properly test them in a vertical jump the results could be different.
Ways to test you max vertical jump:
Measure distance between reached out arm whilst on floor against a wall vs your jump reach against a wall (cheap option)
Buy a vertec (Expensive option)
Buy a force plate (Most expensive option)
P.S. Jumping on to loads of high boxes and plates normally ends in tears.