Fix Jump position- rounding my back?

[MB1201]

Hi I have a tendency when jumping to hunch over with my shoulders and collapse my chest rather than folding from my hip, my back has a round shape - how can I fix this knowing that likewise it isn't good to have an arched back from trying to flatten too much, thanks

 

[Illusion100]

Imagine you have a literal stick up your bum!

 

[alonerawnut]

An old instructor used to tell me to imagine I was "putting my bum on display" like those baboons that have brightly coloured bottoms! Stick it up and out for everyone to see - feels v. embarrassing but puts you in a good position!