Sheep jumps

[Invisible Duck]

I am trying to improve my sheep jumps (on floor).

I cannot get my feet high enough consistently. Does anyone have any ideas or tips for doing them??

I have been doing them with light weights on my ankles but it does not seem to be helping that much..... (on my other jumps the difference is very noticeable!!)

Is it necessary to have a really flexible back to do sheep jumps? If so, how can I improve back flexibility?

thanks!!