to train the spinal erectors in a dynamically way i generally use back extensions with a rounded back and it works well.
but do you have other excercises? perhaps seated good mornings but instead of a straight back all the time round the back and then raise it up on each rep? or the same execution on a seated back training machine?
it's important for me, that all these excercises training the spinal erectors dynamically and not statically!
thank you all for your inputs.