Foam Roll Back Extensors

hi

i just recently got totally into foam rolling, and i am still testing out whats good and what not.

so now i was wondering about the back extensors especially the lower part starting right at the ass.

with the foam roll u dont really get to them because the spine is in the way, so i taped 2 tennis balls together as i read on this page.

now i am not sure if it is even advisable to work on that part because in all articles it is left out.

id be greatfull for any help!

Do you guys work on the lowest part of the back extensors???

sebastian Fischer