I had back surgery a few years ago and before it float tubing did not particularly aggravate it ... and after the surgery I was able to float tube pretty quickly...and the kicking activity seemed to help....but beware..there are so many variables that it is very individual...e.g. slumping did not bother me but it would a lot of folks with bad backs....also some sitting bothers , others standing, others walking, and it goes on...not much help was I....