: Unless you're paddling in rough conditions, or really snapping a
: lot of rolls, there's not much about kayaking that is going to
: aggravate a disk problem... except for all the sitting.

Certainly in my case I've gone from persistent back pain to feeling just... fine, by taking up an entry level grade canoe polo at the local pool (and really just paddling in general). I'm convinced it's the variety of motion that's helped - I think repeating the same actions over and over again, or just lots of static sitting, is going to give problems. My personal experience is mix your exercise up as much as possible. Another observation - some people seem to push themselves to the edge, others hold back just a bit and I think that adds up over the years. Avoid overdoing it.