I also often find that i pile up a lot of tension in my body after sitting at the computer for too long (which is not jobwise, but in my free time), but i’m not aware of it at that time. So i think i should put an alarm clock and oblige myself every X number of time (every half hour or hour or whatever) to get up and move a bit, walk a few steps or do a few stretchings.. And then i usually see that i’m getting tensed. But if i don’t take this little break i don’t notice this so it keeps piling up.

Perhaps it could help you to set certain times that you have to get up from your desk for a moment and pay attention to your body and move it a bit?

Me too i have a back problem and i agree with chuminette that strenght training helps a lot, i had that for a while as treatment in the hospital and it did so much for me.

And, have you tried yoga?