Back to backs
Hi Aviator,
I expect it's just because you're a knackered old fart like so many of us. Seriously, though, it is a common problem for helicopter jockeys.
My back started to play up about 10 years ago when I jumped a ditch with a golf bag on my back! Forgot I wasn't twenty five any more.
These days, when I feel it's about to give me problems, I hang myself up by my feet for as long as I can bear it. [For those PPruners with prurient imaginations I remain fully clothed throughout]. It allows the vertabrae to re-allign as well as to let the discs to, as it were, reinflate with fluid a bit.
This practice was recommended to me by a superb back specialist who I see when the above is insufficient.
You can buy a frame designed to facilitate getting upside down but I made my own, you do need something to ease you into the right position.
Uncle Ian