I generally have a desk-bound job, which is no god for your back anyway. I've had back problems on and off for about 10 yrs. This has involved being stuck in the shower unable to move, similarly during a bouts of digging at the allotment and when driving long distances – having a spasm down the fast lane is slightly disconcerting.
Things came to head a few years back with a chronic chest infection. I was on the loo at the time, hacking away with a cough then I suddenly sneezed and that was it – I just couldn't move. Ended up being off for 2-3 weeks diagnosed with sciatica after seeing the GP. I had to be careful for quite some weeks after that. I eventually got round to fixing up the old bike a month or two on and then decided to try some short rides. After gradually building up the rides, my back just kept improving. I decided to start commuting by bike. For me, adopting a longer lower riding position with 150mm zero degree stem helped.
Three years on, after I rarely have any twinges. There's something about the way you move and flex when cycling that for me has been the best form of physio and remedy. I feel that I if keep moving and flexing regularly in some way during the day, it prevents the problem from returning. At work, I actively fidget, making sure that I regularly get up and walk about.