Doc looking at MRIs of my spine said, Do you over-sit?
I once had the Romantic notion that I wouldn't live beyond my thirties, but I did, go figure, and accumulating hours upon hours, year after year in a chair, as writers do, ultimately wrecks your spine. Doesn't matter if you sit straight or on an expensive task chair or a medicine ball; bodies weren't made to sit for hours. Ergonomic gear is designed to make workers more productive, not healthier. And spinal degeneration doesn't go away. I've taken to spending half my writing day standing up, my computer on the dishwasher top. It's just the right height.
Seeking prevention advice (my favorite here), I find unanimous agreement on this: Get up and move, hourly. Stretching arms upward and back while still seated is ineffective; you must rise from the chair and move, or at least touch your toes. I know it sounds like a pain to get up every hour, but just as you wouldn't smoke because it's bad for you, or read in poor light, you wouldn't want to oversit. I know how it is when we're on deadline or pursuing a big inspiration. But be aware. "If I'd known I was going to live this long, I would have taken better care of myself." - Eubie Blake