So, when I'm not able to get outside and play, I'm in the unfortunate position of having to sit in a chair before a computer for many, many hours (of course, that allows me to do cool things like build Uncooped). But for me, sitting = slouching, and slouching = back problems.
Enter the Nada Chair, I tried one of these today and I swear it's going to be my next business expense. Weird as it looks, it forces you (comfortably) to maintain correct posture while sitting. And they're portable (zipping up into a nize self-contained pouch), which makes them great for things like canoeing, yoga fishing, etc.
If you don't want to shell out the dough for one of these at least do yourself a favor and get up to stretch every half hour or so. Here are some good stretches for alleviating back pain.