Use a dynamic lumbar support.
You probably can't avoid sitting. But you can lessen the strain of sitting by using a specifically designed lumbar support. This doesn't mean getting a little cushion you toss behind your back. McGill says that, for a lumbar support to be effective, it needs to be dynamic, or change shape, so that it continually shifts your posture and the load on your spine. McGill sells proprietary lumbar supports with inflatable air bladders – check them out at backfitpro.com; they're also available at many other online retailers. Additionally, you can also find dynamic back supports at some massage stores and sports rehab clinics.