it ain't easy but one can move one's center while seated.
I've actually been working on moving the hara for a while while driving. With good sport seats, your hips and shoulders are held in place--great for isolating the hara.
I was at a party the other night with a guy who's doing guided meditation with PTSD survivors, and that conversation got me thinking--do you think breathwork and basic connected-movement practice would help people who have mobility issues? My mother is having a harder time getting around as she gets older, and this MS thread got me thinking about that--you think that kind of practice would be helpful to these folks?