answer:Taking regular breaks might help. Also, stretching. Just raising your arms above your head and linking your fingers and stretching up can reset your spine to a degree. Breaks are really the key though. Even if you just walk up and down for a few moments. Push your shoulders back. The muscles of the back lengthen and those in the chest shorten, so trying to counteract this is helpful. Also, make sure your work area is set up properly. Even if you have to use books to put your laptop on (if you have a laptop), feet firmly on the floor. So you aren’t hunching over. Lower or raise the chair. I know you are in a public place, but as much as you can set up where you are working so you aren’t putting strain on your back.