Sitting during a long time with a bad posture can be bad for the back, and can develop back pain.
Many papers coincide that sitting in a bad posture can harm your musculo-skeletal back system, and some say that can be bad for the respiratory sistem too. The importance of mantaining a good posture and standing up every certain time is clear in all of the papers, being active is also essential, doing sport should be a must and not only a hobby for everyone.
You have here some papaers in case you want to read about this.
How to sit propperly
There are a few things you should control to sit correctly, here are some of them:
1 Do not slouch, mantain you neck stright and try not to get very close to the screen or the table.
2. Do not separate the lower back from the chair backrest, lumbars should be lean on the chair backrest.
3. Lean your arms on the armrest or on the table.
4. Your feet should be flat on the floor.
So, knowing that
DO NOT SLOUCH
GET ERGONOMIC FURNITURE
REST YOUR LOWER BACK ON THE CHAIR BACKREST
IF YOU HAVE DOUBTS OR BACK PROBLEMS GO TO AN EXPERT