Well there are many possible reasons why you are experiencing back pain from sitting in chair working, here are a few reasons...
1. You're looking down at your screen, phone, or desk. As your head tilts forward your head weighs on average 10 lbs, any slight angle forward puts strain on the muscles of the neck and upper back. If you keep that position your neck and upper back has to put in extra work on the muscles.
2.Your shoulders are rolled forward. Another term for this position is "hunchback." This may happen if your chair is too soft because lack of lumbar support or someone who doesn't have good posture. When your shoulders are rolled forward it strains your upper back and could cause cramps.
3. You're leaning forward from your lower back. This posture puts a lot more stress on the vertebrae of your lower spine by compressing your spinal disks or the lumbar area.
4. Your elbows are too far away from your body. When your elbows are far apart it puts stress on your shoulders and upper back. People who experience this may have a job where they are typing or writing at a desk or table for many hours a day.
5. If you sit for too long. My information is referenced by Dr. Joan Vernikos, a former director of NASA's Life Sciences Division and the author of the Sitting Kills, Moving Heals Book. She explains that "humans weren't designed to sit, the body is a perpetual motion machine." When your sitting, your muscles get less oxygen and nutrients from your blood. One easy way to prevent this is to change positions many times for every 30 minutes. Also drink a lot of water because it hydrates you and also forces you to get up and use the bathroom.
