Support your back (Tip 1)

[pioneer]

Use a chair that supports your lower back. Adequate lumbar support helps prevent muscle fatigue, which causes many people to lean their heads and upper backs too far forward or to slouch downward. With good lower back support, spinal muscles are relaxed and the spine is able to maintain its neutral position. (ririanproject.com)

[MikeLigalig.com]

commercially-made plastic chairs here in the philippines seem to be not spinal cord-friendly.