Are you sitting at a desk in front of a screen right now? Take note of what your back is doing. Are you hunched over? Are your shoulders rounded?
Here is what you should be doing: sitting with your back against the chair and feet flat on the floor. Your eyes should be level with the centre of your computer screen.
Poor posture can cause back pain and fatigue. Check out these other common posture mistakes and fixes from the National Health Service UK.