The impact sleeping can have on your posture is often over looked. When your twisting and turning in your sleep, you can get into all sorts of positions, some damaging to your back. Some mattresses do not provide the correct support for your back, talk to your doctor or go to a mattress specialist to ask for advice if you are experiencing severe back pain. To improve your posture whilst you sleep, it is best to sleep on your side or back. If this is uncomfortable, then place a pillow under your lower back/pelvis area