Sleeping in a wrong position can accentuate the curvatures of your spine and reduce your height. The lower back is especially prone to ailments like swayback if it is not taken care of. Improving sleeping posture is one of the effective ways to gain height. The best position to sleep in is flat on the back. Always sleep on a firm mattress and never use a pillow supporting your neck. Place a thick pillow or pad under your knees to alleviate pressure on the lower back as you sleep. The pelvis and back muscles get adequate rest in this position. This position will also make sure that your brain gets more blood supply. The next best position to sleep in is on your side. Bend your knees and hips in when you sleep on your side to avoid swayback. Place a pillow between your knees to better support your spine.