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Although doctors used to recommend a firm mattress for bad backs, research suggests that medium-firm mattresses are best. If your mattress is too soft, place a sheet of plywood between your mattress and box spring or place your mattress directly on the floor. Medium-firm mattresses are especially beneficial if your hips are wider than your waist. However, opt for a firmer mattress if your hips and waist are equal in width. A foam mattress topper can add support to your back and keep your spine aligned. If you have a foam topper hanging around, place it on top of your bed so your back can remain in a neutral position. Although sleeping on your back may seem counterintuitive, it is the best way to reduce pain.  Sleeping on your back keeps your head, neck, and spine in a neutral position. Try this position first to relieve pressure on your back.  Sleeping on your back may induce snoring because it can constrict the airways.  Resting on your back can also induce sleep apnea—if you've struggled with apnea in the past, you may want to choose a different position. Lying on your side, with your torso and legs approximately aligned, can ward off back and neck pain simultaneously while elongating your spine. Because it keeps your airways open, it can also prevent snoring. Choose this position if your sore neck does not find relief from sleeping on your back. Side-sleeping is also useful for relieving hip pain. Avoid curving your back as much as possible to prevent additional pain. If you sleep on your back, place one pillow at the base of your back and one underneath your knees. For side sleepers, place a pillow between your knees to keep your hips aligned. This will help your body maintain your spine's natural curve, preventing muscle or tissue aggravation. Sleeping in the fetal position, with your torso hunched and knees bent, is the most common sleeping position. It can, however, cause a sore back if you have arthritis or sore joints. If you usually sleep in the fetal position, place a pillow in between your knees and straighten your back as much as possible. Sleeping on your stomach can exacerbate neck and back pain because it interferes with the natural curve of your spine. It can also put more pressure on your joints and muscles, which may lead to pain or paresthesia (pins and needles). If you're sleeping while upright, letting your head drop to one side can cause neck and spine soreness. Horseshoe-shaped pillows are ideal for sleeping with back pain in a car, plane, train, or reclining chair.  Pillows made of memory foam can contour to your body and are best at alleviating back pain. Feather pillows can also conform to your head and neck, though they can lose support and collapse over time.

Summary:
Use a medium-firm mattress to reduce pressure on your back. Try a mattress topper to keep your back in a neutral position. Sleep on your back to alleviate strain on your spine. Sleep on your side if lying on your back doesn’t work. Keep your head, neck, spine, and hips aligned. Use pillows as support if you sleep in the fetal position. Avoid sleeping on your stomach. Use a horseshoe-shaped pillow while sleeping upright.