Summary: Place a spare duvet onto your matress before you place your cover sheet on.
Extra info: After spending many months in bed for up to 23 hours a day I wondered why I didn't suffer from the usual back pain problems. I soon worked out that it was the above technique that protected my back. You also get extra heat from below which is great if you live in a cold climate.
Try it and let me know if it works for you?
Disclaimer: This method works wonders for me. Try at your own risk.
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