Why do my husband get bachsche when sleeping on his back?

Soft mattress: Sleepiness on a soft mattress can cause a backache. Spending several hours without significant movement of the back can also cause backaches, in which case moving after getting up should help the pain. Generally, if you do have backaches, the back with a pillow under the knees is the best position to sleep in. Another option is to sleep on the side with the knees bent and a pillow between them.