They are better for people who do not already have a bad back. Because firmer options do not collapse the lower back, it will be easier to breathe. Harder ones avoid the problem of sagging and distribute the weight of the body more evenly. This is especially beneficial for those who are heavy. And because most of the tension will be absorbed by the bones in this case, the muscles will remain relaxed. But the downside is that if you are used to sleeping on a soft mattress, switching to a firmer mattress can feel uncomfortable.