The best mattress for stomach sleepers in one that keeps your hips in a neutral position and reduces the amount of twisting in your neck.
Sleeping on your stomach is not generally regarded as an effective way to sleep.
The reason is that in order to position your head in such a way that you can breathe effectively you must place incredible strain on your neck.
However most people who sleep on their stomach have been indirectly forced to do so in the sense that they find that side sleeping or back sleeping does not provide an adequate night's rest.
So if you find yourself sleeping on your stomach you must ensure you have the right mattress and pillow combination to ensure that you get a good sleep without placing unnecessary strain on your body.
The key aim in determining the right mattress for stomach sleepers, or any sleep style for that matter, is ensuring the spine is kept in a neutral position. If you sleep with too firm or too soft a mattress, or with the wrong pillow it can cause your spine to arch too much or too little.
The issue with stomach sleeping is that the hips may be forced too high or allowed to sink too far. If they sink too far into a soft mattress it will cause the back to arch too much. If the mattress is too firm there will not be enough give to find the neutral spot and it will unnaturally flatten the arch in your lower back.
When determining the best mattress for stomach sleepers you have to consider the role of the pillow as well. Ideally a stomach sleeper should sleep with no pillow or a very thin pillow. This is for the health of the neck and to prevent too much twisting. In this case the upper layer of the mattress needs to be soft enough too be comfortable.
However that means the mattress must still have enough support to prevent the hips sinking too far. If you prefer an innerspring mattress the best combination is one with firm springs and a pillow top for comfort.
Overall when it comes to mattress firmness for stomach sleepers a medium firm mattress will be your safest bet however you will need to adjust towards firmer or softer depending on your body weight.