We decided to break things down in shorter (but still informative) essays more focused on main sleeping position.
Go look in the mirror at yourself in a relaxed, standing position. Note the position of your shoulders in relation to both your hips and waist region. This is your neutral position.
This is what the best mattress for you will do: it will allow your body to rest in that alignment while you’re sleeping.
For the side-sleeping individual, imagine replicating your standing position while in bed.
The shoulders and hips need to “get in” to the mattress, compressing the materials just enough so that the midsection gets proper support. There should be contact on every part of your body: no gap under the midsection.
The firmness of the best bed for you depends on your build and weight.
When side-sleeping, if the shoulders and/or hips do not compress the surface of the mattress enough, the mattress will essentially repel them. So comparing the two:
Plenty of room for shoulder/hips and support through the midsection. Spine in a straight alignment.
Shoulders and/or hips get forced upward (towards the ceiling), which flexes the spine into a “U” position. Pain in the low back area will occur. Also, compression upon the shoulders/hips can cause numbness in the arm, tingly fingers, mid-back pain, hip/shoulder pointers, etc.
If a mattress is too soft, the heaviest parts of the body (hip zone) get too far into the mattress; once again, the spine is flexed in an unnatural position. Different problem with the same results: Low back pain and more.
So there you have it, yet again. The proper mattress for YOU will be dictated by: