Hi The Toddler,
Mattress plushness terms of course are relative descriptors, so of course your own personal thoughts are the most accurate guidance. It seems that your alignment is good (low back feels good) and that your upper back issues gradually reduced as time went on, which could be a sign of you losing some of your “learned alignment” for your old mattress, your new mattress adjusting to you, or just you overall adjusting to your new mattress.
Unfortunately, it’s not possible to “diagnose” mattress comfort issues on a forum with any certainty because they can be very complex and there are too many unique unknowns, variables, and complexities involved that can affect how each person sleeps on a mattress in terms of “comfort”, firmness, and PPP or any “symptoms” they experience. However, there is more about the most common symptoms that people may experience when they sleep on a mattress and the most likely (although not the only) reasons for them in post #2 here, specifically:
[i]Mid and upper back issues can also come from several sources. In the case of the upper body then good horizontal alignment is important but lateral (side to side) alignment is also important. For example if you bend your head and neck forward towards your stomach and bend the upper body forward into a forward hunched position then it can bend the upper spine and create tension and pain in the mid and upper back. This can happen during the night if your pillow is too high for example and pushes your head forward when you sleep on your back. It can also happen if the upper layers are too thick and soft.
In the same way … if you push your arms and shoulders forward into a forward slouched position then it can also create tension and soreness in your mid or upper back. This can come from a mattress that has comfort layers that are too thick and/or soft and allows your torso to sink in a little too far but “holds up” the lighter shoulders (pushing them forward).
In both cases your muscles will be tense and working throughout the night to maintain alignment.
Upper back issues can also point to a pillow that is either too high or too low for your body type or sleeping position and doesn’t maintain the gap between your head and the mattress and keep your head and neck if good alignment over the course of the night which can affect the upper back as well.[/i]
There is also new research coming out showing an increase in upper back issues due to rounding from people working on keyboard and tablets and texting, resulting is poor posture and flexibility issues. With your issues being very specific to one small area and coming and going, my thoughts run to the possibility of something environmental and not necessarily mattress related.
The first place I would start is assessing your pillow, making sure that it is a proper thickness to help maintain a more neutral alignment. As you sleep upon your side, you may also wish to consider a pillow placed behind you to lean slightly against while sleeping, and a pillow placed in front of you which you may use to support your free arm while sleeping on your side. Both of these things can help with some upper back issues.
There is some great information in this PHD thesis by Vincent+Verhaer (who is one of a group of researchers that I greatly respect) about the importance of good spinal alignment that clearly indicates that for healthy individuals it has the single biggest effect on the depth and quality of sleep, versus surface plushness. Of course, the ideal is to have both comfort and alignment. Good alignment doesn’t mean that a mattress necessarily needs a very hard surface comfort, and it seems that right now you have something that offers this good alignment, so I would be hesitant of changing your deep support characteristics.
Good spinal alignment is the most important factor that leads to deep and restful sleep and is important for all people whether or not they have back pain but making sure that a mattress is firm enough to prevent the heavier parts of the body from sinking down too far so you can maintain good spinal alignment over the course of the night in all your sleeping positions is especially important for those with back issues because the risks involved and the pain and discomfort that can come from a mattress that is too soft can be higher than for those that are more flexible and don’t have any back issues. I would also keep in mind that a mattress that is too firm (for you) can also lead to poor support and back pain. In the end, the only way to know for certain whether any specific mattress will be a “good enough” match for you in terms of comfort, firmness, and PPP will be based on your own careful testing and/or your own personal experience when you sleep on it.
The information in the post I linked to earlier, as well as a few of the suggestions I’ve mentioned here, are the “tools” that can help with the analysis, detective work, or trial and error that may be necessary to help you learn your body’s language and “translate” what your body is trying to tell you so you can identify the types of changes that have the best chance of reducing or eliminating any “symptoms” you are experiencing (at least to the degree that any symptoms are from your mattress rather than the result of any other circumstances or pre-existing issues you may have that aren’t connected to a mattress).
Phoenix