Hi healthysleep,
There is no specific configuration or type of mattress that is “good for fibromyalgia” in general because each person is unique, and a mattress that works well for one person with a specific condition such as fibromyalgia may be completely unsuitable for someone else with the same conditions to sleep on. In very general terms … softer and more pressure relieving materials that provide a more “relaxed” sleeping surface will tend to work better than firmer materials because for most people with fibromyalgia a softer more pressure relieving sleeping surface is a more important priority, but I know that this does vary with individuals, as well as varying day to day. Muscle spasms can have multiple causes, many of which can have nothing to do with the mattress, so there would be no recommendation I could make for a type of component that might be appropriate for a muscle spasm unless that spasm was directly related to a deficiency in your current sleeping surface.
A forum search on fibromyalgia (you can just click the link) will bring up more comments and feedback from others that are in similar circumstances that may be helpful (but it will also confirm that there isn’t a single “best” combination of materials that will work for everyone with fibromyalgia).
Nothing can replace your own personal testing, as you do have some very specific health considerations. You’d obviously want to consider something that allows for enough surface comfort while sleeping upon your side and back, and also assists with pressure point relief, while still overall being resilient enough and provide enough support while sleeping. Overall, the two basic functions of a mattress are to support and to provide comfort (you can read more about that here if you like), with alignment being the first priority and then comfort coming second.
The mattress you mentioned uses innersprings and polyurethane foam, which I believe is a material you are trying to avoid.
Zinus is a Chinese manufacturer that makes a wide range of brands including Enso, Vivon, Spirit Sleep, Night Therapy, Keetsa and many others (see post #2 here ). They tend to use lower quality/density and less durable materials in their mattresses than I would normally consider. A forum search on Zinus (you can just click the link) will also bring up more information about them as well. They are all manufactured in China and shipped compressed to North America so I would also read post #6 here for more about Chinese imports and some of the additional uncertainty and risk that can be involved in purchasing them.
Before you go visiting mattress stores I would recommend you take a few minutes and browse through the mattress shopping tutorial here which includes all the basic information, steps, and guidelines that can help you make the best possible choice.
Two of the most important links in the tutorial that I would especially make sure you’ve read are post #2 here which has more about the different ways to choose a suitable mattress (either locally or online) that is the best “match” for you in terms of “comfort”, firmness, and PPP (Posture and alignment, Pressure relief, and your own Personal preferences) that can help you assess and minimize the risks of making a choice that doesn’t turn out as well as you hoped for, and post #13 here which has more about the most important parts of the “value” of a mattress purchase which can help you make more meaningful quality/value comparisons between mattresses in terms of suitability (how well you will sleep), durability (how long you will sleep well), and the overall value of a mattress compared to your other finalists based on all the parts of your personal value equation that are most important to you (including the price of course and the options you have available after a purchase if your choice doesn’t turn out as well as you hoped for).
Outside of PPP (which is the most important part of “value”), the next most important part of the value of a mattress purchase is durability which is all about how long you will sleep well on a mattress. This is the part of your research that you can’t see or “feel” and assessing the durability and useful life of a mattress depends on knowing the specifics of its construction and the type and quality of the materials inside it regardless of the name of the manufacturer on the label or how a mattress feels in a showroom or when it is relatively new so I would always make sure that you find out the information listed here so you can compare the quality of the materials and components to the durability guidelines here to make sure there are no lower quality materials or weak links in a mattress that would be a cause for concern relative to the durability and useful life of a mattress before making any purchase.
Phoenix