Hi brass,
It can certainly be more difficult to check alignment when you are alone and don’t have someone to help “eyeball” you (either a partner of a retailer).
While no testing will be 100% reliable … the goal of good testing is to shift the odds of success as much as possible in your favor.
It’s still possible to do a reasonably good job if you pay careful attention to the signals your body is giving you and if you spend long enough on the mattress. Some of the things that would be important is that your testing “approximates” your sleeping experience as closely as possible so it’s important to wear loose clothing, make sure you are testing with a good pillow, and spend long enough on the mattress that your muscles are completely relaxed. Your muscles will generally take about 10 or 15 minutes or so to relax when you are “going to sleep” and this is when good testing begins and you will be more likely to be able to “feel” how your body is doing on the mattress by listening to the more subtle signals and seeing if your muscles can “let go” or if they resist relaxing completely to keep you in alignment.
There is also a range of alignment that works for each person (younger more flexible bodies that haven’t developed any “issues” will generally have a wider range) so the goal is not to have alignment that is “ruler straight” because everyone’s natural alignment isn’t “ruler straight” (just like all feet don’t fit a “perfect” shoe).
If you do well and make a choice that is inside your range … you may still have some initial discomfort or “symptoms” on the mattress just because it’s different from what your body is used to sleeping on (just like a new pair of shoes can take a while to become comfortable) and your different muscle memory will feel it’s different from your old mattress (see post #7 here) but if your alignment is good then the symptoms will diminish and disappear vs if your alignment isn’t good then any “symptoms” can get worse as you spend more time on the mattress (just like a pair of good shoes that has better arch support can be uncomfortable until you get used to better arch support).
So good testing is the best way to “predict” your experience on a mattress and have the highest possible odds of success even though it may not be 100% accurate and you may still go through an adjustment period.
Some local retailers I know don’t have any exchange or return policy at all because they don’t feel good making people who don’t return or exchange a mattress pay for the ones who do and have the skills and confidence to help their customers make good choices they have a very high success rate. Of course they may also lose a sale to a customer who is more uncertain that a mattress is a good “match” for them and is willing to pay a higher price for a return or exchange option.
Of course if you are buying online and making a choice based on averages that you can’t test in person then of course a good return or exchange policy can become much more important.
I also believe that many years of sleeping out of alignment are certainly one of the factors that can help lead to back issues over the years even if the symptoms don’t become obvious right away.
Phoenix