Having trouble telling when mattress is too soft (if hips sink in too much)

Something my husband and I noticed when we were trying to help each other check for alignment during testing different firmness levels was that neither of us ever felt like our spines were truly straight.

The images you can find online depicting a correct spinal alignment position always show the spine exactly parallel to the ground. But our spines even when they seemed close to straight always kind of angled up at the head.

Are the completely parallel images realistic? Or is it just models posing? If they are realistic, then the angle we keep encountering is frustrating.

It feels very easy to evaluate and tell whether our shoulders were encountering too much resistance and not being allowed to sink in. If the mattress was too hard our shoulders would end up feeling and looking scrunched up the way one would hold up a phone to one’s ear without hands.

But I can’t understand how to tell whether my hips sink in too much.

I do know that coming from an “old school” harder bed is better background that I really really dislike mushy beds. To my dismay it seems like only the softest mushy mattresses were allowing my shoulders to sink in enough. (Top 2" 65kg/m3, Middle 3" 65kg/m3, Bottom 3" 75kg/m3) When I moved up to a firmer mattress that I liked the feel of better (Top 2" N3 Talalay, Middle 3" 65kg/m3, Bottom 3" 80kg/m3) my shoulder felt a little high.

But for all the softer options I felt clueless whether my hips sunk in too far. There were definitely no gaps around my waist so I know they probably weren’t too hard.

Are there some tricks or certain positions or sensations to try and look for to test for too soft in the hips?

Hi amnj,

While “proper” alignment is one of the keys to achieving more time in the deeper stages of sleep, it is rare to find someone that has an exactly “straight” spine (when on their side), nor is a perfectly straight spine necessary to achieve good comfort. We all have our individual abnormalities, so the key is finding what works best for us as individuals. Additionally, unless you were experiencing something quite a bit outside of your “normal” alignment, it would be difficult for you to discern personally if your spine was “straight” or not. And even with very accurate measuring techniques like white-light raster triangulation, research shows that many people achieve their own personal “neutral” alignment with hip tilt and some thoracic curvature. So it is all very individualized.

I would tell you to use the images you find online as guides as to what you might see in the extremes of a mattress that was “too soft” or “too firm”, but not necessarily as an ultimate guide which must be achieved. Your personal comfort and impressions when carefully testing out a product will be more important than “ideals” from a drawing or graph.

The best way to determine if the surface of the mattress was too hard would be with your initial perception of surface comfort (“comfort” of course is different from “alignment”). How much your shoulders sink in can also be determined by how you roll your shoulder into the mattress (shoulder blade abducted or adducted) and how you hold your arm underneath you. And finally, having a pillow that is the proper thickness (thicker with a firmer mattress) will also make a difference, so you have to be sure to adjust eh pillow thickness when you try out different firmnesses of a mattress.

Again, I would trust your own careful testing when trying out the product, as opposed to trying to achieve a “theoretically perfect” alignment. It’s usually quite easy to tell if you’re sinking in too much when you’re on your side, as the downward tilt of the pelvis will also cause lateral curving of the lumbar spine and lower thoracic region, which can be uncomfortable. It can also place a bit more pressure on the waist area, as the hips are sinking down quite a bit. Here are some steps I came up with a few years ago that may be helpful to you:

First of all … it’s important when you are testing for pressure relief or alignment to make sure you lie on a mattress for long enough that your mind and muscles are fully relaxed. A mattress can feel very different when you are fully relaxed than it does when you are tense. For most people this means spending at least 15 minutes on a mattress that you are seriously considering and focus on the relaxed feeling that you have when you are going to sleep.

The second key is to focus specifically on testing for alignment and its symptoms rather than comfort in all your sleeping positions. There are several things here that can help.

  • Try to sense whether your muscles are able to completely “let go” and allow the mattress to support your natural alignment rather than using muscle tension to keep you in alignment. This means that you can sense your body and muscles fully relaxing without a tendency for any area to be tense.

  • Next is to pay particular attention to any tension or discomfort (or even pain) in the areas where poor alignment tends to produce symptoms for you. This can be different for different people but is usually in the lower back or lumbar curve, and the upper back and neck where the spine also curves. Test in all your sleeping positions making sure to move slowly when you change position and stay relaxed. Bear in mind that minor discomfort when you are testing can be amplified when you are sleeping for longer periods of time.

  • Next is to make sure that all the inner curves of the spine are filled in so that there are no “gaps” in between your body and the mattress. It should be fairly difficult to slide you hand under the lower back or waist (if the mattress is too firm then this area will not be filled in well enough and sliding a hand under it will not have enough resistance and will be too easy).

  • Finally you can use the help of someone who can see you on the mattress to make sure there are no obvious issues of alignment such as those in some of the diagrams you provided. If you stand up with “good posture” then your “helper” will be able to get a sense of your natural curves from the side and back and this can help them see if your posture is close to what it is when you are standing up and whether any part of your body is sinking in a little too far (usually the hips/ pelvis) or not enough (usually the upper body and shoulders). They can also make sure that your head and neck is also in good alignment when you are testing because this can affect how a mattress feels in the upper body area.

On your side … your spine should be “relatively” straight (like it is when you look at someone from behind) and your body profile along the side of your body should be similar to your standing position (shoulders and hips in roughly the same relative position). On your back … the spine and body profile should be similar to the side view when you are standing with no obvious areas where parts of you are sagging or sinking in too far or not enough (within reason).

Alignment itself is quite complex and involves different factors. The most important is spinal alignment from top to bottom of the spine and maintaining the natural curvature of the spine however it also involves “side to side” and “rotational” alignment and the alignment of the joints all of which can have a “natural” or “neutral” position along with a “learned” position. All of these interact with the ability of a layer to re-distribute weight throughout the surface of the body in each sleeping position (and there are many variations of the 3 basic positions).

An example of a “learned” position is people who over the course of many years have become used to a more “hunched” posture or a posture where the shoulders are more forward than back. This creates a learned position and in these cases a more “correct” position can actually be less comfortable or cause pain or discomfort.

A soft pillowtop will “allow” these types of positions more easily because of the characteristics of the foam. Latex has a higher compression modulus or “sag factor” than polyfoam and also a higher resiliency (stores more energy instead of absorbing and dispersing it and “bounces back” more readily). What this means is that on latex like you are testing … people who have good posture both top to bottom and side to side will be more supported in this “good posture”. Those who have a more “learned” posture (or even a natural posture or body type or weight distribution that is outside of the “norm”) may have a feeling that the latex is “pushing back” as it tries to even out the alignment in all directions. Polyfoam will “allow” more sagging into the material. This feeling of “pushback” as many people call it will be on the areas that are more “hunched” or need to sink in more relative to the lighter areas of the body.

This has been the subject of many conversations I have had with various people (including various chiropractors and other “experts” in medical, health, or training professions) about the difference between sleeping on a mattress that provides a theoretical “best” alignment which for some people may be uncomfortable because it is different from the “learned” position and involves stretching muscles and ligaments and tendons that have “tightened” in various positions over the years vs the benefits of a mattress that may not provide “perfect” alignment but are more comfortable and closer to the “learned” position. The general consensus is usually along the lines of “somewhere in between” often works better because it can encourage a sleeping position closer to natural alignment but not in such large steps that the process is too uncomfortable and the body has smaller adjustments to make.

So in these cases (or in cases where the natural alignment of the spine or the body’s weight distribution is outside of the norm for other reasons), then the challenge becomes how to find the “in between” that works best for each individual.

As a general rule … the deeper layers will have more effect on support and alignment and the upper layers will have more effect on pressure relief and comfort (which are easier to “feel”). Any middle layers will have an effect on both. How much each person feels each of these depends on what they are most sensitive to but for most it’s the comfort which is the most obvious short term factor which is less affected by the deeper layers.

Each person has a different weight distribution and also a different surface area in each part of the body that contacts the mattress and it’s the pounds of force per square inch in each area of contact that controls how far that area of the body sinks in to the mattress. As you sink in deeper, then the surface area changes while the weight stays the same (the hips for example are wider and have more contact area as they sink in more which spreads the weight around a larger surface area and reduces pressure) and once the shoulders sink in enough then the torso also begins to contact the mattress and the surface area of contact becomes much larger there as well. The reason that this is so important and that I’m mentioning it is because it’s complexity makes it impossible to predict which set of mattress specs will create good alignment in any individual person, and only your own personal testing and/or experience can tell if a mattress has the “support” you need in all the different areas of the body to keep your spine in good alignment in all your sleeping positions.

It would be very uncommon that you are not sinking in “enough” with your pelvis to allow for firm contact with the lumbar curve and it’s much more likely that something needs to be “held up” more than it needs to be “allowed”. Sinking in deeper with your pelvis may allow for firmer support (more compressed foam) under the arch of your back (which in some cases can be helpful) but it will also “allow” your pelvis to sink in deeper and “tilt” more as well. It’s the “relative” firmness of the different areas of the mattress underneath the different parts of your body that is most important. In most cases a foam material like latex that has a good compression modulus can accommodate both because of its ability to get firmer faster as you sink in deeper.

In general, you want firm enough deep support and then comfort layers that are “just enough” in terms of thickness and softness to “fill in” and support the more recessed parts of your sleeping profile and relieve pressure in your most pressure prone sleeping position (usually side sleeping for those who sleep in this position) so that there is less risk to alignment in your other sleeping positions.

While this answer has been much longer than you probably anticipated, you really have asked a question for which there is no one perfect answer, and researchers spend their entire careers trying to come up with an algorithm to predict such things (none yet exists of which I’ve become aware). My concern is that you’re deferring too much to an “overly soft” product with too little deep down support, sacrificing alignment to achieve a “theoretical optimal position”. The research from Haex and his group will point you toward alignment first, with enough comfort on top to avoid uncomfortable pressure, but not so much that you sink in too deeply.

I’m worried that the more information I present, the further I’m “muddying the waters” here, so I would have you defer to the steps I listed previously and trust in those results, and not be too overly concerned with a perfectly straight spine like in the photos.

I hope that I helped more than I confused you with this reply. If I didn’t, please let me know.


Thanks for the reply Phoenix. I think even though this whole thing has had me confused and indecisive that after revisiting I’ve been able to get a better feel of what happens when things are too soft.

I had one salesperson explain that usually a too soft mattress will cause a tendency for the pelvis to tilt backwards involuntarily when the body is trying to relax, and I started to notice that more.

So now I’ve got things narrowed down to:

Top 2" 65kg/m3, Middle 3" 75kg/m3, Bottom 3" 95kg/m3
Top 2" N3 Talalay, Middle 3" 75kg/m3, Bottom 3" 95kg/m3
Top 2" 65kg/m3, Middle 3" 80kg/m3, Bottom 3" 95kg/m3
Top 2" N2 Talalay, Middle 3" 80kg/m3, Bottom 3" 95kg/m3 [Untested]

I unfortunately couldn’t test N2 Talalay and N3, 80kg, 95kg was a little too firm for me so I’m curious if N2 would work better, but that’ll involve ordering it from somewhere without testing it.

I’m torn between 65kg/m3 Dunlop vs. N3 Talalay for the top layer. My initial comfort level when lying on the N3 Talalay is much better, but I think it must be slightly more firm than 65kg/m3 Dunlop because my shoulders aren’t able to sink in as much.

And then I’m torn between the 75kg/m3 vs. 80kg/m3 for the transition layer. I know these differences are small so it’s really hard for me to choose.

What are your thoughts about whether it’s better to err on the softer or firmer side for top layer?

What about for the middle transition layer?

I don’t think anything will be perfect since I’m a combo side and back sleeper, so my guess is any of those 4 choices will be approximately good enough. I just don’t know which way to lean.

(As an aside, can I just say how frustrating it is when your partner doesn’t care as much about finding the “best” mattress? Heh. My husband is really tired of testing and he just wants me to pick something for him. Sigh.)

Hi amnj,

I’m glad some of the information was helpful to you.

The tilt of the pelvis actually can be similar in mattresses that are too hard or too soft, as “sinking in” of the hips is different than pelvic tilt. So while I’m not quite sure what the salesperson meant by the pelvis tilting backwards, if the point they made to you made sense and assisted you in quantifying what you feel, then that’s all that matters.

[quote]So now I’ve got things narrowed down to:

Top 2" 65kg/m3, Middle 3" 75kg/m3, Bottom 3" 95kg/m3
Top 2" N3 Talalay, Middle 3" 75kg/m3, Bottom 3" 95kg/m3
Top 2" 65kg/m3, Middle 3" 80kg/m3, Bottom 3" 95kg/m3
Top 2" N2 Talalay, Middle 3" 80kg/m3, Bottom 3" 95kg/m3 [Untested]

I’m torn between 65kg/m3 Dunlop vs. N3 Talalay for the top layer. My initial comfort level when lying on the N3 Talalay is much better, but I think it must be slightly more firm than 65kg/m3 Dunlop because my shoulders aren’t able to sink in as much.[/quote]

Your first and third combinations (65/75/95 and 65/80/95) will be closer in “comfort” than to the second combination (N3/75/95), as comfort is determined mostly by the uppermost layer. While Dunlop and Talalay certainly have different feels (the Dunlop being softer initially and then tending to firm up faster – it has a higher compression modulus), the 65 kgM3 is an “approximate” ILD rating in the upper teens, while the N3 (I’m guessing from Talalay Global) is more in the upper 20s ILD, so you are correct that it is firmer, which I believe you felt when trying out the product.

If a Dunlop layer is the same ILD as a Talalay layer and the same thickness (and disregarding the effect of all the other layers and components in the mattress) then for many people the Dunlop will feel firmer than the Talalay because it has a higher compression modulus than Talalay (the rate that a foam material becomes firmer as you compress it more deeply) which can affect the perception of firmness. A Dunlop layer that is a few ILD softer than a Talalay layer will often feel similar in terms of firmness for many people although the Talalay will generally have a more resilient or lively feel than Dunlop which can also affect how some people perceive firmness.

You are correct, the difference here, especially in the deeper transition layer, will be less noticeable. The 75kgM3 is approximately in the low to mid-20s for ILD, with the 80 kgM3 in the upper 20s-low 30s for ILD.

[quote]What are your thoughts about whether it’s better to err on the softer or firmer side for top layer?
What about for the middle transition layer?[/quote]
As I think you’re already well aware, the first “rule” of mattress shopping is to always remember that you are the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved that are unique to each person to use a formula or for anyone to be able to predict or make a specific suggestion or recommendation about which mattress or combination of materials and components or which type of mattress would be the best “match” for you in terms of “comfort” or PPP (Posture and alignment, Pressure relief, and your Personal preferences) or how a mattress will “feel” to you based on specs (either yours or a mattress) or “theory at a distance” that can possibly be more accurate than your own careful testing or your own personal sleeping experience.

The initial surface comfort between your choices #1 and #3 would be similar, but when the top layers “bends in” to the transition layer on option #3, it will firm up just a bit quicker than in option #1, which you may notice a little more when you’re on your side. In option #2, even though you’re mixing Talalay and Dunlop, the two layers are “similar” a little bit more in ILDs so the transition might feel a bit more as a “continuation” of the upper layer, but as it is compressed more it will certainly feel firmer. I think the largest difference here would be would obviously be your personal preference on how the upper layer initial comfort felt to you and which one was the most desirable to you personally.

You are really at the point though where your own experience will really be the most reliable way to know. It’s “somewhat” simple to predict the effect of a single minor change to the design of a mattress (say one increment of firmness for a single layer or an additional inch of material) but it’s more difficult to predict the effect of two or more changes or larger changes because of how all the layers can interact differently with each other and with different body types and sleeping positions. You’re really at a point of choosing between “good and good”, and I would really trust your impressions through careful testing at this point.