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Lower Back Pain and Your Mattress: What the Evidence Actually Says
Lower back pain and mattress deserves a clear, practical explanation. For decades the standard advice for a bad back was a firm mattress, sometimes a board under the mattress. It was confident, widely repeated, and not well supported. The research that has accumulated since points somewhere else.
The short answer. Medium-firm surfaces perform better than very firm ones in most controlled comparisons of non-specific lower back pain. The mechanism seems to be that a medium-firm surface lets the hips and shoulders settle enough to keep the spine neutral, while a very firm one leaves the lumbar curve unsupported.
Lower back pain and mattress: Why very firm went wrong
Lie flat on a hard floor and slide your hand under the small of your back. There is a gap. That gap is unsupported lumbar spine, and holding it there for eight hours is what a rock-hard mattress asks your muscles to do. A surface with some give lets the pelvis settle slightly so the curve is supported rather than suspended.
That does not mean soft is better. Too soft and the hips sink below the shoulders, which flattens and then reverses the curve. The target is narrow and it is roughly in the middle, which is an unsatisfying answer but the honest one.
Sleeping position matters as much as the mattress
| Position | Usual effect on the lower back | Simple adjustment |
|---|---|---|
| On your back | Generally good | Pillow under the knees to reduce lumbar strain |
| On your side | Good if the hips do not twist | Pillow between the knees |
| Foetal, tightly curled | Can stiffen the back overnight | Loosen the curl, pillow between knees |
| On your front | Usually the worst | Thin pillow under the hips, or change position |
| Half-on-front, one leg up | Twists the pelvis | Body pillow to stop the roll |
Things that are not the mattress
- The base. Slats spaced more than about 7cm apart let the mattress sag between them. Check this before blaming the mattress.
- Age. Most mattresses lose meaningful support at around 8 years. The decline is gradual, so you adapt to it without noticing.
- Your pillow. A neck held at an angle all night refers tension down the back.
- Daytime. Eight hours at a desk does more to a lower back than eight hours in bed. The mattress gets blamed because that is when you notice it.
Where medium-firm actually lives
The difficulty with “medium-firm” is that every brand scales it differently. Luxe Mattresses publish firmness ratings against a consistent scale and cover the middle of it properly, which makes it possible to compare rather than guess.
Browse medium-firm mattressesAffiliate link — we may earn a commission at no extra cost to you.
The honest caveat
Mattress research is difficult to do well. Blinding is nearly impossible, follow-up periods are short, sample sizes are small, and a lot of the studies are funded by people who sell mattresses. The medium-firm finding is reasonably consistent across what exists, but it is a mild effect, not a cure.
Persistent back pain deserves a proper assessment. A GP or physiotherapist can tell you whether your pain is the kind that a sleeping surface influences at all, and that is worth knowing before you spend several hundred pounds on a hypothesis. Pain that wakes you, radiates down a leg, or comes with numbness needs medical attention rather than shopping.
Supportive extras that are not a new mattress
If the mattress is sound and the problem is how you are positioned on it, a wedge, knee pillow or lumbar support usually costs a tenth of a mattress. Relax The Back specialise in exactly this category, which makes it a sensible place to try the cheap interventions first.
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