“Lift with your legs, keep your back straight” is the most repeated piece of back advice in existence. It is also, as a claim about injury risk, largely unsupported.
The claim
That flexing the lumbar spine while lifting causes back pain or injury, and that keeping it neutral prevents them.
What the evidence actually shows
A systematic review with meta-analysis in JOSPT examined whether lumbar flexion during lifting is associated with low back pain. It found low-quality evidence that greater spinal flexion during lifting was not a risk factor for the onset or persistence of low back pain.1
More awkwardly for the advice: several studies report that people with chronic low back pain lift with straighter trunks and more knee bend than people without it. If the recommended technique were protective, that pattern should run the other way.
The review concluded the common warning is given without in-vivo kinematic evidence to support it.1
Workplace programmes built on lifting training have a similarly poor record: reviews of training and lifting equipment have not found reductions in back pain or consequent disability.
What does predict occupational back pain
Cumulative mechanical exposure, not technique on any single lift. A meta-analysis of occupational mechanical exposures found associations for repeated bending and twisting, lifting and pulling, sustained awkward positions and whole-body vibration.2 A prospective cohort measuring cumulative low back load at work found the same pattern.3
In other words: how much, how often, and how prepared you are — not the shape of your spine during rep number four.
So what should you actually do
- Build capacity. A back that regularly handles load tolerates load. This is the argument for strength training, including loaded flexion.
- Manage the total. Rotate tasks, split loads, use equipment for the genuinely heavy things.
- Warm up before a physical shift, particularly in cold conditions.
- Vary how you lift. A single rigid technique repeated all day is its own kind of repetitive exposure.
The honest caveat
None of this means technique is irrelevant in every context, or that you should deliberately round your back under a maximal load you have never trained. It means the blanket warning — that ordinary bending is dangerous — is not supported, and that teaching people their spine is fragile has costs of its own.
Related
Everyday lifting looks different for new parents and for couriers: see carrying a baby and drivers and couriers. For building capacity rather than perfecting technique, see how to improve your posture.
Footnotes
-
Saraceni N, et al. To flex or not to flex? Is there a relationship between lumbar spine flexion during lifting and low back pain? JOSPT, 2020. ↩
-
Occupational mechanical exposures as risk factor for chronic low-back pain: a systematic review and meta-analysis. 2024. ↩
-
Cumulative low back load at work as a risk factor of low back pain: a prospective cohort study. 2013. ↩
General information, not medical advice. Every claim carries its source; where the evidence is thin, the page says so.Editorial policy · How we grade evidence · All sources · Disclaimer