To Flex or Not to Flex? Is There a Relationship Between Lumbar Spine Flexion During Lifting and Low Back Pain? A Systematic Review With Meta-analysis.
Level 3 - non-randomized controlled study
Systematic review and meta-analysis of observational (predominantly cross-sectional) studies
PubMed 31775556 · doi:10.2519/jospt.2020.9218
What was done
A systematic review and meta-analysis searching ProQuest, CINAHL, MEDLINE, and Embase through August 21, 2018, evaluated whether lumbar spine position during lifting is a risk factor for low back pain (LBP) onset or persistence, or differentiates individuals with and without LBP. Meta-analysis calculated n-weighted pooled mean ± SD differences in peak lumbar flexion during lifting tasks, including only one task comparison per study.
What was found
Four studies (1 longitudinal and 3 cross-sectional across 5 articles) measuring intralumbar angles found no difference in peak lumbar flexion when lifting: longitudinal difference 1.5° (95% CI: -0.7° to 3.7°; P = .19) and cross-sectional difference -0.9° (95% CI: -2.5° to 0.7°; P = .29). Seven cross-sectional studies measuring thoracopelvic angles found people with LBP lifted with 6.0° less lumbar flexion than asymptomatic controls (95% CI: -11.2° to -0.9°; P = .02). Overall, 9 of 11 studies reported no significant between-group differences.
Why it matters
This paper challenges common ergonomic and clinical guidance advising against spinal flexion during lifting, showing that current evidence does not link lumbar flexion to low back pain development or persistence.
Limits
The evidence base is rated as low quality and consists almost entirely of cross-sectional studies (with only 1 longitudinal study), precluding clear causal conclusions. Measurement methodologies varied widely (intralumbar vs. thoracopelvic angles), and only a single lifting task variation was analyzed per study despite differences in weights and directions.
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