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

To evaluate whether lumbar spine flexion during lifting is a risk factor for low back pain (LBP) onset/persistence or a differentiator of people with and without LBP.Etiology systematic review with meta-analysis.Database search of ProQuest, CINAHL, MEDLINE, and Embase up to August 21, 2018.We included peer-reviewed articles that investigated whether lumbar spine position during lifting was a risk factor for LBP onset or persistence or a differentiator of people with and without LBP.Lifting-task comparison data were tabulated and summarized. The meta-analysis calculated an n-weighted pooled mean ± SD of the results in the LBP and no-LBP groups. If a study contained multiple comparisons (ie, different lifting tasks that used various weights or directions), then only 1 result from that study was included in the meta-analysis.Four studies (1 longitudinal study and 3 cross-sectional studies across 5 articles) included in meta-analysis measured lumbar flexion with intralumbar angles and found no difference in peak lumbar spine flexion when lifting (1.5°; 95% confidence interval [CI]: -0.7°, 3.7°; P = .19 for the longitudinal study and -0.9°; 95% CI: -2.5°, 0.7°; P = .29 for the cross-sectional studies). Seven cross-sectional studies measured lumbar flexion with thoracopelvic angles and found that people with LBP lifted with 6.0° less lumbar flexion than people without LBP (95% CI: -11.2°, -0.9°; P = .02). Most (9/11) studies reported no significant between-group differences in lumbar flexion during lifting. The included studies were of low quality.There was low-quality evidence that greater lumbar spine flexion during lifting was not a risk factor for LBP onset/persistence or a differentiator of people with and without LBP. J Orthop Sports Phys Ther 2020;50(3):121-130. Epub 28 Nov 2019. doi:10.2519/jospt.2020.9218.