Objective: Lumbar curvature is an important factor in posture and body movement that help us to understand low back pain problems. The aim of this study was evaluation of external load and trunk posture effect on lumbar curvature under static condition. 

Materials & Methods: This study is an interventional, quasi-experimental and case-control study. Ten women with non specific chronic low back pain and ten matched without low back pain women were participated in this study. We used simple and non random method for sampling. Two clinometers sensors were used to evaluate lumbar curvature. Six static tasks while holding three levels of load (0, 6, 12 Kg) and two levels of trunk position (neutral and 30 degree of flexion) were simulated for subjects. Data were analyzed by using Kolmogroff-Smirnoff, ANOVA (Repeated Measurement) and independent T-test.

Results: Findings revealed lumbar lordosis in patients with low back pain does not change to kyphosis while increasing external load from 0kg to 6kg and 12kg in neutral trunk position (P<0.05).

Conclusion: Dysfunction in passive system due to soft tissue disorder, afraid of pain, changes trunk muscles recruitment and reduction of moment arm are likely reasons for increased lumbar lordosis in patients with low back pain during loading.