Joint coordination during whole-body lifting in women with low back pain after pregnancy

Objective: To quantify differences in the kinematics of lifting between women with low back and/or pelvic pain after pregnancy and women without. Design: Comparison study. Setting: Research laboratory. Participants: Volunteer sample of 7 women with pain (positive pain drawing, no physical examination) and 9 female controls (not matched). Interventions: Not applicable. Main Outcome Measures: Duration of downward and upward phases, relative instant of box lift-off, joint angles, spatial angles of trunk and pelvis, pelvic angle relative to trunk, and phase angle relationships between joints. Results: The duration of the upward phase +/- standard deviation was longer in the pain group (1731+/-290ms vs 1489+/-187ms, P=.031). At box lift-off, this group had less hip joint flexion (101.9degrees+/-20.8degrees vs 78.7degrees+/-12.4degrees, P=.015) but more backward pelvis tilt relative to the trunk, that is, more lumbar spine flexion (126.3degrees+/-16.8degrees vs 109.0degrees+/-12.3degrees, P=.031). The pain group showed an immediate transition from lumbar spine flexion to extension, whereas the controls maintained peak flexion for about 600ms. The peak phase lag between knee and hip joint extension in the upward phase was larger for the pain group (-29.7degrees+/-8.3degrees vs -17.2degrees+/-5.5degrees, P=.003). Conclusion: Women with low back and/or pelvic pain after pregnancy showed different kinematics of lifting. Further research is needed to determine the exact relationship between the altered kinematics and the underlying disorder.