Abstract
Purpose and Background:
Healthy adults with a curvy (lordotic) lumbar spine were shown to lift a load from the floor by stooping, while straight (flat) spines squatted. Since skin-surface motion capture often misrepresents internal curvature this study calculated internal lumbar curvature during lifting in the same cohort and compared lumbosacral motion.
Methods:
Magnetic resonance imaging (MRI) was performed in standing and bending forward to 30, 45 and 60°, with markers on the skin at L1, L3, L5 and S1. Lumbar spine shape was characterised using statistical shape modelling and participants grouped into ‘curvy’ and ‘straight’ spine sub-groups (N=8). On a separate day participants lifted a box (6–15 kg) from the floor without instruction while Vicon cameras tracked sagittal movement of L1, L3 and L5 skin markers. Sacral angle (to horizontal) was calculated from pelvic markers. Matching markers during MRI and lifting sessions allowed vertebral centroid positions (L1, L3, L5, S1) during lifting to be calculated using custom MATLAB code.
Results:
The curvy group had more internal lumbar lordosis at pick up despite stooping to lift the load. From upright standing motion occurred earlier at the upper lumbar levels (L1–L3) compared with lower lumbar (L3–L5). During lifting straight spines had greater rigid-body motion of the entire lumbar spine compared with curvy spines who demonstrated more varied intersegmental motion with greater sacral flexion.
Conclusion:
Individuals with very lordotic spines retained some degree of internal lordosis despite stooping when lifting. The lumbar spine appears more mobile at the upper levels, L1–L3, and constrained motion was seen in those with the least lordosis.
