How do persons with chronic low back pain speed up and slow down? Trunk-pelvis coordination and lumbar erector spinae activity during gait.

In healthy walking, the timing between trunk and pelvic rotations, as well as erector spinae (ES) activity varies systematically with walking velocity, whereas a comparable velocity-dependent adaptation of trunk-pelvis coordination is often reduced or absent in persons with low back pain (LBP). Based on the hypothesis that trunk-pelvis coordination is linked to overall gait stability, persons with LBP can be expected to have difficulties in dealing with perturbations. We examined the ability of 12 persons with LBP and 12 controls to adapt trunk and pelvis rotations and ES activity to sudden changes in velocity. 3D angular movements of thoracic, lumbar, and pelvic segments and surface EMG were recorded during treadmill walking at six different velocities, which increased or decreased unexpectedly. Relative phases of segmental rotations were determined and (in-)variant properties of kinematics and ES activity were studied using principal component analysis. Compared to healthy controls, persons with LBP exhibited a reduced ability to adapt trunk-pelvis coordination and ES muscle activity to changes in velocity. Altered coordination and muscular control may reflect an attempt to stabilise the spine and prevent the occurrence of unexpected perturbations. The assessment of gait patterns in terms of coordination may help clinicians to quantify movement impairments and may suggest interventions aimed at facilitating the emergence of desired coordination patterns.