Samenvatting

Background: Development of more effective interventions for nonspecific chronic low back pain (LBP), requires a
robust theoretical framework regarding mechanisms underlying the persistence of LBP. Altered movement
patterns, possibly driven by pain-related cognitions, are assumed to drive pain persistence, but cogent evidence is
missing.
Aim: To assess variability and stability of lumbar movement patterns, during repetitive seated reaching, in people
with and without LBP, and to investigate whether these movement characteristics are associated with painrelated
cognitions.
Methods: 60 participants were recruited, matched by age and sex (30 back-healthy and 30 with LBP). Mean age
was 32.1 years (SD13.4). Mean Oswestry Disability Index-score in LBP-group was 15.7 (SD12.7). Pain-related
cognitions were assessed by the ‘Pain Catastrophizing Scale’ (PCS), ‘Pain Anxiety Symptoms Scale’ (PASS) and
the task-specific ‘Expected Back Strain’ scale(EBS). Participants performed a seated repetitive reaching movement
(45 times), at self-selected speed. Lumbar movement patterns were assessed by an optical motion capture
system recording positions of cluster markers, located on the spinous processes of S1 and T8. Movement patterns
were characterized by the spatial variability (meanSD) of the lumbar Euler angles: flexion-extension, lateralbending,
axial-rotation, temporal variability (CyclSD) and local dynamic stability (LDE). Differences in movement
patterns, between people with and without LBP and with high and low levels of pain-related cognitions,
were assessed with factorial MANOVA.
Results: We found no main effect of LBP on variability and stability, but there was a significant interaction effect
of group and EBS. In the LBP-group, participants with high levels of EBS, showed increased MeanSDlateral-bending
(p = 0.004, η2 = 0.14), indicating a large effect. MeanSDaxial-rotation approached significance (p = 0.06).
Significance: In people with LBP, spatial variability was predicted by the task-specific EBS, but not by the general
measures of pain-related cognitions. These results suggest that a high level of EBS is a driver of increased spatial
variability, in participants with LBP.