Lumbar stabilization programs reduce pain and disability, but the mechanisms of action underlying this treatment are unknown. Trunk postural control during unstable sitting represents a surrogate measure of motor control mechanisms involved to maintain the dynamic stability of the spine. This exploratory study aimed to determine the reliability of trunk postural control measures over an 8-week interval, their sensitivity to low back pain status and treatment and their relationship with clinical outcomes. Trunk postural control measures were determined in patients with low back pain before and after an 8-week lumbar stabilization exercise program. Healthy controls were assessed over the same interval, but without any treatment, to determine the reliability of the measures and act as a control group at baseline. The kinematics of a wobble chair during unstable sitting was summarized using different linear and nonlinear measures quantifying the quantity and quality of movement, respectively. The reliability of the measures was moderate to excellent. The results showed significant reduction in pain and disability following the intervention. While no impairment at baseline scores was found, some linear and nonlinear measures changed over the intervention period among the patient group. However, for nonlinear measures only, significant correlations were detected with the change scores of pain and disability. The change of measures over the intervention period was likely due to learning rather than the intervention as similar alteration was detected in the healthy subjects. The results suggest that only the quality (not the quantity) of movement may have relationship with pain and disability.
Keywords: Fractal dimension; Lumbar stabilization; Recurrence quantification analysis; Reliability; Spine stability; Unstable sitting.
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