Individuals with recurrent low back pain exhibit further altered frontal plane trunk control in remission than when in pain.

Background: Movement alterations due to low back pain (LBP) could lead to long-term adverse consequences if they do not resolve after symptoms subside. This study aims to determine if altered trunk control associated with recurrent low back pain persists beyond symptom duration.
Methods: Twenty young adults with recurrent LBP were tested once during an LBP episode and once in symptom remission, and twenty matched back-healthy participants served as controls. Participants walked on a treadmill with five prescribed step widths (0.33, 0.67, 1, 1.33, 1.67 × preferred step width). Motion capture and surface electromyography were used to record trunk kinematics and muscle activation. Thorax-pelvis coordination was calculated using vector coding, and longissimus activation and co-activation were analyzed.
Findings: Young adults with recurrent LBP exhibited a "looser" trunk control strategy in the frontal plane during gait that was persistent regardless of pain status across multiple step widths compared to controls. The looser trunk control was demonstrated by a greater pelvis-only, less thorax-only coordination pattern, and decreased bilateral longissimus co-activation in individuals with recurrent LBP compared to controls. The looser trunk control strategy was further amplified when individuals were in symptom remission and exhibited greater trunk excursion and reduced in-phase coordination in the frontal plane.
Interpretation: The amplification of aberrant movement during symptom remission may suggest that movement patterns or anatomical factors existing prior to the tested painful episode underlie altered trunk control in individuals with recurrent LBP. The symptom remission period of recurrent LBP may be a critical window into clinical evaluation and treatment.
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