Spatial distribution of erector spinae activity is related to task-specific pain-related fear during a repetitive object lifting task

Abstract

ABSTRACTFear-avoidance beliefs, particularly the fear of lifting an object with a flexed spine, were shown to be associated with reduced spinal motion during object lifting in both individuals with and without low back pain (LBP). LBP patients thereby also showed potentially clinically relevant changes in the spatial distribution of back muscle activity, but it remains unknown whether such associations are also present in pain-free individuals. The aim of this study was therefore to investigate the relationship between fear-avoidance beliefs and the change in spatial distribution of lumbar paraspinal muscle activity in pain-free individuals during a repetitive object lifting task. Thirty participants completed two pain-related fear questionnaires and performed 25 repetitions of lifting a 5kg-box from a lower to an upper shelf and back, while multi-channel electromyographic signals were recorded bilaterally from the lumbar erector spinae muscles. Changes in spatial distribution were determined by calculating the differences in vertical position of the weighted centroids of muscle activity (centroid shift) between the first and last few repetitions. Multiple linear regression analyses were performed to examine the relationship between the centroid shift and fear-avoidance belief scores. The analyses showed that the fear of lifting an object with a flexed spine was negatively associated with erector spinae activity centroid shift (R2 adj. = 0.1832; p = 0.045), which might be an expression of behavioral alterations in order to prevent the back from possible harm.